U.S. patent application number 14/024288 was filed with the patent office on 2014-01-09 for fluid storage in compressed-gas energy storage and recovery systems.
The applicant listed for this patent is Benjamin R. Bollinger, Richard Brody, Jan Johansson, Dax Kepshire, Troy O. McBride, David Perkins, Adam Rauwerdink. Invention is credited to Benjamin R. Bollinger, Richard Brody, Jan Johansson, Dax Kepshire, Troy O. McBride, David Perkins, Adam Rauwerdink.
Application Number | 20140010594 14/024288 |
Document ID | / |
Family ID | 49756046 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140010594 |
Kind Code |
A1 |
McBride; Troy O. ; et
al. |
January 9, 2014 |
FLUID STORAGE IN COMPRESSED-GAS ENERGY STORAGE AND RECOVERY
SYSTEMS
Abstract
In various embodiments, lined underground reservoirs and/or
insulated pipeline vessels are utilized for storage of compressed
fluid in conjunction with energy storage and recovery systems.
Inventors: |
McBride; Troy O.; (Norwich,
VT) ; Johansson; Jan; (Stockholm, SE) ;
Perkins; David; (Kensington, NH) ; Kepshire; Dax;
(Amesbury, MA) ; Bollinger; Benjamin R.;
(Topsfield, MA) ; Rauwerdink; Adam; (West Lebanon,
NH) ; Brody; Richard; (West Hartford, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
McBride; Troy O.
Johansson; Jan
Perkins; David
Kepshire; Dax
Bollinger; Benjamin R.
Rauwerdink; Adam
Brody; Richard |
Norwich
Stockholm
Kensington
Amesbury
Topsfield
West Lebanon
West Hartford |
VT
NH
MA
MA
NH
CT |
US
SE
US
US
US
US
US |
|
|
Family ID: |
49756046 |
Appl. No.: |
14/024288 |
Filed: |
September 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13827465 |
Mar 14, 2013 |
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14024288 |
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61659164 |
Jun 13, 2012 |
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61695393 |
Aug 31, 2012 |
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Current U.S.
Class: |
405/55 |
Current CPC
Class: |
F17C 1/14 20130101; F17C
2203/0639 20130101; F17C 2223/0123 20130101; F17C 2203/0617
20130101; F17C 2270/0581 20130101; F17C 2203/0604 20130101; F17C
1/007 20130101; F17C 2201/019 20130101; F17C 2201/052 20130101;
E21D 13/00 20130101; F17C 2203/0678 20130101; F17C 2227/0192
20130101; F17C 2260/046 20130101; E21D 11/38 20130101; F17C
2201/0138 20130101; F17C 2201/035 20130101; F17C 2201/0109
20130101; F17C 2223/036 20130101; F17C 2203/0304 20130101; E21D
11/00 20130101; F17C 2201/037 20130101; F17C 2221/031 20130101;
F17C 2203/0619 20130101; F17C 2223/035 20130101; E21B 36/00
20130101; F17C 2205/0142 20130101; F17C 2221/033 20130101 |
Class at
Publication: |
405/55 |
International
Class: |
E21D 11/38 20060101
E21D011/38 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] This invention was made with government support under
DE-OE0000231 awarded by the DOE. The government has certain rights
in the invention.
Claims
1. A method of fabricating a lined underground reservoir, the
method comprising: excavating rock at a site location to form an
open shaft extending below ground level; assembling within or above
the shaft a fluid-impermeable liner substantially enclosing an
interior volume for containing at least one of compressed gas or
heat-transfer liquid, the interior volume being smaller than a
total volume of the open shaft, wherein the liner comprises: an
invert section enclosing a bottom of the interior volume, a dome
section enclosing a top of the interior volume opposite the bottom,
and a sidewall section substantially gaplessly spanning the invert
and dome sections, wherein after assembly, the liner is disposed
within the shaft below ground level; disposing a surround material
to at least partially fill a gap between an outer surface of the
liner and an inner surface of the shaft around at least a portion
of the outer surface of the liner; after assembly of the liner and
disposal of the surround material so as to form a surrounded liner,
disposing an overfill material over the surrounded liner to fill at
least a portion of a space between the ground level and the
surrounded liner; and fluidly connecting the interior volume
enclosed by the liner to a fluid source or fluid sink external to
the surrounded liner, thereby forming the lined underground
reservoir.
2. The method of claim 1, wherein the surround material comprises
concrete or metal-reinforced concrete.
3. The method of claim 1, wherein the liner comprises at least one
of steel or plastic.
4. The method of claim 1, wherein the overfill material comprises
at least one of rock, concrete, or metal-reinforced concrete.
5. The method of claim 1, wherein the overfill material comprises a
volume of heat-transfer liquid.
6. The method of claim 1, further comprising, prior to disposing
the overfill material, forming within the shaft a plug shaped to
laterally distribute upward-acting forces resulting when the liner
contains pressurized fluid, wherein a width of the shaft around the
plug is larger than a width of the shaft around the surrounded
liner.
7. The method of claim 6, wherein a cross-section of the plug in a
plane approximately perpendicular to ground level is substantially
trapezoidal or hexagonal.
8. The method of claim 1, further comprising, prior to disposing
the surround material, disposing a spacer on the liner that defines
at least a portion of the gap between the outer surface of the
liner and the inner surface of the shaft around at least a portion
of the outer surface of the liner.
9. The method of claim 1, further comprising: disposing within the
interior volume of the liner a mechanism for generating a foam or
droplet spray; fluidly connecting the mechanism to a source of
heat-transfer fluid external to the surrounded liner; and fluidly
connecting an area within the interior volume of the liner
proximate the invert section to a sink of heat-transfer fluid
external to the surrounded liner.
10. The method of claim 1, wherein assembling the liner comprises:
supporting a first portion of the liner above a bottom surface of
the shaft such that a top surface of the first portion of the liner
is proximate ground level; disposing a second portion of the liner
on the top surface of the first portion of the liner to form an at
least partially assembled liner; and lowering the at least
partially assembled liner such that a top surface of the second
portion of the liner is proximate ground level.
11. The method of claim 10, wherein supporting the first portion of
the liner comprises floating the first portion of the liner on a
liquid within the shaft.
12. The method of claim 11, wherein lowering the at least partially
assembled liner comprises removing liquid from the shaft.
13. The method of claim 1, further comprising, during disposal of
the surround material, at least partially filling the interior
volume of the liner with a liquid such that a top surface of the
liquid is approximately coplanar with a top surface of the surround
material.
14. The method of claim 1, wherein (i) the sidewall section of the
liner comprises a plurality of substantially cylindrical segments,
and (ii) each cylindrical segment comprises a plurality of discrete
curved portions connected at interfaces therebetween.
15. The method of claim 14, further comprising welding the
plurality of discrete curved portions together at the interfaces to
form each of the substantially cylindrical segments.
16. The method of claim 1, wherein the fluid source or fluid sink
external to the surrounded liner is a compressed-gas energy storage
and recovery system configured to store gas in the interior volume
after compression thereof and extract gas from the interior volume
before expansion thereof.
17. The method of claim 1, further comprising disposing between the
outer surface of the liner and the inner surface of the shaft a
network of drainage pipes for channeling liquid away from the
liner.
18. The method of claim 17, further comprising spraying concrete on
the network of drainage pipes.
19. The method of claim 1, wherein a portion of the surround
material is disposed over the dome section of the liner.
20. The method of claim 1, wherein the surround material comprises
a concrete layer and, disposed between the concrete layer and the
liner, a viscous layer for mitigating force on the liner.
21. The method of claim 20, wherein the concrete layer comprises
therewithin a network of metal.
22. The method of claim 1, wherein the shaft is substantially
vertical.
23. The method of claim 1, wherein, during assembly of the liner
and disposal of the surround material, the site location is free of
sub-surface access tunnels having a sufficiently large size and
sufficiently shallow slope to accommodate vehicular traffic.
24. The method of claim 1, wherein excavating rock comprises: (a)
excavating one or more holes at the site location where the shaft
is to be formed; (b) placing an explosive in the one or more holes;
(c) detonating the explosive to pulverize the rock; (d) removing
the pulverized rock; and (e) optionally, repeating steps
(a)-(d).
25. The method of claim 1, wherein excavating rock comprises: (a)
pulverizing rock with a cutting mechanism mounted on a translatable
telescoping boom to form at least a portion of the shaft; (b)
removing the pulverized rock; and (c) optionally, lowering the
cutting mechanism and boom into the at least a portion of the shaft
and repeating steps (a) and (b).
26. The method of claim 1, wherein (i) the surrounded liner is
configured to contain a fluid pressure of at least 200 bar, and
(ii) the rock at the site location has a rock mass rating of at
least 50.
27. The method of claim 1, wherein (i) the rock at the site
location has a rock mass rating RMR, and (ii) the surrounded liner
is configured to contain a maximum fluid pressure P in MPa defined
by P.ltoreq.(RMR.times.0.83)-25.
28. The method of claim 1, wherein (i) a thickness of the liner is
insufficient to withstand a maximum internal fluid pressure of the
lined underground reservoir, and (ii) the lined underground
reservoir is configured to withstand the maximum internal fluid
pressure, notwithstanding the insufficient thickness of the liner,
via at least one of the overfill or rock surrounding the surrounded
liner withstanding a portion of the internal fluid pressure.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/827,465, filed Mar. 14, 2013, which claims
the benefit of and priority to U.S. Provisional Patent Application
No. 61/659,164, filed Jun. 13, 2012, and U.S. Provisional Patent
Application No. 61/695,393, filed Aug. 31, 2012. The entire
disclosure of each of these applications is hereby incorporated
herein by reference.
FIELD OF THE INVENTION
[0003] In various embodiments, the present invention relates to gas
storage, gas distribution, pneumatics, power generation, and energy
storage, and more particularly, to fluid systems for energy storage
and recovery.
BACKGROUND
[0004] It is often desirable to store energy in the form of a
fluid, such as compressed air or a fluid fuel (e.g., methane), that
may be at non-ambient temperature and under high pressure (e.g.,
3,000 psi). The energy may be stored at times of low demand or over
supply, and the stored energy may be utilized at times of high
demand or low supply in various ways: for example, methane may be
used to generate industrial process heat, compressed air may be
used to power mechanical devices directly, and methane or
compressed air may be used by power generators that produce
electricity. Retrievable or reversible modes of energy storage
include chemical potential energy (i.e., fuel), elastic potential
energy (i.e., the energy inherent in a compressed gas or liquid or
in a compressed or stretched elastic solid), gravitational
potential energy (i.e., the energy inherent in any mass by virtue
of its altitude), latent energy (i.e., the energy inherent in a
body by virtue of its phase state), electric energy (e.g., the
energy inherent in separated electrical charges, as in a charged
battery or capacitor), and exergy (i.e., the extractable work
latent in a body that is at a temperature higher or lower than the
temperature of a heat reservoir such as the body's environment). In
systems that employ an energy-storing fluid, the cost of insulated
and/or pressure-resistant vessels to contain the fluid is often a
large part of the net cost, over the lifetime of the system, of
storing and retrieving an average unit of energy.
[0005] Storing energy in the form of compressed gas has a long
history and components tend to be well tested and reliable, and
have long lifetimes. The general principle of compressed-gas or
compressed-air energy storage (CAES) is that generated energy
(e.g., electric energy) is used to compress gas (e.g., air), thus
converting the original energy to pressure potential energy; this
potential energy is later recovered in a useful form (e.g.,
converted back to electricity) via gas expansion coupled to an
appropriate mechanism. Advantages of compressed-gas energy storage
include low specific-energy costs, long lifetime, low maintenance,
reasonable energy density, and good reliability.
[0006] If a body of gas is at the same temperature as its
environment, and expansion occurs slowly relative to the rate of
heat exchange between the gas and its environment, then the gas
will remain at approximately constant temperature as it expands.
This process is termed "isothermal" expansion. Isothermal expansion
of a quantity of high-pressure gas stored at a given temperature
recovers approximately three times more work than would "adiabatic
expansion," that is, expansion where no heat is exchanged between
the gas and its environment--e.g., because the expansion happens
rapidly or in an insulated chamber. Gas may also be compressed
isothermally or adiabatically.
[0007] An ideally isothermal energy-storage cycle of compression,
storage, and expansion would have 100% thermodynamic efficiency. An
ideally adiabatic energy-storage cycle would also have 100%
thermodynamic efficiency, but there are many practical
disadvantages to the adiabatic approach. These include the
production of higher temperature and pressure extremes within the
system, heat loss during the storage period, and inability to
exploit environmental (e.g., cogenerative) heat sources and sinks
during expansion and compression, respectively. In an isothermal
system, the cost of adding a heat-exchange system is traded against
resolving the difficulties of the adiabatic approach. In either
case, mechanical energy from expanding gas is typically converted
to electrical energy before use.
[0008] An efficient and novel design for storing energy in the form
of compressed gas utilizing near isothermal gas compression and
expansion has been shown and described in U.S. Pat. No. 7,832,207,
filed Apr. 9, 2009 (the '207 patent) and U.S. Pat. No. 7,874,155,
filed Feb. 25, 2010 (the '155 patent), the disclosures of which are
hereby incorporated herein by reference in their entireties. The
'207 and '155 patents disclose systems and techniques for expanding
gas isothermally in staged cylinders and intensifiers over a large
pressure range in order to generate electrical energy when
required. Mechanical energy from the expanding gas may be used to
drive a hydraulic pump/motor subsystem that produces electricity.
Systems and techniques for hydraulic-pneumatic pressure
intensification that may be employed in systems and methods such as
those disclosed in the '207 and '155 patents are shown and
described in U.S. Pat. No. 8,037,678, filed Sep. 10, 2010 (the '678
patent), the disclosure of which is hereby incorporated herein by
reference in its entirety.
[0009] In the systems disclosed in the '207 and '155 patents,
reciprocal mechanical motion is produced during recovery of energy
from storage by expansion of gas in the cylinders. This reciprocal
motion may be converted to electricity by a variety of techniques,
for example as disclosed in the '678 patent as well as in U.S. Pat.
No. 8,117,842, filed Feb. 14, 2011 (the '842 patent), the
disclosure of which is hereby incorporated herein by reference in
its entirety. The ability of such systems to either store energy
(i.e., use energy to compress gas into a storage reservoir) or
produce energy (i.e., expand gas from a storage reservoir to
release energy) will be apparent to any person reasonably familiar
with the principles of electrical and pneumatic machines.
[0010] The net monetary cost at which energy-storage systems
deliver from storage a unit of energy (e.g., a kilowatt hour [kWh]
of electrical energy, a BTU of natural gas) depends in part on the
cost at which the system stores each unit of compressed gas. The
net cost of energy storage by a system employing compressed gas is
also influenced by the cost of conditioning the stored, compressed
gas by heating, cooling, and/or the addition and removal of other
gases or fluids. There is therefore a need for facilities that can
store and in some cases thermally condition large quantities of
compressed gas at relatively low cost, including the costs of
construction and maintenance.
SUMMARY
[0011] In various embodiments, the invention includes the
employment of one or more pressure vessels and/or one or more
insulated pipeline vessels (IPVs) and/or one or more lined
underground reservoirs (LURs) as pressurized-fluid storage
containers for a system that stores energy in the form of a
compressed fluid (e.g., high pressure gas). The terms "IPV" and
"LUR" will be clarified shortly, below. In general, the quantity of
energy to be stored may be characterized as "low," "medium," or
"large." The cost-effectiveness of a storage container type is, in
general, affected by the quantity of energy (i.e., fluid) to be
stored. For storage of low energy quantities, pressure vessels
(e.g., commercially-produced cylindrical tanks) and/or IPVs will in
general be most cost-effective for fluid storage; for storage of
medium energy quantities, IPVs and/or LURs will in general be most
cost-effective for fluid storage; and for storage of large energy
quantities, LURs and/or large scale geological storage (e.g., salt
cavern, aquifer) will be in general be most cost-effective for
fluid storage.
[0012] Herein, the terms "thermal energy" and "exergy" are employed
interchangeably, usually to signify extractable work latent in a
body that is at a temperature higher than that of the body's
environment. Hybrid systems that store energy in one or more fluids
that contain energy in one or more retrievable or reversible forms
can also be envisaged and are contemplated herein even when not
explicitly mentioned or described.
[0013] The term "insulated pipeline vessel" or "IPV" refers herein
to a segment of pressure-resistant pipeline (e.g., pipeline
designed to transport natural gas), of whatever length, that has
been sealed at its ends (other than to the extent that perforations
are provided for the delivery of fluids into and removal of fluids
from the IPV) and covered by one or more layers of insulation and
possibly by other protective materials as well. Herein, "IPV" may
also refer to a series of pipe segments joined together and sealed,
or an array of such segments or series of joined segments. An array
of pipe segments employed as an IPV is herein referred to as an
"IPV array." An IPV also may be equipped with perforations, valves,
and other devices to control the admission and release of gas
and/or liquid; may be equipped with sensors for detecting and
reporting flow, volume, temperature, pressure, strain, or other
qualities of the vessel's contents or of the vessel's own fabric;
may contain devices for the exchange of heat between the vessel's
fluid contents and external sources or sinks of thermal energy; and
may be encased in or buried under a layer or layers of earth,
gravel, or other materials. The term "insulated pipeline vessel" or
"IPV" may also refer herein to two or more IPVs, as just described,
interconnected so as to form a single system for the storage of
fluid. IPVs may have lengths well in excess (e.g., >100.times.)
of their diameters, and may not fall within ASME regulations for
pressure vessels. IPVs may include or consist essentially of (i) a
thermally insulating material (e.g., one or more plastics or
polymers) or (ii) a base material that is more conductive (e.g.,
one or more metals or metal alloys such as steel) that is (a) at
least partially buried within an insulating material (e.g., earth,
soil, gravel, etc.), (b) has a thermally insulating material
impregnated therewithin, and/or (c) has a thermally insulating
material disposed on its inner and/or outer surface. In various
embodiments, the thermal heat conduction through the walls of the
IPV is no greater than 5 Watts per degree Celsius per cubic meter
of storage volume (e.g., no more than 250 Watts lost due to heat
conduction for fluid contained in an IPV, where the fluid is
50.degree. C. warmer than the surroundings, for every 1.3 meter
length of a 1 meter inner diameter pipe), and in preferred
embodiments the thermal conductance is no greater than 2 Watts per
degree Celsius per cubic meter of storage volume, or even no
greater than 1 Watt per degree Celsius per cubic meter of storage
volume. For reference, an uninsulated pipe may lose more than 1000
watts (W) per degree Celsius per cubic meter of storage volume
(e.g., more than 50,000 W lost due to heat conduction for fluid
contained in the pipe, where the fluid is 50.degree. C. warmer than
the surroundings, for every 1.3 meter length of a 1 meter inner
diameter pipe).
[0014] An LUR is a cavity in rock (primarily crystalline bedrock)
that is lined with steel, concrete, and/or other materials that
enable the cavity to serve as a vessel containing fluids (e.g.,
natural gas, air, an air-water mixture) at high pressure (e.g., 150
atmospheres, 250 atmospheres, or higher) without significant fluid
leakage either into or out of the cavity. Various embodiments of
the invention employ techniques for the excavation of open,
vertical shafts in the construction of LURs and for the thermal
conditioning of fluids stored in LURs that have been constructed by
open-shaft and other techniques.
[0015] Typically, construction of an LUR entails excavation of a
large, vertically cylindrical cavity (e.g., 20-50 meters in
diameter and 50-115 meters tall) with a domed roof and rounded
invert (floor). Excavation may be via sloping access tunnels or the
sinking of a vertical shaft. The domed roof may be constructed
after excavation of the cavity. A vertically oriented shape
enhances the stability of the excavation by minimizing roof area,
while rounding of the roof and the invert increases roof strength
and enables fluid-pressure stresses on the inner liner (e.g., steel
skin) to be distributed more evenly.
[0016] An LUR cavity may be located at various depths below the
ground (e.g., 100 meters to 200 meters), depending on rock type and
other constraints, and may be lined with a multi-layer lining that
may be constructed, wholly or partly, either during excavation or
after excavation. The lining typically includes a layer of
reinforced concrete (e.g., approximately 1 meter thick) and a thin
(e.g., 12-15 mm) inner liner of carbon steel. The lining may also
include other layers, such as a layer of thermal insulation (e.g.,
perlite concrete) and/or a network of pipes to drain groundwater
away from the cavity liner. One purpose of the inner liner is to
act as an impermeable barrier, both to retain the fluid contents of
the cavity and to keep fluids (e.g., groundwater) from entering the
cavity. A purpose of the concrete layer is to act as a distributor
of forces exerted by the contents of the LUR on the surrounding
lining layers and rock mass, and by the surrounding rock mass on
the LUR lining layers: that is, the concrete layer assures the most
even possible transfer of forces from fluid within the LUR to the
surrounding rock mass and distributes any local strains in the rock
mass (e.g., from the opening of natural rock fractures) at the
concrete/rock interface) as evenly as possible across the concrete
and thus across the inner liner. Smooth distribution of forces
across the inner liner is desirable because the inner liner is
typically thin (to conserve materials and so reduce cost): its
composition and thickness, and hence its cost, will depend on the
maximum local circumferential strain that any part of it must be
able to resist during operation. Therefore, preventing the
occurrence of excessive local strain on any part of the inner liner
is advantageous.
[0017] To further minimize local circumferential strains on the
inner liner, a viscous layer (e.g., approximately 5 mm thick and
made of a bituminous (tarry) material) may be placed between the
steel and the concrete layers of the liner. This viscous layer will
allow some slippage between the inner liner and the concrete,
contributing to the reduction of local strains.
[0018] These and other features and advantages of LUR linings in
various embodiments of the invention will be further disclosed and
clarified in the drawings and accompanying explanations. The
foregoing description of liner construction techniques and
materials is exemplary: other techniques for construction, and
other materials for the inner liner and various other portions of
the cavity liner, may be employed.
[0019] Conventional storage facilities for compressed gas rely
primarily on (a) compressed-gas bottles, or (b) depleted oil
fields, salt caverns, or aquifer formations, into which compressed
gas may be injected. The use of oil fields, salt caverns, and
aquifers tightly constrains site selection, which is
disadvantageous. The various surface-vessel options tend to occupy
relatively large areas of land, which can be site-constraining, and
are materials-intensive, which raises cost. For a commercially
realistic energy-storage capacity, the areal footprint of a
compressed gas energy storage and generation facility located at or
near the surface of the earth will typically consist mostly of
storage.
[0020] A number of advantages are realized by using LURs with
energy storage systems relying on compressed gas. An LUR facility,
both during and after construction, tends to disturb its surface
environs relatively little compared to surface-sited storage
facilities of comparable capacity, which, as noted above, can
occupy significant area. The ability to site an LUR wherever
suitable earth material (e.g., bedrock) allows for the construction
of energy storage and generation facilities nearer to demand in
some cases, reducing transmission costs. Herein, any earth material
suitable for the construction of an LUR is referred to as
"bedrock." Being embedded deeply in bedrock, LURs are relatively
secure from accidental or malicious damage, making compressed-gas
LURs a particularly safe way to store large amounts of energy;
indeed, compressed-air LUR storage is probably one of the safest
ways to store large amounts of energy yet devised, since LUR air
storage is not accompanied by the possibility of detonation,
deflagration, explosive decompression, dam bursting, release of
toxins, release of suffocating gases, and other hazards associated
with various other energy-storage technologies. The environmental
impact of a compressed-air LUR is low both because its surface
footprint is low and its water usage is low compared to
pumped-reservoir storage, the latter being especially of advantage
in arid or semiarid regions.
[0021] Another advantage of compressed-gas LUR storage is that an
LUR may enable the storage of compressed gas fluids at lower
per-unit cost than most other methods of storage. Lower cost is
achieved because in an LUR, outward-acting pressure forces are
borne by surrounding bedrock rather than by the constructed fabric
of the vessel itself. This greatly reduces the quantities of
relatively expensive materials (e.g., steel, carbon fiber,
reinforced concrete) needed to contain each unit of pressurized
fluid as compared to free-standing high-pressure vessels that must
bear all loads internally. Further, because an LUR may be
relatively large (e.g., approximately 30,000 m.sup.3), its
surface-to-volume ratio is low compared to that of a multiplicity
of smaller vessels, further reducing material and construction
costs per unit of fluid stored.
[0022] Another potential advantage is that an LUR may, when the
temperature of its contents is lower than that of the surrounding
rock, harvest energy from the earth's innate heat. Heat that flows
from surrounding rock to fluids in an LUR may be partially
converted to electricity by the energy-conversion portion of an
energy storage and generation system.
[0023] Provisions may be made for the exchange of heat between a
heat-transfer fluid (e.g., water with additives) and the air (or
other gas) within an LUR: for example, water may be sprayed or
foamed into the LUR to either warm or cool the air within, and may
then be pumped out to partake in further heat exchanges and/or to
be recycled within the system. Such provisions may be advantageous
for the operation of an energy storage and generation system. For
example, lowering the temperature of fluids within an LUR may be
employed to reduce energy loss to, or increase energy gain from,
surrounding rock, or may be employed to reduce pressure changes and
associated mechanical stresses on the LUR's lining layers and
surrounding rock. Such provisions may enable the conveyance of heat
obtained from external surface sources (e.g., waste heat from a
thermal power plant) to the fluid contents of the LUR, in which
case the LUR will store energy both as the elastic potential energy
of compressed air and as the thermal energy of warm fluids.
[0024] The construction of LURs as storage reservoirs for
energy-storage systems employing compressed air and near-isothermal
compression and expansion is therefore advantageous as regards
surface footprint, siting flexibility, safety, cost per unit of
energy stored, and other aspects of cost and operation.
[0025] Embodiments of the present invention may be utilized in
energy storage and generation systems utilizing compressed gas. In
a compressed-gas energy storage system, gas is stored at high
pressure (e.g., approximately 3,000 psi). This gas may be expanded
into a cylinder having a first compartment (or "chamber") and a
second compartment separated by a piston slidably disposed within
the cylinder (or by another boundary mechanism). A shaft may be
coupled to the piston and extend through the first compartment
and/or the second compartment of the cylinder and beyond an end cap
of the cylinder, and a transmission mechanism may be coupled to the
shaft for converting a reciprocal motion of the shaft into a rotary
motion, as described in the '678 and '842 patents. Moreover, a
motor/generator may be coupled to the transmission mechanism.
Alternatively or additionally, the shaft of the cylinders may be
coupled to one or more linear generators, as described in the '842
patent.
[0026] As also described in the '842 patent, the range of forces
produced by expanding a given quantity of gas in a given time may
be reduced through the addition of multiple, series-connected
cylinder stages. That is, as gas from a high-pressure reservoir is
expanded in one chamber of a first, high-pressure cylinder, gas
from the other chamber of the first cylinder is directed to the
expansion chamber of a second, lower-pressure cylinder. Gas from
the lower-pressure chamber of this second cylinder may either be
vented to the environment or directed to the expansion chamber of a
third cylinder operating at still lower pressure; the third
cylinder may be similarly connected to a fourth cylinder; and so
on.
[0027] The principle may be extended to more than two cylinders to
suit particular applications. For example, a narrower output force
range for a given range of reservoir pressures is achieved by
having a first, high-pressure cylinder operating between, for
example, approximately 3,000 psig and approximately 300 psig and a
second, larger-volume, lower-pressure cylinder operating between,
for example, approximately 300 psig and approximately 30 psig. When
two expansion cylinders are used, the range of pressure within
either cylinder (and thus the range of force produced by either
cylinder) is reduced as the square root relative to the range of
pressure (or force) experienced with a single expansion cylinder,
e.g., from approximately 100:1 to approximately 10:1 (as set forth
in the '853 application). Furthermore, as set forth in the '678
patent, N appropriately sized cylinders can reduce an original
operating pressure range R to R.sup.1/N. Any group of N cylinders
staged in this manner, where N.gtoreq.2, is herein termed a
cylinder group.
[0028] Every compression or expansion of a quantity of gas, where
such a compression or expansion is herein termed "a gas process,"
is generally one of three types: (1) adiabatic, during which the
gas exchanges no heat with its environment and, consequently, rises
or falls in temperature, (2) isothermal, during which the gas
exchanges heat with its environment in such a way as to remain at
constant temperature, and (3) polytropic, during which the gas
exchanges heat with its environment but its temperature does not
remain constant. Perfectly adiabatic gas processes are not
practical because some heat is always exchanged between any body of
gas and its environment (ideal insulators and reflectors do not
exist); perfectly isothermal gas processes are not practical
because for heat to flow between a quantity of gas and a portion of
its environment (e.g., a body of liquid), a nonzero temperature
difference must exist between the gas and its environment--e.g.,
the gas must be allowed to heat during compression in order that
heat may be conducted to the liquid. Hence real-world gas processes
are typically polytropic, though they may approximate adiabatic or
isothermal processes.
[0029] The Ideal Gas Law states that for a given quantity of gas
having mass m, pressure p, volume V, and temperature T, pV=mRT,
where R is the gas constant (R=287 J/Kkg for air). For an
isothermal process, T is a constant throughout the process, so
pV=C, where C is some constant.
[0030] For a polytropic process, as will be clear to persons
familiar with the science of thermodynamics, pV.sup.n=C throughout
the process, where n, termed the polytropic index, is some constant
generally between 1.0 and 1.6. For n=1, pV.sup.n=pV.sup.1=pV=C,
i.e., the process is isothermal. In general, a process for which n
is close to 1 (e.g., 1.05) may be deemed approximately
isothermal.
