U.S. patent application number 13/623075 was filed with the patent office on 2013-08-01 for compressed gas energy storage system using turbine.
This patent application is currently assigned to Light Sail Energy Inc.. The applicant listed for this patent is Light Sail Energy Inc.. Invention is credited to AmirHossein Pourmousa Abkenar, Edwin P. BERLIN, JR., Stephen E. Crane, Danielle A. Fong, Karl E. Stahlkopf.
Application Number | 20130192216 13/623075 |
Document ID | / |
Family ID | 47914837 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130192216 |
Kind Code |
A1 |
BERLIN, JR.; Edwin P. ; et
al. |
August 1, 2013 |
COMPRESSED GAS ENERGY STORAGE SYSTEM USING TURBINE
Abstract
An energy storage system utilizing compressed gas as a storage
medium, may include one or more turbines configured to convert
energy in gas expansion and compression processes. One or more
axial and centrifugal turbines may be used to store energy by
compressing gas, and to recover energy from expanding gas. A
plurality of orifices/nozzles may introduce a liquid into the gas
as a heat exchange medium. Orifices/nozzles may be disposed on
various surfaces of a turbine and/or in a separate mixing chamber
flowing to a turbine. Structures of the turbine may be designed to
mitigate damage caused by liquid injection, for example the turbine
blades may be flexible and/or comprise impact-resistant
materials.
Inventors: |
BERLIN, JR.; Edwin P.;
(Oakland, CA) ; Crane; Stephen E.; (Santa Rosa,
CA) ; Abkenar; AmirHossein Pourmousa; (Walnut Creek,
CA) ; Fong; Danielle A.; (Oakland, CA) ;
Stahlkopf; Karl E.; (Honolulu, HI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Light Sail Energy Inc.; |
Berkeley |
CA |
US |
|
|
Assignee: |
Light Sail Energy Inc.
Berkeley
CA
|
Family ID: |
47914837 |
Appl. No.: |
13/623075 |
Filed: |
September 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61536813 |
Sep 20, 2011 |
|
|
|
Current U.S.
Class: |
60/327 ;
60/413 |
Current CPC
Class: |
F01K 13/00 20130101;
F02C 6/16 20130101; F02C 6/003 20130101; Y02E 20/16 20130101; F05D
2260/212 20130101; F02C 1/05 20130101; F22B 1/1853 20130101; Y02E
60/15 20130101; Y02E 60/16 20130101; F05D 2260/42 20130101; F02C
3/30 20130101; Y02T 50/60 20130101; F01D 15/10 20130101; Y02T
50/676 20130101; Y02T 50/672 20130101 |
Class at
Publication: |
60/327 ;
60/413 |
International
Class: |
F01K 13/00 20060101
F01K013/00 |
Claims
1. A system to recover energy from compressed gas, the system
comprising: a compressed gas storage unit; a first chamber defined
within walls and in selective fluid communication with the
compressed gas storage unit to receive compressed gas; a first
airfoil configured to drive a rotor within the first chamber in
response to the compressed gas expanding in an absence of
combustion; and an element configured to effect gas-liquid heat
exchange with the expanding compressed gas.
2. A system as in claim 1 wherein the first airfoil and the rotor
within the first chamber define an axial turbine.
3. A system as in claim 1 wherein the first airfoil and the rotor
within the first chamber define a centrifugal turbine.
4. A system as in claim 1 wherein the turbine comprises a
unidirectional turbine.
5. A system as in claim 1 wherein the turbine comprises a
bidirectional turbine.
6. A system as in claim 1 wherein the first chamber is in selective
fluid communication with the compressed gas storage unit through a
heat exchanger.
7. A system as in claim 6 wherein the heat exchanger is in
selective thermal communication with a thermal storage unit.
8. A system as in claim 6 wherein the thermal storage unit
comprises liquid water at atmospheric pressure.
9. A system as in claim 1 wherein the element comprises a liquid
sprayer in fluid communication with the first chamber.
10. A system as in claim 9 wherein the liquid sprayer is in fluid
communication with the first chamber through an upstream mixing
chamber.
11. A system as in claim 1 further comprising a second airfoil
located downstream from the first airfoil and configured to be
driven by further expanding gas.
12. A system as in claim 11 further comprising: first liquid
sprayer positioned upstream of the first airfoil to effect
gas-liquid heat exchange with the expanding gas; and a second
liquid sprayer positioned between the first airfoil and the second
airfoil to effect gas-liquid heat exchange with the further
expanding gas.
13. A system as in claim 12 wherein the second airfoil is located
in the first chamber to define another turbine stage.
14. A system as in claim 1 wherein the first airfoil comprises a
flexible material.
15. A system as in claim 1 wherein the first airfoil is designed
for periodic replacement based upon a wear profile over time.
16. A system as in claim 1 further comprising an electrical
generator in communication with the rotor.
17. A system as in claim 1 wherein the rotor is in selective
communication with an energy source to drive the first airfoil to
compress gas within the chamber and flow compressed gas to the
compressed gas storage unit.
18. A system as in claim 17 wherein the energy source comprises a
motor, a combustion turbine, a wind turbine, or a steam
turbine.
19. A system as in claim 1 further comprising a control system
configured to: receive a signal; and based upon the received
signal, controlling a valve to flow compressed gas into the first
chamber such that an electrical generator in communication with the
rotor supplies electrical power to a power supply network to cover
a ramp up period of a generation asset.
20. A method of recovering energy from compressed gas, the method
comprising: flowing compressed gas from a compressed gas storage
unit into a chamber having a moveable member coupled to a rotor;
allowing the compressed gas to expand within the chamber and drive
rotation of the moveable member and the rotor in an absence of
combustion; effecting gas-liquid heat exchange with the compressed
gas expanding within the chamber; and generating electricity from
rotation of the rotor.
21. A method as in claim 20 wherein gas-liquid heat exchange is
effected by spraying liquid into the chamber.
22. A method as in claim 20 wherein gas-liquid heat exchange is
effected by spraying liquid into a mixing chamber located upstream
from the chamber.
23. A method as in claim 20 wherein gas-liquid heat exchange is
effected by bubbling the compressed gas through a liquid.
24. A method as in claim 20 further comprising: flowing expanded
gas from the moveable member to a second moveable member; allowing
the expanded gas to further expand and drive rotation of the second
moveable member; effecting gas-liquid heat exchange with the
further expanding gas.
25. A method as in claim 20 further comprising: placing the rotor
into selective communication with an energy source; causing the
rotor to rotate the moveable member and compress gas within the
chamber; effecting gas-liquid heat exchange between the gas
compressed within the chamber; and flowing the gas compressed
within the chamber to a compressed gas storage unit or to a next
higher pressure stage.
26. A method as in claim 25 wherein the energy source comprises a
motor or a second turbine.
27. An apparatus comprising: a chamber in selective fluid
communication with a compressed gas storage unit; an element
configured to effect gas-liquid heat exchange with gas expanding
within the chamber in an absence of combustion within the chamber;
and a turbine rotatable within the chamber to transmit a power of
expanding gas out of the chamber via a mechanical linkage, the
turbine comprising a flexible turbine blade configured to assume a
shape in response to a rotational force.
28. An apparatus as in claim 27 wherein the flexible turbine blade
is also configured to be selectively driven to compress gas within
the turbine.
29. An apparatus as in claim 27 wherein the chamber is in selective
fluid communication with the compressed gas storage unit through a
counterflow heat exchanger.
30. An apparatus as in claim 27 further comprising: a second
chamber in selective fluid communication with a compressed gas
storage unit; a second element configured to effect gas-liquid heat
exchange with gas being compressed within the second chamber; and a
second turbine configured to be driven by a second mechanical
linkage to rotate within the second chamber to cause a second
flexible turbine blade to compress gas within the second
chamber.
31. An apparatus as in claim 30 wherein the turbine comprises an
axial turbine.
32. An apparatus as in claim 30 wherein the turbine comprises a
centrifugal turbine.
33. An apparatus as in claim 30 wherein the turbine comprises a
unidirectional turbine.
34. An apparatus as in claim 30 wherein the turbine comprises a
bidirectional turbine.
35. An apparatus comprising: a chamber in selective fluid
communication with a source of stored gas, and in selective fluid
communication with a source of steam; an element configured to
selectively effect gas-liquid heat exchange with the stored gas
expanding within the chamber in an absence of combustion within the
chamber; and a member moveable within the chamber to transmit a
power of expanding stored gas or of steam out of the chamber via a
mechanical linkage.
36. An apparatus as in claim 35 wherein the moveable member is
configured to rotate within the chamber.
37. An apparatus as in claim 36 wherein the moveable member
comprises a turbine rotor.
38. An apparatus as in claim 35 wherein the moveable member is
configured to reciprocate within the chamber.
39. An apparatus as in claim 38 wherein the moveable member
comprises a solid piston.