[0031] For an adiabatic process, pV.sup..gamma.=C, where .gamma.,
termed the adiabatic coefficient, is equal to the ratio of the
gas's heat capacity at constant pressure C.sub.P to its heat
capacity at constant volume, C.sub.V, i.e.,
.gamma.=C.sub.P/C.sub.V. In practice, .gamma. is dependent on
pressure. For air, the adiabatic coefficient .gamma. is typically
between 1.4 and 1.6.
[0032] Herein, we define a "substantially isothermal" gas process
as one having n.ltoreq.1.1. The gas processes conducted within
cylinders described herein are preferably substantially isothermal
with n.ltoreq.1.05. Herein, wherever a gas process taking place
within a cylinder assembly or storage reservoir is described as
"isothermal," this word is synonymous with the term "substantially
isothermal."
[0033] The amount of work done in compression or expansion of a
given quantity of gas varies substantially with polytropic index n.
For compressions, the lowest amount of work done is for an
isothermal process and the highest for an adiabatic process, and
vice versa for expansions. Hence, for gas processes such as
typically occur in the compressed-gas energy storage systems
described herein, the end temperatures attained by adiabatic,
isothermal, and substantially isothermal gas processes are
sufficiently different to have practical impact on the operability
and efficiency of such systems. Similarly, the thermal efficiencies
of adiabatic, isothermal, and substantially isothermal gas
processes are sufficiently different to have practical impact on
the overall efficiency of such energy storage systems. For example,
for compression of a quantity of gas from initial temperature of
20.degree. C. and initial pressure of 0 psig (atmospheric) to a
final pressure of 180 psig, the final temperature T of the gas will
be exactly 20.degree. C. for an isothermal process, approximately
295.degree. C. for an adiabatic process, approximately 95.degree.
C. for a polytropic compression having polytropic index n=1.1 (10%
increase in n over isothermal case of n=1), and approximately
60.degree. C. for a polytropic compression having polytropic index
n=1.05 (5% increase in n over isothermal case of n=1). In another
example, for compression of 1.6 kg of air from an initial
temperature of 20.degree. C. and initial pressure of 0 psig
(atmospheric) to a final pressure of approximately 180 psig,
including compressing the gas into a storage reservoir at 180 psig,
isothermal compression requires approximately 355 kilojoules of
work, adiabatic compression requires approximately 520 kilojoules
of work, and a polytropic compression having polytropic index
n=1.045 requires approximately 375 kilojoules of work; that is, the
polytropic compression requires approximately 5% more work than the
isothermal process, and the adiabatic process requires
approximately 46% more work than the isothermal process.
[0034] It is possible to estimate the polytropic index n of gas
processes occurring in cylinder assemblies such as are described
herein by empirically fitting n to the equation pV.sup.n=C, where
pressure p and volume V of gas during a compression or expansion,
e.g., within a cylinder, may both be measured as functions of time
from piston position, known device dimensions, and
pressure-transducer measurements. Moreover, by the Ideal Gas Law,
temperature within the cylinder may be estimated from p and V, as
an alternative to direct measurement by a transducer (e.g.,
thermocouple, resistance thermal detector, thermistor) located
within the cylinder and in contact with its fluid contents. In many
cases, an indirect measurement of temperature via volume and
pressure may be more rapid and more representative of the entire
volume than a slower point measurement from a temperature
transducer. Thus, temperature measurements and monitoring described
herein may be performed directly via one or more transducers, or
indirectly as described above, and a "temperature sensor" may be
one of such one or more transducers and/or one or more sensors for
the indirect measurement of temperature, e.g., volume, pressure,
and/or piston-position sensors.
[0035] The systems described herein, and/or other embodiments
employing foam-based heat exchange, liquid-spray heat exchange,
and/or external gas heat exchange, may draw or deliver thermal
energy via their heat-exchange mechanisms to external systems (not
shown) for purposes of cogeneration, as described in U.S. Pat. No.
7,958,731, filed Jan. 20, 2010 (the '731 patent), the entire
disclosure of which is incorporated by reference herein.
[0036] The compressed-air energy storage and recovery systems
described herein are preferably "open-air" systems, i.e., systems
that take in air from the ambient atmosphere for compression and
vent air back to the ambient atmosphere after expansion, rather
than systems that compress and expand a captured volume of gas in a
sealed container (i.e., "closed-air" systems). The systems
described herein generally feature one or more cylinder assemblies
for the storage and recovery of energy via compression and
expansion of gas. The systems also include (i) a reservoir for
storage of compressed gas after compression and supply of
compressed gas for expansion thereof, and (ii) a vent for
exhausting expanded gas to atmosphere after expansion and supply of
gas for compression. The storage reservoir may include or consist
essentially of, e.g., one or more IPVs, LURs, pressure vessels,
(i.e., containers for compressed gas that may have rigid exteriors
or may be inflatable, that may be formed of various suitable
materials such as metal or plastic, and that may or may not fall
within ASME regulations for pressure vessels), or caverns (i.e.,
naturally occurring or artificially created cavities that are
typically located underground). Open-air systems typically provide
superior energy density relative to closed-air systems.
[0037] Furthermore, the systems described herein may be
advantageously utilized to harness and recover sources of renewable
energy, e.g., wind and solar energy. For example, energy stored
during compression of the gas may originate from an intermittent
renewable energy source of, e.g., wind or solar energy, and energy
may be recovered via expansion of the gas when the intermittent
renewable energy source is nonfunctional (i.e., either not
producing harnessable energy or producing energy at
lower-than-nominal levels). As such, the systems described herein
may be connected to, e.g., solar panels or wind turbines, in order
to store the renewable energy generated by such systems.
[0038] In an aspect, embodiments of the invention feature a method
of fabricating a lined underground reservoir. Rock is excavated at
a site location to form an open shaft extending below ground level.
A fluid-impermeable (i.e., impermeable to liquid such as water
and/or gas such as air or natural gas) liner substantially
enclosing an interior volume for containing at least one of
compressed gas or heat-transfer liquid is assembled within or above
the shaft. The interior volume is smaller than the total volume of
the open shaft. The liner includes or consists essentially of an
invert section enclosing a bottom of the interior volume, a dome
section enclosing a top of the interior volume opposite the bottom,
and a sidewall section substantially gaplessly spanning the invert
and dome sections. After assembly, the liner is disposed within the
shaft below ground level. A surround material is disposed to at
least partially fill a gap between an outer surface of the liner
and an inner surface of the shaft around at least a portion of the
outer surface of the liner. After assembly of the liner and
disposal of the surround material so as to form a surrounded liner,
an overfill material is disposed over the surrounded liner to fill
at least a portion of a space between the ground level and the
surrounded liner. The interior volume enclosed by the liner is
fluidly connected to a fluid source or fluid sink external to the
surrounded liner, thereby forming the lined underground
reservoir.
[0039] Embodiments of the invention may feature one or more of the
following in any of a variety of different combinations. The
surround material may include or consist essentially of concrete or
metal-reinforced concrete (e.g., concrete internally reinforced
with a network of metal such as rebar). The liner may include or
consist essentially of steel and/or plastic. The overfill material
may include or consist essentially of rock, concrete, and/or
metal-reinforced concrete. The overfill material may include or
consist essentially of a volume of heat-transfer liquid (e.g.,
water). The overfill material may be the fluid source and/or fluid
sink. Prior to disposing the overfill material, a plug, shaped to
laterally distribute upward-acting forces resulting when the liner
contains pressurized fluid, may be formed within the shaft. A width
of the shaft around the plug may be larger than a width of the
shaft around the surrounded liner. A cross-section of the plug,
e.g., a cross-section in a plane approximately perpendicular to
ground level, may be substantially trapezoidal or hexagonal. Prior
to disposing the surround material, spacer may be disposed on the
liner that defines at least a portion of the gap between the outer
surface of the liner and the inner surface of the shaft around at
least a portion of the outer surface of the liner. The shaft may be
substantially fully formed prior to any portion of the liner being
disposed therein. At least a portion of the surround material may
be disposed within the shaft prior to the liner being disposed
within the shaft. A mechanism for generating a foam or droplet
spray may be disposed within the interior volume. The mechanism may
be fluidly connected to a source of heat-transfer fluid external to
the surrounded liner. An area within the interior volume of the
liner proximate the invert section may be fluidly connected to a
sink of heat-transfer fluid external to the surrounded liner.
[0040] Assembling the liner may include or consist essentially of
supporting a first portion of the liner above a bottom surface of
the shaft such that a top surface of the first portion of the liner
is proximate ground level, disposing a second portion of the liner
on the top surface of the first portion of the liner to form an at
least partially assembled liner, and lowering the at least
partially assembled liner such that a top surface of the second
portion of the liner is proximate ground level. Supporting the
first portion of the liner may include or consist essentially of
floating the first portion of the liner on a liquid within the
shaft. Lowering the at least partially assembled liner may include
or consist essentially of removing liquid from the shaft.
Assembling the liner may include or consist essentially of filling
at least a portion of the shaft with a liquid, floating a first
portion of the liner on the liquid, proximate ground level,
disposing a second portion of the liner on the first portion of the
liner, and removing liquid from the shaft until a top surface of
the second portion of the liner is proximate ground level. At least
a portion of the surround material may be disposed on the inner
surface of the shaft prior to filling the at least a portion of the
shaft with the liquid. A spacer may be disposed on the first
portion of the liner. The spacer may define at least a portion of
the gap between the outer surface of the liner and the inner
surface of the shaft around at least a portion of the outer surface
of the liner. After the surround material is disposed within the
gap, the surround material may have a substantially uniform
thickness, defined by the spacer, around the liner. A portion of
the surround material may be attached to each of the first and
second sections of the liner proximate ground level. Each portion
of the surround material may include or consist essentially of a
network of metal.
[0041] During disposal of the surround material, the interior
volume of the liner may be at least partially filled with a liquid
such that a top surface of the liquid is approximately coplanar
with a top surface of the surround material. The sidewall section
of the liner may include or consist essentially of a plurality of
substantially cylindrical segments, and each cylindrical segment
may include or consist essentially of a plurality of discrete
curved portions connected at interfaces therebetween. The plurality
of discrete curved portions may be welded together at the
interfaces to form each of the substantially cylindrical segments.
The fluid source or fluid sink external to the surrounded liner may
be a compressed-gas energy storage and recovery system configured
to store gas in the interior volume after compression thereof and
extract gas from the interior volume before expansion thereof. The
energy storage and recovery system may store, e.g., compressed air
or natural gas, within the interior volume and/or extract it
therefrom. A network of drainage pipes for channeling liquid away
from the liner may be disposed between the outer surface of the
liner and the inner surface of the shaft. Concrete may be sprayed
on the network of drainage pipes. At least a portion of the
surround material may be disposed within the shaft before the liner
is assembled. The surround material may include or consist
essentially of (i) a network of drainage pipes and (ii) concrete
reinforced with metal. The shaft may be deepened after a first
portion of the surround material is disposed within the shaft, and,
thereafter, a second portion of the surround material may be
disposed on the first portion of the surround material. The
assembled liner may not be self-supporting in the absence of the
surround material. The shaft may be deepened after a first portion
of the liner is assembled within the shaft, and, thereafter, a
second portion of the liner may be attached to the first portion of
the liner.
[0042] A portion of the surround material may be disposed over the
dome section of the liner. The surround material may include or
consist essentially of a concrete layer and, disposed between the
concrete layer and the liner, a viscous layer for mitigating force
on the liner. The concrete layer may include therewithin a network
of metal (e.g., the concrete may be metal-reinforced concrete). The
shaft may be substantially vertical. A region of the shaft disposed
above the assembled liner may have a width or diameter
approximately equal to or greater than a width or diameter of the
assembled liner. The entire shaft may have a width or diameter
approximately equal to or greater than a width or diameter of the
assembled liner. During assembly of the liner and disposal of the
surround material, the site location may be free of sub-surface
access tunnels having a sufficiently large size and/or sufficiently
shallow slope to accommodate vehicular traffic. Excavating rock may
include or consist essentially of (a) excavating one or more holes
at the site location where the shaft is to be formed, (b) placing
an explosive in the one or more holes, (c) detonating the explosive
to pulverize the rock, (d) removing the pulverized rock, and (e)
optionally, repeating steps (a)-(d). Excavating rock may include or
consist essentially of (a) pulverizing rock with a cutting
mechanism mounted on a translatable telescoping boom to form at
least a portion of the shaft, (b) removing the pulverized rock, and
(c) optionally, lowering the cutting mechanism and boom into the at
least a portion of the shaft and repeating steps (a) and (b). The
surrounded liner may be configured to contain a fluid pressure of
at least 200 bar, and the rock at the site location may have a rock
mass rating of at least 50. The rock at the site location may have
a rock mass rating RMR, and the surrounded liner may be configured
to contain a maximum fluid pressure P in MPa defined by
P.ltoreq.(RMR.times.0.83)-25. A thickness of the liner may be
insufficient to withstand a maximum internal fluid pressure of the
lined underground reservoir, and the lined underground reservoir
may be configured to withstand the maximum internal fluid pressure,
notwithstanding the insufficient thickness of the liner, via at
least one of the overfill or rock surrounding the surrounded liner
withstanding a portion of the internal fluid pressure.
[0043] In another aspect, embodiments of the invention feature a
method of energy storage utilizing a compressed-gas energy storage
system selectively fluidly connected to a lined underground
reservoir at least partially surrounded by rock. Gas is
substantially isothermally compressed with the energy storage
system at a compression temperature. The compressed gas is
transferred to the lined underground reservoir for storage.
Thereafter, heat is exchanged between the stored compressed gas and
the rock at least partially surrounding the lined underground
reservoir to change a temperature of the stored gas to a storage
temperature different from the compression temperature. The
compressed gas may be thermally conditioned during transfer to the
lined underground reservoir by (i) spraying droplets of a
heat-transfer liquid into the gas and/or (ii) forming a foam
comprising the gas and a heat-transfer liquid. The storage
temperature may be lower than the compression temperature. The
storage temperature may be higher than the compression
temperature.
[0044] In yet another aspect, embodiments of the invention feature
a compressed-gas energy storage and recovery system that includes
or consists essentially of a cylinder assembly for compressing gas
to store energy and/or expanding gas to recover energy, a
heat-exchange subsystem for thermally conditioning the gas during
the compression and/or expansion via heat exchange between the gas
and a heat-transfer liquid, a lined underground reservoir for
storing compressed gas and/or heat-transfer fluid in an interior
volume thereof, the lined underground reservoir being substantially
impermeable to fluid and comprising an inner steel layer surrounded
by an outer concrete layer, a source of heat-transfer fluid fluidly
connected to the interior volume of the lined underground
reservoir, and a sink for heat-transfer fluid fluidly connected to
the interior volume of the lined underground reservoir.
[0045] Embodiments of the invention may feature one or more of the
following in any of a variety of different combinations. A nozzle
for introducing heat-transfer fluid into the interior volume as a
spray of droplets or as a foam may be disposed within the interior
volume of the lined underground reservoir. A first pipe may fluidly
connect the cylinder assembly to the interior volume of the lined
underground reservoir. A second pipe may fluidly connect the source
of heat-transfer fluid to the nozzle. A third pipe may fluidly
connect an area proximate a bottom portion of the interior volume
of the lined underground reservoir and the sink for heat-transfer
fluid. A pump may be configured to transfer heat-transfer fluid
through the third pipe to the sink for heat-transfer fluid. The
source of heat-transfer fluid and the sink for heat-transfer fluid
may be the same body of liquid. The source of heat-transfer fluid
and the sink for heat-transfer fluid may be two discrete and
separate bodies of liquid.
[0046] In a further aspect, embodiments of the invention feature a
compressed-gas energy storage and recovery system that includes or
consists essentially of a cylinder assembly for at least one of
compressing gas to store energy or expanding gas to recover energy,
a heat-exchange subsystem for thermally conditioning the gas via
heat exchange between the gas and a heat-transfer liquid, and
selectively fluidly connected to the cylinder assembly, one or more
insulated pipeline vessels (IPVs) for at least one of (i) storage
of gas after compression, (ii) supply of compressed gas for
expansion, (iii) storage of heat-transfer liquid, or (iv) supply of
heat-transfer liquid.
[0047] Embodiments of the invention may feature one or more of the
following in any of a variety of different combinations. Each IPV
may include or consist essentially of a base material at least
partially surrounded by insulation for retarding heat exchange
between contents of the IPV and surroundings of the IPV. Each IPV
may include, disposed on at least a portion of its interior
surface, a corrosion-resistant coating. At least one IPV may
contain gas at a pressure higher than an ambient pressure and/or at
a temperature higher than an ambient temperature. The one or more
IPVs may be at least partially buried underground. At least one IPV
may include an unburied access point for the inflow and outflow of
gas and/or heat-transfer liquid. Each IPV may be at least partially
disposed within a separate fill capsule (i) containing insulating
fill and (ii) including an outer envelope substantially impermeable
to liquid and/or air. Each fill capsule may be at least partially
buried underground. The one or more IPVs may include or consist
essentially of a plurality of IPVs, and two or more IPVs may be at
least partially disposed within a fill capsule (i) containing
insulating fill and (ii) including an outer envelope substantially
impermeable to at least one of liquid or air. The fill capsule may
be at least partially buried underground. All of the plurality of
IPVs may be at least partially disposed within the fill capsule.
The one or more IPVs may be each substantially linear and disposed
lengthwise at a first non-zero angle to the horizontal such that a
downhill end of each IPV is lower than an uphill end. At least one
IPV may include, proximate the downhill end thereof, a first access
point for the inflow and outflow of heat-transfer liquid. The at
least one IPV may include, proximate the first access point, a
second access point for the inflow and outflow of gas. The second
access point may be disposed at a distance from the downhill end
sufficient to prevent blockage of the second access point by
heat-transfer liquid accumulating proximate the downhill end. A
manifold pipe may be fluidly connectable to the first access points
of one or more IPVs. The manifold pipe may be inclined lengthwise
at a second non-zero angle to the horizontal. The manifold pipe may
be disposed approximately perpendicular to lengths of the one or
more IPVs. The second non-zero angle may be different from the
first non-zero angle. At least two of the one or more IPVs may be
fluidly connected by a connector. The connector may include or
consist essentially of a manifold and/or a U-bend connector. At
least one IPV may include therewithin a mechanism for the
introduction of heat-transfer liquid. The mechanism for the
introduction of heat-transfer liquid may include or consist
essentially of a nozzle, a spray head, and/or a spray rod. A pump
may supply heat-transfer liquid to the mechanism. Each IPV may have
a length exceeding its diameter by a factor of at least 100. Each
IPV may not fall within ASME regulations for pressure vessels. The
heat-exchange subsystem may include a mechanism for (i) the
introduction of heat-transfer liquid into gas in the form of
droplets and/or (ii) the mingling of heat-transfer liquid with gas
to form foam.
[0048] In yet a further aspect, embodiments of the invention
feature a compressed-gas energy storage and recovery system that
includes or consists essentially of a cylinder assembly for
compressing gas to store energy and/or expanding gas to recover
energy, and a storage system for the storage of compressed gas
and/or heat-transfer liquid. The storage system includes or
consists essentially of a first approximately planar array of
insulated pipeline vessels (IPVs). The first array is inclined at a
first non-zero angle to the horizontal in a first direction and
disposed at a second angle to the horizontal in a second direction
perpendicular to the first direction.
[0049] Embodiments of the invention may feature one or more of the
following in any of a variety of different combinations. The second
angle may be approximately zero or may be non-zero. The second
angle may be different from the first angle. At least two of the
IPVs of the first array may be fluidly connected to each other via
at least one connector. The at least one connector may include or
consist essentially of a manifold and/or at least one U-bend
connector. The storage system may include, disposed over the first
array, a second approximately planar array of IPVs. The second
array may be approximately parallel to the first array. The second
array may be inclined at a third non-zero angle to the horizontal
in the first direction and disposed at a fourth angle to the
horizontal in the second direction. The fourth angle may be
approximately zero or may be non-zero. The second angle may be
approximately equal to the fourth angle. The first angle may be
approximately equal to the third angle. The first angle may be
different from the third angle. Relative to the horizontal, an
absolute value of the first angle may be approximately equal to an
absolute value of the third angle. At least one of the IPVs of the
first array may be fluidly connected to at least one of the IPVs of
the second array by at least one connector. The at least one
connector may include or consist essentially of a manifold or at
least one U-bend connector. Each IPV may include or consist
essentially of a base material at least partially surrounded by
insulation for retarding heat exchange between contents of the IPV
and surroundings of the IPV.
[0050] In another aspect, embodiments of the invention feature a
compressed-gas energy storage and recovery system that includes or
consists essentially of a cylinder assembly for at least one of
compressing gas to store energy or expanding gas to recover energy,
a heat-exchange subsystem for thermally conditioning the gas via
heat exchange between the gas and a heat-transfer liquid, and
selectively fluidly connected to the cylinder assembly, a lined
underground reservoir for at least one of (i) storage of gas after
compression, (ii) supply of compressed gas for expansion, (iii)
storage of heat-transfer liquid, or (iv) supply of heat-transfer
liquid.
[0051] Embodiments of the invention may feature one or more of the
following in any of a variety of different combinations. The lined
underground reservoir may include a liner at least partially
surrounded by at least one of earth, dirt, or gravel. The liner may
include or consist essentially of steel and/or concrete. A coating
for sealing the liner to prevent fluid flow therethrough,
preventing corrosion or degradation of the liner, and/or for
thermally insulating the liner may be disposed on an inner surface
of the liner and/or an outer surface of the liner. At least a
portion of the lined underground reservoir may be disposed below
ground level. The lined underground reservoir may include therein a
liquid containment region disposed above a bottom surface of the
lined underground reservoir. A spray head and/or nozzle for
introducing heat-transfer liquid and/or foam may be disposed within
the lined underground reservoir. The lined underground reservoir
may include a container buried beneath and surrounded by at least
one of earth, dirt, or gravel. The container may include or consist
essentially of steel. Concrete, an insulating material, fiberglass,
and/or carbon fiber may be disposed between the container and the
earth, dirt, and/or gravel. The concrete, insulating material,
fiberglass, and/or carbon fiber may be disposed directly on the
container with substantially no gap or air therebetween. A
circulation apparatus for pumping liquid disposed proximate a
bottom surface of the lined underground reservoir to a point
outside of the lined underground reservoir may be disposed within
the lined underground reservoir. The lined underground reservoir
may include therein a liquid containment region disposed above a
bottom surface of the lined underground reservoir. A second
circulation apparatus for pumping liquid disposed in the liquid
containment region to a point outside of the lined underground
reservoir may be disposed within the lined underground reservoir. A
pipe for transferring gas between the cylinder assembly and the
lined underground reservoir may extend from the cylinder assembly
to a point within an interior volume of the lined underground
reservoir. The lined underground reservoir may include or consist
essentially of a plurality of discrete containers disposed within a
shaft extending below ground level.
[0052] These and other objects, along with advantages and features
of the invention, will become more apparent through reference to
the following description, the accompanying drawings, and the
claims. Furthermore, it is to be understood that the features of
the various embodiments described herein are not mutually exclusive
and can exist in various combinations and permutations. Note that
as used herein, the terms "pipe," "piping" and the like shall refer
to one or more conduits that are rated to carry gas or liquid
between two points. Thus, the singular term should be taken to
include a plurality of parallel conduits where appropriate. Herein,
the terms "liquid" and "water" interchangeably connote any mostly
or substantially incompressible liquid, the terms "gas" and "air"
are used interchangeably, and the term "fluid" may refer to a
liquid, a gas, or a mixture of liquid and gas (e.g., a foam) unless
otherwise indicated. As used herein unless otherwise indicated, the
terms "approximately" and "substantially" mean.+-.10%, and, in some
embodiments, .+-.5%. Herein, any fluid at a pressure higher than
ambient atmospheric pressure is said to be "pressurized." A "valve"
is any mechanism or component for controlling fluid communication
between fluid paths or reservoirs, or for selectively permitting
control or venting. The term "cylinder" refers to a chamber, of
uniform but not necessarily circular cross-section, which may
contain a slidably disposed piston or other mechanism that
separates the fluid on one side of the chamber from that on the
other, preventing fluid movement from one side of the chamber to
the other while allowing the transfer of force/pressure from one
side of the chamber to the next or to a mechanism outside the
chamber. At least one of the two ends of a chamber may be closed by
end caps, also herein termed "heads." As utilized herein, an "end
cap" is not necessarily a component distinct or separable from the
remaining portion of the cylinder, but may refer to an end portion
of the cylinder itself. Rods, valves, and other devices may pass
through the end caps. A "cylinder assembly" may be a simple
cylinder or include multiple cylinders, and may or may not have
additional associated components (such as mechanical linkages among
the cylinders). The shaft of a cylinder may be coupled
hydraulically or mechanically to a mechanical load (e.g., a
hydraulic motor/pump or a crankshaft) that is in turn coupled to an
electrical load (e.g., rotary or linear electric motor/generator
attached to power electronics and/or directly to the grid or other
loads), as described in the '678 and '842 patents. As used herein,
"thermal conditioning" of a heat-exchange fluid does not include
any modification of the temperature of the heat-exchange fluid
resulting from interaction with gas with which the heat-exchange
fluid is exchanging thermal energy; rather, such thermal
conditioning generally refers to the modification of the
temperature of the heat-exchange fluid by other means (e.g., an
external heat exchanger). The terms "heat-exchange" and
"heat-transfer" are generally utilized interchangeably herein.
Unless otherwise indicated, motor/pumps described herein are not
required to be configured to function both as a motor and a pump if
they are utilized during system operation only as a motor or a pump
but not both. Gas expansions described herein may be performed in
the absence of combustion (as opposed to the operation of an
internal-combustion cylinder, for example). The term "thermal well"
refers herein to any mass (e.g., a quantity of fluid in an
insulated container, or a solid thermal mass in an insulated
container, or a portion of the earth) with which heat may be
exchanged, whose temperature may be raised or lowered compared to
some other mass (e.g., the environment), and which tends to retain
rather than to dissipate any thermal energy stored within itself.
Alternatively or additionally, a thermal well may employ material
phase changes (e.g., melting and solidifying of a material) to
store and release energy. As used herein, a "recessed" or
"underground" storage reservoir is at least partially surrounded by
and/or buried in material such as earth, dirt, gravel, and/or water
or other liquid. Recessed storage reservoirs may be formed in (and
may occupy substantially all of the space of) artificial and/or
natural caverns.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] In the drawings, like reference characters generally refer
to the same parts throughout the different views. Cylinders, rods,
and other components are depicted in cross section in a manner that
will be intelligible to all persons familiar with the art of
pneumatic and hydraulic cylinders. Also, the drawings are not
necessarily to scale, emphasis instead generally being placed upon
illustrating the principles of the invention. In the following
description, various embodiments of the present invention are
described with reference to the following drawings, in which:
[0054] FIG. 1A is a schematic drawing of an energy storage and
generation facility employing lined underground reservoirs,
accordance with various embodiments of the invention;
[0055] FIG. 1B is a schematic drawing of an energy storage and
generation facility employing insulated pipeline vessels,
accordance with various embodiments of the invention;
[0056] FIG. 1C is a schematic drawing of an energy storage and
generation facility employing lined underground reservoirs,
accordance with various embodiments of the invention;
[0057] FIG. 1D is a schematic drawing of an energy storage and
generation facility employing lined underground reservoirs,
accordance with various embodiments of the invention;
[0058] FIG. 2 is a schematic drawing of various components of a
compressed-gas energy storage system in accordance with various
embodiments of the invention;
[0059] FIG. 3 is a schematic drawing of the major components of a
compressed air energy storage and recovery system in accordance
with various embodiments of the invention;
[0060] FIG. 4 is a schematic drawing of various components of a
compressed-gas energy storage system in accordance with various
embodiments of the invention;
[0061] FIG. 5 is a schematic drawing of various components of a
multi-cylinder compressed-gas energy storage system in accordance
with various embodiments of the invention;
[0062] FIG. 6A is a schematic drawing of an insulated pipeline
vessel in accordance with various embodiments of the invention;
[0063] FIG. 6B is a schematic drawing of an insulated pipeline
vessel and piping for accessing the contents thereof in accordance
with various embodiments of the invention;
[0064] FIG. 6C is a schematic drawing of an insulated pipeline
vessel and a device for thermally regulating the contents thereof
in accordance with various embodiments of the invention;
[0065] FIG. 7A is a schematic drawing of an array of insulated
pipeline vessels in accordance with various embodiments of the
invention;
[0066] FIG. 7B is a schematic drawing of an illustrative
liquid-collection scheme for an IPV array in accordance with
various embodiments of the invention;
[0067] FIG. 7C is a schematic drawing of an illustrative,
generalized, single-layer IPV array in accordance with various
embodiments of the invention;
[0068] FIG. 7D is a schematic drawing of an illustrative,
generalized, two-layer IPV array with parallel layers in accordance
with various embodiments of the invention;
[0069] FIG. 7E is a schematic drawing of an illustrative,
generalized, two-layer IPV array with layers at different angles in
accordance with various embodiments of the invention;
[0070] FIG. 7F is a schematic drawing of an illustrative,
generalized, serpentine IPV array in accordance with various
embodiments of the invention;
[0071] FIG. 8 is a schematic drawing of a lined underground
reservoir system for the storage and thermal conditioning of
pressurized fluid in accordance with various embodiments of the
invention;
[0072] FIG. 9A is a schematic drawing of a lined underground
reservoir system for the storage and thermal conditioning of
pressurized fluid in accordance with various embodiments of the
invention;
[0073] FIG. 9B is a schematic drawing of a lined underground
reservoir system for the storage and thermal conditioning of
pressurized fluid, showing access tunnels built with level
topography in accordance with various embodiments of the
invention;
[0074] FIG. 9C is a schematic drawing of a lined underground
reservoir system for the storage and thermal conditioning of
pressurized fluid, showing access tunnels built with high-relief
topography in accordance with various embodiments of the
invention;
[0075] FIG. 10 is a schematic drawing of a lined underground
reservoir system for the storage and thermal conditioning of
pressurized fluid, showing a spiraling access tunnel in accordance
with various embodiments of the invention;
[0076] FIG. 11 is a schematic drawing of stages in the excavation
of an open shaft for the creation of a recessed lined underground
reservoir in accordance with various embodiments of the
invention;
[0077] FIG. 12A is a schematic drawing of a device for excavating
an open shaft in accordance with various embodiments of the
invention;
[0078] FIG. 12B is a schematic drawing of a device for excavating
an open shaft in accordance with various embodiments of the
invention;
[0079] FIG. 13 is a schematic drawing of a pipe network draining
water from the vicinity of a lined underground reservoir in
accordance with various embodiments of the invention;
[0080] FIG. 14A is a schematic drawing of a multilayered lining for
a lined underground reservoir in accordance with various
embodiments of the invention;
[0081] FIG. 14B is a schematic drawing of a multilayered lining for
a lined underground reservoir in accordance with various
embodiments of the invention;
[0082] FIGS. 15A and 15B are schematic drawings of the effects of
pressure-driven expansion upon a lined underground reservoir and
surrounding rock in accordance with various embodiments of the
invention;
[0083] FIG. 16 is a plot of the deformation of a steel reservoir
lining for three temperature and pressure cycles in accordance with
various embodiments of the invention;
[0084] FIG. 17 is a schematic drawing of stages in the construction
of an inner liner for a lined underground reservoir in accordance
with various embodiments of the invention;
[0085] FIG. 18 is a schematic drawing of stages in the construction
of a lined underground reservoir in accordance with various
embodiments of the invention;
[0086] FIG. 19 is a schematic drawing of stages in the construction
of a lined underground reservoir in accordance with various
embodiments of the invention;
[0087] FIG. 20 is a schematic drawing of stages in the construction
of a lined underground reservoir in accordance with various
embodiments of the invention;
[0088] FIG. 21A is a schematic drawing of stages in the
construction of a lined underground reservoir in accordance with
various embodiments of the invention;
[0089] FIG. 21B is a schematic drawing of stages in the
construction of a lined underground reservoir in accordance with
various embodiments of the invention;
[0090] FIG. 21C is a schematic drawing of stages in the
construction of a lined underground reservoir in accordance with
various embodiments of the invention;
[0091] FIG. 21D is a schematic drawing showing details of the liner
of a lined underground reservoir in accordance with various
embodiments of the invention;
[0092] FIG. 22 is a schematic drawing of a stage in the assembly of
the liner of a lined underground reservoir in accordance with
various embodiments of the invention;
[0093] FIG. 23 is a schematic drawing of stages in the construction
and lining of a lined underground reservoir in accordance with
various embodiments of the invention;
[0094] FIG. 24A is a schematic drawing of a lined underground
reservoir showing a first design for a pressure barrier in
accordance with various embodiments of the invention;
[0095] FIG. 24B is a schematic drawing of a lined underground
reservoir showing a second design for a pressure barrier in
accordance with various embodiments of the invention;
[0096] FIG. 24C is a schematic drawing of a lined underground
reservoir showing the action of forces in the absence of a pressure
barrier in accordance with various embodiments of the
invention;
[0097] FIG. 24D is a schematic drawing of a lined underground
reservoir showing the action of forces in the presence of a
pressure barrier in accordance with various embodiments of the
invention;
[0098] FIG. 25 is a schematic drawing of a lined underground
reservoir employing construction cavities for the housing of
machinery and storage of liquid in accordance with various
embodiments of the invention;
[0099] FIG. 26 is a schematic drawing of a lined underground
reservoir employing a portion of a shaft for the storage of liquid
in accordance with various embodiments of the invention;
[0100] FIG. 27 is a schematic drawing of a lined underground
reservoir system in which the lined cavity protrudes above the
surface in accordance with various embodiments of the
invention;
[0101] FIG. 28 is a schematic drawing of a lined underground
reservoir system in which the lined cavity protrudes above the
surface and provisions are made for the circulation of a
heat-transfer fluid within the reservoir in accordance with various
embodiments of the invention;
[0102] FIG. 29 is a schematic drawing of a cylinder assembly with
apparatus for the generation of foam external to the cylinder in
accordance with various embodiments of the invention;
[0103] FIG. 30 is a schematic drawing of a cylinder assembly with
apparatus for the generation of foam external to the cylinder and
provision for bypassing the foam-generating apparatus in accordance
with various embodiments of the invention;
[0104] FIG. 31 is a schematic drawing of a cylinder assembly with
apparatus for the generation of foam in a vessel external to the
cylinder in accordance with various embodiments of the
invention;
[0105] FIG. 32 is a schematic drawing of a cylinder assembly with
apparatus for the generation of foam in a vessel external to the
cylinder in accordance with various embodiments of the
invention;
[0106] FIG. 33A is a plot of metal stress range as a function of
cycle number for a lined underground reservoir pressurized gas
storage system in accordance with various embodiments of the
invention;
[0107] FIG. 33B, incorporating, as shown, partial views FIG. 33B-1,
FIG. 33B-2, and FIG. 33B-3, is a tabular presentation of the rock
mass rating system utilized in accordance with various embodiments
of the invention;
[0108] FIG. 34 is a table and plot of criteria for rock quality
pertaining to the construction of lined underground reservoirs in
accordance with various embodiments of the invention;
[0109] FIG. 35 is a plot of the total construction cost of a lined
underground reservoir as a function of reservoir volume and
overlying topography in accordance with various embodiments of the
invention;
[0110] FIG. 36 is a plot of the construction cost per cubic meter
of a lined underground reservoir as a function of reservoir volume
and overlying topography in accordance with various embodiments of
the invention;
[0111] FIG. 37 is a plot of the total construction cost of a lined
underground reservoir as a function of reservoir volume, broken out
by cost sector, in accordance with various embodiments of the
invention; and
[0112] FIG. 38 is a plot of the construction time of a lined
underground reservoir as a function of reservoir volume and
overlying topography in accordance with various embodiments of the
invention.
DETAILED DESCRIPTION
[0113] FIG. 1A schematically depicts an illustrative facility 100A
for the storage and generation of energy that employs two lined
underground reservoirs (LURs) 102, 104 to store pressurized fluids.
The LURs 102, 104 may exchange fluids with an above-ground facility
106 via piping 108. The LURs 102, 104 depicted in FIG. 1A are of a
capsule-like form typical for such reservoirs, namely, cylindrical
with rounded inverts (floors) 110, 112 and domed ceilings (114,
116). Linings and other details of the LURs 102, 104 and other
components of the system 100A are omitted from FIG. 1A for clarity.
The above-ground facility 106 may be a gas processing facility that
injects high-pressure gas for storage in the LURs 102, 104 and
extracts the gas for distribution, or the facility 106 may be a
generating facility that burns a fuel, e.g., natural gas, stored in
the LURs 102, 104. Alternatively, the facility 106 may be a storage
and generating facility that burns natural gas and renders such
combustion more efficient by using compressed air from LURs 102,
104, where the compressed air in the LURs 102, 104 may be provided
by pumping air during hours of low electrical demand. The facility
106 may even be a compressed-air-only energy storage and generation
facility that pumps air into both LURs 102, 104 during hours of low
electrical demand or high generation by an associated
renewable-energy facility (e.g., wind farm and/or solar cells; not
shown) and generates energy by running generators using the energy
released by expanding air from the LURs 102, 104. In particular,
the above-ground facility 106 may be a compressed-air energy
storage and generation facility that uses approximately isothermal
compression and storage as detailed herein.
[0114] FIG. 1B schematically depicts an illustrative system 100B
that employs LUR 102 to store an energy-storing fluid (e.g.,
methane, hydrogen, compressed gas). LUR 102 exchanges the fluid
through piping 108 at a surface access point 118, which features
attachment points for piping and valves for directing and measuring
fluid flow. The surface access point 118 receives the fluid from a
source/sink 120 (e.g., well, hydrogen generator, shipping terminal)
and may, in some modes of operation, direct the fluid to the
source/sink 120. The surface access point 118 may also be connected
to an aboveground fluid-handling facility 122. The fluid-handling
facility 122 may process the fluid (e.g., cool and compress methane
or reform methane with steam to produce hydrogen), or may utilize
the energy contained within the fluid to produce electricity. The
product of the fluid-handling facility 122 (i.e., a fluid,
electricity, etc.) may be delivered to an external user 124 (e.g.,
power grid) or may, in some modes of operation, be directed to the
LUR 102 or to the external source/sink 120. In various other
embodiments, some or all components of system 100B, in addition to
the LUR 102, are located underground.
[0115] FIG. 1C schematically depicts an illustrative system 100C
for the storage of energy and the generation of electricity that
employs an LUR 102 to store compressed air. System 100C
interconverts electrical energy with both thermal energy and the
elastic potential energy of compressed air. To compress air for
storage, system 100C draws electrical power from a source/sink 126
(e.g., power grid). The electrical power from the source/sink 126
may be passed through a transformer 128. After transformation, the
power drives a motor/generator 130. The motor/generator 130 drives
a compressor/expander 132 (e.g., turbine, reciprocating piston,
systems depicted in FIGS. 2-5, etc.) that raises ambient air to a
higher-than-ambient pressure. The pressurized air is stored in the
LUR 102. Heat from the pressurized air is extracted and stored in a
thermal energy sink 134 (e.g., atmosphere, body of water, thermal
well).
[0116] To generate electricity from compressed air released from
storage, compressed air from the LUR 102 is expanded to a
near-ambient pressure in the compressor/expander 132 in a manner
that performs mechanical work. Heat from a thermal energy source
(e.g., combusted methane, waste heat from a fuel-burning generator)
may be added to the air being expanded in the compressor/expander
132 and is partially converted to mechanical work. The mechanical
work derived from the compressed air and the thermal energy added
thereto is directed to the motor/generator 130. Electricity
produced by the motor/generator 130 is directed through the
transformer 128 and thence to the source/sink 126.
[0117] In various other embodiments, system 100C does not include a
discrete thermal energy sink 134 or thermal energy source 136.
Motor/generator 130 may be a single electric machine, or may
consist of a separate motor and separate generator.
Compressor/expander 132 may be a single system or may be separate
compressor unit and separate expander unit.
[0118] FIG. 1D schematically depicts an illustrative system 100D
that employs an array of insulated pipeline vessels (IPVs) 138 to
store an energy-storing fluid (e.g., methane, hydrogen, compressed
gas). The IPV array 138, which may be located either aboveground or
partially or substantially wholly belowground, exchanges the fluid
through piping 108 at access point 118, which includes attachment
points for piping and valves for directing and measuring fluid
flow. The surface access point 118 receives the fluid from
source/sink 120 (e.g., well, hydrogen generator, shipping terminal)
and may, in some modes of operation, direct the fluid to the
source/sink 120. The surface access point 118 is also connected to
aboveground fluid-handling facility 122. The fluid-handling
facility 122 may process the fluid (e.g., cool and compress methane
or reform methane with steam to produce hydrogen), or may utilize
the energy contained within the fluid to produce electricity. The
product of the fluid-handling facility 122 (i.e., a fluid,
electricity, or other) may be delivered to an external user 124
(e.g., power grid) or may, in some modes of operation, be directed
to the IPV array 138 or to the external source/sink 120. In various
other embodiments, some or all components of system 100D are
located underground, including the IPV array 138; also in various
other embodiments, more than one IPV array may be employed by
system 100D, in addition to one or more LURs (not shown).
[0119] FIG. 2 depicts an illustrative system 200 that may be part
of a larger system, not otherwise depicted, for the storage and
release of energy. Subsequent figures will clarify the application
of embodiments of the invention to such a system. The system 200
depicted in FIG. 2 features an assembly 201 for compressing and
expanding gas. Expansion/compression assembly 201 may include or
consist essentially of either one or more individual devices for
expanding or compressing gas (e.g., turbines or cylinder assemblies
that each may house a movable boundary mechanism) or a staged
series of such devices, as well as ancillary devices (e.g., valves)
not depicted explicitly in FIG. 2.
[0120] An electric motor/generator 202 (e.g., a rotary or linear
electric machine) is in physical communication (e.g., via hydraulic
pump, piston shaft, or mechanical crankshaft) with the
expansion/compression assembly 201. The motor/generator 202 may be
electrically connected to a source and/or sink of electric energy
not explicitly depicted in FIG. 2 (e.g., an electrical distribution
grid or a source of renewable energy such as one or more wind
turbines or solar cells).
[0121] The expansion/compression assembly 201 may be in fluid
communication with a heat-transfer subsystem 204 that alters the
temperature and/or pressure of a fluid (i.e., gas, liquid, or
gas-liquid mixture such as a foam) extracted from
expansion/compression assembly 201 and, after alteration of the
fluid's temperature and/or pressure, returns at least a portion of
it to expansion/compression assembly 201. Heat-transfer subsystem
204 may include pumps, valves, and other devices (not depicted
explicitly in FIG. 2) ancillary to its heat-transfer function and
to the transfer of fluid to and from expansion/compression assembly
201. Operated appropriately, the heat-transfer subsystem 204
enables substantially isothermal compression and/or expansion of
gas inside expansion/compression assembly 201.
[0122] Connected to the expansion/compression assembly 201 is a
pipe 206 with a control valve 208 that controls a flow of fluid
(e.g., gas) between assembly 201 and a storage reservoir 212 (e.g.,
one or more pressure vessels, IPVs, and/or LURs). The storage
reservoir 212 may be in fluid communication with a heat-transfer
subsystem 214 that alters the temperature and/or pressure of fluid
removed from storage reservoir 212 and, after alteration of the
fluid's temperature and/or pressure, returns it to storage
reservoir 212. A second pipe 216 with a control valve 218 may be in
fluid communication with the expansion/compression assembly 201 and
with a vent 220 that communicates with a body of gas at relatively
low pressure (e.g., the ambient atmosphere).
[0123] A control system 222 receives information inputs from any of
expansion/compression assembly 201, storage reservoir 212, and
other components of system 200 and sources external to system 200.
These information inputs may include or consist essentially of
pressure, temperature, and/or other telemetered measurements of
properties of components of system 201. Such information inputs,
here generically denoted by the letter "T," are transmitted to
control system 222 either wirelessly or through wires. Such
transmission is denoted in FIG. 2 by dotted lines 224, 226.
[0124] The control system 222 may selectively control valves 208
and 218 to enable substantially isothermal compression and/or
expansion of a gas in assembly 201. Control signals, here
generically denoted by the letter "C," are transmitted to valves
208 and 218 either wirelessly or through wires. Such transmission
is denoted in FIG. 2 by dashed lines 228, 230. The control system
222 may also control the operation of the heat-transfer assemblies
204, 214 and of other components not explicitly depicted in FIG. 2.
The transmission of control and telemetry signals for these
purposes is not explicitly depicted in FIG. 2.
[0125] The control system 222 may be any acceptable control device
with a human-machine interface. For example, the control system 222
may include a computer (for example a PC-type) that executes a
stored control application in the form of a computer-readable
software medium. More generally, control system 222 may be realized
as software, hardware, or some combination thereof. For example,
control system 222 may be implemented on one or more computers,
such as a PC having a CPU board containing one or more processors
such as the Pentium, Core, Atom, or Celeron family of processors
manufactured by Intel Corporation of Santa Clara, Calif., the 680x0
and POWER PC family of processors manufactured by Motorola
Corporation of Schaumburg, Ill., and/or the ATHLON line of
processors manufactured by Advanced Micro Devices, Inc., of
Sunnyvale, Calif. The processor may also include a main memory unit
for storing programs and/or data relating to the methods described
above. The memory may include random access memory (RAM), read only
memory (ROM), and/or FLASH memory residing on commonly available
hardware such as one or more application specific integrated
circuits (ASIC), field programmable gate arrays (FPGA),
electrically erasable programmable read-only memories (EEPROM),
programmable read-only memories (PROM), programmable logic devices
(PLD), or read-only memory devices (ROM). In some embodiments, the
programs may be provided using external RAM and/or ROM such as
optical disks, magnetic disks, or other storage devices.
[0126] For embodiments in which the functions of controller 222 are
provided by software, the program may be written in any one of a
number of high-level languages such as FORTRAN, PASCAL, JAVA, C,
C++, C#, LISP, PERL, BASIC or any suitable programming language.
Additionally, the software can be implemented in an assembly
language and/or machine language directed to the microprocessor
resident on a target device.
[0127] As described above, the control system 222 may receive
telemetry from sensors monitoring various aspects of the operation
of system 200, and may provide signals to control valve actuators,
valves, motors, and other electromechanical/electronic devices.
Control system 222 may communicate with such sensors and/or other
components of system 200 (and other embodiments described herein)
via wired or wireless communication. An appropriate interface may
be used to convert data from sensors into a form readable by the
control system 222 (such as RS-232 or network-based interconnects).
Likewise, the interface converts the computer's control signals
into a form usable by valves and other actuators to perform an
operation. The provision of such interfaces, as well as suitable
control programming, is clear to those of ordinary skill in the art
and may be provided without undue experimentation.
[0128] System 200 may be operated so as to compress gas admitted
through the vent 220 and store the gas thus compressed in reservoir
212. For example, in an initial state of operation, valve 208 is
closed and valve 218 is open, admitting a quantity of gas into
expansion/compression assembly 201. When a desired quantity of gas
has been admitted into assembly 201, valve 218 may be closed. The
motor/generator 202, employing energy supplied by a source not
explicitly depicted in FIG. 2 (e.g., the electrical grid), then
provides mechanical power to expansion/compression assembly 201,
enabling the gas within assembly 201 to be compressed.
[0129] During compression of the gas within assembly 201, fluid
(i.e., gas, liquid, or a gas-liquid mixture) may be circulated
between assembly 201 and heat-exchange assembly 204. Heat-exchange
assembly 204 may be operated in such a manner as to enable
substantially isothermal compression of the gas within assembly
201. During or after compression of the gas within assembly 201,
valve 208 may be opened to enable high-pressure fluid (e.g.,
compressed gas or a mixture of liquid and compressed gas) to flow
to reservoir 212. Heat-exchange assembly 214 may be operated at any
time in such a manner as alter the temperature and/or pressure of
the fluid within reservoir 212.
[0130] That system 200 may also be operated so as to expand
compressed gas from reservoir 212 in expansion/compression assembly
201 in such a manner as to deliver energy to the motor/generator
202 will be apparent to all persons familiar with the operation of
pneumatic, hydraulic, and electric machines.
[0131] FIG. 3 depicts an illustrative system 300 that features a
cylinder assembly 301 (i.e., an embodiment of assembly 201 in FIG.
2) in communication with a reservoir 322 (212 in FIG. 1) and a vent
to atmosphere 323 (220 in FIG. 2). In the illustrative system 300
shown in FIG. 3, the cylinder assembly 301 contains a piston 302
slidably disposed therein. In some embodiments the piston 302 is
replaced by a different boundary mechanism dividing cylinder
assembly 301 into multiple chambers, or piston 302 is absent
entirely, and cylinder assembly 301 is a "liquid piston." The
cylinder assembly 301 may be divided into, e.g., two pneumatic
chambers or one pneumatic chamber and one hydraulic chamber. The
piston 302 is connected to a rod 304, which may contain a
center-drilled fluid passageway with fluid outlet 312 extending
from the piston 302. The rod 304 is also attached to, e.g., a
mechanical load (e.g., a crankshaft or a hydraulic system) that is
not depicted. The cylinder assembly 301 is in liquid communication
with a heat-transfer subsystem 324 that includes or consists
essentially of a circulation pump 314 and a spray mechanism 310 to
enable substantially isothermal compression/expansion of gas.
Heat-transfer fluid circulated by pump 314 may be passed through a
heat exchanger 303 (e.g., tube-in-shell- or parallel-plate-type
heat exchanger). Spray mechanism 310 may include or consist
essentially of one or more spray heads (e.g., disposed at one end
of cylinder assembly 301) and/or spray rods (e.g., extending along
at least a portion of the central axis of cylinder assembly 301).
In other embodiments, a foam, rather than a spray of droplets, is
created to facilitate heat exchange between liquid and gas during
compression and expansion of gas within the cylinder assembly 301,
as described in U.S. patent application Ser. No. 13/473,128, filed
May 16, 2012 (the '128 application), the entire disclosure of which
is incorporated by reference herein. Foam may be generated by
foaming gas with heat-exchange liquid in a mechanism (not shown,
described in more detail below) external to the cylinder assembly
301 and then injecting the resulting foam into the cylinder
assembly 301. Alternatively or additionally, foam may be generated
inside the cylinder assembly 301 by the injection of heat-exchange
liquid into cylinder assembly 301 through a foam-generating
mechanism (e.g., spray head, rotating blade, one or more nozzles),
partly or entirely filling the pneumatic chamber of cylinder
assembly 301. In some embodiments, droplets and foams may be
introduced into cylinder assembly 301 simultaneously and/or
sequentially. Various embodiments may feature mechanisms (not shown
in FIG. 3) for controlling the characteristics of foam (e.g.,
bubble size) and for breaking down, separating, and/or regenerating
foam.
[0132] System 300 further includes a first control valve 320 (208
in FIG. 2) in communication with a storage reservoir 322 and
cylinder assembly 301, and a second control valve 321 (218 in FIG.
2) in communication with a vent 323 and cylinder assembly 301. A
control system 326 (222 in FIG. 2) may control operation of, e.g.,
valves 322 and 321 based on various system inputs (e.g., pressure,
temperature, piston position, and/or fluid state) from cylinder
assembly 301 and/or storage reservoir 322. Heat-transfer fluid
(liquid or circulated by pump 314 enters through pipe 313. Pipe 313
may be (a) connected to a low-pressure fluid source (e.g., fluid
reservoir (not shown) at the pressure to which vent 323 is
connected or thermal well 342); (b) connected to a high-pressure
source (e.g., fluid reservoir (not shown) at the pressure of
reservoir 322); (c) selectively connected (using valve arrangement
not shown) to low pressure during a compression process and to high
pressure during an expansion process; (d) connected to
changing-pressure fluid 308 in the cylinder 301 via connection 312;
or (e) some combination of these options.
[0133] In an initial state, the cylinder assembly 301 may contain a
gas 306 (e.g., air introduced to the cylinder assembly 301 via
valve 321 and vent 323) and a heat-transfer fluid 308 (which may
include or consist essentially of, e.g., water or another suitable
liquid). When the gas 306 enters the cylinder assembly 301, piston
302 is operated to compress the gas 306 to an elevated pressure
(e.g., approximately 3,000 psi). Heat-transfer fluid (not
necessarily the identical body of heat-transfer fluid 308) flows
from pipe 313 to the pump 314. The pump 314 may raise the pressure
of the heat-exchange fluid to a pressure (e.g., up to approximately
3,015 psig) somewhat higher than the pressure within the cylinder
assembly 301, as described in U.S. Pat. No. 8,359,856, filed Jan.
19, 2011 (the '856 patent), the entire disclosure of which is
incorporated by reference herein. Alternatively or in conjunction,
embodiments of the invention add heat (i.e., thermal energy) to, or
remove heat from, the high-pressure gas in the cylinder assembly
301 by passing only relatively low-pressure fluids through a heat
exchanger or fluid reservoir, as detailed in U.S. patent
application Ser. No. 13/211,440, filed Aug. 17, 2011 (the '440
application), the entire disclosure of which is incorporated by
reference herein.
[0134] Heat-transfer fluid is then sent through a pipe 316, where
it may be passed through a heat exchanger 303 (where its
temperature is altered) and then through a pipe 318 to the spray
mechanism 310. The heat-transfer fluid thus circulated may include
or consist essentially of liquid or foam. Spray mechanism 310 may
be disposed within the cylinder assembly 301, as shown; located in
the storage reservoir 322 or vent 323; or located in piping or
manifolding around the cylinder assembly, such as pipe 318 or the
pipes connecting the cylinder assembly to storage reservoir 322 or
vent 323. The spray mechanism 310 may be operated in the vent 323
or connecting pipes during compression, and a separate spray
mechanism may be operated in the storage reservoir 322 or
connecting pipes during expansion. Heat-transfer spray 311 from
spray mechanism 310 (and/or any additional spray mechanisms),
and/or foam from mechanisms internal or external to the cylinder
assembly 101, enable substantially isothermal compression of gas
306 within cylinder assembly 301.
[0135] In some embodiments, the heat exchanger 303 is configured to
condition heat-transfer fluid at low pressure (e.g., a pressure
lower than the maximum pressure of a compression or expansion
stroke in cylinder assembly 301), and heat-transfer fluid is
thermally conditioned between strokes or only during portions of
strokes, as detailed in the '440 application. Embodiments of the
invention are configured for circulation of heat-transfer fluid
without the use of hoses that flex during operation through the use
of, e.g., tubes or straws configured for non-flexure and/or pumps
(e.g., submersible bore pumps, axial flow pumps, or other in-line
style pumps) internal to the cylinder assembly (e.g., at least
partially disposed within the piston rod thereof), as described in
U.S. patent application Ser. No. 13/234,239, filed Sep. 16, 3011
(the '239 application), the entire disclosure of which is
incorporated by reference herein.
[0136] At or near the end of the compression stroke, control system
326 opens valve 320 to admit the compressed gas 306 to the storage
reservoir 322. Operation of valves 320 and 321 may be controlled by
various inputs to control system 326, such as piston position in
cylinder assembly 301, pressure in storage reservoir 322, pressure
in cylinder assembly 301, and/or temperature in cylinder assembly
301.
[0137] As mentioned above, the control system 326 may enforce
substantially isothermal operation, i.e., expansion and/or
compression of gas in cylinder assembly 301, via control over,
e.g., the introduction of gas into and the exhausting of gas out of
cylinder assembly 301, the rates of compression and/or expansion,
and/or the operation of the heat-exchange subsystem in response to
sensed conditions. For example, control system 326 may be
responsive to one or more sensors disposed in or on cylinder
assembly 301 for measuring the temperature of the gas and/or the
heat-exchange fluid within cylinder assembly 301, responding to
deviations in temperature by issuing control signals that operate
one or more of the system components noted above to compensate, in
real time, for the sensed temperature deviations. For example, in
response to a temperature increase within cylinder assembly 301,
control system 326 may issue commands to increase the flow rate of
spray 311 of heat-exchange fluid 308.
[0138] Furthermore, embodiments of the invention may be applied to
systems in which cylinder assembly 301 (or a chamber thereof) is in
fluid communication with a pneumatic chamber of a second cylinder
(e.g., as shown in FIG. 5). That second cylinder, in turn, may
communicate similarly with a third cylinder, and so forth. Any
number of cylinders may be linked in this way. These cylinders may
be connected in parallel or in a series configuration, where the
compression and expansion is done in multiple stages.
[0139] The fluid circuit of heat exchanger 303 may be filled with
water, a coolant mixture, an aqueous foam, or any other acceptable
heat-exchange medium. In alternative embodiments, a gas, such as
air or refrigerant, is used as the heat-exchange medium. In
general, the fluid is routed by conduits to a large reservoir of
such fluid in a closed or open loop. One example of an open loop is
a well or body of water from which ambient water is drawn and the
exhaust water is delivered to a different location, for example,
downstream in a river. In a closed-loop embodiment, a cooling tower
may cycle the water through the air for return to the heat
exchanger. Likewise, water may pass through a submerged or buried
coil of continuous piping where a counter heat-exchange occurs to
return the fluid flow to ambient temperature before it returns to
the heat exchanger for another cycle.
[0140] In various embodiments, the heat-exchange fluid is
conditioned (i.e., pre-heated and/or pre-chilled) or used for
heating or cooling needs by connecting the fluid inlet 338 and
fluid outlet 340 of the external heat-exchange side of the heat
exchanger 303 to an installation such as a heat-engine power plant,
an industrial process with waste heat, a heat pump, and/or a
building needing space heating or cooling, as described in the '731
patent. Alternatively, the external heat-exchange side of the heat
exchanger 303 may be connected to a thermal well 342 as depicted in
FIG. 3. The thermal well 342 may include or consist essentially of
a large water reservoir that acts as a constant-temperature thermal
fluid source for use with the system. Alternatively, the water
reservoir may be thermally linked to waste heat from an industrial
process or the like, as described above, via another heat exchanger
contained within the installation. This allows the heat-exchange
fluid to acquire or expel heat from/to the linked process,
depending on configuration, for later use as a heating/cooling
medium in the energy storage/conversion system. Alternatively, the
thermal well 342 may include two or more bodies of energy-storage
medium, e.g., a hot-water thermal well and a cold-water thermal
well, that are typically maintained in contrasting energy states in
order to increase the exergy of system 300 compared with a system
in which thermal well 342 includes a single body of energy-storage
medium. Storage media other than water may be utilized in the
thermal well 342; temperature changes, phase changes, or both may
be employed by storage media of thermal well 342 to store and
release energy. Thermal or fluid links (not shown) to the
atmosphere, ground, and/or other components of the environment may
also be included in system 300, allowing mass, thermal energy, or
both to be added to or removed from the thermal well 342. Moreover,
as depicted in FIG. 3, the heat-transfer subsystem 324 does not
interchange fluid directly with the thermal well 342, but in other
embodiments, fluid is passed directly between the heat-transfer
subsystem 324 and the thermal well 342 with no heat exchanger
maintaining separation between fluids.