40. An apparatus as in claim 35 wherein the steam source comprises
combustion of a fuel.
41. An apparatus as in claim 35 wherein the steam source comprises
a steam turbine.
42. An apparatus as in claim 35 wherein the chamber is configured
to be in fluid communication with the steam source upon receipt of
a signal indicating a loss of power from an intermittent renewable
energy source.
43. An apparatus comprising: a chamber in selective fluid
communication with a liquid circuit comprising a liquid; a bubbler
configured to introduce bubbles of gas from a compressed gas
storage unit into the liquid; and a first moveable member rotatable
to transmit out of the chamber via a mechanical linkage, a power of
the gas bubbles expanding within the liquid, wherein a gas-liquid
separator of the liquid circuit is configured to receive a
gas-liquid mixture from the chamber.
44. An apparatus as in claim 43 wherein the first moveable member
comprises a liquid turbine.
45. An apparatus as in claim 44 wherein the liquid turbine
comprises a centrifugal turbine.
46. An apparatus as in claim 44 wherein the liquid turbine
comprises a reversible turbine.
47. An apparatus as in claim 44 wherein the liquid turbine
comprises a Francis turbine.
48. An apparatus as in claim 44 wherein the liquid turbine
comprises a dedicated turbine, the apparatus further comprising a
dedicated compressor.
49. An apparatus as in claim 43 wherein the first moveable member
comprises a blade.
50. An apparatus as in claim 43 wherein the first moveable member
comprises a bucket.
51. An apparatus as in claim 44 wherein the liquid turbine
comprises an axial turbine.
52. An apparatus comprising: an element configured to effect
gas-liquid heat exchange with gas inside a chamber; and a
mechanical linkage selectively configured to transmit power into
the chamber to cause a rotatable member to compress gas within the
chamber, the mechanical linkage configured to be in selective
communication with a baseline generation asset when a load falls
below a baseline.
53. An apparatus as in claim 52 wherein when the load rises above
the baseline: the chamber is configured to be in selective fluid
communication with a compressed gas storage unit; and the
mechanical linkage is configured to transmit out of the chamber to
an electrical generator, a power of gas expanding within the
chamber.
54. An apparatus as in claim 52 wherein the mechanical linkage is
in selective communication with an intermittent renewable energy
source to cause the rotatable member to compress gas within the
chamber.
55. An apparatus as in claim 52 wherein the rotatable member
comprises a turbine.
56. An apparatus as in claim 55 wherein the turbine comprises a gas
turbine.
57. An apparatus as in claim 55 wherein the turbine comprises a
liquid turbine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The instant nonprovisional patent application claims
priority to U.S. Provisional patent application No. 61/536,813
filed Sep. 20, 2011 and incorporated by reference in its entirety
herein for all purposes.
BACKGROUND
[0002] U.S. patent application Ser. No. 13/010,683 is hereby
incorporated by reference in its entirety.
BRIEF SUMMARY
[0003] Embodiments relate generally to energy storage systems, and
in particular to energy storage systems using one or more turbines
to compress and/or expand a gas. In various embodiments, a
compressed gas storage system may include a plurality of turbines
configured to convert energy in gas expansion and compression
processes. One or more axial and centrifugal turbines may be used
to store energy by compressing gas, and to recover energy from
expanding gas. A plurality of orifices/nozzles may introduce a
liquid into the gas as a heat exchange medium. Orifices/nozzles may
be disposed on various surfaces of a turbine and/or in a separate
mixing chamber flowing to a turbine. Structures of the turbine may
be designed to mitigate damage caused by liquid injection, for
example the turbine blades may be flexible and/or composed of
impact-resistant materials.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a simplified cross-sectional view of an embodiment
of an axial turbine.
[0005] FIG. 2a and FIG. 2b are cross-sectional views of an
embodiment of an axial turbine.
[0006] FIG. 2c is a cut-away view of an embodiment of axial
turbine.
[0007] FIG. 3 is a cut-away view of an embodiment of centrifugal
turbine.
[0008] FIG. 4 is a schematic diagram of an embodiment of an energy
storage system.
[0009] FIG. 5a is a cross-sectional view of an embodiment of an
axial turbine showing orifice locations.
[0010] FIG. 5b is a plan view of an embodiment of an axial turbine
showing orifice locations.
[0011] FIG. 6 is a cut-away view of embodiments of a turbine and
stator.
[0012] FIG. 7 is a cut-away view of an embodiment of a turbine with
orifices disposed as stators.
[0013] FIG. 8a is a cross-sectional view of an embodiment of an
orifice.
[0014] FIG. 8b is a cross-sectional view of an embodiment of a
removable nozzle in an orifice location.
[0015] FIG. 9 is a cut-away view of an embodiment of a turbine with
orifices disposed in the shaft.
[0016] FIG. 10 is a cut-away view of an embodiment of a centrifugal
turbine and orifice locations.
[0017] FIG. 11 is a plan view of an embodiment of a centrifugal
turbine shaft and blades.
[0018] FIG. 12 is a cut-away view of an embodiment of a turbine and
a mixing chamber.
[0019] FIG. 13 is a schematic view illustrating the relationship
between a reversible compressor/expander apparatus and various
other system elements.
[0020] FIG. 14A-B illustrating one embodiment of a reversible
turbine having flexible, low mass blades.
[0021] FIG. 14C illustrates an embodiment of a unidirectional
turbine(s) having flexible, low mass blades.
[0022] FIG. 14D illustrates an embodiment of a reversible turbine
having flexible, low mass blades.
[0023] FIG. 15A shows operation of a rotating-type expander
apparatus operating based upon liquid injection for heat exchange
with expanding gas.
[0024] FIG. 15B shows selective operation of the apparatus of FIG.
15A based upon steam input.
[0025] FIG. 15C shows operation of a reciprocating-type expander
apparatus operating based upon liquid injection for heat exchange
with expanding gas.
[0026] FIG. 15D shows selective operation of the apparatus of FIG.
15C based upon steam input.
[0027] FIG. 16A-16C show views of an embodiment of a reversible
compressor/expander comprising a rotating member and utilizing gas
present as bubbles in a heat exchange liquid.
[0028] FIG. 17 generically depicts interaction between a compressed
gas system and external elements.
[0029] FIG. 18 is a simplified schematic view of a network
configured to supply electrical power to end users.
[0030] FIG. 19 is a table listing possible functions for an energy
storage system incorporated within a power supply network.
[0031] FIG. 20 shows a simplified view of the levelizing function
that may be performed by a compressed gas energy storage and
recovery system according to an embodiment of the present
invention.
[0032] FIG. 21 shows a simplified view of an embodiment of a
compressed gas energy storage and recovery system according to the
present invention, which is co-situated with a power generation
asset.
[0033] FIG. 21A shows a simplified view of an embodiment of a
compressed gas energy storage and recovery system utilizing a
combined motor/generator and a combined compressor/expander.
[0034] FIG. 21B shows a simplified view of an embodiment of a
compressed gas energy storage and recovery system utilizing
dedicated motor, generator, compressor, and expander elements.
[0035] FIG. 21C shows a simplified view of an embodiment of a
compressed gas energy storage and recovery system in accordance
with the present invention utilizing a multi-node gearing
system.
[0036] FIG. 22 shows a simplified top view of one embodiment of a
planetary gear system which could be used in embodiments of the
present invention. FIG. 22A shows a simplified cross-sectional view
of the planetary gear system of FIG. 22 taken along line
22A-22A'.
[0037] FIG. 23 is a table listing heating and cooling functions for
an energy storage system according to an embodiment of the present
invention.
[0038] FIG. 24 shows a simplified view of an embodiment of a
compressed gas energy storage and recovery system according to the
present invention, which is co-situated with an end user behind a
meter.
[0039] FIG. 25 plots power over time showing an example of a
transition of grid capacity from a renewable energy source to a
long-term generation asset.
[0040] FIG. 25A is a simplified schematic view of a system
including a processor configured to coordinate operation of an
energy system with a power supply network.
[0041] FIGS. 26A-B show different views of an embodiment of a
system according to the present invention, configured to receive
various inputs and to produce various outputs.
[0042] FIG. 27A shows a simplified view of an embodiment of an
apparatus according to the present invention.
[0043] FIGS. 27BA-BF are highly simplified depictions of the flow
of gases through the apparatus of FIG. 27A in various
configurations.
[0044] FIGS. 27C-EB are tables showing different energy pathways of
an embodiment of a system in various configurations.
[0045] FIG. 28 shows a flowchart of apportioning inputs and outputs
of an embodiment of a system.
[0046] FIG. 29 shows a schematic view of incorporation of an
embodiment of an energy storage system with generation and
transmission resources of a power supply network.
[0047] FIG. 30 plots energy output of an energy storage system and
of a baseline combined cycle turbine apparatus over time, according
to an embodiment.
DETAILED DESCRIPTION
[0048] Compressed air is capable of storing energy at densities
comparable to lead-acid batteries. However, compressed gas does not
involve issues associated with a battery such as limited lifetime,
materials availability, or environmental friendliness.
[0049] A compressed gas storage system performs the functions of
compressing a gas to store energy, and recovering the energy by
restoring the gas to a lower pressure. To decrease size,
complexity, and cost of such as system, it may be desirable to use
the same equipment for both the compression and expansion phases of
the process. Examples of such a system can be found in U.S. Patent
Publication No. 2011/0115223 ("the Publication"), which is hereby
incorporated by reference in its entirety.
[0050] It should be appreciated that concepts discussed below may
include one or more concepts discussed in the Publication. For
instance, gas bubbling may be used in place of or in combination
with spraying to achieve gas-liquid heat exchange with expanding or
compressed gas. For example, the gas could be introduced to the
chamber for compression or expansion by rotating blades of a
turbine, through a liquid.
[0051] A turbine-based design may be employed to convert energy
between rotational motion and compressed gas. As illustrated by
FIG. 1, an axial turbine according to an embodiment includes at
least one rotor 2 which is coupled to a shaft 4.
[0052] The rotor and portions of the shaft are typically enclosed
by a housing 10 to protect the blades and contain the gas. The
housing 10 includes a first port 8 and a second port 6. When, for
example, the first port is configured to be an inlet port, gas
moves from the first port 8 across the rotor 2, causing the shaft 4
to rotate. In the axial turbine, the gas flows parallel to the axis
of the shaft 4.
[0053] Such a system can be used to convert electrical energy into
potential energy stored by compressed gas. For example, the
rotation of shaft 4 can be caused by electricity supplied to an
electric motor-generator 14 coupled to shaft 4, causing the shaft
to rotate.
[0054] According to certain embodiments, the motor-generator may
comprise a wire coil in magnetic communication with magnetic
element(s) present on the shaft. Rotation of the shaft and the
magnetic elements relative to the wire coil, creates a current
within the wire coil based upon inductive principles.
[0055] Due to the shape and orientation of the blades on the rotor,
the blades function as an airfoil, causing a resultant force in a
predetermined direction when the shaft is rotated. The force causes
air to flow through the housing 10, which creates a vacuum at inlet
8, and compresses air through outlet 6.
[0056] When a compressed gas storage unit is coupled to outlet 6 or
to a next higher pressure stage, the system effectively stores
energy in the form of compressed gas. Examples of suitable
compressed gas storage units include man-made structures such as
metal or composite pressure vessels. Alternative structures which
may be suitable for storage of compressed gas include depleted oil
or gas fields, as well as naturally-occurring features such as
subterranean caverns, and porous geological formations.
[0057] Gas flowing from the turbine can be exposed to certain
processes prior to being stored or passed onto a next higher
pressure stage. For example, as described in detail below liquid
may be introduced to the gas to effect heat exchange. The gas can
be flowed through a gas-liquid separator to recover liquid
therefrom, potentially for storage and/or reuse. Gas can also be
flowed through structures such as condensers and heat
exchangers.
[0058] The system as in FIG. 1 or other embodiments described
herein can be operated to convert energy stored in the form of
compressed gas, into electricity. Specifically, compressed gas can
be introduced from a compressed gas storage unit into inlet 8,
which acts on rotor 2 to rotate the shaft. Rotation of the shaft of
a motor/generator can generate electricity.
[0059] Again, as discussed below liquid may be introduced to effect
heat exchange with the expanding gas. Accordingly, the expanded gas
can be flowed from the turbine through a gas-liquid separator to
recover liquid therefrom, potentially for storage and/or reuse.
Expanded gas can also be flowed through structures such as
condensers, noise reducers, and/or heat exchangers prior to flowing
to a next lower pressure stage or to ambient.
[0060] While the particular embodiment of FIG. 1 shows a turbine
configured to selectively receive energy from motor/generator to
compress gas for storage, this is not required. According to
alternative embodiments, a turbine rotor could be in selective
communication with sources of energy other than a
motor/generator.
[0061] For example, in certain embodiments a turbine rotor could be
in communication with another turbine as an energy source. In some
embodiments this other turbine could be a wind turbine, Still other
forms of turbine that may selectively communicate energy for gas
compression, include combustion turbines such as those operating on
natural gas. Yet other forms of turbine that may be in selective
communication to compress gas, include steam turbines.
[0062] In certain embodiments, energy from the energy source could
be communicated directly to the rotor of the turbine utilized for
energy storage by gas compression. For example, the rotor of the
turbine used for gas compression could be located on a same shaft
as a second (wind, combustion, steam) turbine responsible for
driving the first turbine. Alternatively, the energy source could
be in communication with the turbine used for gas compression,
through one or more linkages, for example a hydraulic linkage,
electronic linkage, electrostatic linkage, magnetic linkage, or
mechanical linkage.
[0063] Embodiments of the present invention that employ a
turbine-based system for gas compression and/or expansion, may
offer one or more benefits over various other designs. For example,
a design having a reciprocating piston may employ a seal between
sidewalls of the piston and sidewalls of the housing. This seal
adds cost and complexity to the system, and is a possible point of
failure that may require regular maintenance.
[0064] In addition, movement of the additional seal of the
piston-based system against the sidewalls of the housing, may
result in losses to friction. Such friction also contributes
additional heat in the system. A turbine-based system lacking such
a seal between a reciprocating piston and sidewall avoids both
types of losses.
[0065] Moreover, a piston-based system must withstand the forces
caused by repeated compression, without deforming to the point
where the seal fails. Accordingly, such a piston may have a
substantial mass. A significant amount of energy is therefore
consumed to move the mass of the piston, reducing the efficiency of
the system. In contrast, a lower amount of energy is required to
move the shaft in a turbine-based system.
[0066] In order to achieve high levels of gas compression,
embodiments of the present invention may utilize a multi-stage
turbine. As illustrated by the particular embodiment of FIG. 2a, a
multi-stage axial turbine 224 has a plurality of rotors 202, each
of which has a plurality of blades, arranged around a shaft
204.
[0067] The axial turbine 224 may further include a stator 226
disposed between rotors. While the rotors 202 rotate with the
shaft, the stator 226 is static. The blades of the stator 226 are
arranged to oppose the blades of the rotors. The stator may be
coupled to housing 210.
[0068] The stator serves a number of functions in the turbine. The
stator may increase pressure in the system. The stator may also
keep gas flowing in an axial direction.
[0069] As shown in FIG. 2a, in certain embodiments the inner
sidewalls of the housing 210 and the outer sidewalls of the shaft
204 may be parallel to one another. In some embodiments (for
example as shown by FIG. 2b) the inner diameter of the inner
sidewalls of the housing 210 may decrease along the axis of shaft
204.
[0070] In other embodiments (for example as shown in FIG. 2c), the
outer diameter of the rotor 202 may vary along its axis to
progressively change the space between the rotor and the housing.
FIG. 2c also shows communication between the shaft 204 of the rotor
202 and a generator 211 (which may be a motor/generator).
[0071] It is noted that separate and distinct shaft/rotor
combinations are not necessarily required for all embodiments. In
certain embodiments, the rotor may comprise an integral structure
configured to rotate, with magnetic elements for generating
electricity being disposed proximate to wire coil(s) located at an
end of the rotor opposite the end comprising the turbine blades.
The coil(s) may be arranged with their axes pointing towards the
axis of the shaft.
[0072] In the particular embodiments of FIG. 2b and FIG. 2c, the
volume of the turbine chamber decreases along a left-to-right
direction. The reduction in volume serves to match mass flow as the
gas is compressed through each stage.
[0073] In some embodiments, the system may include a relatively
high number of compression and/or expansion stages. If each stage
has a pressure ratio of 1.1, a top pressure of 300 atmospheres
would utilize about 60 stages. Examples of ranges of a number of
stages in a turbine include, but are not limited to, 1-10, 1-20,
1-30, 1-40, 1-50, or 1-60 or more. In order to optimize the
efficiency of such systems, various rotors may be coupled to a
plurality of concentric shafts rotating at different
velocities.
[0074] Another form of turbine that may be used to compress gas in
an energy storage system according to various embodiments, is a
centrifugal turbine. A simplified view of an embodiment of a
centrifugal turbine is shown in FIG. 3.
[0075] The centrifugal turbine 330 includes a shaft 304 disposed at
the center of the turbine. The shaft is coupled to a rotor 332,
which has a three-dimensional geometry optimized to move gas
radially through the chamber, perpendicular to the axis of rotation
of shaft 304. For example, the turbine shown in FIG. 3 may have an
inlet port disposed towards the shaft 304 where gas enters the
chamber. A spinning shaft 304 turns rotor 332 so that the system
acts as a centrifuge, forcing gas to the outer sides of the
chamber. The gas then passes through outlet 334 disposed in a
sidewall of the chamber as a compressed gas.