[0141] FIG. 4 is a schematic of the major components of an
illustrative system 400 that employs a pneumatic cylinder 402 to
efficiently convert (i.e., store) mechanical energy into the
potential energy of compressed gas and, in another mode of
operation, efficiently convert (i.e., recover) the potential energy
of compressed gas into mechanical work. The pneumatic cylinder 402
may contain a slidably disposed piston 404 that divides the
interior of the cylinder 402 into a distal chamber 406 and a
proximal chamber 408. A port or ports (not shown) with associated
pipes 412 and a bidirectional valve 416 enables gas from a
high-pressure storage reservoir 420 (e.g., one or more pressure
vessels, IPVs, and/or LURs) to be admitted to chamber 406 as
desired. A port or ports (not shown) with associated pipes 422 and
a bidirectional valve 424 enables gas from the chamber 406 to be
exhausted through a vent 426 to the ambient atmosphere as desired.
In alternate embodiments, vent 426 is replaced by additional
lower-pressure pneumatic cylinders (or pneumatic chambers of
cylinders). A port or ports (not shown) enables the interior of the
chamber 408 to communicate freely at all times with the ambient
atmosphere. In alternate embodiments, cylinder 402 is double-acting
and chamber 408 is, like chamber 406, equipped to admit and exhaust
fluids in various states of operation. The distal end of a rod 430
is coupled to the piston 404. The rod 430 may be connected to a
crankshaft, hydraulic cylinder, or other mechanisms for converting
linear mechanical motion to useful work as described in the '678
and '842 patents.
[0142] In the energy recovery or expansion mode of operation,
storage reservoir 420 is filled with high-pressure air (or other
gas) 432 and a quantity of heat-transfer fluid 434. The
heat-transfer fluid 434 may be an aqueous foam or a liquid that
tends to foam when sprayed or otherwise acted upon. The liquid
component of the aqueous foam, or the liquid that tends to foam,
may include or consist essentially of water with 2% to 5% of
certain additives; these additives may also provide functions of
anti-corrosion, anti-wear (lubricity), anti-biogrowth (biocide),
freezing-point modification (anti-freeze), and/or surface-tension
modification. Additives may include a micro-emulsion of a
lubricating fluid such as mineral oil, a solution of agents such as
glycols (e.g. propylene glycol), or soluble synthetics (e.g.
ethanolamines). Such additives tend to reduce liquid surface
tension and lead to substantial foaming when sprayed. Commercially
available fluids may be used at an approximately 5% solution in
water, such as Mecagreen 127 (available from the Condat Corporation
of Michigan), which consists in part of a micro-emulsion of mineral
oil, and Quintolubric 807-WP (available from the Quaker Chemical
Corporation of Pennsylvania), which consists in part of a soluble
ethanolamine. Other additives may be used at higher concentrations
(such as at a 50% solution in water), including Cryo-tek 100/Al
(available from the Hercules Chemical Company of New Jersey), which
consists in part of a propylene glycol. These fluids may be further
modified to enhance foaming while being sprayed and to speed
defoaming when in a reservoir.
[0143] The heat-transfer fluid 434 may be circulated within the
storage reservoir 420 via high-inlet-pressure,
low-power-consumption pump 436 (such as described in the '731
patent). In various embodiments, the fluid 434 may be removed from
the bottom of the storage reservoir 420 via piping 438, circulated
via pump 436 through a heat exchanger 440, and introduced (e.g.,
sprayed) back into the top of storage reservoir 420 via piping 442
and spray head 444 (or other suitable mechanism). Any changes in
pressure within reservoir 420 due to removal or addition of gas
(e.g., via pipe 412) generally tend to result in changes in
temperature of the gas 432 within reservoir 420. By spraying and/or
foaming the fluid 434 throughout the storage reservoir gas 432,
heat may be added to or removed from the gas 432 via heat exchange
with the heat-transfer fluid 434. By circulating the heat-transfer
fluid 434 through heat exchanger 440, the temperature of the fluid
434 and gas 432 may be kept substantially constant (i.e.,
isothermal). Counterflow heat-exchange fluid 446 at near-ambient
pressure may be circulated from a near-ambient-temperature thermal
well (not shown) or source (e.g., waste heat source) or sink (e.g.,
cold water source) of thermal energy, as described in more detail
below.
[0144] In various embodiments of the invention, reservoir 420
contains an aqueous foam, either unseparated or partially separated
into its gaseous and liquid components. In such embodiments, pump
436 may circulate either the foam itself, or the separated liquid
component of the foam, or both, and recirculation of fluid into
reservoir 420 may include regeneration of foam by apparatus not
shown in FIG. 4.
[0145] In the energy recovery or expansion mode of operation, a
quantity of gas may be introduced via valve 416 and pipe 412 into
the upper chamber 406 of cylinder 402 when piston 404 is near or at
the top of its stroke (i.e., "top dead center" of cylinder 402).
The piston 404 and its rod 430 will then be moving downward (the
cylinder 402 may be oriented arbitrarily but is shown vertically
oriented in this illustrative embodiment). Heat-exchange fluid 434
may be introduced into chamber 406 concurrently via optional pump
450 (alternatively, a pressure drop may be introduced in line 412
such that pump 450 is not needed) through pipe 452 and directional
valve 454. This heat-exchange fluid 434 may be sprayed into chamber
406 via one or more spray nozzles 456 in such a manner as to
generate foam 460. (In some embodiments, foam 460 is introduced
directly into chamber 406 in foam form.) The foam 460 may entirely
fill the entire chamber 406, but is shown in FIG. 4, for
illustrative purposes only, as only partially filling chamber 406.
Herein, the term "foam" denotes either (a) foam only or (b) any of
a variety of mixtures of foam and heat-exchange liquid in other,
non-foaming states (e.g., droplets). Moreover, some non-foamed
liquid (not shown) may accumulate at the bottom of chamber 406; any
such liquid is generally included in references herein to the foam
460 within chamber 406.
[0146] System 400 is instrumented with pressure, piston position,
and/or temperature sensors (not shown) and controlled via control
system 462. At a predetermined position of piston 404, an amount of
gas 432 and heat-transfer fluid 434 have been admitted into chamber
406 and valve 416 and valve 454 are closed. (Valves 416 and 454 may
close at the same time or at different times, as each has a control
value based on quantity of fluid desired.) The gas in chamber 406
then undergoes free expansion, continuing to drive piston 404
downward. During this expansion, in the absence of foam 460, the
gas would tend to decrease substantially in temperature. With foam
460 largely or entirely filling the chamber, the temperature of the
gas in chamber 406 and the temperature of the heat-transfer fluid
460 tend to approximate to each other via heat exchange. The heat
capacity of the liquid component of the foam 460 (e.g., water with
one or more additives) may be much higher than that of the gas
(e.g., air) such that the temperature of the gas and liquid do not
change substantially (i.e., are substantially isothermal) even over
a many-times gas expansion (e.g., from 250 psig to near atmospheric
pressure, or in other embodiments from 3,000 psig to 250 psig).
[0147] When the piston 404 reaches the end of its stroke (bottom
dead center), the gas within chamber 406 will have expanded to a
predetermined lower pressure (e.g., near atmospheric). Valve 424
will then be opened, allowing gas from chamber 406 to be vented,
whether to atmosphere through pipe 422 and vent 426 (as illustrated
here) or, in other embodiments, to a next stage in the expansion
process (e.g., chamber in a separate cylinder), via pipe 422. Valve
424 remains open as the piston undergoes an upward (i.e., return)
stroke, emptying chamber 406. Part or substantially all of foam 460
is also forced out of chamber 406 via pipe 422. A separator (not
shown) or other means such as gravity separation is used to recover
heat-transfer fluid, preferably de-foamed (i.e., as a simple liquid
with or without additives), and to direct it into a storage
reservoir 464 via pipe 466.
[0148] When piston 404 reaches top of stroke again, the process
repeats with gas 432 and heat-transfer fluid 434 admitted from
vessel 420 via valves 416 and 454. If additional heat-transfer
fluid is needed in reservoir 420, it may be pumped back into
reservoir 420 from reservoir 464 via piping 467 and optional
pump/motor 468. In one mode of operation, pump 468 may be used to
continuously refill reservoir 420 such that the pressure in
reservoir 420 is held substantially constant. That is, as gas is
removed from reservoir 420, heat-transfer fluid 434 is added to
maintain constant pressure in reservoir 420. In other embodiments,
pump 468 is not used or is used intermittently, the pressure in
reservoir 420 continues to decrease during an energy-recovery
process (i.e., involving removal of gas from reservoir 420), and
the control system 462 changes the timing of valves 416 and 454
accordingly so as to reach approximately the same ending pressure
when the piston 404 reaches the end of its stroke. An
energy-recovery process may continue until the storage reservoir
420 is nearly empty of pressurized gas 432, at which time an
energy-storage process may be used to recharge the storage
reservoir 420 with pressurized gas 432. In other embodiments, the
energy-recovery and energy-storage processes are alternated based
on operator requirements.
[0149] In either the energy-storage or energy-compression mode of
operation, storage reservoir 420 is typically at least partially
depleted of high-pressure gas 432, as storage reservoir 420 also
typically contains a quantity of heat-transfer fluid 434. Reservoir
464 is at low pressure (e.g., atmospheric or some other low
pressure that serves as the intake pressure for the compression
phase of cylinder 402) and contains a quantity of heat-transfer
fluid 470.
[0150] The heat-transfer fluid 470 may be circulated within the
reservoir 464 via low-power-consumption pump 472. In various
embodiments, the fluid 470 may be removed from the bottom of the
reservoir 464 via piping 467, circulated via pump 472 through a
heat exchanger 474, and introduced (e.g., sprayed) back into the
top of reservoir 464 via piping 476 and spray head 478 (or other
suitable mechanism). By spraying the fluid 470 throughout the
reservoir gas 480, heat may be added or removed from the gas via
the heat-transfer fluid 470. By circulating the heat-transfer fluid
470 through heat exchanger 474, the temperature of the fluid 470
and gas 480 may be kept near constant (i.e., isothermal).
Counterflow heat-exchange fluid 482 at near-ambient pressure may be
circulated from a near-ambient-temperature thermal well (not shown)
or source (e.g., waste heat source) or sink (e.g., cold water
source) of thermal energy. In one embodiment, counterflow
heat-exchange fluid 482 is at high temperature to increase energy
recovery during expansion and/or counterflow heat-exchange fluid
482 is at low temperature to decrease energy usage during
compression.
[0151] In the energy-storage or compression mode of operation, a
quantity of low-pressure gas is introduced via valve 424 and pipe
422 into the upper chamber 406 of cylinder 402 starting when piston
404 is near top dead center of cylinder 402. The low-pressure gas
may be from the ambient atmosphere (e.g., may be admitted through
vent 426 as illustrated herein) or may be from a source of
pressurized gas such as a previous compression stage. During the
intake stroke, the piston 404 and its rod 430 will move downward,
drawing in gas. Heat-exchange fluid 470 may be introduced into
chamber 406 concurrently via optional pump 484 (alternatively, a
pressure drop may be introduced in line 486 such that pump 484 is
not needed) through pipe 486 and directional valve 488. This heat
exchange fluid 470 may be introduced (e.g., sprayed) into chamber
406 via one or more spray nozzles 490 in such a manner as to
generate foam 460. This foam 460 may fill the chamber 406 partially
or entirely by the end of the intake stroke; for illustrative
purposes only, foam 460 is shown in FIG. 4 as only partially
filling chamber 406. At the end of the intake stroke, piston 404
reaches the end-of-stroke position (bottom dead center) and chamber
406 is filled with foam 460 generated from air at a low pressure
(e.g., atmospheric) and heat-exchange liquid.
[0152] At the end of the stroke, with piston 404 at the
end-of-stroke position, valve 424 is closed. Valve 488 is also
closed, not necessarily at the same time as valve 424, but after a
predetermined amount of heat-transfer fluid 470 has been admitted,
creating foam 460. The amount of heat-transfer fluid 470 may be
based upon the volume of air to be compressed, the ratio of
compression, and/or the heat capacity of the heat-transfer fluid.
Next, piston 404 and rod 430 are driven upwards via mechanical
means (e.g., hydraulic fluid, hydraulic cylinder, mechanical
crankshaft) to compress the gas within chamber 406.
[0153] During this compression, in the absence of foam 460, the gas
in chamber 406 would tend to increase substantially in temperature.
With foam 460 at least partially filling the chamber, the
temperature of the gas in chamber 406 and the temperature of the
liquid component of foam 460 will tend to equilibrate via heat
exchange. The heat capacity of the fluid component of foam 460
(e.g., water with one or more additives) may be much higher than
that of the gas (e.g., air) such that the temperature of the gas
and fluid do not change substantially and are near-isothermal even
over a many-times gas compression (e.g., from near atmospheric
pressure to 250 psig, or in other embodiments from 250 psig to
3,000 psig).
[0154] The gas in chamber 406 (which includes, or consists
essentially of, the gaseous component of foam 460) is compressed to
a suitable pressure, e.g., a pressure approximately equal to the
pressure within storage reservoir 420, at which time valve 416 is
opened. The foam 460, including both its gaseous and liquid
components, is then transferred into storage reservoir 420 through
valve 416 and pipe 412 by continued upward movement of piston 404
and rod 430.
[0155] When piston 404 reaches top of stroke again, the process
repeats, with low-pressure gas and heat-transfer fluid 470 admitted
from vent 426 and reservoir 464 via valves 424 and 488. If
additional heat-transfer fluid is needed in reservoir 464, it may
be returned to reservoir 464 from reservoir 420 via piping 467 and
optional pump/motor 468. Power recovered from motor 468 may be used
to help drive the mechanical mechanism for driving piston 404 and
rod 430 or may be converted to electrical power via an electric
motor/generator (not shown). In one mode of operation, motor 468
may be run continuously, while reservoir 420 is being filled with
gas, in such a manner that the pressure in reservoir 420 is held
substantially constant. That is, as gas is added to reservoir 420,
heat-transfer fluid 434 is removed from reservoir 420 to maintain
substantially constant pressure within reservoir 420. In other
embodiments, motor 468 is not used or is used intermittently; the
pressure in reservoir 420 continues to increase during an
energy-storage process and the control system 462 changes the
timing of valves 416 and 488 accordingly so that the desired ending
pressure (e.g., atmospheric) is attained within chamber 406 when
the piston 404 reaches bottom of stroke. An energy-storage process
may continue until the storage reservoir 420 is full of pressurized
gas 432 at the maximum storage pressure (e.g., 3,000 psig), after
which time the system is ready to perform an energy-recovery
process. In various embodiments, the system may commence an
energy-recovery process when the storage reservoir 420 is only
partly full of pressurized gas 432, whether at the maximum storage
pressure or at some storage pressure intermediate between
atmospheric pressure and the maximum storage pressure. In other
embodiments, the energy-recovery and energy-storage processes are
alternated based on operator requirements.
[0156] FIG. 5 depicts an illustrative system 500 that features at
least two cylinder assemblies 502, 506 (i.e., an embodiment of
assembly 201 in FIG. 2; e.g., cylinder assembly 301 in FIG. 3) and
a heat-transfer subsystem 504, 508 (e.g., subsystem 324 in FIG. 3
associated with each cylinder assembly 502, 506. Additionally, the
system includes a thermal well 510 (e.g., thermal well 342 in FIG.
3) which may be associated with either or both of the heat-transfer
subsystems 504, 508 as indicated by the dashed lines.
[0157] Assembly 502 is in selective fluid communication with a
storage reservoir 512 (e.g., 212 in FIG. 2, 322 in FIG. 3) capable
of holding fluid at relatively high pressure (e.g., approximately
3,000 psig). Assembly 506 is in selective fluid communication with
assembly 502 and/or with optional additional cylinder assemblies
between assemblies 502 and 506 as indicated by ellipsis marks 522.
Assembly 506 is in selective fluid communication with an
atmospheric vent 520 (e.g., 220 in FIG. 2, 323 in FIG. 3).
[0158] System 500 may compress air at atmospheric pressure
(admitted to system 500 through the vent 520) stagewise through
assemblies 506 and 502 to high pressure for storage in reservoir
512. System 500 may also expand air from high pressure in reservoir
512 stagewise through assemblies 502 and 506 to a low pressure
(e.g., approximately 5 psig) for venting to the atmosphere through
vent 520.
[0159] As described in U.S. Pat. No. 8,191,362, filed Apr. 6, 2011
(the '362 patent), the entire disclosure of which is incorporated
by reference herein, in a group of N cylinder assemblies used for
expansion or compression of gas between a high pressure (e.g.,
approximately 3,000 psig) and a low pressure (e.g., approximately 5
psig), the system will contain gas at N-1 pressures intermediate
between the high-pressure extreme and the low pressure. Herein each
such intermediate pressure is termed a "mid-pressure." In
illustrative system 500, N=2 and N-1=1, so there is one
mid-pressure (e.g., approximately 250 psig during expansion) in the
system 500. In various states of operation of the system,
mid-pressures may occur in any of the chambers of a
series-connected cylinder group (e.g., the cylinders of assemblies
502 and 506) and within any valves, piping, and other devices in
fluid communication with those chambers. In illustrative system
500, the mid-pressure, herein denoted "mid-pressure P1," occurs
primarily in valves, piping, and other devices intermediate between
assemblies 502 and 506.
[0160] Assembly 502 is a high-pressure assembly: i.e., assembly 502
may admit gas at high pressure from reservoir 512 to expand the gas
to mid-pressure P1 for transfer to assembly 502, and/or may admit
gas at mid-pressure P1 from assembly 506 to compress the gas to
high pressure for transfer to reservoir 512. Assembly 506 is a
low-pressure assembly: i.e., assembly 506 may admit gas at
mid-pressure P1 from assembly 502 to expand the gas to low pressure
for transfer to the vent 520, and/or may admit gas at low pressure
from vent 520 to compress the gas to mid-pressure P1 for transfer
to assembly 502.
[0161] In system 500, extended cylinder assembly 502 communicates
with extended cylinder assembly 506 via a mid-pressure assembly
514. Herein, a "mid-pressure assembly" includes or consists
essentially of a reservoir of gas that is placed in fluid
communication with the valves, piping, chambers, and other
components through or into which gas passes. The gas in the
reservoir is at approximately at the mid-pressure which the
particular mid-pressure assembly is intended to provide. The
reservoir is large enough so that a volume of mid-pressure gas
approximately equal to that within the valves, piping, chambers,
and other components with which the reservoir is in fluid
communication may enter or leave the reservoir without
substantially changing its pressure. Additionally, the mid-pressure
assembly may provide pulsation damping, additional heat-transfer
capability, fluid separation, and/or house one or more
heat-transfer sub-systems such as part or all of sub-systems 504
and/or 508. As described in the '362 patent, a mid-pressure
assembly may substantially reduce the amount of dead space in
various components of a system employing pneumatic cylinder
assemblies, e.g., system 500 in FIG. 5. Reduction of dead space
tends to increase overall system efficiency.
[0162] Alternatively or in conjunction, pipes and valves (not shown
in FIG. 5) bypassing mid-pressure assembly 514 may enable fluid to
pass directly between assembly 502 and assembly 506. Valves 516,
518, 524, and 526 control the passage of fluids between the
assemblies 502, 506, 512, and 514.
[0163] A control system 528 (e.g., 222 in FIG. 2, 326 in FIG. 3,
462 in FIG. 4) may control operation of, e.g., all valves of system
500 based on various system inputs (e.g., pressure, temperature,
piston position, and/or fluid state) from assemblies 502 and 506,
mid-pressure assembly 514, storage reservoir 512, thermal well 510,
heat transfer sub-systems 504, 508, and/or the environment
surrounding system 520.
[0164] It will be clear to persons reasonably familiar with the art
of pneumatic machines that a system similar to system 500 but
differing by the incorporation of one, two or more mid-pressure
extended cylinder assemblies may be devised without additional
undue experimentation. It will also be clear that all remarks
herein pertaining to system 500 may be applied to such an
N-cylinder system without substantial revision, as indicated by
elliptical marks 522. Such N-cylinder systems, though not discussed
further herein, are contemplated and within the scope of the
invention. As shown and described in the '678 patent, N
appropriately sized cylinders, where N.gtoreq.2, may reduce an
original (single-cylinder) operating fluid pressure range R to
R.sup.1/N and correspondingly reduce the range of force acting on
each cylinder in the N-cylinder system as compared to the range of
force acting in a single-cylinder system. This and other
advantages, as set forth in the '678 patent, may be realized in
N-cylinder systems. Additionally, multiple identical cylinders may
be added in parallel and attached to a common or separate drive
mechanism (not shown) with the cylinder assemblies 502, 506 as
indicated by ellipsis marks 532, 536, enabling higher power and
air-flow rates.
[0165] Pressurized fluids may also be stored in accordance with
various embodiments of the present invention, alternatively or
additionally to the use of LURs, in insulated pipeline vessels
(IPVs). FIG. 6A is a cross-sectional schematic drawing of an
illustrative insulated pipeline vessel (IPV) system 600 for the
storage of fluid at pressures up to some relatively high value
(e.g., 3,000 psig) and at temperatures up to some relatively
elevated temperature (e.g., 100.degree. C.). The drawing in FIG. 6A
shows a side view. The IPV system 600, which may be part of the
storage subsystem of an energy storage-and-recovery system (not
shown), features a single length of pipeline 602, e.g., natural-gas
pipeline, which in this illustrative case has length L (e.g., an
interval of 40 or 80 foot sections) and an interior diameter of D
(e.g., 32 inches). The cross-sectional shape of the pipeline 602 is
circular in this illustrative system 600, but various other
embodiments have other cross-sectional shapes. Additional
components of illustrative system 600, some optional, are depicted
in subsequent figures. All illustrative IPV systems depicted
herein, including arrays of IPV pipeline sections, may be utilized
in energy-storage-and-recovery systems whose other components are
not depicted.
[0166] The single length of pipeline 602 may include or consist
essentially of two or more shorter lengths of pipe (e.g., in this
illustrative pipeline 602, the sub-lengths 604, 606), welded
together or otherwise joined in fluid-proof manner at one or more
joints 608. End caps 610, 612 seal the ends of the pipeline 602 to
form an enclosed volume: in this illustrative case, end-caps 610,
612 are bolted to flanges on the ends of pipeline 602. Pipeline 602
is generally tilted at some angle .theta..sub.1 from the
horizontal. A layer of insulation 614 covers the outer surface of
the pipeline 602. Additional insulation or protective coatings (not
shown) may be applied as layers to the interior of the pipeline
602. Pipeline 602 may be substantially or wholly buried within a
berm or fill capsule 616 including or consisting essentially of
fill 618 and a substantially impermeable envelope 620. The fill 618
may include or consist essentially of various forms of earth (e.g.,
sand, crushed rock), an artificial thermal insulation material, or
a mixture of earth and insulating material. The fill 618 is
preferably dry (i.e., contains no substantial fraction of liquid
water), in order that the thermal insulating power of the fill
capsule 616 may be maximal. The impermeable envelope 620 prevents
circulation of liquid and possibly air into and through the fill
capsule 616, increasing the thermal insulating power of the fill
capsule 616. The thickness of the fill capsule 616 as measured from
various points on the outer surface of the pipeline 612 to the
impermeable envelope 620 may vary from point to point, but will
preferably be chosen to meet structural requirements and produce an
insulating effect on the pipeline 602 that justifies the cost of
constructing the fill capsule 616 (e.g., justifies the cost of
constructing the fill capsule 616 in terms of levelized cost of
energy of the storage subsystem comprising IPV system 600).
[0167] The lower end 622 of the pipeline 602 in the illustrative
IPV system 600 is allowed to protrude from the fill capsule 616.
The system 600 may be partly or entirely buried in earth (e.g., the
earth naturally present at a given installation site; not shown),
in which case a trench, pit, or vault (not shown) may be
constructed to allow maintenance access to the lower end 622 of the
pipeline 602.
[0168] The first insulation layer 614 and the insulating fill
capsule 616 serve jointly to slow to an acceptable rate the
exchange of thermal energy between the fluid contents of pipeline
616 and the ambient environment of system 600.
[0169] FIG. 6B shows additional components of the illustrative IPV
system 600 of FIG. 6A. An accumulation of liquid 624 may exist at
the lower end 622 of the pipeline 602. The pipeline 602 may also
contain gas and aqueous foam or droplets (not shown). A pipe 626
enables the withdrawal of liquid from (or the introduction of gas
or liquid into) pipeline 602 through an access point 628. A pipe
630 enables the withdrawal of gas from (or the introduction of gas
or liquid into) pipeline 602 through an access point 632.
Alternatively or additionally, both pipes 626 and 630 may enable
the exchange of two-phase fluids with the pipeline 602. System 600
may include valves (e.g., valves controlling flow through pipes 626
and 630), pumps, and other components not depicted in FIG. 6B.
Preferably, the liquid accumulation 624 is not allowed to achieve a
depth that blocks the point where pipe 630 is connected to the
interior of pipeline 602. The points at which pipes 626 and 630
connect to the interior of pipeline 602 in system 600 (i.e., the
insertion points 634, 636 of pipes 626 and 630) are not necessarily
drawn to scale; e.g., the insertion point 636 of pipe 630 may be
farther from end 622 than shown in FIG. 6B, allowing the liquid
accumulation 624 to achieve a greater depth without blocking the
insertion point 636 of pipe 630. In other embodiments, angle
.theta..sub.1 is negative, and the insertion point 634 of pipe 626
is at the far end of the pipe 602 from end 622.
[0170] FIG. 6C shows optional components of the illustrative IPV
system 600 of FIG. 6A. In particular, a spray rod 638 is positioned
inside pipeline 602. In other embodiments, the spray rod 638 is
external to the pipeline 602 with spaced nozzle holes penetrating
the pipeline 602 at appropriate intervals (e.g., one nozzle
penetration per meter). Liquid or a two-phase mixture (e.g., foam)
640 may be injected, indicated in FIG. 6C by a row of short arrows,
into the interior of pipeline 602, where it may proceed to exchange
heat with the fluid contents of pipeline 602 (e.g., stored,
expanding, or compressing gas). In other embodiments, devices other
than spray rods (e.g., spray heads) are employed (alone or in
conjunction with spray rods) to inject the fluid 640. The fluid 640
may be fluid withdrawn from pipeline 602 via pipe 626 and
circulated through a pump (not shown), heat exchanger (not shown),
and/or other devices (not shown) before being injected through
spray rod 638; or, the fluid 640 may be supplied to spray rod 638
from a reservoir (not shown) or other source or subsystem. By the
injection of fluid 640 at an appropriate temperature and rate, the
temperature of the fluid contents of pipeline 602 may be kept
approximately constant as gas and liquid are added or removed from
pipeline 602; or, the temperature of the fluid contents of pipeline
602 may be increased or decreased at any time, or may be kept
approximately constant during the addition of fluid to pipeline 602
(which will tend to increase pressure and temperature of the fluid
contents of pipeline 602) or during the withdrawal of fluid from
pipeline 602 (which will tend to decrease pressure and temperature
of the fluid contents of pipeline 602). Holding the temperature of
the fluid contents of pipeline 602 approximately equal throughout
the volume of pipeline 602 and/or approximately constant during the
addition or removal of fluid (i.e., realizing a substantially
isothermal process) will tend to increase the overall efficiency of
the energy storage system of which system 600 is a part, and is
therefore advantageous.
[0171] The preferable value of the angle .theta..sub.1, and of
other angles of IPV tilt in other illustrative systems described
herein, depends on the amounts of liquid found in each IPV in
various states of system operation, the rates at which liquid is
introduced into and removed from each IPV, and the inner dimensions
of each IPV (e.g., diameter, length, locations of points of piping
insertion). In accordance with various embodiments of the
invention, the angle of IPV tilt may even be altered during
operation via mechanical means, e.g., a tiltable stage.
[0172] FIG. 7A is a schematic diagram of components of an
illustrative IPV array 700 including or consisting essentially of
an array of N IPV pipeline sections (only one IPV pipeline section
702 is explicitly labeled in FIG. 7A). Herein, the terms "IPV
pipeline section" and "IPV" are synonymous. FIG. 7A shows the IPV
array 700 from an overhead point of view. The N IPVs 702 are joined
in pairs by N/2 U-shaped connector pipes (only one U-shaped
connector pipe 704 is explicitly labeled in FIG. 7A). In various
other embodiments, the U-shaped connectors 704 are omitted or their
function is performed by other forms of piping. Vertical ellipses
706 indicate the presence of an indefinite number of additional
pipeline sections in the array 700. Each IPV section in FIG. 7A
(e.g., section 702) is similar to IPV system 600 in FIGS. 6A, 6B,
6C and may include any or all of the arrangements described or
depicted for system 600, as well as additional arrangements. For
example, array 700 may be enclosed by a fill capsule with an
impermeable envelope to slow the exchange of thermal energy between
the fluid contents of array 700 and the ambient environment, or a
separate fill capsule may enclose each IPV section in the array
700. Although the number N of IPV pipeline sections in FIG. 7A is
depicted as equal to or greater than 6, any N equal to or greater
than 1 is contemplated and within the scope of the invention.
[0173] The pipeline sections 702 of the illustrative array 700 are
parallel to each other and lie in a common plane; in various
embodiments, the pipeline sections 702 may not be co-planar. The
plane in which the pipeline sections 702 lie is tilted at some
angle .theta..sub.1 from the horizontal, with the lower end of the
plane at the left-hand side of FIG. 7A. By gravity, liquid and
two-phase mixtures will tend to flow downhill to the downhill ends
of the IPVs, i.e., the ends at the left-hand side of FIG. 7A. The
angle .theta..sub.1 is preferably larger than but close to the
minimum angle that will cause acceptably rapid flow of fluid to the
downhill end of each IPV in the array 700 without causing fluid
blockage of the insertion points of the pipes (e.g., 708) that
permit exchange of gas with each IPV section.