[0076] Various combinations of axial and centrifugal turbines are
possible in compression and/or expansion. A plurality of
centrifugal and axial turbines may be coupled to one another in
series to optimize the efficiency of the process at different
pressures.
[0077] In some embodiments, a turbine may be operated in a
unidirectional manner for compression and expansion. For example,
gas flows in one direction through a centrifugal turbine.
[0078] According to certain embodiments, a bi-directional turbine
structure may be used. For example, an axial turbine can be
operated in a bidirectional manner.
[0079] Particular embodiments may employ both unidirectional and
bidirectional turbine structures. An example is shown in the
multi-stage embodiment of FIG. 4.
[0080] Under operation in the compression mode, the inlet 440 takes
in low pressure gas and delivers it to centrifugal turbine 430. At
this time, a valve 442 is closed to the compressed gas storage unit
444, but open between the inlet and the centrifugal turbine.
Electricity is delivered to rotate centrifugal turbine 430 so that
it compresses gas and sends it through multi-way valve 450 to a low
pressure side of axial turbine 424. In some embodiments, there may
be a plurality of axial turbines connected in series. A valve 446
is open between the high pressure side of the axial turbine and the
compressed gas storage unit 444, so that the tank is filled with
compressed gas.
[0081] An expansion process can be achieved by altering the valve
states. Specifically, valve 446 is opened to allow fluid
communication between the compressed gas storage unit and the high
pressure side of the axial turbine. The flow of gas through the
axial turbine 424 drives it to generate electricity.
[0082] The gas expanded by this stage, is then flowed through
valves 450, 448, and 442 to the inlet of the centrifugal turbine.
The further expanding gas drives the centrifugal turbine to
generate even more electricity. The expanded gas is then routed
through multi-way valve 450 to exhaust port 452.
[0083] In the embodiment of FIG. 4, the valve 448 is in selective
communication with the storage unit 444. This allows a single-stage
mode of operation in both compression and expansion, utilizing just
the centrifugal compressor.
[0084] Although the particular embodiment of FIG. 4 uses
centrifugal turbine 430 as a first stage, this is not required.
Other embodiments may use another type of turbine arranged in
series, in the compression and/or expansion process.
[0085] In some embodiments, a system may include one or more
bypasses. This allows only selected turbines out of a total
plurality of available turbines, to be used for either compression
or expansion processes.
[0086] For example, in a compression process, valve 442 may be open
between inlet 440 and valve 448, while valve 448 is open between
valve 442 and valve 450, and valve 450 is open between valve 448
and the axial turbine 424. This configuration bypasses centrifugal
turbine 430 in a compression process. Similarly, in an expansion
process, valve 452 can be configured to exhaust expanded gas
directly to the outlet, bypassing centrifugal turbine 430.
[0087] Multiple turbines may be disposed on a single shaft with one
or more motor/generators, or on separate shafts with separate
motor/generators. For example, in the multi-stage embodiment of
FIG. 4, the centrifugal turbine will always turn in the same
direction, while the axial turbine will turn one way during
compression and in the opposite direction during expansion. Thus
the centrifugal turbine 430 may be coupled to a first
motor/generator, and axial turbine 424 may be coupled to a second
motor/generator. Alternatively, both turbines may be in
communication with one motor-generator, with a mechanical reversing
linkage used on either the axial or the centrifugal turbine to keep
the shafts rotating in the same direction as each other.
[0088] In various embodiments, the same turbine(s) may be used for
both the gas compression and gas expansion processes. In certain
embodiments, separate turbine(s) may be dedicated to performing
these gas compression or expansion functions.
[0089] A property of certain embodiments is to maintain gas within
a desired temperature range during compression and/or expansion. In
some embodiments this temperature range provides for isothermal or
near-isothermal energy transfer.
[0090] Operation of embodiments according the present invention may
be characterized by a magnitude of temperature change of the gas
being compressed or expanded. According to one embodiment, during a
compression cycle the gas may experience an increase in temperate
of 100 degrees Celsius or less, a temperature increase of 60
degrees Celsius or less, a temperature increase of 50 degrees
Celsius or less, a temperature increase of 40 degrees Celsius or
less, a temperature increase of 30 degrees Celsius or less, a
temperature increase of 20 degrees Celsius or less, a temperature
increase of 10 degrees Celsius or less, or a temperature increase
of 5 degrees Celsius or less.
[0091] In some embodiments, during an expansion cycle the gas may
experience a decrease in temperature of 100 degrees Celsius or
less, 15 degrees Celsius or less, or 11 degrees Celsius or
less.
[0092] In order to achieve isothermal compression and expansion,
embodiments of the present invention may use liquid for heat
exchange with gas in the system. The liquid may be introduced into
the gas itself as a heat exchange medium.
[0093] In a compression process, liquid may be added to a gas which
is heated during compression, thereby absorbing heat from the gas.
Conversely, in an expansion process, liquid may be introduced into
the gas which is cooled during expansion, thereby contributing heat
to the system. System performance may be improved by introducing
liquid at a lower temperature during compression and at a higher
temperature during expansion.
[0094] In embodiments utilizing injected liquid as a heat exchange
medium, the temperature change experienced by the expanding gas may
near the freezing point of the liquid from an initial point of room
temperature. In certain embodiments, the liquid that is injected
for heat exchange may comprise water having a freezing point of 0
degrees Celsius.
[0095] In general, liquid introduced to accomplish heat exchange
according to embodiments of the present invention, is not expected
to undergo combustion within that chamber. Thus while the liquid
being injected to perform heat exchange may be combustible (for
example an oil, alcohol, kerosene, diesel, or biodiesel), in many
embodiments it is not anticipated that the liquid will combust
within the chamber. In at least this respect, liquid introduction
according to embodiments of the present invention may differ from
cases where liquids are introduced into turbines and motors for
combustion.
[0096] A system according to embodiments of the present invention
may include a thermal energy storage component. For example, a
system may retain in an insulated vessel, liquid that has been
heated during a compression process. This stored heated liquid may
be used later for adding heat to an expansion process and thereby
increase energy efficiency.
[0097] Conversely, a system may retain in an insulated vessel,
liquid that has been cooled by an expansion process. This stored
cooled liquid may be later used to absorb heat during a compression
process.
[0098] In some embodiments, a thermal storage medium may comprise
the same liquid that is introduced to the gas for heat exchange. In
certain embodiments, the thermal storage medium may comprise a
different liquid that has itself exchanged heat with the introduced
liquid. An example is where water is introduced to
compressed/expanding gas for heat exchange, and then the water
exchanges heat with an oil that is stored in an insulated
vessel.
[0099] FIG. 5(a) is a cross-sectional view of an embodiment of an
axial turbine 524 including a shaft 504, a housing 510, and five
rotors 502. The turbine may include a plurality of liquid orifices
disposed in sidewalls of housing 510 between the rotors 502 at
locations b1-b4 and a1-a4. A liquid orifice may be disposed between
each rotor as shown. Alternatively, an orifice may be disposed
between every other rotor 502, such as locations a1 and a3.
[0100] Various embodiments may determine the number and spacing of
orifices depending upon certain factors. One example of such a
factor is a number of rotors in a particular turbine.
[0101] The orifices may be disposed in a single row along a
sidewall of the housing 510, as shown by orifices a1-a4.
Alternatively, the orifices may be diametrically opposed to one
another, as shown by orifices a1-a4 and b1-b4. In some embodiments,
the orifices may be arranged in a particular pattern, such as an
alternating pattern as shown by FIG. 5(b).
[0102] Returning to FIG. 5(a), one or more orifices may be disposed
upstream or downstream to rotors 502 at the inlet or outlet of the
turbine, as indicated by orifice locations X and Y. There may be a
plurality of orifices X and Y along both axial and circumferential
planes in various embodiments. The orifices may be configured to
discharge either hot or cold liquid depending on whether a
compression or expansion process is being conducted.
[0103] Orifices at only one end of the turbine may be active during
a particular process. For example, in a compression process,
orifice X may be active to introduce lower temperature liquid into
the gas stream while orifice Y is inactive.
[0104] As discussed above with respect to FIG. 2a, an axial turbine
may have a stator 226 disposed next to a rotor 202. FIG. 6 shows an
axial turbine 624 with two rotors 602 coupled to shaft 604, and a
stator disposed between the rotors.
[0105] As shown by section "A" in the figure, an orifice may be
located directly on the stator. A plurality of orifices may be
disposed on various surfaces of the stator to optimize desired
characteristics, such as atomization and liquid concentration. As
shown in section A, orifices C1-3 and D1-3 may be mounted, for
example, on leading and trailing edges of stator blade 628.