[0174] At the downhill end of each IPV section in FIG. 7A (e.g.,
pipe section 702), piping 708 permits fluid (e.g., liquid) to be
added to or withdrawn from the pipe section through a manifold pipe
710 and a surface access point 712. Also at the lower end of each
IPV section in FIG. 7A (e.g., pipe section 702), piping 714 permits
fluid (e.g., gas or foam) to be added to or withdrawn from the pipe
section through a manifold pipe 716 and a surface access point
718.
[0175] Uniformly spaced, straight, parallel (at least in one plane)
IPV pipeline sections of uniform diameter and identical length and
diameter are depicted in FIG. 7A and in various depictions of
illustrative IPV arrays herein, but in various other embodiments,
arrayed IPV sections need not be straight, parallel, uniformly
spaced, uniform in diameter, or identical in length and/or
diameter. Alternative embodiments of all illustrative IPV arrays
depicted herein may be readily devised in which the arrayed IPV
pipeline sections are not straight, parallel, uniformly spaced,
uniform in diameter, or identical in length and/or diameter in
accordance with embodiments of the invention. In various
embodiments, IPV arrays are interconnected with other forms of
fluid storage, e.g., lined or unlined underground reservoirs and
non-IPV storage vessels, to provide energy and fluid storage for
one or more energy storage-and-recovery systems.
[0176] FIG. 7B is a schematic cross-section of portions of the IPV
array 700 of FIG. 7A. The cross-section shows the downhill ends of
the array 700, with a liquid accumulation 720 in each IPV. (Only
one liquid accumulation 720, i.e., that in the Nth IPV, is
explicitly labeled in FIG. 7B. Although similar liquid
accumulations are shown in other IPVs in FIG. 7B, each IPV may
contain a different amount of liquid accumulation.) At the downhill
end of each IPV depicted in cross-section in FIG. 7B, piping 708
permits liquid to be added to or withdrawn from the IPV through a
manifold pipe 710 and access point 712. Also at the downhill ends
of the IPVs depicted in cross-section in FIG. 7B, piping 714
permits fluid (e.g., gas or foam) to be added to or withdrawn from
the pipe section through manifold pipe 716 and surface access point
718. The plane in which the N IPVs of array 700 lie is tilted only
along the lengthwise dimension of the IPVs themselves: i.e., any
perpendicular cross-sectional view of array 700, such as FIG. 7B,
will show a level row of pipeline cross-sections, although the
altitude of that level row will be higher for cross-sections closer
to the elevated edge of the array (the right-hand edge of the array
in FIG. 7A).
[0177] In illustrative IPV array 700, the manifold pipe 710 is
tilted at some angle .theta. with sufficient to guarantee downhill
flow of liquid from all N IPV pipeline sections to the low point
722 of manifold 710. A sump or reservoir (not shown) located
approximately at point 722 may allow an accumulation of liquid. A
pump (not shown) may be employed to raise liquid from point 722 or
from a sump located approximately at point 722 to the liquid access
point 712. Gas pressure in the N IPV pipeline sections may
contribute to or entirely cause the movement of liquid from the IPV
s to the access point 712. In various other embodiments, angle
.theta. is zero and pumping and/or gas pressure are entirely
responsible for the movement of liquid from the N IPV pipeline
sections to the access point 712.
[0178] FIG. 7C is a schematic diagram of components of an
illustrative rectangular IPV array 723 including or consisting
essentially of N similar, parallel IPV pipeline sections (only one
IPV 724 is explicitly labeled in FIG. 7C). Each IPV section in FIG.
7C is similar to IPV system 600 in FIGS. 6A, 6B, 6C and may include
any or all of the arrangements described or depicted for system
600, as well as additional arrangements. The IPV array 723 may also
include any or all of the arrangements described or depicted for
array 700 in FIGS. 7A and 7B, as well as additional arrangements.
FIG. 7C indicates the level plane ABCD (726) and the orientation of
three standard orthogonal axes x, y, and z (728). The N IPV
pipeline sections of array 723 are parallel to one another and lie
in a common plane that is tilted at angle .theta..sub.1 with
respect to the y axis and at angle .theta..sub.2 with respect to
the x axis. Herein, the edge of the IPV array 723 that lies along a
straight line at angle .theta..sub.2 with respect to the x axis is
termed the CD edge (because of its proximity to the line segment
CD). By extension of this convention, the other three edges of the
array 723 are herein termed the AB, AC, and BD edges. One or more
manifolds or U-connector pipes (not shown) enable fluid
communication between the interiors of the N IPV pipeline sections
of array 723 and the delivery of gas to, or removal of gas from,
the pipeline sections. Optional manifolds or U-connector pipes (not
shown) may allow passive downhill liquid flow along the CD and/or
AB edges of array 723. Manifolds or piping (not shown) may also
allow fluid to pass between the N IPV pipeline sections at points
located anywhere along the pipeline sections. The angles
.theta..sub.1 and .theta..sub.2 may be selected, in combination
with optional manifolds and piping, to provide acceptable
gravity-assisted flow, pooling, and collection through manifolds of
liquid or other flowing fluid (e.g., foam) within array 723 without
interfering with access to the gaseous contents of array 723 (e.g.,
by liquid blockage of openings intended for the passage of gas or
two-phase mixtures). Preferably, manifolds and piping of the array
723 are arranged so that gas and liquid (and/or two-phase mixtures
of gas and liquid) may be delivered to or removed from the array
723 from a closely clustered set of surface access points (e.g.,
near the A corner of array 723 or at some point along the AB edge
of array 723).
[0179] FIG. 7D is a schematic diagram of components of an
illustrative rectangular IPV array 729 including or consisting
essentially of 2N similar, parallel pipeline sections (only one IPV
pipeline section 724 is explicitly labeled in FIG. 7D). Each IPV
section in FIG. 7D is similar to IPV system 600 in FIGS. 6A, 6B, 6C
and may include any or all of the arrangements described or
depicted for system 600, as well as additional arrangements. The
IPV array 729 may also include any or all of the arrangements
described or depicted for arrays 700, 723 in FIGS. 7A, 7B, and 7C,
as well as additional arrangements. FIG. 7D indicates the level
plane ABCD (726) and the orientation of three standard orthogonal
axes x, y, and z (728). The 2N IPV pipeline sections of array 729
are parallel to one another and lie in two parallel planes, each
tilted at angle .theta..sub.1 with respect to the y axis and at
angle .theta..sub.2 with respect to the x axis. Array 729 thus
includes or consists essentially of two parallel, tilted layers or
ranks of N IPV pipeline sections each. Piping or U-connectors may
connect IPVs in the upper rank to pipes in the lower layer (e.g.,
each IPV in the upper rank may be connected to the IPV directly
below it, or to some other IPV in the lower rank). Such piping may
be arranged to allow for the delivery to or extraction from the
array 729 of gas, liquid, or two-phase mixtures of gas and liquid.
Such piping may be arranged in a wide variety of configurations to
allow the passive drainage of liquid from IPVs in the upper rank to
IPVs in the lower rank, or, in general, from any portion of any IPV
where liquid may accumulate to any portion of any other IPV if that
portion of the latter IPV is at lower elevation than the liquid
accumulation in the former IPV. The angles .theta..sub.1 and
.theta..sub.2 may be selected, in combination with optional
manifolds and piping, to provide acceptable gravity-assisted flow,
pooling, and collection through manifolds of liquid or other
flowing fluid (e.g., foam) within array 729 without interfering
with access to the gaseous contents of array 729 (e.g., by liquid
blockage of openings intended for the passage of gas or two-phase
mixtures). Preferably, manifolds and piping of the array 729 are
arranged so that gas and liquid (and/or two-phase mixtures of gas
and liquid) may be delivered to or removed from the array 729 from
a closely clustered set of surface access points (e.g., near the A
corner of array 729 or at some point along the AB edge of array
729). FIG. 7D depicts what is in effect a stack of two IPV arrays,
each containing N IPV pipeline sections, but similar stacks of M
IPV layers, where M is any integer number greater than or equal to
1 and where the M layers may contain varying numbers of IPV
pipeline sections, are contemplated and within the scope of the
invention.
[0180] FIG. 7E is a schematic diagram of components of an
illustrative rectangular IPV array 730 including or consisting
essentially of 2N similar, parallel pipeline sections (only one IPV
pipeline section 724 is explicitly labeled in FIG. 7E). Each IPV
section in FIG. 7E is similar to IPV system 600 in FIGS. 6A, 6B, 6C
and may include any or all of the arrangements described or
depicted for system 600, as well as additional arrangements. The
IPV array 730 may also include any or all of the arrangements
described or depicted for 700, 723, 729 in FIGS. 7A-7D, as well as
additional arrangements. FIG. 7E indicates the level plane ABCD
(726) and the orientation of three standard orthogonal axes x, y,
and z (728). The N IPV pipeline sections of the lower layer of
array 730 are parallel to one another and lie in a common plane
that is tilted at angle .theta..sub.1 with respect to the y axis
and at angle .theta..sub.2 with respect to the x axis. The N IPV
pipeline sections of the upper layer of array 730 are parallel to
one another and lie in a common plane that is tilted at angle
.theta..sub.3 with respect to the y axis and at angle .theta..sub.2
with respect to the x axis. Array 730 thus includes or consists
essentially of two layers or ranks of N IPV pipeline sections each.
Piping or U-connectors may connect IPVs in the upper rank to pipes
in the lower layer (e.g., each IPV in the upper rank may be
connected to the IPV directly below it, or to some other IPV in the
lower rank). Such piping may be arranged to allow for the separate
delivery to, or extraction from, the array 730 of gas, liquid, or
two-phase mixtures of gas and liquid. Such piping may be arranged
in a wide variety of configurations to allow the passive drainage
of liquid from IPVs in the upper rank to IPVs in the lower rank,
or, in general, from any portion of any IPV where liquid may
accumulate to any portion of any other IPV if that portion of the
latter IPV is at lower elevation than the liquid accumulation in
the former IPV. For example, connecting each IPV in the upper layer
of array 730 to IPV in the lower rank at the CD edge (where the two
layers of IPVs approximate), e.g., by a vertically oriented
U-connector, would be advantageous because no further connections
to the upper layer of IPVs would be necessary in order for gas to
be exchanged freely between each IPV of the upper layer and the
corresponding IPV of the lower layer, while liquid would flow by
gravity from each IPV of the upper layer into the corresponding IPV
of the lower layer, to be further directed and collected for
removal from the array 730. The angles .theta..sub.1,
.theta..sub.2, and .theta..sub.3 may be selected, in combination
with optional manifolds and piping, to provide acceptable
gravity-assisted flow, pooling, and manifold collection of liquid
or other flowing fluid (e.g., foam) within array 730 without
interfering with access to the gaseous contents of array 730 (e.g.,
by liquid blockage of openings intended for the passage of gas or
two-phase mixtures). Preferably, manifolds and piping of the array
730 are arranged so that gas and liquid (and/or two-phase mixtures
of gas and liquid) may be delivered to or removed from the array
730 from a closely clustered set of surface access points (e.g.,
near the A corner of array 730). Similar stacks of M IPV layers
tipped at various angles, where M is any integer number greater
than or equal to 2 and the M layers may contain varying numbers of
IPVs, are contemplated and within the scope of the invention.
[0181] FIG. 7F is a schematic representation of portions of an
illustrative embodiment of the invention. A system 732 includes or
consists essentially of a field or series of pipeline segments 724
(only one of which is explicitly labeled in FIG. 7F) connected into
a serpentine whole by a series of U-connectors 734 (only one of
which is explicitly labeled in FIG. 7F). The pipeline segments 724
and U-connectors 734 are of preferably but not necessarily circular
cross-section. Whatever cross-sectional shape is employed in a
given embodiment, the pipeline segments 724 and U-connectors 734
are preferably of approximately the same cross-section, both in
shape and size. That is, the interior of the system 732 has a
continuous cross-section, that is, is approximately continuous in
shape and dimensions. The continuous cross-section of system 732 is
advantageous in that allows the passage of a "pig" (a device, for
e.g., pipe inspection, inserted into a pipeline and traveling
freely through it) that is large relative to the cross-section
throughout the whole pipe field of system 732, e.g., from an entry
point 736 to an exit point 738.
[0182] FIG. 7F depicts an illustrative system 732 featuring five
pipeline segments 724 and four U-connectors 734, but various
embodiments may contain any number of pipeline segments greater
than two and any number of U-connectors greater than one. The
pipeline segments 724 depicted in FIG. 7F are arranged in an
accordion-like manner to minimize IPV total field width while still
allowing for the required bend radius of the U connectors 734. In
various other embodiments, two or more, or even all, of the
pipeline segments may be substantially parallel to each other.
[0183] FIG. 8 is a schematic representation of portions of another
illustrative embodiment of the invention. A recessed LUR
compressed-gas storage system 800 is formed in a vertical,
artificial cavern or shaft 802, typically but not necessarily
circular in cross-section, and may be part of a larger system (not
shown) for the storage and recovery of energy. Compressed air,
natural gas, or other fuel or non-fuel liquids or gasses may be
stored, either exclusively or in different states of operation,
within system 800, as well as within various other LUR systems and
IPVs described herein and within various embodiments not explicitly
described but within the scope of the invention. As in FIGS. 1A,
1B, 1C, and 1D, one or more LUR systems (e.g., system 800) and/or
IPV systems falling within the scope of the invention may be
employed at a single site, or in a network of sites connected by
piping, in order to store compressed air, natural gas, and/or other
fluids simultaneously. Compressed air stored in individual,
multiple, or networked storage systems may be utilized as an
energy-storage medium by a system, e.g., an adiabatic
compressed-air energy storage system or an isothermal
compressed-air energy storage system, that employs no additional
fuel; alternatively or additionally, compressed air so stored may
be utilized in combination with natural gas or other fuels for the
production of energy. For illustrative purposes, most of the energy
storage and generation systems described and depicted herein are
isothermal compressed-air energy systems, and the storage systems
described and depicted herein are primarily lined underground
reservoirs storing compressed air and heat-exchange liquid;
however, this emphasis should not be taken as in any way
restricting the contemplated scope of the invention.
[0184] In various embodiments, system 800 includes a storage
reservoir recessed into a shaft 802 in the earth and containing
fluid that may be pressurized and/or thermally conditioned (e.g.,
heated, cooled, or maintained at an approximately constant
temperature). Pressurization of the fluid stored by system 800
enables the storage of elastic potential energy; heating or cooling
of the fluid enables the storage of exergy (work available from a
system in disequilibrium). Typically, although not necessarily, the
fluid is thermally conditioned by heating or by maintenance at an
approximately constant temperature rather than by cooling. A fluid
may be both pressurized and thermally conditioned. Such
pressurization and thermal conditioning may be controlled functions
of time. Shaft 802 may be lined with a material that prevents
leakage of fluids into or out of the shaft 802; the material may
also act as a thermal insulator to assist in thermal conditioning
or in mitigating the exchange of heat between the fluid and the
surrounding earth. Alternatively or additionally, shaft 802 may be
lined with a material that acts primarily as a thermal
insulator.
[0185] In the illustrative embodiment depicted in FIG. 8, shaft 802
is vertical and circular in cross-section. Shaft 802 is sunk
preferably in stable earth material, e.g., solid rock, and may be
sunk by a technique and machine for sinking vertical shafts, e.g.,
as described in U.S. Patent Application Publication No.
2011/0139511, filed Jan. 19, 2011, and/or in U.S. Patent
Application Publication No. 2012/0163919, filed Mar. 19, 2012, the
entire disclosure of each of which is incorporated herein by
reference. In one approach to the excavation of a shaft such as
shaft 802 according to embodiments of the present invention, an
excavating machine breaks up rock during boring into particles that
are removed from the bore hydraulically. In other embodiments of
the invention, the rock is removed mechanically (e.g., by scoops).
Herein, the term "rock" signifies all earth material suitable for
excavation for and fabrication of a pressurized underground
fluid-storage reservoir.
[0186] As the shaft 802 is sunk, a shaft liner 804 (which includes
or consists essentially of reinforced concrete and/or some other
material) forming an interior wall of the shaft 802 may be
installed in a series of rings, each ring being added below
previous rings as the excavating machine increases the depth of the
bore by a suitable amount. The inner and/or outer surface of the
shaft liner 804 may be coated with one or more coatings or
additional layers of material (not shown in FIG. 8): these
additional layers may serve to prevent leakage of fluid into or out
of the shaft 802, to preserve the shaft liner 804 from corrosion or
degradation, to thermally insulate the shaft 802 from the
surrounding earth 806, or more perform two or more of these
functions.
[0187] In general, a lined underground reservoir constructed within
a shaft 802 of larger depth and/or radius will be capable of
storing more fluid and more thermal and elastic potential energy
than a shaft 802 of relatively small depth and/or radius.
[0188] In various embodiments including the illustrative embodiment
depicted in FIG. 8, a cavity liner 808 is constructed within the
shaft 802 lined by the shaft liner 804. In this illustrative
embodiment, the cavity liner 808 may include or consist essentially
of multiple layers, not all of which are depicted in FIG. 8: one
layer is a concrete or reinforced-concrete layer 810, and another
layer is an inner lining 812, of an impermeable (e.g., to liquid
and/or gas) material such as steel or a plastic. The cavity liner
808 includes a dome portion 814 that is surmounted and strengthened
by a concrete or reinforced-concrete cap 816. This cap 816 may
extend into the surrounding rock 820 and may serve as or separately
consist of a plug to distribute upward pressure forces from the
dome 814, in part or entirely, to the surrounding rock 820 as
opposed to the infill 818. Above the concrete cap 816, the shaft
802 is filled to approximately surface level primarily with an
infill 818 of one or more materials (e.g., rock particles removed
during excavation of the shaft 802, concrete, earth, water). The
cavity liner 808 may be coated with one or more coatings or
additional layers of material not shown in FIG. 8, interiorly
and/or exteriorly, that may serve to seal, protect, or insulate the
cavity liner 808. The cavity liner 808 is in sufficient contact
with the shaft liner 804 and with the concrete cap 816 in a manner
that enables forces originating with pressurized fluids within the
cavity liner 808 to be communicated to the surrounding rock 820 and
to the infill 818. The strength and weight of the surrounding rock
820 and of the infill 818 bear most of the pressure load of the
fluid within the cavity liner 808. Preferably, the mass and/or
mechanical strength of the dome 814, cap 816, and infill 818 are
collectively capable of bearing all pressure loads exerted by the
fluid contents of the system 800, with a sufficient margin of
safety beyond whatever plausible pressure to which the contents of
system 800 may be intentionally or accidentally raised. Also,
preferably, the mechanical strength of the dome 814, cap 86, and
infill 818 are collectively capable of bearing the load of their
own weight, and of any vehicles, floodwaters, or other surface
loads that might be plausibly superadded above the shaft 802, when
the fluid contents of the system 800 are at relatively low pressure
(e.g., ambient atmospheric pressure). In short, the liner 808 is
generally supported in such a manner that it neither swells
unacceptably or bursts when filled with high-pressure fluid, nor
sags unacceptably or collapses when filled with
atmospheric-pressure fluid. An "acceptable" degree of swelling or
sagging of liner 808, with accompanying displacement of surrounding
rock 820, infill 818, and other materials or components of system
800, is any degree of swelling or sagging that does not cause
breakage or degradation of the materials or components of system
800 (e.g., liner 808, inner liner 812, piping 826, 830, 834).
[0189] The cavity liner 808 (including its dome 814), the
load-bearing cap 816, the infill 818, the shaft liner 804, and the
surrounding rock 820 constitute a sealed recessed storage
reservoir. The reservoir may include other components and materials
in various other embodiments (e.g., an insulating layer within or
around the cavity liner 808).
[0190] In various other embodiments, the invert (floor) and sides
of the cavity liner 808 may be in direct contact with the
surrounding rock 820; the dome 814 may not be a distinct structure
from the concrete cap 816; and/or a system of piping may surround
the cavity liner 808 in a manner that tends to drain water away
from the cavity liner 808. Water so diverted from the cavity liner
808 may be conducted away through piping not depicted in FIG. 8. In
embodiments where the system 800 is constructed by excavation
through relatively small, primarily non-vertical access tunnels,
rather than through vertical shaft excavation, the dome 814 may be
in direct contact with the surrounding rock 820, infill 818 may be
absent, and plugs (or "pressure barriers") of concrete or other
material may prevent loss of fluid from the recessed reservoir
through the tunnels built to enable excavation of the
reservoir.
[0191] In the illustrative embodiment depicted in FIG. 8, the
recessed reservoir 800 contains an accumulation of a non-gaseous
fluid (e.g., foam or liquid) 822 and of gas 824. The gas 824
occupies the portion of reservoir 800 not occupied by the
non-gaseous fluid 822. The fluid contents of reservoir 800 may be
at high pressure (e.g., 3,000 psig) and relatively high temperature
(e.g., 60.degree. C.).
[0192] Piping 826 passes from the surface, through the infill 818
(as shown in FIG. 8) or through the native rock 820 (in various
other embodiments), through the dome portion 814 of liner 808 (or,
in various other embodiments, some portion of the shaft liner 804
and/or through the side or invert of liner 808) and reaches to near
the bottom of the shaft 802. A pump 828 is capable of drawing fluid
822 into piping 826 and expelling the fluid 822 from the shaft 802.
The piping 826 may be enclosed by a conduit of sufficient width to
enable the insertion and removal of the pump 828 from within the
liner 808. Power, control, and data cables (not shown in FIG. 8)
may also enter shaft 802 through piping 826 or through some other
conduit, enabling the control and operation of pump 828 and
communication with sensors (not shown) inside shaft 802 and/or
vessel lining 808 that provide information to operators of
reservoir 800 and/or to an automatic control system on various
physical variables, e.g., pressure and temperature of the fluid
contents of cavity liner 808, forces acting on the liner 808 or
rock 820, depth of fluid 822, and the like.
[0193] Fluid expelled from shaft 802 by pump 828 may be directed
via piping 826 to reservoirs, cylinders, or other components of an
energy storage and recovery system (not shown). Fluid may be
directed via piping 830 to a spray head or nozzle (not explicitly
shown), or array of spray heads and/or nozzles, for the generation
of a foam or droplet spray 832 within the gas-filled portion of
liner 808. The foam or droplet spray 832 may exchange heat with the
fluids inside liner 808. In various embodiments, fluid exiting the
interior of the liner 808 through piping 826 is passed through
pumps, valves, heat exchangers, and other devices (not shown)
before being returned to the interior of liner 808 through piping
830. Additional piping 834 allows the addition to or removal from
the interior of liner 808 of fluid (e.g., gas).
[0194] In another embodiment, not shown, multiple fluid liners 808
may be situated in a single shaft 802. The fluid liners 808 may be
stacked one atop another, or arranged in a vertically-oriented
bundle of tube-like liners, or otherwise arranged in order to
enable convenient construction, spatially even distribution of
forces, and/or other advantages. In some cases, multiple
narrower-diameter fluid liners (e.g., capped pipes, such as one or
more IPVs) may be less expensive than a single liner 808 of
comparable capacity endowed with a single large, welded inner liner
812.
[0195] FIG. 9A is a schematic diagram of portions of another
illustrative embodiment of the invention. A recessed LUR
compressed-gas storage system 900 includes a cavity 902 surrounded
by suitable (e.g., solid-rock) earth material. The materials that
may be stored in the system 900, and the uses to which those
materials may be put, include those described for system 800 in
FIG. 8. The cavity 902 is typically but not necessarily circular in
cross-section, and may be part of a larger system (not shown) for
the storage and recovery of energy.
[0196] Although the storage capacity and functions of system 900
may be similar to those of system 800 in FIG. 8, the method of
construction of system 900 differs. Rather than excavating a
vertical shaft, as for system 800, sloping access tunnels 904, 906,
908 (only partly shown in FIG. 9A) are excavated to the location of
cavity 902 from points on the surface that may be many meters away
from a point on the surface directly above cavity 902. Exemplary
arrangements of the access tunnels 904, 906, 908 are shown more
fully in FIGS. 9B and 9C, FIG. 10, and FIG. 25. The tunnels 904,
906, 908 may be constructed by ordinary techniques for solid-rock
excavation, i.e., drill, blast, and clear, and are of sufficient
size to allow passage for excavating machines, workers, and rock
debris. Excavation of the tunnels 904, 906, 908 begins at one or
more surface points (not shown in FIG. 9A); when the tunnels 904,
906, 908 have reached the intended location of cavity 902, the
cavity 902 is excavated. A vertical shaft 910 is also produced,
leading from a surface point directly above cavity 902 to the
cavity 902. The shaft 910 may be narrow relative to (i.e., have a
cross-sectional area smaller than that of) the cavity 902 and
produced by means of a conventional drill.
[0197] Once cavity 902 has been excavated, it is lined with a
cavity liner 912. In this illustrative embodiment, the cavity liner
912 may include or consist essentially of multiple layers, not all
of which are depicted in FIG. 9A: one layer is a concrete or
reinforced-concrete layer 916 and another layer is an inner liner
914 of an impermeable material such as steel or a plastic.
Moreover, after the construction of the cavity liner 912, the
access tunnels 906, 908 which open upon the cavity 902, and the
drilling 910, are sealed by plugs 918, 920, 922. The plugs may
include or consist essentially of concrete or reinforced concrete
and may be perforated in a manner that allows pipes, wires, and
conduits (not shown) to pass into the interior of the cavity 902.
In particular, the system 900 may be equipped with piping and other
contrivances (not shown in FIG. 9A) similar to the piping 826, 830,
834, pump 828, and spray mechanisms shown and/or described for
system 800.
[0198] System 800 and similar embodiments may have advantages over
system 900 and similar embodiments. In particular, the access
tunnels 904, 906, 908 and cavity 902 are, in general, excavated by
workers working in situ, underground, and the lining 912 of the
cavity 902 is typically excavated by workers working with in the
cavity 902. Such work may be slow, expensive, and relatively
dangerous. In contrast, the wide vertical shaft 802 of system 800
may be excavated, in some instances, mostly or entirely by a
machine operated from the surface, and the cavity liner 808, with
its inside liner 812, may be partly or entirely constructed at the
surface and lowered into the shaft 802. Greater speed, lower cost,
and higher safety for comparable capacity may thus, in some
instances, be achieved in the construction of system 800.
Additionally, system 800 does not need additional access areas and
underground tunnel for access as may be required for system
900.
[0199] FIG. 9B is a schematic diagram of the illustrative system
900 of FIG. 9A shown in a larger geographical context. Four
construction tunnels are shown in FIG. 9B, i.e., shaft tunnel 904,
upper tunnel 906, lower tunnel 908, and access tunnel 924. The need
to move construction machinery through the tunnels places a
practical limit on the steepness of all tunnels (e.g., 8 degrees of
slope). This steepness limit, in combination with an assumption of
linear tunneling and with the topography of the landscape above and
near the cavity 902, typically constrains how closely the surface
entrance 926 to the access tunnel 924 may be to the site of the
cavity 902. In the relatively flat illustrative geographical
conditions sketched in FIG. 9B, the top of the cavity 902 is
approximately 114 meters vertically below the surface, the cavity
is approximately 51 meters high and has a diameter of approximately
35 meters, and the tunnel entrance 926 is approximately 600 meters
away from the cavity 902.
[0200] In various embodiments it may be advantageous to locate the
access tunnel entrance 926 at a point closer a point on the surface
directly above the cavity 902. FIG. 9C is a schematic diagram of
the illustrative system 900 of FIG. 9A shown in a larger
geographical context that is alternative to the geographical
context shown in FIG. 9B. In the context of FIG. 9C, the surface
declines relatively steeply from a point on the surface directly
above the cavity 902. Under these circumstances, a lower tunnel
908, upper tunnel 906, and shaft tunnel 904 may be cut from a
tunnel entrance 926 that is closer to the cavity 902 than the
tunnel entrance 926 in FIG. 9B. Construction of the system 900 may
be less expensive in a geological context resembling that of FIG.
9C than in a geological context resembling that of FIG. 9B because
fewer meters of tunnel are cut in order to construct a cavity 902
of comparable storage capacity. However, acquisition of legal
rights to access the site of tunnel entrance 926, or to
construction tunnels under the land between the tunnel entrance 926
and a point on the surface directly above the cavity 902, may still
be expensive. It may therefore be advantageous to locate the tunnel
entrance 926 at a point directly above, or near to directly above,
the cavity 902.
[0201] FIG. 10 is a schematic diagram of an illustrative LUR system
1000 similar to system 900 of FIG. 9A, 9B, 9C. A cavern 1002 is
excavated in substantially solid rock by removal of pulverized rock
through access tunnels. A main access tunnel 1004 begins at an
access point 1006 that is directly above, or substantially directly
above, the cavity 1002, and descends in a spiraling fashion through
the rock. The steepness of the main access tunnel 1004 typically
never exceeds the working steepness limit for such a tunnel (e.g.,
8 degrees) mandated by the need to safely pass machinery and
vehicles (e.g., cement trucks). A shaft 1008 is drilled from the
point on the surface 1006 to the cavity 1002 to enable access to
the cavity 1002 by piping, electrical cables, data cables, and the
like, as described above for system 900. Access to the lower
portion of the shaft 1008 from the main access tunnel is obtained
by excavating a first approximately horizontal tunnel 1010; access
to the upper portion of the cavity 1002 is obtained by excavating a
second approximately horizontal access tunnel 1012; and access to
the lower portion of the cavity 1002 is obtained by directing the
lower portion of the spiraling main access tunnel 1004 to a point
of contact 1014 with the cavity 1002. The construction of a
spiraling main access tunnel may reduce difficulties associated
with accessing land rights to linear access tunnels potentially
located a distance away from the overhead access and surface
facilities.
[0202] The cavity 902 in FIG. 9A, FIG. 9B, and FIG. 9C and cavity
1002 in FIG. 10 may be lined by a variety of methods, including as
described above for system 800 and further illustratively described
hereinbelow. Also, in various embodiments systems 800, 900, and/or
1000 may include one or more underground chambers or
cavities--e.g., a chamber located directly above the main fluid
storage cavity (e.g., cavity 902 or 1002) and accessed by the shaft
tunnel 904 or first horizontal access tunnel 1010--in addition to
the main fluid storage cavity. The one or more additional chambers
may contain various components of a system for the storage and
retrieval of energy not depicted in FIG. 9A, 9B, 9C, or 10, such as
machinery, liquid, and/or pressurized gas. Examples of machinery
that may be located within in the one or more additional chambers
include systems for control (e.g., computers, control systems as
detailed above), pumps, insulated pipeline vessels, and systems for
the interconversion of electrical, thermal, and elastic-potential
energy in compressed gas and other fluids, and/or for the
combustion of fuels (e.g., natural gas). Liquid (e.g., water)
located in the one or more additional chambers may constitute a
storage reservoir of heat-exchange fluid to be circulated into and
out of the main fluid-storage chamber for the purpose of thermally
regulating the fluid stored within the main fluid-storage chamber.
Alternatively or additionally, liquid located in the one or more
additional chambers may constitute one or more lower or upper
reservoirs enabling gravitational potential energy to be stored or
released by virtue of an altitude difference between the one or
more reservoirs and some other location (e.g., the earth's surface
or another chamber at greater depth).
[0203] FIG. 11 is a schematic representation of three stages in one
method of construction of a vertical shaft 1100, similar to shaft
802 in FIG. 8, sunk into stable earth material 1102 (preferably,
solid rock). Within shaft 1100, a recessed storage reservoir such
as that depicted in FIG. 8, FIG. 9A, FIG. 9B, FIG. 9C, or FIG. 10,
may be constructed. Stage A (upper drawing in FIG. 11) is a stage
at which an incipient shaft 1100 of depth D1 is already in
progress. Drillings (narrow shafts) 1104 are sunk into the invert
of the incipient shaft 1100 to a depth of approximately D2. The
number of drillings 1104 shown in FIG. 11 is illustrative only.
Explosives (e.g., dynamite) are inserted into the drillings 1104
and detonated, creating a pulverized mass of rock 1106. A single
mass of pulverized rock 1106 is shown in Stage B in FIG. 11, but in
practice only portions of the invert of shaft 1100 may be
pulverized in any given blasting operation. The pulverized rock
1106 is removed (e.g., by buckets or as a slurry), creating a new
vacancy 1108 that extends the shaft 1100 deeper into the rock 1102,
as shown in Stage C in FIG. 11. As of Stage C, the shaft 1100 has
attained a depth of D3=D2+D1. A shaft of any width may be sunk to
any depth by these means, subject to the stability of the shaft
1100 thus created. The walls of the shaft 1100 may be segmentally
covered (e.g., by rings or panels) and strengthened by a liner (not
shown) as the shaft 1100 is incrementally deepened.
[0204] The method of shaft-sinking depicted in FIG. 11 may be
time-consuming and expensive, since workers typically descend to
the bottom of the shaft 1100 to operate machinery to produce the
drillings 1104, insert explosives, and operate machinery that
removes the debris 1106. Another method of shaft-sinking is
depicted in FIG. 12A and FIG. 12B. This method of shaft-sinking may
entail less time-consuming and possibly hazardous descent by
workers into the developing shaft.
[0205] FIGS. 12A and 12B are schematic diagrams of a shaft-sinking
system 1200 utilized in various embodiments of the present
invention. Herein, such a system is termed a "roadheader shaft
sinking system" or simply "roadheader system." The system 1200
includes a support rig 1202 erected over the opening of a shaft
1204 (which may have a depth of zero when the process of excavation
begins). A platform or stage 1206 descends by weight-bearing cables
1208 from the support rig 1202. The support rig 1202 is capable of
raising or lowering the stage 1206 and all components attached
thereto, e.g., by means of motor-driven cable drums (not depicted).
To the bottom of the stage 1206 is attached a mechanical housing
1210, which typically contains motors, reservoirs of fluid,
cameras, and/or other components. Adjustable-length cables and
conduits for the conveyance of electrical power, control signals,
fluids, and other services to and from the stage 1206 components
attached thereto are not shown in FIG. 12A but may extend, like the
weight-bearing cables 1208, from the support rig 1202 into the
shaft 1204. To the bottom of the housing 1210 is attached a
controllable joint 1212 which supports and moves a telescoping boom
1214. The joint 1212 is capable of directing the boom 1214 through
the entire hemisphere of action not occluded by the housing 1210
(i.e., a solid angle of approximately 2.pi. steradians). At the end
of the telescoping boom 1214 is a rotating cutting head 1216. As
used herein, the term "roadheader" includes any drilling system
featuring a directable boom surmounted by a cutting head. The stage
1206 and all components attached thereto are herein termed the
"roadheader rig." The roadheader rig is raised and lowered by the
support rig 1202.
[0206] The joint 1212 is capable of raising, lowering, and rotating
the boom 1214; the boom 1214 may extend and retract. By
appropriately combining (e.g., under the direction of a human
operator, automatic control system, or both) the motions of the
stage 1206, joint 1212, and boom 1214, the working surface of the
cutting head 1216 may be brought into contact with any point on the
walls or invert of the shaft 1204.
[0207] Rock fragments broken from the walls and/or invert of the
shaft 1204 by the cutting head 1216 typically accumulate as debris
1218 upon the invert of the shaft 1204. Such debris may be removed
by a variety of techniques. The illustrative system 1200 introduces
water through piping (not shown) that mixes with the debris 1218 to
form a slurry. Alternatively, the shaft 1204 may be wholly or
partly filled with water during operation of the system 1200. The
slurrified debris 1218, whether its water portion is introduced
through piping or through filling of the shaft 1204 with water, is
pumped through a pipe 1220 to the surface. (Two portions of pipe
1220 are depicted in FIGS. 12A and 12B.)
[0208] In FIG. 12B, the system 1200 is shown in a state of
operation different from that depicted in FIG. 12A. In FIG. 12B,
the debris 1218 is not depicted and the cutting head 1216 has been
maneuvered into a position that displays the working face of the
cutting head 1216 and is suitable for removing rock from the face
of the invert.
[0209] It is clear that by lowering the roadheader rig, breaking up
rock with the cutting head, and removing debris from the shaft
1204, the shaft 1204 may be sunk to any depth to which the support
rig 1202 is capable of lowering the roadheader rig and at which the
walls of the shaft 1204 remain stable. The walls of the shaft 1200
may be segmentally covered and strengthened by a liner (not shown)
as the shaft 1200 is incrementally deepened. Within shaft 1200, a
recessed storage reservoir such as that depicted in FIG. 8, FIG.
9A, FIG. 9B, FIG. 9C, or FIG. 10, may be constructed, constituting
a lined underground reservoir.
[0210] FIG. 13 is a schematic representation of an illustrative
lined underground reservoir fluid-storage system 1300 that includes
a lined cavity 1302 (dashed lines) similar to cavity 902 in FIG. 9.
In general, it is desirable that water be controlled during
excavation and construction of the lined cavity 1302. In other
instances, it may be useful to reduce water collecting or impinging
on the exterior of the lining (not shown) of the cavity 1302. In
some instances, water may accelerate the corrosion or cracking of
the various component layers of a lining; moreover, if a cold
liquid (e.g., liquefied natural gas) is stored in the system 1300,
or the gaseous pressure of the contents of the cavity 1302 is
lowered rapidly to a sufficient degree without thermal conditioning
of the contents, freezing temperatures may occur within and in the
vicinity of the cavity 1302, and ice expansion may cause cracking
of the lining and other damage. Therefore, system 1300 includes a
network of pipes 1304 that surrounds the cavity 1302. The
crisscrossing lines superimposed over the cavity 1302 in FIG. 13
are a two-dimensional representation of a three-dimensional network
or basket of interconnecting pipes 1304 surrounding the cavity
1302. The pipes are tilted, perforated, and/or interconnected in a
manner that permits water to enter the pipes and be drained
downward to a collection point 1306. A collection pipe 1308
conducts water from the collection point 1306 to a disposal point
1310 on the surface. A pump or pumps (not shown) impel the water
through the collection pipe 1308. Air from the surface is permitted
to enter the drainage network 1304 through a shaft 1312 in order to
equalize pressure within the drainage network 1304 as water is
pumped out through the collection pipe 1308. In various other
embodiments, the arrangement of pipes in the drainage network 1304
differs from that schematically represented in FIG. 13; water
collected by the drainage network 1304 is directed to more than one
collection point 1306; the collection pipe 1308 may be a part of,
or located within, the drainage network 1304; and/or the collection
pipe 1308 may reach the surface through the same shaft 1312 that
admits air to the drainage network 1304 rather than through a
separate shaft as depicted in FIG. 13. Also in various other
embodiments, fluids for storage in and retrieval from the cavity
1302, fluids for thermal conditioning of the contents of cavity
1302, control cables (not shown), air entering the drainage network
1304, water leaving the drainage network 1304, and other fluids and
components of system 1300 may pass through a multiplicity of
conduits located within a single shaft 1312 and/or may pass through
a multiplicity of shafts (not shown in FIG. 13). This drainage
system may be applied to vertically-excavated LURs such as those
described with reference to FIG. 8. This drainage network 1304,
after initial usage during excavation and construction, may
subsequently be repurposed and used to monitor and detect any
incidents of gas leakage from the LUR. Especially in storage of
potentially hazardous or explosive fluids, the repurposed drainage
network 1304 may serve as a useful safety system for detection,
collection, and evacuation of gas leakage. For example, the air
and/or liquid (e.g., water) within the drainage network 1304 may be
monitored (e.g., via a conventional gas monitor) for the presence
of and/or elevated levels of the gas contained within the LUR
(e.g., natural gas), which may signify leakage from the LUR. In the
event of such leakage, the drainage network 1304 may be used as a
conduit to remove (e.g., with a pump connected thereto) and
potentially recover all or a fraction of the leaking gas from
underground, thereby mitigating contamination and/or unsafe
conditions.
[0211] FIG. 14A is a cross-sectional schematic representation of
portions of an illustrative lining 1400 of a lined underground
reservoir 1402. The lower portion of FIG. 14A shows a portion of
the lining 1400 of the lined underground reservoir 1402 in
cross-section; the upper portion of FIG. 14A is a magnified and
rotated view of a small portion of the lining 1400, as indicated by
dashed lines 1404. Raw rock mass 1406 presents a relatively rough
surface exposed by excavation. In one method of construction of the
lining 1400, a network of water-drainage pipes 1408 similar to that
depicted in FIG. 13 is placed against the surface of the rock mass
1406. The drainage pipes 1408 are covered with a layer of shotcrete
1410, i.e., spray-on concrete. The shotcrete 1410 may be porous to
allow water to flow through it and into the drainage pipes. The
shotcrete 1410 serves both to stabilize the drainage pipes 1408 and
to protect them from displacement or damage during pouring and/or
injection of the next most inward layer, namely, a concrete layer
1412. The concrete layer 1412 may be self-compacting and may be
agitated during or after pouring in order to remove void spaces and
promote uniform density. Within the concrete layer 1412 is embedded
a metal (e.g., steel reinforcement) mesh 1414, one purpose of which
shall be explained below with reference to FIGS. 15A and 15B. The
inward surface of the concrete layer 1412 is comparatively smooth,
and is shaped to form a cavity 1416. The cavity 1416 is lined with
an impermeable liner 1418 (e.g., a liner including or consisting
essentially of steel). Between the impermeable liner 1418 and the
inward face of the concrete 1412 is a viscous or sliding layer 1420
(e.g., a layer of asphalt, a layer of plastic), herein termed "the
viscous layer." The viscous layer 1420 enables slippage between the
impermeable liner 1418 and the concrete layer 1412, mitigating the
buildup of forces (e.g., tensile forces) that could cause strain
(e.g., stretching) in the material of impermeable liner 1418 and
which could thus damage the impermeable liner 1418. The viscous
layer 1420 may also serve to mitigate corrosion of the impermeable
liner 1418.
[0212] FIG. 14B is a schematic cutaway drawing of a portion of the
lining 1400 in FIG. 14A. The rock face 1406, drainage pipes 1408,
concrete layer 1412, mesh 1414, viscous layer 1420, and impermeable
liner 1418 are depicted. The shotcrete layer 1410 is not depicted
in FIG. 14B for clarity. Primary (rock-mass) cracks 1422, secondary
(concrete) cracks 1424, and tertiary (concrete) cracks 1426 are
depicted in FIG. 14B. Rock-mass cracks 1422 tend to propagate
outward (i.e., away from cavity 1416, FIG. 14A) from the face of
the rock mass 1406. Secondary cracks 1424 tend to propagate inward
into the concrete 1414 from the face of the rock mass 1406. Upon
reaching the mesh 1414, the secondary cracks 1424 tend to propagate
still further inward as smaller, more numerous tertiary cracks
1426. The effect of the mesh 1414 is thus to increase the number
of, while decreasing the size of, the cracks that impinge upon the
viscous layer 1420 and impermeable layer 1418. This pattern of
cracking tends, for a given degree of expansion of the cavity 1416,
to decrease the magnitude of forces (e.g., tensile forces) exerted
upon various local portions of the impermeable lining 1418.
Decreasing the forces (e.g., tensile forces) exerted locally within
the impermeable lining 1418 (e.g., during repeated pressurizations
of the cavity 1416) tends to preserve the lining 1418 from damage
and to increase its longevity.
[0213] The network of drainage pipes within the lining 1400 may be
used to pump water out of the shaft during construction. Various
illustrative methods of construction of the lining 1400 are
considered further in FIGS. 17-23.
[0214] FIGS. 15A and 15B are schematic representations of aspects
of the behavior of cracks and other components of a lined
underground reservoir 1500 having a lining similar to that
portrayed in FIG. 14A and FIG. 14B when the contents of the lined
underground reservoir 1500 are raised to a relatively high pressure
(e.g., 3,000 psi). In general, a rock mass 1502 surrounding a
cavity 1504 is not perfectly rigid. Rather, under the influence of
pressure forces exerted by the fluid contents of the cavity 1504,
the rock mass 1502 in the vicinity of the cavity 1504 will tend to
be displaced outward slightly from its original, pre-pressurization
position. As a result of this outward displacement, the rock mass
1502 tends to develop radiating cracks 1506 (primarily by opening
existing cracks that are frequent in blocky crystalline bedrock),
i.e., cracks that tend to (a) impinge edgewise upon the cavity 1504
(b) be widest at their point of impingement upon the cavity 1504,
and (c) narrow as they proceed away from the cavity 1504.
[0215] FIG. 15A portrays a first state in which the cavity 1504 has
hitherto contained fluid only at relatively low pressure (e.g.,
atmospheric) and has diameter D1. Lines 1510 in the upper portion
of FIG. 15 show existing closed cracks in the rock mass 1502 when
the contents of cavity 1504 are sufficiently pressurized. A
concrete liner 1512 surrounds the cavity 1504 and is, in the
unstressed initial condition portrayed in FIG. 15A, uncracked.
[0216] FIG. 15B portrays a second state in which the contents of
cavity 1504 have been raised to relatively high pressure (e.g.,
3,000 psi) and cavity 1504 has expanded to diameter D2. Cracks 1506
have opened up in the rock mass 1502. The rock-mass cracks 1506
give rise to secondary cracks 1514 that tend to propagate into the
concrete layer 1512 from the face of the rock body 1502. In various
embodiments where a mesh is embedded in the concrete layer 1512, as
in the illustrative embodiment depicted in FIG. 14A and FIG. 14B,
the secondary concrete cracks 1514, upon propagating inward to the
mesh, will give rise to tertiary concrete cracks as depicted in
FIG. 14B, distributing forces (e.g., tensile forces) less unevenly
across the surface of the impermeable liner 1508.
[0217] The storage of relatively hot (e.g., 60.degree. C. or
higher) pressurized fluid within a lined underground reservoir
(e.g., cavern 1402 in FIGS. 14A and 14B, or cavern 1500 in FIGS.
15A and 15B) as is contemplated in various embodiments of the
present invention, tends to decrease forces (e.g., tensile forces)
exerted locally within the impermeable lining (e.g., lining 1508 in
FIGS. 15A and 15B) if the impermeable lining 1508 is constructed of
a material (e.g., steel) that expands at higher temperatures. That
is, as regards forces (e.g., tensile forces) exerted within the
impermeable lining 1508, the effects of increasing the pressure of
the fluid contents of lined underground reservoir 1500 tend to be
counteracted by the effects of increasing the temperature of the
fluid contents of lined underground reservoir 1500.
[0218] FIG. 16 is a plot of illustrative data showing the
relationship between cyclic pressure within a lined underground
reservoir (horizontal axis) and the strain or deformation in an
illustrative steel liner of the lined underground reservoir
(vertical axis), for three hypothetical cycles of temperature of
the contents of the lined underground reservoir. In a first
hypothetical temperature-pressure cycle 1602, the contents of the
reservoir, and thus the lining, which is in contact with the
contents, remain at a constant temperature as the pressure within
the reservoir is raised from a low pressure 1604 to a high pressure
1606 and then lowered to the low pressure 1604 again. (The
relationship between temperature and pressure of the contents is
not depicted explicitly in FIG. 16.) The strain undergone by the
steel liner over the first cycle 1602 varies over a range R1.
[0219] In a second hypothetical temperature-pressure cycle 1608,
the contents of the reservoir, and thus the lining in contact with
the contents, vary moderately in temperature as the pressure of the
contents changes from a low pressure 1604 to a high pressure 1606
and then back to the low pressure 1604 again: i.e., the temperature
increases with increasing pressure and decreases with decreasing
pressure. The strain undergone by the steel liner over the second
cycle 1608 varies over a range R2 that is significantly smaller
than the stress range R1 of the first cycle 1602, and the peak
strain undergone by the steel liner for cycle 1608 is less than
that undergone for cycle 1602.
[0220] In a third hypothetical temperature-pressure cycle 1610, the
contents of the reservoir, and thus the lining, vary more widely
than in cycle 1608 as the pressure within the reservoir is raised
from a low pressure 1604 to a high pressure 1606 and then lowered
to the low pressure 1604 again: i.e., the temperature increases
with increasing pressure and decreases with decreasing pressure.
The strain undergone by the steel liner over the second cycle 1608
varies over a range R3 which is smaller than the range R1 and
larger than the range R2; moreover, the sense or sign of the
relationship between strain and pressure/temperature has been
reversed from that of cycle 1602 and cycle 1608, that is, the liner
experiences less strain at peak pressure 1606 and temperature than
at lowest pressure 1604 and temperature. Different relationships
between temperature, pressure, and strain than those shown in FIG.
16 may pertain for various steels, or for materials other than
steel, or for multilayered liners. In general, a
temperature-pressure-strain relationship that entails the lowest
maximum strain on the liner--e.g., cycle 1608 in FIG. 16--is
preferable.
[0221] Illustrative methods of constructing portions of a lined
underground reservoir in various embodiments of the present
invention are now considered. FIG. 17 is a schematic
cross-sectional representation of three stages (Stage A, Stage B,
and Stage C) in the construction of an illustrative lined
underground reservoir 1700 similar to reservoir 900 in FIG. 9.
Cavern 1700 is constructed by excavating a cavity 1702 primarily by
removing rock fragments through access tunnels 1704, 1706, and
1708. In Stage A, a network of drainage pipes (not shown) similar
to network 1408 in FIG. 14A has been placed against the interior
rock mass and covered with a layer of shotcrete (not shown) similar
to layer 1410 in FIG. 14A. In Stage A, a steel invert liner 1710
conforming in shape to the invert of the cavity 1702 has been
constructed and is held above the rock face of the invert by
spacers (not shown). Trucks (e.g., truck 1712) bring concrete to
the worksite through the lower access tunnel 1708 and pour and/or
inject concrete 1714 into the space between the invert liner 1700
and the rock face below. In order to prevent the concrete 1714 from
deforming or floating the invert liner 1710, water 1716 may be
added to the interior of invert liner 1710 through piping (not
shown) as the concrete 1714 is poured. At Stage A, the invert liner
1710 is approximately filled with water and the concrete 1714
between the invert liner 1710 and the rock face is almost
completely poured.
[0222] After the concrete 1714 hardens, firmly undergirding the
invert liner 1700, the water 1716 is removed from the invert liner
1710. A steel liner dome 1718 is then constructed atop the invert
liner 1710 (Stage B). The dome 1718 may be jacked up or otherwise
raised incrementally as sections of wall-lining material 1720 are
assembled (e.g., by welding) into rings 1722 beneath the dome 1718.
In this manner, the steel liner dome 1718 is raised until it is
close to the domed ceiling of the cavity 1702, at which point an
approximately cylindrical set of rings 1722 has been fabricated
thereunder.
[0223] At Stage C, a complete inner steel liner 1724 has been
constructed within the cavity 1702. Trucks (e.g., truck 1726) bring
concrete to the worksite through the middle access tunnel 1706 and
pour and/or inject additional concrete 1728 into the space between
the liner 1724 and the surrounding rock face. Some of the concrete
1728 forms a plug 1730 in the lower access tunnel. Water within the
liner 1724 prevents the liner 1724 from being deformed by the
weight of the concrete 1728.
[0224] After Stage C, in phases of construction not depicted in
FIG. 17, concrete may be added through a top shaft 1732 to fill the
space between the water-filled liner 1724 and the rock face at and
above the level of the middle access tunnel 1706. Middle access
tunnel 1706 is plugged with concrete during the addition of the
concrete, and finally the top shaft 1732 is plugged with concrete.
Other phases of construction, including the addition of pumps,
piping, sensors, power cables, and other components, are not
portrayed in FIG. 17 or discussed herein but are contemplated.
[0225] When the lined underground reservoir 1700 has been
completed, the water within the liner 1724 may be used to
pressure-test the liner 1724. After completed testing, the water is
removed by injection of the stored product, e.g., compressed air.
This procedure ensures the stability of the storage, as there is
always an internal overpressure from the water and/or the stored
product.
[0226] FIG. 18 is a schematic cross-sectional representation of
three stages (Stage A, Stage B, and Stage C) in the construction of
an illustrative lined underground reservoir 1800 similar to
reservoir 800 in FIG. 8. Cavern 1800 is constructed partly by
excavating an open shaft 1802 in suitable rock; a lined reservoir
is produced in the shaft 1802 primarily by assembling portions of
an impermeable (e.g., including or consisting essentially of steel)
liner at or near the surface of the earth and lowering them down
the shaft by means of a support rig 1804 and then surrounding the
resulting liner 1806 with concrete 1808 (Stage C) and other
materials. In Stage A, an invert liner 1810 has already been placed
at the bottom of the shaft 1802. The invert liner 1810 may be
undergirded by concrete 1812 by means similar to those depicted for
undergirding of the invert liner 1710 in FIG. 17; alternatively,
the undergirding concrete 1812 may be formed in situ, prior to the
emplacement of the invert liner 1710, which may be lowered into the
undergirding concrete 1812. In either case, after emplacement of
the invert liner 1710, the cylindrical or wall-lining portion of
the liner 1806 is constructed by constructing or staging rings,
panels, or other segmental portions 1814 of the liner 1806 at or
near the surface and then lowering them down the shaft 1802 by
means of support rig 1804. The segments 1814 may be joined together
(e.g., welded together) in situ upon being lowered into the shaft
1802. A network of drainage pipes (not shown in FIG. 18) and other
lining layers similar to those depicted in FIG. 14A and FIG. 14B
may be emplaced simultaneously with the segmental portions 1814 of
the liner 1806.
[0227] In Stage B, the wall-lining portions of the liner 1806 have
all been emplaced, and a dome liner 1816 is being lowered into the
shaft 1802. Following emplacement of the dome liner 1816, a
concrete liner or surround 1808 may be poured and/or injected into
the space between the liner 1806 and the surrounding rock, as
depicted in FIG. 17. This surround 1808 may additionally include a
plug (not shown) that may extend into the surrounding rock and may
serve as or separately consist of a plug to distribute upward
pressure forces from the dome 1816, in part or entirely, to the
surrounding rock as opposed to the overfill 1818.
[0228] In Stage C, the concrete liner 1808 has been emplaced,
overfill 1818 (e.g., crushed rock; concrete; reinforced concrete)
has been emplaced, and at least three conduits or pipes 1820, 1822,
and 1824 have been emplaced to enable fluid communication (and, in
various embodiments, electrical, informatic, and mechanical
communication) between the interior of the lined underground
reservoir 1800 and facilities (not shown) on the surface. Gas may
be injected into or removed from the reservoir 1800 through pipe
1820, heat-exchange fluid (e.g., liquid, foam; not shown in FIG.
18) may be injected into the reservoir 1800 through pipe 1822 in
order to thermal condition the contents of the reservoir 1800, and
heat-exchange fluid may be removed from the reservoir 1800 through
pipe 1824.
[0229] The method of construction depicted in FIG. 18 typically
requires that most assembly (e.g., joining of segmental portions
1814 to the liner) 1806 is done by workers in situ, deep within the
shaft 1802. It is in general desirable that as little work as
possible be performed at depth, in order to increase worker safety
and to decrease costs.
[0230] FIG. 19 is a schematic cross-sectional representation of
five stages (Stage A, Stage B, Stage C, Stage D, and Stage E) in
the construction of an illustrative lined underground reservoir
1900 similar to reservoir 800 in FIG. 8. Cavern 1900 is constructed
partly by excavating an open shaft 1902 in suitable rock; a lined
cavity may be produced in the shaft 1902 primarily by assembling
portions of an impermeable (e.g., steel) liner 1904 at or near the
surface of the earth and floating the liner 1904 upon a body of
water 1904 (or other liquid) that may be raised or lowered by the
addition or removal of water. The method of construction depicted
in FIG. 19 typically requires the performance of less construction
work within the open shaft 1902 than does the method of
construction depicted in FIG. 18. In Stage A, a partial concrete
lining with drainage system 1908 has been constructed within the
shaft 1902 and a body of water 1906 mostly fills the shaft 1902. An
invert liner 1910 and a segmental portion 1912 of the liner 1904
have been assembled proximate the surface and are floating upon the
body of water 1906. As utilized herein, "proximate the surface" is
defined as at or near the surface (i.e., within reach of a worker
or work crew at the surface or on work surfaces (e.g., scaffolding)
near the surface).
[0231] In Stage B, further segmental portions 1914 have been joined
to the liner 1904. The depth of the body of water 1906 has been
lowered in order to keep the level at which further segmental
portions 1914 are added to the liner 1904 at or near the
surface.
[0232] In Stage C, the liner 1904 has been completed and rests in
the prefabricated undergirding concrete liner 1908.
[0233] In Stage D, additional concrete 1916 has been added to
cover, protect, and strengthen a dome liner 1918, and at least
three conduits or pipes 1920, 1922, and 1924 have been emplaced to
enable fluid communication (and, in various embodiments,
electrical, informatic, and mechanical communication) between the
lined underground reservoir 1900 and facilities (not shown) on the
surface. Gas may be injected into or removed from the reservoir
1900 through pipe 1920, heat-exchange fluid (e.g., liquid, foam;
not shown in FIG. 19) may be injected into the reservoir 1900
through pipe 1922 in order to thermal condition the contents of the
reservoir 1900, and heat-exchange fluid may be removed from the
reservoir 1900 through pipe 1924. The additional concrete 1916 may
additionally include a plug (not shown) that may extend into the
surrounding rock and may serve as or separately consist of a plug
to distribute upward pressure forces from the dome 1918, in part or
entirely, to the surrounding rock as opposed to the overfill
1926.
[0234] In Stage E, overfill 1926 (e.g., crushed rock; concrete;
reinforced concrete) has been added above the concrete 1916. The
weight and/or mechanical strength of the overfill 1916 serve to
restrain expansion of the lined underground reservoir 1900 when the
reservoir 1900 is filled with fluid at high pressure.
[0235] The method of construction partly depicted in FIG. 19
dispenses with the support rig 1804 in FIG. 18 and allows a greater
amount of construction work to be performed at or near the surface
of the earth. In various other embodiments, a method of
construction similar to that depicted in FIG. 19 is employed, but
no prefabricated concrete undergirding 1908 is constructed. Rather,
the liner 1904 is lowered into place as it is constructed, coming
to rest upon spacers (e.g., beams, ribs, struts) that hold the
liner a desired distance away from the surrounding rock face at all
points. Concrete is then poured and/or injected into the space
between the liner 1904 and the surrounding rock face, approximately
as described for the emplacement of the concrete liner 1728 in FIG.
17, producing a result similar to Stage C in FIG. 18. Construction
may then proceed as described for the method of construction partly
depicted in FIG. 18.
[0236] FIG. 20 is a cross-sectional schematic representation of two
stages (Stage A and Stage B) of the first stages of construction of
an illustrative lined underground reservoir 2000 similar to
reservoir 800 in FIG. 8, in accordance with various embodiments of
the present invention. Cavern 2000 is constructed partly by
excavating an open shaft 2002 in suitable rock. Similar to FIG. 19,
a lined cavity is produced in the shaft 2002 primarily by
assembling portions of an impermeable (e.g., including or
consisting essentially of steel) liner 2004 (see Stage B, FIG. 20)
at or near the surface of the earth and floating the liner 2004
upon a body of water 2006 (see Stage B, FIG. 20) that may be raised
or lowered by the addition or removal of water. In Stage A, a
drainage layer 2008 has been constructed within the shaft 2002. The
drainage layer 2008 includes a network of pipes 2010 similar to the
network of pipes 1408 depicted in FIG. 14A and FIG. 14B. The pipe
network 2010 is covered with a layer of shotcrete to stabilize and
protect the pipe network 2010. One or more openings 2012 allow
water to flow from the interior of the shaft 2002 into the pipe
network 2010, or from the pipe network 2010 into the interior of
the shaft 2002. One or more pipes and pumps (not shown) allow water
to be pumped from and to the drainage network 2010. Openings 2012
may be closed (e.g., filled with concrete) or left open after or
during Stage B.