[0106] In such an embodiment, liquid may be delivered to multiple
orifices simultaneously with either high temperature or low
temperature liquid during compression and expansion stages. In some
embodiments, liquid may only be delivered to selected orifices
during a particular process. A single orifice, or a plurality of
orifices, may be disposed on every stator in the turbine, on every
other stator, every third stator, or any combination of stators or
stator blades.
[0107] The inclusion of orifices between stages of certain
embodiments, may increase the length of the turbine. For example,
the inclusion of inter-stage orifices may involve increasing the
distance between the stages. Moreover, in some embodiments a
structure may be present between stages to separate the introduced
liquid from the airflow.
[0108] The stator and other components of the turbine may be fitted
with fluid channels to change the temperature of the components of
the turbine itself. This may further enhance a desired heat
transfer. For example, in certain embodiments the stator and/or
rotor blades could be cooled.
[0109] Possible benefits of including a liquid component in the
system may extend beyond controlling thermal properties of the
compressed/expanding gas. For example, when water and air are used
for the liquid and gas, the increased density of the flowing fluid
due to humidity and the presence of liquid water, may help to
transfer momentum to the turbine. In particular, the liquid
contributes mass to the gas-liquid mixture. As momentum is
dependent upon mass, more momentum may be transferred from a given
volume of an air-water droplet mixture, than from the same volume
of air. This may increase the power density as a result.
[0110] In addition, the presence of water may affect interwarming
in certain embodiments. For example, where liquid is not separated
out between stages, during expansion the presence of liquid water
may serve to transfer heat to cool air between stages.
[0111] The pressure ratio of any given stage in a gas turbine, is
typically low. Accordingly, desired thermal performance of a
turbine could be achieved using intercoolers and/or interwarmers. A
heat exchange mechanism could be present between each stage or
between groups of stages. For example, this heat exchange mechanism
could comprise a liquid spray oriented to substantially avoid
entrainment into the main airflow (e.g. by being sprayed cross-wise
to the gas flow), thus minimizing the amount of droplets impinging
on turbine blades.
[0112] In some embodiments, a plurality of spray orifices may be
arranged to function as a stator. For example, FIG. 7 shows
orifices a1, a2, b1, and b2, disposed in sidewalls of housing 710,
and directed towards rotor 702. Although FIG. 7 only shows four
orifices, a plurality of orifices may be disposed around a
circumference of a housing as shown, for example, in FIG. 5b.
[0113] In an embodiment, when the rotor is turning to move gas from
the left side of the figure to the right side of the figure, liquid
may be forced through orifices a2 and b2. The force of the spray
interacts with the gas, directing the gas towards shaft 704 to
maintain an axial gas flow.
[0114] Although the orifices shown in FIG. 7 are disposed at an
angle towards rotor 702 this is not required. In certain
embodiments the orifices may be disposed perpendicular to shaft
704, or angled in a direction away from the operative rotor.
[0115] When an axial turbine includes a plurality of rotors,
orifices acting as stators may be divided into sets, with only one
set operative for each of a compression and expansion process. For
example, one set of orifices may be disposed to act as a stator
when the flow of gas through the turbine is from right to left, and
another set of orifices may act as a stator when the flow of gas
through the turbine is from left to right.
[0116] The orifices through which liquid enters a turbine chamber
or a mixing chamber can be configured differently from other
orifices of the same embodiment, or from the orifices present in
other embodiments.
[0117] For example, as shown in FIG. 8a, an orifice may be formed
by shaping the material of the surface in which it is disposed.
Surface 880 may thus be a surface of a sidewall in a turbine.
[0118] An orifice may be formed in surface 880 by forming a notch
882, and forming a cavity 884 coupled to the notch. Pressurized
liquid, or a combination of pressurized liquid and gas, are
delivered to the cavity 884 and pass through notch 882 to form a
spray plume within the turbine. The surface 880 can be any interior
surface of a turbine, such as a surface of a housing, a stator, a
rotor, or a shaft.
[0119] As shown in FIG. 8b, an orifice can be present in a
replaceable nozzle installed in surface 880. The nozzle 886 shown
in FIG. 8b includes a liquid channel 888, a gas channel 890, and an
outlet 892. Liquid is delivered through the liquid channel and
meets with pressurized gas, which atomizes the liquid to deliver a
spray plume into the turbine chamber. The gas may be included to
boost the pressure under which the liquid is delivered into the
turbine in order to overcome the pressure in the turbine
chamber.
[0120] The nozzle 886 of FIG. 8b is detachably coupled to surface
880 so that a particular design of nozzle can be separately
fabricated and installed in the storage system. The detachable
coupling may allow for off-the-shelf or custom nozzles to be
installed in a particular surface, as well as ease of maintenance
and easy replacement.
[0121] A variety of different orifices may be formed within a
single turbine, mixing chamber, and/or in different turbines and/or
mixing chambers within an energy storage system. For example, the
pressure within a turbine may increase from one side to another.
Such a turbine may have a first type of orifice disposed at the low
pressure side that is designed to operate under lower pressures,
and a second type of orifice disposed at the high pressure side
that is designed to operate under higher pressures.
[0122] The orifices may be selected to optimize spray
characteristics at particular stages of the compression and
expansion processes. For example, some orifices are better suited
to higher pressure spray applications. Such orifices may be
disposed closer to portions of an energy system with higher
internal pressures, while orifices better suited to lower pressure
applications may be located at low pressure portions of the
system.
[0123] In addition, different orifices can be selected for
different spray characteristics. Examples of such characteristics
include but are not limited to atomization, velocity of the spray
plumes, breakup length, spray pattern, spray cone angle, fan angle,
angle to surface (for fan sprays), and droplet spatial
distribution.
[0124] One specific performance characteristic is droplet size.
Droplet size may be measured using DV50, Sauter mean diameter (also
called SMD, D32, d.sub.32 or D[3, 2]), or other measures.
Embodiments of orifices/nozzles may produce liquid droplets having
SMD's within a range of between about 10-200 um. Examples of
droplet sizes produced by orifice/nozzle embodiments include but
are not limited to those having a SMD of about 200 microns, 150
microns, 100 microns, 50 microns, 25 microns, and 10 microns.
[0125] Another performance characteristic is flow rate. Embodiments
may produce a flow rate of between about 20 and 0.01 liters per
second. Examples of flow rates of embodiments of orifices/nozzles
of the present invention are 20, 10, 5, 2, 1, 0.5, 0.25, 0.1, 0.05,
0.02, and 0.01 liters per second.
[0126] Another performance characteristic is breakup length. Liquid
output by embodiments of nozzles may exhibit a breakup length of
between about 1-100 mm. Examples of breakup lengths of sprays of
liquid from nozzles according to the present invention include 100,
50, 25, 10, 5, 2, and 1 mm.
[0127] Embodiments of orifices/nozzles may produce different types
of spray patterns. Examples of spray patterns which may be produced
by various embodiments include but are not limited to, hollow cone,
solid cone, stream, single fan, and multiple fans.
[0128] Embodiments of orifices/nozzles may produce spray cone
angles of between about 20-180 degrees. Examples of such spray cone
angles include but are not limited to 20.degree., 22.5.degree.,
25.degree., 30.degree., 45.degree., 60.degree., 90.degree.,
120.degree., 150.degree., and 180.degree..
[0129] Embodiments of orifices/nozzles may produce spray fan angles
of between about 20-360 degrees. Examples of such fan angles
include but are not limited to 20.degree., 22.5.degree.,
25.degree., 30.degree., 45.degree., 60.degree., 90.degree.,
120.degree., 150.degree., 180.degree., 225.degree., 270.degree.,
300.degree., 330.degree., or 360.degree.. Examples of fan spray
angles to surfaces include but are not limited to 90.degree.,
80.degree., 60.degree., 45.degree., 30.degree., 22.5.degree.,
20.degree., 15.degree., 10.degree., 5.degree., or 0.degree..
[0130] Droplet spatial distribution represents another performance
characteristic of liquid spray orifices/nozzles. One way to measure
droplet spatial distribution is to measure the angle of a sheet or
cone cross-section that includes most of the droplets that deviate
from the sheet. In orifice/nozzle designs, this angle may be
between 0-90 degrees. Examples of such angles possibly produced by
embodiments include but are not limited to 0.degree., 1.degree.,
2.degree., 5.degree., 7.5.degree., 10.degree., 15.degree.,
20.degree., 25.degree., 30.degree., 45.degree., 60.degree.,
75.degree., or 90.degree..
[0131] According to certain embodiments, it may be important to
control the amount of liquid introduced into the chamber to effect
heat exchange. The ideal amount may depend upon a number of
factors, including the heat capacities of the gas and of the
liquid, and the desired change in temperature during compression or
expansion.