[0237] In Stage B, a body of water 2006 mostly fills the shaft
2002. An invert liner (e.g., dome shaped liner) 2020 and a
segmental portion 2018 of the liner 2004 have been assembled at or
near the surface and are floating upon the body of water 2006. One
or more spacers 2014 (e.g., beams, ribs, struts) that can hold the
liner 2004 a desired distance away from the surrounding rock face
at all points are attached to the outside of the liner 2004. Also,
a network or basket of rebar 2016 has been constructed around and
attached to the portion of the liner 2004 constructed as of Stage
B. As further segmental portions of steel liner 2018 and rebar
network 2016 of the liner 2004 are added to the liner 2004, water
may be removed from the shaft 2002 through the pipe network 2010,
lowering the level of the body of water 2006 and thus permitting
the joining of further segmental portions 2018 and portions of
network 2016 to the liner 2004 to proceed at or near the surface of
the earth. When the liner 2004 is completed, it may be lowered to
the bottom of the shaft 2002 by the removal of all water from the
shaft 2002. Concrete is then poured and/or injected into the space
between the liner 2004 and the surrounding rock face, approximately
as described for the emplacement of the concrete liner 1728 in FIG.
17, producing a result similar to Stage C in FIG. 18. This concrete
may also fill any openings 2012. Construction may then proceed as
described for the method of construction partly depicted in FIG.
18. In other embodiments, water (or other liquid) is not utilized,
and the weight of the liner is supported in part or entirely by
other means, such as via hydraulic jack or crane. In yet other
embodiments, at least a portion of the liner 2004 is assembled
directly on the drainage layer 2008 after lower portion(s) of the
liner 2004 (if any) have been assembled and/or lowered down to the
bottom of the shaft 2002.
[0238] FIG. 21A is a cross-sectional schematic representation in
two stages (Stage A and Stage B) of yet another exemplary method of
construction of an illustrative lined underground reservoir 2000
similar to reservoir 800 in FIG. 8. Cavern 2100 is constructed
partly by excavating an open shaft 2102 in suitable rock; a lined
cavity is produced in the shaft 2102 primarily by assembling
segments of an impermeable (e.g., including or consisting
essentially of steel) liner 2104 (see Stage B, FIG. 20) proximate
(at or near) the surface of the earth and floating the liner 2104
upon a body of water 2106 (see Stage B, FIG. 21A) that may be
raised or lowered by the addition or removal of water as the liner
2004 grows. In Stage A, the shaft 2102 is partially sunk. In Stage
B, the liner 2104 has been partially constructed in a segmented
manner and is being lowered into the shaft 2102 by removal of water
from the shaft 2102.
[0239] FIG. 21B is a cross-sectional schematic representation of
two further stages (Stage C and Stage D) of the method of
construction of the illustrative lined underground reservoir 2100
represented in FIG. 21A. In Stage C, the steel liner 2104 has been
completely constructed and lowered to near the bottom of the shaft
2012. Spacers (not shown) preserve a desired amount of space
between the liner 2104 and the surrounding rock face. In Stage C,
concrete 2108 from a surface source 2110 is being poured and/or
injected into the space between the liner 2104 and the surrounding
rock face while water 2112 is added to the interior of the liner
2104 to balance the pressure of the rising concrete 2108, thus
preventing excessive deformation of the liner 2104. In Stage D, the
liner 2104 has been completely surrounded by a concrete layer 2108,
is filled with water 2112, and is being surmounted by a concrete
plug 2114 that is shaped to contain upward-acting forces generated
by the pressurized fluid contents of reservoir 2100 in various
states of operation. The plug 2114 is shaped in such a manner as to
resist relative movement with respect to the surrounding rock when
exposed to low- or high-pressure forces. The plug 2114 is typically
disc shaped (e.g., a shallow cylinder) to fill the shaft 2102 with
one or more extensions (e.g., a rim) extending into a cutout in the
surrounding rock. The plug 2114 will typically extend into a cutout
region of surrounding rock face, where the cutout region of rock
serves in part as a lip against which the pressure and other (e.g.,
gravity) forces may be transmitted to the bulk surrounding rock.
The cutout may be a triangular, curved, or otherwise shaped to
allow a similarly shaped plug 2114 to be constructed within or
inserted. The plug 2114 may include a manhole (not shown) or other
small access apparatus to allow access to the lower cavity and
liner 2104. In other embodiments, the plug 2114 is solid and
permanent when installed, except holes for access pipes and thus no
easy access to the lower cavity or liner 2104 remains after
construction of the plug 2114. The plug may include or consist
essentially of reinforced concrete or other materials such as
steel. One or more conduits 2118 permits communication (e.g.,
fluid, mechanical, informatic, electrical) between the interior of
the lining 2104 and installations (not shown) on the surface.
[0240] FIG. 21C is a cross-sectional schematic representation of
two further stages (Stage E and Stage F) of the method of
construction of the illustrative lined underground reservoir 2100
represented in FIG. 21A. In Stage E, infill material 2120 (e.g.,
crushed rock, concrete, reinforced concrete) has placed above the
plug 2114. In various embodiments, at least a portion of the space
occupied by infill material 2120 in FIG. 21C may be utilized for
storage of water (or other heat-transfer liquid) or equipment
utilized in the construction, maintenance, and/or operation of LUR
2100. In Stage F, piping 2122 has been inserted through the conduit
2118 into the interior of the steel liner 2104 and a wellhead 2124
has been installed for connection to surface facilities (not
shown). Piping 2122 reaches approximately to the bottom of vessel
2104, enabling the extraction of approximately all settled fluid
(e.g., liquid) from the interior of the liner 2104. In other stages
of construction of the lined underground reservoir 2100, other
components, not shown, may be added, including piping for the
introduction and extraction of fluids, pumps, wiring for power and
telemetry, spray heads, and other components.
[0241] FIG. 21D is a cross-sectional schematic representation of
Stage F (also represented in FIG. 21C) of the method of
construction of the illustrative lined underground reservoir 2100
represented in FIG. 21A. In FIG. 21D, illustrative dimensions are
indicated for some of the components of lined underground reservoir
2100. The shaft 2102, from the top of the wellhead 2124 to the
bottom, is 11 meters in diameter and 153 meters deep. The inner
liner 2104 (steel-lined portion of the reservoir 2100) is 100
meters high and 10 meters in diameter, with a volume of
approximately 7,592 m.sup.3. FIG. 21D also provides a magnified
view of a portion of the layers of the lined underground reservoir
2100, with illustrative approximate dimensions for these layers:
i.e., from the inmost layer to the outermost, (1) steel liner 2104
(8 mm thick), viscous or sliding layer 2126 (6 mm thick), concrete
layer 2108 (455 mm thick), shotcrete layer 2128 (30 mm thick), and
rock face 2130 (500 mm distant from inner surface of steel liner
2104: thickness of rock, indefinite). Embedded within the concrete
layer 2108 is a metal mesh layer 2132. Embedded within the
shotcrete layer 2128 is a drainage pipe network 2134. The layers
depicted in FIG. 21D, and their functions, are similar to those
depicted in FIGS. 14A and 14B. Other sets of layers, which may
include layers not depicted herein (e.g., an insulation layer),
and/or the omission of layers depicted herein, are contemplated in
various other embodiments of the invention.
[0242] The construction of cavity liners for lined underground
reservoirs--e.g., the multi-layered liner depicted in FIG. 14A,
FIG. 14B, and FIG. 21D--may proceed by a variety of means. Aspects
of one illustrative technique of liner construction are depicted in
FIG. 22 and FIG. 23.
[0243] FIG. 22 is a cross-sectional schematic representation of the
assembly of a ring-shaped segmental portion 2202 (e.g., segmental
portion 1814 in FIG. 18) of a cavity liner. Preformed panels 2204,
possibly manufactured at a distant location, include or consist
essentially of concrete; embedded in the concrete is a metal-mesh
or rebar frame 2206. The rebar frame 2206 typically protrudes
beyond the edge-surfaces of each panel 2204. By arranging the
panels 2204 in a circle 2208 and welding the rebar frames 2206
together, panels 2204 may be joined into a ring-shaped segmental
portion 2202. The gaps between panels 2210 may be filled with
concrete or otherwise grouted. The panels may be installed within
an open shaft iteratively during shaft construction or installed
after shaft construction. Alternatively, a fully completely
ring-shaped segmental portion 2202 may be lowered into an open
shaft such as shaft 1100 in FIG. 11. Adjacent ring-shaped segmental
portions 2202 may be joined by rebar welding and gap grouting, just
as the panels 2204 are joined to make each ring-shaped segment
2202.
[0244] In other embodiments, not shown, a cavity liner (e.g., a
reinforced concrete base lining) may be constructed by using
slip-form casting, in which concrete is poured into a continuously
moving form. This may be very efficient for a long vertical shaft
and produces a very smooth surface on which may be installed the
impermeable lining.
[0245] FIG. 23 is a cross-sectional schematic representation of
stages of an illustrative method of emplacing segmental portions of
a cavity liner in an open shaft. In Stage A, excavation of a shaft
2300 has been commenced in a setting where it is desirable to
stabilize the walls of the shaft 2300 as it is deepened. When the
shaft 2300 is deep enough to accommodate a ring-shaped segmental
portion ("segment") 2302 of lining, panels 2304 similar to panel
2204 in FIG. 22 are lowered into the shaft 2300 and assembled into
a segment 2302. In Stage B, the shaft 2300 has been deepened
sufficiently to allow the emplacement of a second segment 2306. In
Stage C, the shaft 2300 has been deepened sufficiently to allow the
emplacement of a third segment 2308. In Stage D, shaft 2300 has
reached its desired final depth and an invert liner 2310 has been
constructed (e.g., by conventional concrete forming or by segmented
assembly). In Stage E, an impermeable liner 2312 (e.g. one
including or consisting essentially of metal and/or plastic) has
been emplaced in the shaft 2300. The impermeable liner 2312 may be
emplaced by the method of segmental assembly depicted in FIG. 18 or
by other methods such as direct attachment to the cavity liner
2304, 2306, 2308, 2310. Because the impermeable liner 2312 may be
attached to the cavity liner, it does not need to support its own
weight as in FIG. 14 and FIG. 18, thus the liner may consist of a
thin steel sheet (e.g. stainless steel sheet metal) or of a plastic
(e.g., one or more polymeric materials) liner connected (e.g.,
welded and/or bonded) together to be impermeable to gas. In fact,
the liner 2312 may not be "self-supporting," i.e., the liner, being
supported by other materials (e.g., the cavity liner) during
assembly, may be of insufficient thickness and/or strength to
support itself in the absence of such support material(s). Thus, in
the absence of such materials, the assembled liner would, at least
to some extent, lose structural stability due to the force of its
own weight.
[0246] Plastic liners may include or consist essentially of
pre-manufactured sheets or plates of polymer material (e.g.,
approximately 10 mm thick) that are welded or melted together in
situ to form a liner, or of liners constructed in situ by spraying
or painting, or by other means (e.g., in situ inflation and
emplacement of a liner manufactured elsewhere). Pre-manufactured
sheet-type polymer liners may include or consist essentially of
thermoplastics such as polypropylene and high-density polyethylene.
Spray-on liners may include or consist essentially of thermosetting
plastics such as epoxy and polyurethane. Liners may also consist of
sandwich or composite materials, e.g., a combination of
polyurethane for flexibility and glass-fiber reinforced epoxy for
high strength and chemical resistance.
[0247] In Stage F, additional material 2314 such as a reinforced
concrete plug (not shown), additional concrete, and overfill has
been emplaced over the liner 2312. The additional material 2314 may
additionally include a plug (not shown) that may extend into the
surrounding rock and may serve as or separately consist of a plug
to distribute upward pressure forces from the dome of the liner
2312, in part or entirely. In other stages of the illustrative
construction process depicted in FIG. 23, other components, not
shown, may be added, including piping for the introduction and
extraction of fluids, pumps, wiring for power and telemetry, spray
heads, and other components.
[0248] FIG. 24A is a cross-sectional schematic representation of
portions of a lined underground reservoir system 2400. System 2400
includes a lined cavity 2402, a lining 2404 including or consisting
essentially of concrete and possibly other materials (e.g., metal
mesh and/or rebar, shotcrete, piping), a plug or pressure barrier
2406 that resists expansive forces exerted by pressurized fluids
within cavity 2402, a first piping 2408 for injecting gas into and
removing gas from cavity 2402, a second piping 2410 for injecting a
heat-exchange fluid 2412 (e.g., liquid, foam) into cavity 2402 in
order to thermally condition fluids within cavity 2402, a third
piping 2414 through which settled fluid 2416 may be extracted from
the cavity 2402, and an infill barrier zone 2418. It is desirable
that the large forces produced by high-pressure fluids within the
cavity 2402 be distributed widely through the rock mass 2422 as
well as potentially through the infill barrier 2418. For example,
for a cylindrical cavity 2402 with a diameter of 10 meters, filled
with gas at 3,000 psi, a total outward-acting force of
6.9.times.10.sup.8 pounds is exerted on the upper domed portion of
the cavity 2402 alone. The uplift and distortion of rock 2422
caused by such forces preferably remains within acceptable limits.
In some designs, the infill barrier zone 2418 may be used for other
purposes, such as storage of water or equipment. In others, the
infill barrier zone 2418 may be filled with various materials to
aid in resistance of the force from the pressurized cylindrical
cavity 2402. The weight and/or mechanical strength of the infill
barrier 2418 contributes to the resistance of expansive forces
exerted by pressurized fluid within cavity 2402. Also, the
mechanical strength of the infill barrier 2418 and the mechanical
strength of the plug 2406 support the weight of the barrier 2418
and plug 2406 during operating conditions when the cavity 2402
contains fluid at relatively low pressure (e.g., atmospheric
pressure), and thus prevent the cavity 2402 from collapsing. In
various embodiments, the plug 2406 includes or consists essentially
of concrete or reinforced concrete. In the illustrative embodiment
depicted in FIG. 24A, the plug 2406 is approximately circular in
transverse cross section (not depicted) and trapezoidal in the
longitudinal cross section depicted in FIG. 24A. When the cavity
2402 is filled, the wider, upper side of the trapezoidal
cross-section tends to transmit forces into the body of the
surrounding rock mass 2422. Transmission of forces from the cavity
2402 into the rock mass 2422, and the influence of an illustrative
plug 2406 on such transmission, will be depicted in FIG. 24C and
FIG. 24D.
[0249] FIG. 24B is a cross-sectional schematic representation of
portions of the illustrative lined underground reservoir system
2400 in FIG. 24A, with the distinction that the plug 2424 has a
hexagonal longitudinal cross-section rather than a trapezoidal
cross section like that of the plug 2406 in FIG. 24A. Depending on
the mechanical properties of the rock mass 2422 and on the
dimensions of the plugs 2406, 2424, the plug design of FIG. 24B may
distribute forces through a larger volume of the rock mass 2422
than the plug design of FIG. 24A.
[0250] A range of materials may be used for the infill barrier
2418: e.g., the infill barrier 2418 may include or consist
essentially of rock tailings produced during the excavation of the
shaft holding system 2400, or of such rock tailings mixed or
grouted with a binding agent (e.g., cement), or of concrete, or of
reinforced concrete. Although infill barrier 2418 is represented in
FIG. 24A and FIG. 24B as a uniform mass of material, in various
embodiments (not depicted) infill barrier 2418 may be a
heterogeneous mass of materials (e.g., crushed rock; metal;
concrete; reinforced concrete; other) structured in a manner that
supports the weight of the infill 2418 itself, resists deformation
by expansive forces from the cavity 2402, and/or partially
transmits forces of weight and/or fluid pressure to the surrounding
rock mass 2422. For example, the infill barrier may include or
consist essentially of a series of layers or cylindrical plugs of
grouted rock fragments alternating with trapezoidal or hexagonal
plugs peripherally embedded in the rock mass 2422 in a manner
similar to that of the plugs 2406 and 2424. Force-transmitting
extensions of metal, concrete, and other materials may be extended
from the mass of any plug or portion of the infill barrier 2418 to
the surrounding rock mass. In general, a more-even distribution of
forces over the widest feasible bulk of material overlying the
cavity 2402 will allow for acceptable mitigation of
pressure-induced deformations at the lowest possible total shaft
depth; this in turn will reduce system costs. The infill barrier
2418 may extend to the ground surface or some distance below it.
The space above the infill barrier may be filled with liquid or
used to house equipment, including compressor/expanders or other
gas processing facilities.
[0251] The depth at which cavity 2402 is located beneath the
earth's surface, the temperatures of the fluids stored within the
cavity 2402 at various times, and the nature of the layering
materials with which the cavity 2402 is surrounded (e.g.,
insulating, non-insulating), are among the factors that may
influence the exchange of thermal energy between the contents of
cavity 2402 and the surrounding rock 2422. Since the mass of the
Earth is effectively infinite compared to the mass of the contents
of cavity 2402, the temperature-depth gradient of rock mass 2422
will tend to retain its undisturbed, natural value away from the
immediate vicinity of the lined underground reservoir 2400.
Therefore, if the cavity 2402 is not lined with an effective
insulator, exchange of heat between the contents of cavity 2402 and
the rock 2422 may constitute either (a) a path of net energy loss
for system 2400, i.e., if the contents of the cavity 2402 are
warmer on average than surrounding rock 2422, or (b) a path of net
energy gain for system 2400, if the contents of the cavity 2402 are
cooler on average than the rock 2422. For example, an adiabatic
compressed-air energy storage system with stored air cycled (stored
and released) daily with a maximum storage pressure of 5 MPa (725
psi) and a constant air injection temperature of 21.5.degree. C.
may experience approximately 3.3% thermal energy loss. For a
relatively deep cavity 2402, and/or relatively cool fluid contents
of cavity 2402, and/or a locally steep temperature/depth gradient,
this relationship may be reversed: i.e., the system 2400 may
function not only as a system for storing energy, but also as a
harvester of geothermal energy. The ability of any particular
embodiment to function partly as a harvester of geothermal energy
may depend on depth, construction materials, fluid operating
temperatures, operational cycling, and/or local geothermal
conditions, among other factors. The concrete used in the lined
underground reservoir walls may be of an insulating type having a
the thermal conductivity less than a standard concrete mixture,
decreasing the rate of exchange between the surrounding rock 2422
and the fluid within the cavity 2402. The insulating concrete may
be located throughout or only at certain layers such as closest to
the surrounding rock 2422. Examples of insulating concrete include
cellular concretes (e.g., where air voids are incorporated into
concrete) and aggregate concretes (e.g., concrete made with
insulating aggregates such as expanded perlite, vermiculate, and/or
polystyrene pellets). Physical properties of insulating concrete
vary according to mix designs, with lower density typically
corresponding to higher insulating value. Insulating concretes may
have thermal conductivities on the order of 2 to 10 times lower
than a non-insulating concrete (where heavyweight non-insulating
concrete may have a thermal conductivity exceeding 1 W/m-K). Thus,
the thermal conductivity of insulating concrete utilized in various
embodiments of the invention may be between approximately 0.1 W/m-K
and approximately 0.5 W/m-K. Insulating layers (not shown) of other
materials (e.g., polyurethane foam) may also be applied interior or
exterior to the cavity 2402, decreasing the rate of exchange
between the surrounding rock 2422 and the fluid with the cavity
2402.
[0252] FIG. 24C is a cross-sectional schematic representation of
portions of an illustrative lined underground reservoir system 2400
like that of FIG. 24A, with the distinction that the plug 2406
depicted in FIG. 24A is absent. In FIG. 24C, illustrative forces
acting on select points in the material above the cavity 2402 are
indicated by arrows. In the state of operation depicted in FIG.
24C, the cavity 2402 is filled with a pressurized gas and a
potential failure mode of the system 2400 is uplift of the material
overlying the cavity 2402. Also, the rock 2422 surrounding the
cavity 2402 is presumed, for this illustrative system, to be so
rigid and so horizontally extensive that any purely lateral
shifting of the rock 2422 by the pressurized contents of cavity
2402 is insignificant. Any displacement of rock 2422 and infill
2418 is, therefore, presumed to occur within a volume centered
above the cavity 2402 and taking, roughly, the form of an inverted
truncated cone with curving sides 2430 indicated by dashed lines.
This volume is herein also termed "the cone." The upper base of the
cone is an area 2428 on the surface and centered above the cavity
2402. The lower base (not indicated in FIG. 24C) of the inverted
cone is a horizontal surface area directly above the cavity 2402.
Shearing (slippage between two portions of a body of material) will
typically tend to occur in the rock 2422 along the surface 2430 if
sufficient upward force is exerted by the pressurized contents of
cavity 2402.
[0253] Given the finite flexibility of real (i.e., not idealized)
earth material, some degree of uplift or doming of the area
2428--though preferably no shearing along surface 2430--may occur
in any real-world setting. Such doming is deemed acceptable if it
does not damage components of the system 2400, either immediately
or over repeated fill-and-empty cycles; such doming is deemed
unacceptable if it destroys components of the system 2400 or
shortens their working lifespan significantly. The system 2400 is
preferably designed, therefore, to contain the upward-acting forces
2432 generated by the pressurized contents of cavity 2402 not only
to the extent that catastrophic failure of the cavity 2402 (i.e.,
breakthrough of gas to the surface, or explosion of part or all of
the overlying area 2428) is practically impossible, but, further,
to the extent that the longevity of system 2400 is not
compromised.
[0254] In the absence of an advantageously shaped top-plug, as
depicted in FIG. 24C, forces 2432 exerted by the contents of cavity
2402 act vertically and laterally throughout the volume of the cone
having curved lateral surface 2430. Directly above the cavity 2402,
a substantially vertical force 2434 is exerted upon the infill
2418. Elsewhere within the cone, angled forces 2436 (i.e., forces
having both horizontal and vertical components) are exerted within
the infill 2418 and rock 2422. At a given depth above the cavity
2402, the magnitude of both the vertical force 2434 and the angled
forces 2436 depends primarily on the magnitude of the force 2432
exerted by the contents of cavity 2402 and on the width, at the
given depth, of the cone.
[0255] FIG. 24D is a cross-sectional schematic representation of
portions of the illustrative lined underground reservoir system
2400 in FIG. 24A, including the plug 2406 having a trapezoidal
cross section. The primary effect of the plug 2406, with respect to
the transmission of forces throughout the rock 2422 and infill
2418, is to broaden both the lower and upper bases of the inverted,
truncated cone described above with regard to FIG. 24C Likewise,
the plug 2406 may transmit nearly all the uplift force to the rock
2422 with little force transmitted to the infill 2418. As a result,
at any given depth the vertical force 2434 is much smaller in
magnitude and the angled forces are widely distributed throughout
the rock 2422. In general, the upward forces 2432 originated at the
top of the cavity 2402 are spread over a larger area, at any given
depth, than for the plugless system depicted in FIG. 24C. This
relative transmission and dissipation of force at a given depth is
indicated by the greater number of the force arrows (2434, 2436) in
FIG. 24D, compared to those in FIG. 24C. Doming of area 2428 is
lessened, shearing along surface 2430 is rendered less likely, and,
in general, damage to or failure of components of system 2400 as a
result of material displacement within or above the cone is
rendered less likely. The force-spreading effect of the plug 2406,
or, in various other embodiments, a plug of some other form (e.g.,
plug 2424 of FIG. 24B), may thus be used to (a) increase the safety
factor of the system 2400, (b) enable a cavity 2402 at a certain
depth to store fluid at a higher peak pressure than would be
feasible without the plug 2424, (c) enable a cavity 2402 storing
fluid at a given peak pressure to be constructed at a lesser depth
(and therefore more economically) than would be feasible without
the plug 2424, or (d) some combination of two or more of (a), (b),
and (c).
[0256] Plugs (pressure barriers) of orientations or cross-sectional
forms different from those illustratively depicted in FIG. 24A,
FIG. 24B, and FIG. 24D are also contemplated and in some cases may
be more effective than those depicted. For example, the pressure
barrier 2406 of FIG. 24A might be constructed, in various
embodiments, with a smoothly curved surface (e.g., a surface
protruding into the surrounding rock at one or more points).
[0257] FIG. 25 is a cross-sectional schematic representation of
portions of an illustrative energy storage and generation system
2500 that includes a lined underground reservoir 2502. The lined
underground reservoir 2502 is similar to that depicted in FIG. 9C,
albeit with certain differences. The system 2500 includes a power
system 2504, which may resemble systems shown and described in the
'207 patent and the '155 patent, for the interconversion of
electrical, thermal, and elastic potential energy. Primarily, the
power system 2504 (a) interconverts electricity with the elastic
potential energy of gas expanded and/or compressed at approximately
constant temperature (i.e., isothermally) and (b) interconverts the
thermal energy of gas and/or a heat-exchange liquid with the
elastic potential energy of gas to be expanded and/or compressed.
Herein, the system 2504 is termed an "isothermal power system."
Bodies of heat-exchange liquid (or liquids) may be employed both
for the exchange of heat with gas stored in the reservoir 2502 and
as thermal reservoirs (i.e., thermal wells); in various other
embodiments, they may be employed additionally or alternatively as
reservoirs of gravitational potential energy. It may be desirable,
in various circumstances (e.g., installation in an urban area) to
minimize the surface area occupied by facilities associated with
system 2500; in such circumstances, the isothermal power system
2504 may be located, as in system 2500, in a chamber 2506 beneath
the surface of the ground. Chamber 2506 may be excavated during the
excavation of reservoir 2502 through upper, middle, and lower
access tunnels 2508, 2510, and 2512, and access to the isothermal
power system 2504 may be maintained through upper access tunnel
2508. Since the lower ends of sloping access tunnels 2510 and 1512
are sealed by plugs 2514 to prevent fluids from escaping reservoir
2502, heat-exchange liquid 2516 may be stored in the portions of
the lower access tunnel 2512 and middle access tunnel 2510. The
isothermal power system 2504 may add liquid to or extract liquid
from the tunnels 2510, 2512 through piping 2518. In the system
2500, all major components--power system, liquid storage, and gas
storage--are located underground, out of sight. Moreover, an energy
storage and retrieval system thus located would be to a large
extent safeguarded from natural forces, accidents, and deliberate
attack. The power system 2504 may also be a gas processing facility
or other energy storage power unit.
[0258] Storage of a volume of heat-exchange liquid may also be
achieved in various other embodiments without use of surface
vessels for liquid storage. FIG. 26 is a cross-sectional schematic
representation of portions of a lined underground reservoir system
2600 that is similar in most respects to lined underground
reservoir system 2400 of FIG. 24A, with the distinction that
instead of a solid infill barrier 2418 (FIG. 24A), the shaft of
system 2600 is infilled with a reservoir 2620 of heat-exchange
liquid on top of the plug 2606. Also, system 2600 is equipped with
piping 2622 for the addition of liquid to and subtraction of liquid
from the reservoir 2620.
[0259] If the lining surrounding the inner cavity of a lined
underground reservoir storage system is of sufficient strength,
infilling may be dispensed with, and the lined portion of the
storage system may protrude above the surface of the ground. FIG.
27 is a schematic representation of portions of an illustrative
embodiment of the invention in which the lined portion of the
storage system protrudes above the surface of the ground. LUR
system 2700 is disposed at least partially within a vertical,
artificial cavern or shaft 2702, typically but not necessarily
circular in cross-section, which may be part of a larger system
(not shown) for the storage and recovery of energy.
[0260] In various embodiments, system 2700 is a recessed LUR
containing fluid that may be pressurized and/or heated.
Pressurization of the fluid enables the storage of elastic
potential energy; heating of the fluid enables the storage of
thermal energy; and a stored fluid may be both pressurized and
heated. Shaft 2702 may be lined with an impermeable material that
prevents leakage of fluids into or out of the shaft 2702; the
material may also act as a thermal insulator. Alternatively or
additionally, shaft 2702 may be lined with a distinct layer that
acts primarily as a thermal insulator.
[0261] In the illustrative embodiment depicted in FIG. 27, shaft
2702 is vertical and circular in cross-section. As the shaft 2702
is sunk, a liner 2704 (which includes or consists essentially of
reinforced concrete such as in a pre-stressed concrete storage
vessel and/or some other material) for the interior wall of the
shaft 2702 may be installed in a series of rings, each ring being
added below previous rings as the excavating machine increases the
depth of the bore by a suitable amount. The inner and/or outer
surface of the liner 2704 may be coated with one or more coatings
or additional layers of material (not shown in FIG. 27), which may
serve to prevent leakage of fluid into or out of the shaft 2702, to
preserve the liner 2704 from corrosion or degradation, to thermally
insulate the shaft 2702 from the surrounding earth 2706, or more
perform two or more of these functions. In general, a shaft 2702 of
greater depth and/or radius will be capable of storing more thermal
and elastic potential energy than a shaft 2702 of smaller depth
and/or radius.
[0262] Additionally, a cap or dome 2708 is connected to the top of
the shaft 2702 and liner 2704 in order to produce a sealed recessed
storage reservoir. Cap 2708 may include or consist essentially of
reinforced concrete and/or one or more other durable materials and,
like the liner 2704 of shaft 2702, may be coated with one or more
coatings or additional layers of material (not shown in FIG. 27),
interiorly and/or exteriorly, that may serve to seal, protect, or
insulate the cap 2708.