[0132] The amount of liquid to be introduced may also depend on the
size of droplets formed by the spray orifice/nozzle. One measure of
the amount of liquid to be introduced, is a ratio of the total
surface area of all the droplets, to the number of moles of gas in
the chamber. This ratio, in square meters per mole, could range
from about 1 to 250 or more. Examples of this ratio which may be
suitable for use in embodiments of the present invention include 1,
2, 5, 10, 15, 25, 30, 50, 100, 125, 150, 200, or 250.
[0133] Certain designs may facilitate the fabrication of individual
orifices/nozzles. Certain designs may also permit the placement of
a plurality of orifices/nozzles in a given surface proximate to one
another, which can enhance performance.
[0134] A variety of different types of spray structures can be
employed. Examples of spray structures which may be suited for use
according to various embodiments, include but are not limited to
impingement nozzles, rotating disk atomizers, electrostatic
atomizers, pressure swirl nozzles, fan nozzles, impact nozzles,
air-assisted nozzles, jets, and rotating cup atomizers.
[0135] In certain embodiments, a plurality of sprayers may be
configured to interact with one another to produce a spray having
the desired character. For example, the spray of one nozzle may
fill a vacant portion of the spray pattern of an adjacent
nozzle.
[0136] Certain characteristics of an energy storage system may
prompt different orifice locations and types. The liquid that is
sprayed through the nozzles will have different physical
characteristics depending on the temperature of the liquid, so
different orifices may be disposed within a system to optimize
spray characteristics based on liquid temperature. When the liquid
has a different temperature for a compression process than for an
expansion process, a single system may have two sets of orifices,
with only one set operative for each process. In addition, the
direction and type of orifice may vary between the sets, and within
particular areas of a system within a particular set.
[0137] As shown by the embodiment of FIG. 9, orifices may be
disposed in outer surfaces of the turbine shaft 904. In such an
embodiment, liquid is fed into channels within the shaft, and the
centrifugal force of the spinning shaft acts to supply force to the
liquid so that it is sprayed though the orifices. The spinning
shaft 904 thus acts to pump liquid out through the orifices. This
pump action can reduce the need to supply pressure to the liquid
through some other mechanism, such as an actively powered pump
device.
[0138] As shown in FIG. 9, orifices may be disposed at a plurality
of positions along the shaft, including between rotors 902 such as
orifices e1 and e2, and at an end of the shaft, such as orifices f1
and f2. A plurality of orifices may be disposed around a
circumference of the shaft. As discussed with respect to FIGS. 8a
and 8b, different embodiments may have different orifices and
nozzles, and only selected orifices may be active for a compression
or expansion process. For example, two sets of nozzles could be fed
through two different channels through the shaft, so that one
channel or the other could be supplied with liquid during
compression or expansion.
[0139] When a centrifugal turbine is used in an energy storage
system, different types and configurations of orifices and nozzles
may be disposed at different locations, in a manner similar to an
axial turbine. For example, with reference to the embodiment of
FIG. 10, orifice locations i1-i8 may be disposed in sidewalls of
the housing, and orifices may be disposed towards the entrance to
the turbine chamber as indicated by locations j1 and j2.
[0140] In a manner similar to embodiments utilizing the axial
turbine, different types of orifices and nozzles can be disposed at
these locations to optimize spray characteristics for different
liquid temperatures, chamber pressures, orifice locations, and
compression and expansion processes.
[0141] A centrifugal turbine may comprise a plurality of blades
shaped to move gas from the inlet to an outlet disposed in a
sidewall of the housing.
[0142] In an embodiment, some of the blades in the rotor may be
shaped differently from one another. For example, as shown in FIG.
11, a blade 1110 mounted to shaft 1104 is shaped with a curvature
that is opposite to adjacent blade 1112. In such a configuration,
the turbulence in the turbine is increased, thereby keeping more of
the liquid entrained.
[0143] Thus according to certain embodiments, the turbine blades
may be designed to accomplish multiple purposes. While their main
purpose may be to compress (or expand) flowing gas, the aerodynamic
surfaces of the blades may impart additional motion to the
air/water mixture. This motion may maintain separation of the water
droplets, allowing them to be passed on while retaining a large
gas-liquid interface surface and hence effective heat exchange
properties.
[0144] Although the blades in FIG. 11 are mirror images of one
another, the differences between blade shapes may be less drastic.
For example, alternating blades may be curved and flat, or only a
portion of adjacent blades may be different from one another. Every
other blade may be different, or every third or fourth blade, etc.
In an embodiment, only one blade may be differently shaped from the
others.
[0145] Due to the relatively high velocity at which a turbine rotor
spins, the presence of liquid droplets in the gas stream may damage
the spinning rotors on impact. Although the damage caused by a
single collision is minimal, the cumulative damage imparted by many
collisions over time may shorten the useful life of an ordinary
rotor. Embodiments of the present invention may use one or more
techniques to minimize damage to the rotors.
[0146] The energy in a particular collision is proportional to the
masses of the colliding objects. Accordingly, one technique to
minimize rotor damage is to introduce a highly atomized liquid
spray. Higher levels of atomization results in smaller individual
liquid droplets, so that the energy in each collision between a
liquid droplet and a rotor is reduced.
[0147] The above approach reduces energy of collision by reducing
mass, as the energy in a collision is proportional to the mass of
the droplet. In addition, smaller droplets are more quickly
entrained in the air, following streamlines which are generally
tangential near the surface of a turbine blade. This reduces the
normal component of the droplet velocity. Energy is proportional to
the square of that velocity.
[0148] The type of orifice, or nozzle, through which the liquid is
sprayed may be selected to increase atomization. For a nozzle
similar to the nozzle shown in FIG. 8b, the gas pressure in gas
channel 890 may be increased to improve atomization. In addition,
smaller orifice sizes can cause higher degrees of atomization, so a
larger quantity of small nozzles may be used in a particular
system.
[0149] Further techniques for mitigating damage to the turbine,
include the design and materials of the turbine blades and rotors
themselves. For example, the blades of a rotor in an energy storage
system may be thin and flexible to better absorb energy and locally
deflect under the impact of the droplets.
[0150] Moreover, while many conventional gas turbine designs
require cooling through channels embedded in the blades to prevent
excessive temperatures, operating near isothermally according to
embodiments of the present invention allows for thin blades
(without cooling channels) to be used. Such thin blades can be more
aerodynamically efficient, lighter weight, and less expensive.
[0151] Another possible benefit of using thin, lightweight blades
in a turbine, is that lighter blades must withstand lower stresses
resulting from rotating at high speed. This, in turn, allows less
material to be used in the blades.
[0152] Still another potential benefit of using thin, inexpensive
turbine blades is the possibility of replacement during regular
maintenance. Even if some pitting occurs due to liquid droplets
hitting the blades, a blade lifetime of one year or so is practical
for a regular replacement schedule.
[0153] Significant levels of centrifugal and pneumatic force are
experienced by an operating turbine blade, so flexible blades may
be configured so that they assume a shape optimized to convey gas
when they are spinning. Examples of flexible materials include
metals such as titanium alloy and nitinol.
[0154] Suitable materials also include thermosetting composites
such as carbon fiber with an epoxy matrix or fiberglass with a
polyester matrix. The material may also include a thermoplastic
material such as polyurethane, polyamide, polyether-ether-ketone,
polyetheramide, polycarbonate, or another suitable engineering
thermoplastic, that is reinforced with a fiber such as glass,
carbon, carbon nanotubes, or other commercially available
materials.
[0155] In some embodiments non-reinforced polymers may be used for
the blades, or for a portion of the blades, to enhance the
elasticity of impacted surfaces. A blade may comprise a substrate,
such as a metal, over which a polymer is formed to make the surface
more elastic, thereby preventing damage from impacts with liquid
droplets.
[0156] A blade may be coated with an elastic material for the same
reason. The material may be a low modulus rubber or a high modulus
polymer such as polyamide. In an embodiment, the blade coating may
be stripped and replaced periodically to extend the life of the
blades.
[0157] In certain embodiments, the rotor blades may comprise a
high-hardness material, such as a ceramic including alumina,
zirconia, or silicon glass. The high-hardness material may be a
coating over a substrate, for example diamond-like carbon
(DLC).
[0158] In some embodiments, the blade material may be a hydrophilic
material. A fully wetted hydrophilic surface may serve as a cushion
between the droplets and the blades, and may distribute the impact
force between blade and droplet over a larger area than a
non-hydrophilic surface.
[0159] In certain embodiments, the blade material may be a
hydrophobic material. The use of hydrophobic materials for exposed
surfaces within the turbine may prevent or reduce wetting. This may
maintain more droplets entrained in the gas by causing droplets to
bounce off of the surface rather than wetting it.
[0160] The blades of a turbine rotor are typically disposed as
close to sidewalls of a housing as possible in order to create a
seal, or near-seal, between the rotor and the housing. Both the
blades and housing expand and contract as a function of their
coefficient of thermal expansion (CTE).