[0263] In the illustrative embodiment depicted in FIG. 27,
reservoir 2700 contains an accumulation of fluid (e.g., foam or
liquid) 2710 and gas 2712. The gas 2712 occupies the portion of
shaft 2702 not occupied by non-gaseous fluid 2710. The contents of
reservoir 2700 may be at high pressure (e.g., 3,000 psig) and
relatively high temperature (e.g., 60.degree. C.).
[0264] Piping 2714 passes through cap 2708 (or, in various other
embodiments, some portion of the liner 2704 of reservoir 2700) and
extends to near the bottom of the shaft 2702. A pump 2716 is
capable of drawing fluid 2710 into piping 2714 and expelling the
fluid from the shaft 2702. Power, control, and data cables (not
shown) may also enter reservoir 2700, enabling the control and
operation of pump 2716 and communication with sensors (not shown)
inside shaft 2702 that provide information to operators of
reservoir 2700 on various physical variables, e.g., pressure and
temperature of the fluid contents of reservoir 2700 and depth of
fluid 2710.
[0265] Fluid expelled from reservoir 2700 by pump 2716 may be
directed via piping 2718 to reservoirs, cylinders, or other
components of an energy storage and recovery system (not shown), or
may be directed via piping 2720 to a spray head or nozzle (not
explicitly shown) for the generation of a foam or droplet spray
2722 within the gas-filled portion of reservoir 2700. The foam or
droplet spray 2722 may exchange heat with the fluids inside
reservoir 2700. In various embodiments, fluid passing through
piping 2720 is additionally passed through pumps, valves, heat
exchangers, and other devices (not shown) before being returned to
the interior of reservoir 2700. Additional piping 2724 allows the
addition to or removal from reservoir 2700 of gas 2712.
[0266] FIG. 28 is a schematic representation of portions of another
illustrative embodiment of the invention. Recessed reservoir 2800
is at least partially disposed within a vertical, artificial cavern
or shaft 2802, typically but not necessarily circular in
cross-section, and may be part of a larger system (not shown) for
the storage and recovery of energy. Shaft 2802 may be constructed
by means similar to shaft 2702 in FIG. 27, and may be lined in a
manner similar to shaft 2702 in FIG. 27.
[0267] A liner 2804 (which may include or consist essentially of,
e.g., reinforced concrete and steel and/or other durable materials)
within the interior wall of the shaft 2802 may be installed to
construct a recessed reservoir capable of holding fluids at high
pressure and/or at elevated temperature, as described with respect
to FIG. 27. Liquid may be separated from the gaseous component
prior to storage by a separator (e.g., a gravity separator), not
shown, prior to delivery at elevated pressure into shaft 2802.
Liquid at high pressure and/or elevated temperature may be
delivered via a pipe 2820 to a secondary containment unit 2814 as
illustrated in FIG. 28. This secondary containment unit 2814 may be
at higher elevation than the bottom of the vertical shaft 2802. The
secondary containment unit may be an open container within the
liner 2804 as illustrated in FIG. 28, or may be a separate pressure
vessel or vertical shaft at a higher elevation or above ground
level. By keeping the liquid portion of the storage at higher
elevation (closer to the elevation of the ground level), lower
power (and energy) may be required to pump the liquid into and out
of reservoir 2800. (That is, the vertical distance (head) is less
between the ground level and secondary reservoir 2814 than between
the ground level and the bottom of the vertical shaft 2802).
[0268] The separated high pressure and/or elevated temperature gas
may be delivered to shaft 2802 via a pipe 2824. Liquid 2810 and
2830 may be removed from shaft 2802 via pumps 2816 and 2836. Pump
2836 will generally consume less power to pump the liquid 2830 (at
least as a function of volume of liquid pumped) than will pump 2816
to pump liquid 2810, as the vertical distance from liquid 2830 to
the ground surface is much less. Thus, in preferred embodiments of
the invention, most or substantially all of the liquid in shaft
2802 is directed to secondary containment 2814, with only a
fraction of the liquid being at the bottom of shaft 2802.
[0269] Fluid expelled from shaft 2802 by pump 2816 and from
secondary containment 2814 by pump 2836 may be directed via piping
2818 to reservoirs, cylinders, or other components of an energy
storage and recovery system (not shown), or may be directed via to
a spray head or nozzle for the generation of a foam or droplet
spray 2822 within the gas-filled portion of shaft 2802 and/or
secondary containment 2814 (spray or foam in containment 2814 is
not shown). The foam or droplet spray 2822 may exchange heat with
the fluids inside shaft 2802 and/or secondary containment 2814. In
various embodiments, fluid passing through piping 2818 is
additionally passed through pumps, valves, heat exchangers, and
other devices (not shown) before being returned to the interior of
shaft 2802. Additional piping 2824 allows the addition to or
removal from shaft 2802 of gas 2812.
[0270] Generally, the systems described herein featuring IPVs, LURs
and/or recessed reservoirs may be operated in both an expansion
mode and in compression mode as part of a full-cycle energy storage
system with high efficiency. For example, the systems described
herein may be operated so as to efficiently (e.g., substantially
isothermally) store pressure and thermal potential energy delivered
from an energy storage system and possibly from other sources as
well, or so as to efficiently deliver to the energy storage system
pressure and thermal potential energy stored within the systems
described herein.
[0271] Heat-exchange liquid may be caused to exchange heat with
pressurized gas in a lined underground reservoir or IPV by several
methods, e.g., bringing the heat-exchanged fluid and pressurized
gas into direct contact with each other or by employing a
non-mixing heat exchanger that permits the liquid and gas to
exchange heat through impermeable, heat-conductive barriers. If
heat-exchange liquid is brought into contact with pressurized gas
for the purpose of exchanging heat, it is in general preferable
that the heat-exchange liquid be divided into droplets or mixed
with the gas in the form of a foam in order to increase surface
area over which the gas and liquid may exchange heat; or, if the
volume of liquid is large relative to the volume of gas, the gas
may be bubbled through the liquid to increase the surface area of
contact. Lower cost for a given rate of heat exchange between
bodies of liquid and gas is generally achieved by bringing the
liquid and gas into direct contact with each other.
[0272] Gas stored in lined underground reservoirs or IPVs may be
thermally conditioned either in situ, that is, within the reservoir
or IPV, or in external devices (e.g., sprayers, bubblers, or heat
exchangers located in a facility on the surface of the earth). It
is generally preferable, for in situ thermal conditioning, that the
heat-exchange liquid and stored gas be brought into direct contact
with each other by spraying or foaming the heat-exchange liquid
into the stored gas. Alternatively or additionally, heat-exchange
fluid may be mixed with stored gas in order to maintain the gas at
an approximately constant temperature as it is expanded in, e.g.,
cylinder. That is, approximately isothermal expansion of the gas
may be achieved by mixing of heat-exchange liquid at an appropriate
rate and temperature, as droplets or the liquid component of a
foam, with the gas. Thermal conditioning of a gas may occur during
compression of the gas, storage of the gas, or expansion of the
gas.
[0273] FIGS. 29-32 schematically depict several illustrative
methods for thermally conditioning gas released from a lined
underground reservoir, IPV, or other reservoir as or before the gas
is expanded in a cylinder.
[0274] FIG. 29 is a schematic diagram showing components of a
system 2900 for achieving approximately isothermal compression and
expansion of a gas for energy storage and recovery using a
pneumatic cylinder 2902 (shown in partial cross-section) according
to embodiments of the invention. The cylinder 2902 typically
contains a slidably disposed piston 2904 that divides the cylinder
2902 into two chambers 2906, 2908. A reservoir 2910, which may
consist essentially of one or more pressure vessels and/or one or
more IPVs, and/or one or more LURs, contains gas at high pressure
(e.g., 3,000 psi); the reservoir 2910 may also contain a quantity
of heat-exchange liquid 2912. The heat-exchange liquid 2912 may
contain an additive that increases the liquid's tendency to foam
(e.g., by lowering the surface tension of the liquid 2912).
Additives may include surfactants (e.g., sulfonates), a
micro-emulsion of a lubricating fluid such as mineral oil, a
solution of agents such as glycols (e.g., propylene glycol), or
soluble synthetics (e.g., ethanolamines). Foaming agents such as
sulfonates (e.g., linear alkyl benzene sulfonate such as Bio-Soft
D-40 available from Stepan Company of Illinois) may be added, or
commercially available foaming concentrates such as firefighting
foam concentrates (e.g., fluorosurfactant products such as those
available from ChemGuard of Texas) may be used. Such additives tend
to reduce liquid surface tension of water and lead to substantial
foaming when sprayed. Commercially available fluids may be used at
an approximately 5% solution in water, such as Mecagreen 127
(available from the Condat Corporation of Michigan), which consists
in part of a micro-emulsion of mineral oil, and Quintolubric 807-WP
(available from the Quaker Chemical Corporation of Pennsylvania),
which consists in part of a soluble ethanolamine. Other additives
may be used at higher concentrations (such as at a 50% solution in
water), including Cryo-tek 100/Al (available from the Hercules
Chemical Company of New Jersey), which consists in part of a
propylene glycol. These fluids may be further modified to enhance
foaming while being sprayed and to speed defoaming when in a
reservoir.
[0275] A pump 2914 and piping 2916 may convey the heat-exchange
liquid to a device herein termed a "mixing chamber" 2918. Gas from
the reservoir 2910 may also be conveyed (via piping 2920) to the
mixing chamber 2918. Within the mixing chamber 2918, a
foam-generating mechanism 2922 combines the gas from the reservoir
2910 and the liquid conveyed by piping 2916 to create foam 2924 of
a certain grade (i.e., bubble size variance, average bubble size,
void fraction), herein termed Foam A, inside the mixing chamber
2918.
[0276] The mixing chamber 2918 may contain a screen 2926 or other
mechanism (e.g., source of ultrasound) to vary or homogenize foam
structure. Screen 2926 may be located, e.g., at or near the exit of
mixing chamber 2918. Foam that has passed through the screen 2926
may have a different bubble size and other characteristics from
Foam A and is herein termed Foam B (2928). In other embodiments,
the screen 2926 is omitted, so that Foam A is transferred without
deliberate alteration to chamber 2906.
[0277] The exit of the mixing chamber 2918 is connected by piping
2930 to a port in the cylinder 2902 that is gated by a valve 2932
(e.g., a poppet-style valve) that permits fluid from piping 2930 to
enter the upper chamber (air chamber) 2906 of the cylinder 2902.
Valves (not shown) may control the flow of gas from the reservoir
2910 through piping 2920 to the mixing chamber 2918, and from the
mixing chamber 2918 through piping 2928 to the upper chamber 2906
of the cylinder 2902. Another valve 2934 (e.g., a poppet-style
valve) permits the upper chamber 2906 to communicate with other
components of the system 2900, e.g., an additional separator device
(not shown), the upper chamber of another cylinder (not shown), or
a vent to the ambient atmosphere (not shown).
[0278] The volume of reservoir 2910 may be large (e.g., at least
approximately four times larger) relative to the volume of the
mixing chamber 2918 and cylinder 2902. Foam A and Foam B are
preferably statically stable foams over a portion or all of the
time-scale of typical cyclic operation of system 2900: e.g., for a
120 RPM system (i.e., 0.5 seconds per revolution), the foam may
remain substantially unchanged (e.g., less than 10% drainage) after
5.5 seconds or a time approximately five times greater than the
revolution time.
[0279] In an initial state of operation of a procedure whereby gas
stored in the reservoir 2910 is expanded to release energy, the
valve 2932 is open, the valve 2934 is closed, and the piston 2904
is near top dead center of cylinder 2902 (i.e., toward the top of
the cylinder 2902). Gas from the reservoir 2910 is allowed to flow
through piping 2920 to the mixing chamber 2918 while liquid from
the reservoir 2910 is pumped by pump 2914 to the mixing chamber
2918. The gas and liquid thus conveyed to the mixing chamber 2918
are combined by the foam-generating mechanism 2922 to form Foam A
(2924), which partly or substantially fills the main chamber of the
mixing chamber 2918. Exiting the mixing chamber 2918, Foam A passes
through the screen 2926, being altered thereby to Foam B. Foam B,
which is at approximately the same pressure as the gas stored in
reservoir 2910, passes through valve 2932 into chamber 2906. In
chamber 2906, Foam B exerts a force on the piston 2904 that may be
communicated to a mechanism (e.g., an electric generator, not
shown) external to the cylinder 2902 by a rod 2936 that is
connected to piston 2904 and that passes slideably through the
lower end cap of the cylinder 2902.
[0280] The gas component of the foam in chamber 2906 expands as the
piston 2904 and rod 2936 move downward. At some point in the
downward motion of piston 2904, the flow of gas from reservoir 2910
into the mixing chamber 2918 and thence (as the gas component of
Foam B) into chamber 2906 may be ended by appropriate operation of
valves (not shown). As the gas component of the foam in chamber
2906 expands, it will tend, unless heat is transferred to it, to
decrease in temperature according to the Ideal Gas Law; however, if
the liquid component of the foam in chamber 2906 is at a higher
temperature than the gas component of the foam in chamber 2906,
heat will tend to be transferred from the liquid component to the
gas component. Therefore, the temperature of the gas component of
the foam within chamber 2906 will tend to remain constant
(approximately isothermal) as the gas component expands.
[0281] When the piston 2904 approaches bottom dead center of
cylinder 2902 (i.e., has moved down to approximately its limit of
motion), valve 2932 may be closed and valve 2934 may be opened,
allowing the expanded gas in chamber 2906 to pass from cylinder
2902 to some other component of the system 2900, e.g., a vent or a
chamber of another cylinder for further expansion.
[0282] In some embodiments, pump 2914 is a variable-speed pump,
i.e., may be operated so as to transfer liquid 2912 at a slower or
faster rate from the reservoir 2910 to the foam-generating
mechanism 2922 and may be responsive to signals from the control
system (not shown). If the rate at which liquid 2912 is transferred
by the pump 2914 to the foam-mechanism 2922 is increased relative
to the rate at which gas is conveyed from reservoir 2910 through
piping 2920 to the mechanism 2922, the void fraction of the foam
produced by the mechanism 2922 may be decreased. If the foam
generated by the mechanism 2922 (Foam A) has a relatively low void
fraction, the foam conveyed to chamber 2906 (Foam B) will generally
also tend to have a relatively low void fraction. When the void
fraction of a foam is lower, more of the foam consists of liquid,
so more thermal energy may be exchanged between the gas component
of the foam and the liquid component of the foam before the gas and
liquid components come into thermal equilibrium with each other
(i.e., cease to change in relative temperature). When gas at
relatively high density (e.g., ambient temperature, high pressure)
is being transferred from the reservoir 2910 to chamber 2906, it
may be advantageous to generate foam having a lower void fraction,
enabling the liquid fraction of the foam to exchange a
correspondingly larger quantity of thermal energy with the gas
fraction of the foam.
[0283] All pumps shown in subsequent figures herein may also be
variable-speed pumps and may be controlled based on signals from
the control system. Signals from the control system may be based on
system-performance (e.g., gas temperature and/or pressure, cycle
time, etc.) measurements from one or more previous cycles of
compression and/or expansion.
[0284] Embodiments of the invention increase the efficiency of a
system 2900 for the storage and retrieval of energy using
compressed gas by enabling the surface area of a given quantity of
heat-exchange liquid 2912 to be greatly increased (with
correspondingly accelerated heat transfer between liquid 2912 and
gas undergoing expansion or compression within cylinder 2902) with
less investment of energy than would be required by alternative
methods of increasing the surface of area of the liquid, e.g., the
conversion of the liquid 2912 to a spray.
[0285] In other embodiments, the reservoir 2910 is a separator
rather than a high-pressure storage reservoir as depicted in FIG.
29. In such embodiments, piping, valves, and other components not
shown in FIG. 29 are supplied that allow the separator to be placed
in fluid communication with a high-pressure gas storage reservoir
as well as with the mixing chamber 2918, as shown and described in
the '128 application.
[0286] FIG. 30 is a schematic diagram showing components of a
system 3000 for achieving approximately isothermal compression and
expansion of a gas for energy storage and recovery using a
pneumatic cylinder 3004 (shown in partial cross-section) according
to embodiments of the invention. System 3000 is similar to system
2900 in FIG. 29, except that system 3000 includes a bypass pipe
3038. Moreover, two valves 3040, 3042 are explicitly depicted in
FIG. 30. Bypass pipe 3038 may be employed as follows: (1) when gas
is being released from the storage reservoir 3010, mixed with
heat-exchange liquid 3012 in the mixing chamber 3018, and conveyed
to chamber 3006 of cylinder 3004 to be expanded therein, valve 3040
will be closed and valve 3042 open; (2) when gas has been
compressed in chamber 3006 of cylinder 3004 and is to be conveyed
to the reservoir 3010 for storage, valve 3040 will be open and
valve 3042 closed. Less friction will tend to be encountered by
fluids passing through valve 3040 and bypass pipe 3038 than by
fluids passing through valve 3042 and screen 3026 and around the
foam-generating mechanism 3022. In other embodiments, valve 3042 is
omitted, allowing fluid to be routed through the bypass pipe 3038
by the higher resistance presented by the mixing chamber 3018, and
valve 3040 is a check valve preventing fluid flow when gas is being
released in expansion mode. The direction of fluid flow from
chamber 3006 to the reservoir 3010 via a lower-resistance pathway
(i.e., the bypass pipe 3038) will tend to result in lower
frictional losses during such flow and therefore higher efficiency
for system 3000.
[0287] In various other embodiments, the reservoir 3010 is a
separator rather than a high-pressure storage reservoir as depicted
in FIG. 30. In such embodiments, piping, valves, and other
components not shown in FIG. 30 are supplied that allow the
separator to be placed in fluid communication with a high-pressure
gas storage reservoir as well as with the mixing chamber 3018 and
bypass pipe 3038.
[0288] FIG. 31 is a schematic diagram showing components of a
system 3100 for achieving approximately isothermal compression and
expansion of a gas for energy storage and recovery using a
pneumatic cylinder 3102 (shown in partial cross-section) according
to embodiments of the invention. System 3100 is similar to system
2900 in FIG. 29 except that system 3100 omits the mixing chamber
2918 and instead generates foam inside the storage reservoir 3110.
In system 3100, a pump 3114 circulates heat-exchange liquid 3112 to
a foam-generating mechanism 3122 (e.g., one or more spray nozzles)
inside the reservoir 3110. The reservoir 3110 may, by means of the
pump 3114 and mechanism 3122, be filled partly or entirely by foam
of an initial or original character, Foam A (3124). The reservoir
3110 may be placed in fluid communication via pipe 3120 with a
valve-gated port 3144 in cylinder 3102. Valves (not shown) may
govern the flow of fluid through pipe 3120. An optional screen 3126
(or other suitable mechanism such as an ultrasound source), shown
in FIG. 31 inside pipe 3120 but locatable anywhere in the path of
fluid flow between reservoir 3110 and chamber 3106 of the cylinder
3102, serves to alter Foam A (3124) to Foam B (3128), regulating
characteristics such as bubble-size variance and average bubble
size.
[0289] In other embodiments, the reservoir 3110 is a separator
rather than a high-pressure storage reservoir as depicted in FIG.
31. In such embodiments, piping, valves, and other components not
shown in FIG. 31 will be supplied that allow the separator to be
placed in fluid communication with a high-pressure gas storage
reservoir as well as with the cylinder 3102. In other embodiments,
a bypass pipe similar to that depicted in FIG. 30 is added to
system 3100 in order to allow fluid to pass from cylinder 3102 to
reservoir 3110 without passing through the screen 3126.
[0290] FIG. 32 is a schematic diagram showing components of a
system 3200 for achieving approximately isothermal compression and
expansion of a gas for energy storage and recovery using a
pneumatic cylinder 3202 (shown in partial cross-section) according
to embodiments of the invention. System 3200 is similar to system
2900 in FIG. 29, except that system 3200 omits the mixing chamber
2918 and instead generates foam inside the air chamber 3206 of the
cylinder 3202. In system 3200, a pump 3214 circulates heat-exchange
liquid 3212 to a foam-generating mechanism 3222 (e.g., one or more
spray nozzles injecting into cylinder and/or onto a screen through
which admitted air passes) either located within, or communicating
with (e.g., through a port), chamber 3206. The chamber 3206 may, by
means of the pump 3214 and mechanism 3222 (and by means of gas
supplied from reservoir 3210 via pipe 3220 through a port 3244), be
filled partly or substantially entirely by foam. The reservoir 3210
may be placed in fluid communication via pipe 3220 with valve-gated
port 3244 in cylinder 3202. Valves (not shown) may govern the flow
of fluid through pipe 3220.
[0291] FIG. 33A is a plot of relationships between stress range (in
this case, referring to fluid storage pressure) and lifespan cycle
number for an illustrative LUR system utilized as a facility for
storage of compressed air, herein referred to as the "Demo Plant."
The Demo Plant resembles system 900 in FIGS. 9A and 9B and has a
volume of 40,000 m.sup.3. Herein, a "cycle" is complete filling of
an empty storage vessel to a specified storage pressure (e.g.,
3,000 psi) followed by emptying of the vessel to a lower pressure
(e.g., 500 psi). The Demo Plant employs a cavity lining resembling
those shown in FIG. 14A, FIG. 14B, and FIG. 21D, and a design cycle
demand 3302 for the Demo Plant is to withstand 100 full operating
pressure cycles. In FIG. 33A, a [Steel] Fatigue Design Curve 3304
is based on the Eurocode 3 standard (i.e., "EN 1993--Eurocode 3:
Design of Steel Structures," European Committee for
Standardization, 2004, the entire disclosure of which is
incorporated by reference herein). The Design Stress Range 3306
(i.e., value of the maximum stress range sustainable by the steel
lining) is approximately 218 MPa. As FIG. 33A shows, the design
values of 218 MPa and 100 cycles were well below the Fatigue Design
Curve 3304. In fact, with a design stress range of 218 MPa, and
given the lifespan limitation imposed by the Fatigue Design Curve
3304, the Demo Plant operating life is estimated at nearly 40,000
cycles. In fact, the actual stress range (based on measured
rock-mass deformations) is estimated to be only approximately 73
MPa. With a stress range of 73 MPa, an Allowable Life 3310 would be
about one million cycles (2,700 years of operation, at the rate of
one full cycle per day). Thus, the longevity of lined underground
reservoirs employed as storage vessels for rapid-cycling,
large-scale storage of pressurized gasses (e.g., compressed air) is
likely, in practice, very long.
[0292] The geophysical properties of a given site may affect the
feasibility of constructing a lined underground reservoir at the
site. To rate the geological suitability of proposed lined
underground reservoir sites, a rock mass rating may be assigned to
the rock mass in which construction of a lined underground
reservoir is being considered. The rock mass rating system is a
geological classification system developed by Z. T. Bieniawski in
1973 and revised in 1989, and is tabulated in FIG. 33B.
[0293] FIG. 34 shows illustrative geological criteria for use in
early stages in site selection of a viable lined underground
reservoir for storage of pressurized fluids (e.g., air, natural
gas). A table 3402 shows a classification table for the Rock Mass
Rating (RMR) system shown in FIG. 33B, matching numerical RMR
values to rock quality. A plot 3404 shows the relationship between
RMR rating for a rock mass (horizontal axis) and maximum storage
pressure (vertical axis) of a lined underground reservoir storage
pressure constructed within the rock mass. The point 3406 shows the
rock-mass quality and storage pressure of the Demo Plant described
with reference to FIG. 33A. In the plot 3404, a first region 3408
of generally low rock quality and pressure above approximately 7
MPa generally does not permit the construction of a viable lined
underground reservoir; a second region 3410 of low-to-moderate rock
quality and low-to-high pressure may permit the construction of a
viable lined underground reservoir, but this is not certain; and a
third region 3412 of low-to-high rock quality and low-to-high
pressure does permit the construction of a viable lined underground
reservoir.
[0294] In FIG. 34, a dashed line 3414 indicates a substantially
linear boundary that approximately divides the region of possibly
or definitely nonfeasible RMR-pressure space from the region of
definitely feasible RMR-pressure space. The region of possibly or
definitely nonfeasible RMR-pressure space is to the left of the
dashed line 3412. The feasible region, to the right of dashed line
3412, is defined by the equation P.ltoreq.(RMR.times.0.83)-25,
where P is storage pressure in MPa (vertical axis) and RMR is the
horizontal axis.
[0295] FIG. 35 shows an illustrative plot of estimated construction
cost per lined underground reservoir (in units of MEUR, millions of
Euros, 2012 value) as a function of reservoir volume (in units of
m.sup.3) under two different conditions of local (overlying)
topography. Curve 3502 shows construction cost as a function of
reservoir volume for flat overlying topography (e.g., similar to
that depicted in FIG. 9B). Curve 3504 shows construction cost as a
function of reservoir volume for some high-relief overlying
topographies (e.g., similar to that depicted in FIG. 9C) that
permit minimal access-tunnel length. Flat topography requires, in
general, longer access tunnels (which cannot be made excessively
steep while still enabling access by standard construction
vehicles, e.g., cement trucks and drilling rigs) and therefore
longer construction time; high-relief topography may allow shorter
access tunnels and therefore shorter construction time (and thus
may enable lower construction cost). The data represented in FIG.
35 are based on utilization of the access-tunnel approach of, e.g.,
FIG. 9B, rather than the open-shaft approach of, e.g., FIGS.
21A-21D. The cost level reflects the approximately present European
market at time of filing; the accuracy of the estimates is believed
to be within .+-.20%.
[0296] FIG. 36 shows an illustrative plot of estimated construction
cost (in units of Euros, 2012 value) per cubic meter for lined
underground reservoirs of the same types referred to by FIG. 35.
Curve 3602 shows construction cost as a function of reservoir
volume for flat overlying topography (e.g., similar to that
depicted in FIG. 9B). Curve 3604 shows construction cost as a
function of reservoir volume for some high-relief overlying
topographies (e.g., similar to that depicted in FIG. 9C) that
permit minimal access-tunnel length.
[0297] FIG. 37 shows an illustrative plot of estimated construction
cost (in units of MEUR, millions of Euros, 2012 value) for a lined
underground reservoir of the same type referred to by FIG. 35 and
FIG. 36 as a function of reservoir volume (in units of m.sup.3),
broken out by cost for (a) installations, (b) concrete lining, (c)
steel lining, (d) underground reservoir construction, including
support and drainage, and (e) access tunnels.
[0298] FIG. 38 shows an illustrative plot of estimated construction
time (units of years) for a lined underground reservoir of the same
type referred to by FIG. 35 and FIG. 36 as a function of reservoir
volume (units of m.sup.3) under two different conditions of local
(overlying) topography. Curve 3802 shows construction time as a
function of reservoir volume for flat overlying topography (e.g.,
similar to that depicted in FIG. 9B). Curve 3804 shows construction
time as a function of reservoir volume for some high-relief
overlying topographies (e.g., similar to that depicted in FIG. 9C)
that permit minimal access-tunnel length.
[0299] Construction time for open-shaft-style construction of a
lined underground reservoir (e.g., as depicted in FIGS. 21A-21D)
may be as low as one-fifth that for access-tunnel-style
construction of a reservoir of comparable volume for small-scale
(e.g. 10,000 m.sup.3) high-pressure storage (e.g., 3000 psi). This
drastic difference in estimated construction time arises from the
rapidity with which a roadheader type shaft-excavating device or
other mechanized rock drilling machine such as that depicted FIG.
12A-12B can excavate a volume of rock as compared to excavation of
access tunnels and a cavity by the standard drill-blast-and-clear
method, which is comparatively slow, expensive, and hazardous to
workers. For large volume (e.g., 100,000 m.sup.3) LURs,
drill-and-blast techniques may proceed more rapidly than mechanized
excavating machines due to both better area/volume ratio and
quicker excavation.
[0300] In various embodiments of the invention, the heat-exchange
fluid utilized to thermally condition gas within one or more
cylinders and/or storage vessels (e.g., IPVs and/or recessed
storage reservoirs) incorporates one or more additives and/or
solutes, as described in U.S. Pat. No. 8,171,128, filed Apr. 8,
2011 (the '128 patent), the entire disclosure of which is
incorporated herein by reference. As described in the '128 patent,
the additives and/or solutes may reduce the surface tension of the
heat-exchange fluid, reduce the solubility of gas into the
heat-exchange fluid, and/or slow dissolution of gas into the
heat-exchange fluid. They may also (i) retard or prevent corrosion,
(ii) enhance lubricity, (iii) prevent formation of or kill
microorganisms (such as bacteria), and/or (iv) include an agent to
modify surface tension, as desired for a particular system design
or application.
[0301] Embodiments of the invention may, during operation, convert
energy stored in the form of compressed gas and/or recovered from
the expansion of compressed gas into gravitational potential
energy, e.g., of a raised mass, as described in U.S. patent
application Ser. No. 13/221,563, filed Aug. 30, 2011, the entire
disclosure of which is incorporated herein by reference.
[0302] Generally, the systems described herein may be operated in
both an expansion mode and in the reverse compression mode as part
of a full-cycle energy storage system with high efficiency. For
example, the systems may be operated as both compressor and
expander, storing electricity in the form of the potential energy
of compressed gas and producing electricity from the potential
energy of compressed gas. Alternatively, the systems may be
operated independently as compressors or expanders.
[0303] The terms and expressions employed herein are used as terms
of description and not of limitation, and there is no intention, in
the use of such terms and expressions, of excluding any equivalents
of the features shown and described or portions thereof, but it is
recognized that various modifications are possible within the scope
of the invention claimed.
* * * * *