[0161] A traditional turbine design may be configured to operate at
high temperatures or over broad temperature ranges. Thus, a
material may be used for the turbine blade having a CTE compatible
with the housing or other components, to optimize efficiency while
preventing contact/abrasion between the rotor and the housing.
[0162] By contrast, certain embodiments of the present invention
may introduce liquid to effect gas-liquid heat exchange during gas
compression and/or expansion. This allows gas compression and/or
expansion to occur under isothermal or near-isothermal conditions,
and/or within a predetermined temperature range. Expected operation
under this relatively narrow temperature range, allows materials
with relatively high CTE's to be employed for turbine components,
including the turbine blades.
[0163] Moreover, another potential problem faced by traditional
turbines operating at high temperatures and/or across broad
temperature ranges, is the difference in CTE between different
materials. For example, mismatch in CTE between components of
different materials can cause leaks or cracks when joints expand or
contract, and can cause fasteners to loosen over time. However,
because certain embodiments are expected to operate over a limited
temperature range, the effects CTE differential for turbine
components is not as pronounced, allowing a broader variety of
materials to be used.
[0164] In an embodiment, the liquid spray may be configured to
accumulate continuous liquid over sidewalls of the housing. This
may desirably create a viscous seal between the rotors and the
housing.
[0165] In a manner analogous to the sealing mechanism of a liquid
ring compressor, the liquid introduced for gas-liquid heat exchange
may fill the small gap between the turbine rotor and the housing.
In some embodiments this gap may be increased to reduce viscous
drag forces.
[0166] Although the above embodiments are described with orifices
disposed within a turbine chamber, this is not required. In some
embodiments, liquid can be sprayed into an upstream mixing chamber
in addition to, or in place of, spraying into the turbine
itself.
[0167] As shown by FIG. 12, a plurality of orifices g1-g4 and h1-h4
may be disposed along sidewalls of mixing chamber 1220, which is
coupled to axial turbine 1224. Such a configuration allows the
spray droplets to disperse evenly through the gas stream before
entering a turbine.
[0168] In another embodiment, a mixing chamber may be coupled to a
centrifugal turbine. The sidewalls of the mixing chamber 1220 may
have a larger diameter than sidewalls of turbine housing 1210, as
shown in FIG. 12. In other embodiments, the sidewalls may have the
same diameter, or a smaller diameter, than housing 1210.
[0169] 1. A system to recover energy from compressed gas, the
system comprising:
[0170] a compressed gas storage unit;
[0171] a first chamber defined within walls and in selective fluid
communication with the compressed gas storage unit to receive
compressed gas;
[0172] a first airfoil configured to drive a rotor within the first
chamber in response to the compressed gas expanding in an absence
of combustion; and
[0173] an element configured to effect gas-liquid heat exchange
with the expanding compressed gas.
[0174] 2. A system as in clause 1 wherein the first airfoil and the
rotor within the first chamber define an axial turbine.
[0175] 3. A system as in clauses 1 or 2 wherein the first airfoil
and the rotor within the first chamber define a centrifugal
turbine.
[0176] 4. A system as in clauses 1, 2, or 3 wherein the element
comprises a liquid sprayer in fluid communication with the first
chamber.
[0177] 5. A system as in clauses 1, 2, 3, or 4 wherein the liquid
sprayer is in fluid communication with the first chamber through an
upstream mixing chamber.
[0178] 6. A system as in clauses 1, 2, 3, 4, or 5 further
comprising a second airfoil located downstream from the first
airfoil and configured to be driven by further expanding gas.
[0179] 7. A system as in clause 6 further comprising:
[0180] first liquid sprayer positioned upstream of the first
airfoil to effect gas-liquid heat exchange with the expanding gas;
and
[0181] a second liquid sprayer positioned between the first airfoil
and the second airfoil to effect gas-liquid heat exchange with the
further expanding gas.
[0182] 8. A system as in clause 6 or 7 wherein the second airfoil
is located in the first chamber to define another turbine
stage.
[0183] 9. A system as in clause 6 or 7 wherein the second airfoil
is located in a second chamber in fluid communication with the
first chamber to define a second turbine.
[0184] 10. A system as in any of clauses 1-9 wherein the first
airfoil comprises a flexible material.
[0185] 11. A system as in any of clauses 1-9 wherein the first
airfoil comprises a first material having a first coefficient of
thermal expansion matched to a second material of the walls having
a second coefficient of thermal expansion, over a temperature range
of within about 15 degrees Celsius.
[0186] 12. A system as in any of clauses 1-9 further comprising a
liquid seal formed between the first airfoil and the walls.
[0187] 13. A system as in any of clauses 1-9 further comprising an
electrical generator in communication with the rotor.
[0188] 14. A system as in any of clauses 1-13 wherein the
electrical generator comprises a motor/generator.
[0189] 15. A system as in any of clauses 1-13 wherein electrical
generator is in communication with the rotor through a shaft.
[0190] 16. A system as in any of clauses 1-15 wherein the rotor is
in selective communication with an energy source to drive the first
airfoil to compress gas within the chamber and flow compressed gas
to the compressed gas storage unit.
[0191] 17. A system as in any of clauses 1-16 wherein the energy
source comprises a motor.
[0192] 18. A system as in any of clauses 1-17 wherein the motor
comprises a motor/generator.
[0193] 19. A system as in any of clauses 1-18 wherein the energy
source comprises a combustion turbine.
[0194] 20. A system as in any of clauses 1-19 wherein the energy
source comprises a wind turbine.
[0195] 21. A system as in any of clauses 1-20 wherein the energy
source comprises a steam turbine.
[0196] 22. A system as in any of clauses 1-21 wherein the first
airfoil is designed for periodic replacement based upon a wear
profile over time.
[0197] 23. A system as in any of clauses 1-22 wherein the first
airfoil comprises a hydrophilic material.
[0198] 24. A system as in any of clauses 1-23 wherein the first
airfoil comprises a hydrophobic material.
[0199] 25. A system as in any of clauses 1-24 wherein the first
airfoil comprises a high-hardness material.
[0200] 26. A method of recovering energy from compressed gas, the
method comprising:
[0201] flowing compressed gas from a compressed gas storage unit
into a chamber having an airfoil coupled to a rotor;
[0202] allowing the compressed gas to expand within the chamber and
drive rotation of the airfoil and the rotor in an absence of
combustion;
[0203] effecting gas-liquid heat exchange with the compressed gas
expanding within the chamber; and
[0204] generating electricity from rotation of the rotor.
[0205] 27. A method as in clause 26 wherein gas-liquid heat
exchange is effected by spraying liquid into the chamber.
[0206] 28. A method as in clause 26 or 27 wherein gas-liquid heat
exchange is effected by spraying liquid into a mixing chamber
located upstream from the chamber.
[0207] 29. A method as in clause 26-28 wherein gas-liquid heat
exchange is effected by bubbling the compressed gas through a
liquid.
[0208] 30. A method as in clause 26-29 wherein effecting the
gas-liquid heat exchange maintains a temperature of the expanding
compressed gas within about 15 degrees Celsius of ambient
temperature.
[0209] 31. A method as in any of clauses 26-30 further
comprising:
[0210] flowing expanded gas from the airfoil to a second
airfoil;
[0211] allowing the expanded gas to further expand and drive
rotation of the second airfoil;
[0212] effecting gas-liquid heat exchange with the further
expanding gas.
[0213] 32. A method as in any of clauses 26-31 further
comprising:
[0214] placing the rotor into selective communication with an
energy source;
[0215] causing the rotor to rotate the airfoil and compress gas
within the chamber;
[0216] effecting gas-liquid heat exchange between the gas
compressed within the chamber; and
[0217] flowing the gas compressed within the chamber to a
compressed gas storage unit or to a next higher pressure stage.
[0218] 33. A method as in any of clauses 26-32 wherein the energy
source comprises a motor.
[0219] 34. A method as in any of clauses 26-33 wherein the energy
source comprises a second turbine.
[0220] 35. A method as in any of clauses 26-34 wherein the second
turbine is in communication with the turbine through a linkage.
[0221] In general, liquid introduced to a gas compression or
expansion chamber to accomplish heat exchange according to
embodiments of the present invention, is not expected to undergo
combustion within that chamber. Thus while the liquid being
injected to perform heat exchange with a compressed or expanding
gas may be combustible (for example an oil, alcohol, kerosene,
diesel, or biodiesel), in many embodiments it is not anticipated
that the liquid will combust within the chamber. In at least this
respect, liquid introduction according to various embodiments may
differ from cases where liquids are introduced into turbines for
combustion.
[0222] FIG. 13 is a schematic view illustrating the relationship
between a reversible compressor/expander apparatus and various
other system elements. In particular, the reversible
compressor/expander apparatus 1300 is in selective fluid
communication with compressed gas storage unit 1306. The reversible
compressor/expander apparatus may also be in selective thermal
communication with thermal storage unit 1308.
[0223] In a storage mode of operation, the reversible
compressor/expander apparatus 1300 is configured to operate as a
compressor. Power received from first power source 1302 (which may
be based upon the combustion of fossil fuel) through a linkage 1303
and/or power received from second power source 1304 (which may be
based upon an intermittent renewable energy) through a linkage 1305
is used to compress gas for storage in compressed gas storage unit
1306.
[0224] In certain embodiments one or more linkages may be
mechanical in nature (for example a rotating shaft). Alternatively,
this received power may be communicated through other types of
linkages, including but not limited to electrical, magnetic,
electro-magnetic, hydraulic, pneumatic, or thermal.
[0225] In an energy generation mode of operation, the reversible
compressor/expander apparatus 1300 is configured to operate as an
expander. Compressed gas is flowed from storage unit 1306 to
apparatus 1300, where its expansion drives generator 1310 to output
electrical power, for example to grid 1312.
[0226] In certain embodiments this generator 1310 may also have a
link 1309 with the energy source 1304 in order to generate power
directly therefrom. Thus embodiments could leverage the use of a
generator already present in an existing power source (for example
the generator of a wind turbine).
[0227] In certain embodiments, the reversible compressor/expander
1300 may operate based upon reciprocation of a moveable member
(e.g. a piston) within a chamber. According to other embodiments,
the reversible compressor/expander 1300 may operate based upon
rotation of a moveable member within a chamber. For example, the
reversible compressor/expander may comprise a turbine whose blades
are rotated to compress gas, and whose blades are in turn driven to
rotate by expanding gas.
[0228] As is described extensively in the Publication, the
reversible compressor/expander may operate in conjunction with the
introduction of liquid for gas-liquid heat exchange with the gas
that is being compressed or expanding. Such gas-liquid heat
exchange allows the gas compression and/or expansion to take place
within a limited temperature range, which may be close to ambient
temperature.
[0229] By avoiding large temperature changes in the compression or
expansion of gas, embodiments employing gas-liquid heat exchange
allow energy to be stored and recovered under thermodynamically
favorable conditions. Moreover, gas compression and expansion under
a limited temperature regime close to ambient, may offer additional
benefits.
[0230] Specifically, traditional combustion turbines typically
employ thick blades. These blade thicknesses can accommodate
internal channels for carrying a cooling fluid, allowing the blades
to cope with high temperatures. For example, blades of combustion
turbines may be exposed to temperatures as high as
1100-1700.degree. C.
[0231] Such conventional turbine blades may be made from
corrosion-resistant materials exhibiting relatively low
coefficients of thermal expansion such as stainless steel, and are
designed to be rigid in order to maintain tight clearance with the
inner wall of the turbine housing. The complex structure and
stringent temperature requirements required for conventional
turbine blades can render them relatively expensive and difficult
to replace.
[0232] By contrast, gas compression/expansion for energy storage in
conjunction with gas-liquid heat exchange, may take place within a
limited temperature range that is close to ambient. Gas undergoing
compression or expansion may experience temperature change within a
range between ambient and a phase change temperature of a liquid
being introduced for heat exchange.
[0233] Accordingly, FIG. 14A shows a partial simplified view of a
turbine 1400 comprising rotor 1401 and attached blades 1402
according to an embodiment. The rotor and blades are configured to
rotate about an axis A within housing 1403.
[0234] In this embodiment, the turbine blades are fashioned out of
a smaller amount of material in order to reduce their cost. Hence
when the rotor of the turbine is stationary or moving at a low
speed as shown in FIG. 14A, the blades do not necessarily assume a
position optimal to be driven by expanding gas (or to be driven to
efficiently compress gas).
[0235] Once the turbine rotor turns at a certain rate about the
axis A, however, FIG. 14B shows that the resulting centripetal
force F causes flexion in the blades to assume this optimal
profile. In this manner, inherent energy of rotation in the turbine
is relied to impart a structural feature (rigidity) and thereby
reduce the cost of replaceable components (i.e. the blades). This
characteristic is allowed by the expected operation of the turbine
over a relatively narrow temperature range.
[0236] One potential benefit of the use of flexible turbine blades,
is the possibility of regular replacement over the lifetime of a
turbine. That is, the reduced mass of the blades may reduce their
replacement cost and facilitate handing for regular
insertion/removal from the turbine (e.g. as a cartridge or other
modular form factor). Such regular replacement of turbine blades
can address issues relating to wear of the blades resulting from
regular introduction of liquid droplets into the turbine. Thus even
if some pitting of the blades is attributable to the impact of
liquid droplets, replacement of the reduced mass blades at low cost
according to a regular schedule, could avoid future failures.
[0237] Examples of materials from which flexible blades may be
fashioned (in whole or in part), include metals such as aluminum,
stainless steel, titanium alloy, and nitinol. Other examples of
suitable materials also include thermosetting composites such as
carbon fiber with an epoxy matrix, or fiberglass with a polyester
matrix. The blade material may also include a thermoplastic
material such as polyurethane, polyamide, polyether-ether-ketone,
polyetheramide, polycarbonate, or another suitable engineering
thermoplastic, that is reinforced with a fiber such as glass,
carbon, carbon nanotubes, or other commercially available
materials.
[0238] Particular embodiments could employ a bimetallic material,
such as a sandwich of two metals. Certain such embodiments could
bend more or less depending upon the temperature and materials'
coefficients of thermal expansion.
[0239] In some embodiments non-reinforced polymers may be used for
the blades, or for a portion of the blades, to enhance the
elasticity of impacted surfaces. A blade may comprise a substrate,
such as a metal, over which a polymer is formed to make the surface
more elastic, thereby preventing damage from impacts with liquid
droplets.
[0240] A blade may be coated with an elastic material for the same
reason. The material may be a low modulus rubber or a high modulus
polymer such as polyamide. In an embodiment, the blade coating may
be stripped and replaced periodically to extend the life of the
blades.
[0241] In certain embodiments, the rotor blades may comprise a
high-hardness material. According to various embodiments the
material of the blades may be selected from carbon composites,
aluminum, titanium, stainless steel, other alloys, various
plastics, or ceramics including alumina, zirconia.
[0242] In some embodiments, the blade material may be a hydrophilic
material. A wetted hydrophilic surface may serve as a cushion
between the droplets and the blades, distributing impact force
between blade and droplet over a larger area than a non-hydrophilic
surface.
[0243] In certain embodiments, the blade material or a coating of
the blade may be hydrophobic. The use of hydrophobic materials for
exposed surfaces within the turbine may prevent or reduce wetting.
This may maintain more droplets being entrained in the gas by
causing droplets to bounce off of the surface rather than wetting
it.
[0244] FIGS. 14A-B show an embodiment of a turbine that is
simplified. In many embodiments, a turbine may feature a relatively
high number of compression and/or expansion stages. If each stage
has a pressure ratio of 1.1, a top pressure of 300 atmospheres
would utilize about 60 stages. Examples of ranges of a number of
stages in a turbine include, but are not limited to, 1-10, 1-20,
1-30, 1-40, 1-50, or 1-60 or more. In order to optimize the
efficiency of such systems, various rotors may be coupled to a
plurality of concentric shafts rotating at different
velocities.
[0245] FIG. 14C shows an embodiment of a multi-stage turbine 1430
that is unidirectional in nature. That is, the turbine blades 1432
are configured with an airfoil profile that allows the flow of gas
from low pressure region 1431 to high pressure region 1434 to
create a dedicated compressor.
[0246] As further indicated in the FIG. 14C, such a unidirectional
turbine could be thermally coupled via the technique of
counter-flow heat exchange, with another unidirectional turbine
1435 acting as a dedicated expander, to create an apparatus capable
of storing energy in the form of compressed gas within compressed
gas storage unit 1436.
[0247] In the particular embodiment of FIG. 14C, a counter-flow
heat exchanger 1439 actually comprises two counterflow heat
exchangers 1439a and 1439b, each in selective thermal communication
with a common thermal storage unit 1450. The first counterflow heat
exchanger could be configured to move heat from the output of the
gas compressor to the thermal storage unit (e.g. water or oil at 1
atm pressure) at a given time, and the second counterflow heat
exchanger could be configured to move heat back from that thermal
store into the gas feed of the expander at a later time.
[0248] Other configurations are possible, including one utilizing a
single counterflow heat exchanger between simultaneous-flows of
gases. Such an embodiment could be employed, for example, in a heat
engine mode of operation.
[0249] Other embodiments, however, could employ a reversible
(bidirectional) turbine. FIG. 14D is a simplified view of such an
embodiment of a reversible turbine 1440. For compression, the gas
enters at low pressure on the left and leaves at a higher pressure
(but lower volume) on the right to flow to a compressed gas storage
unit. For expansion, the gas would flow in the opposite direction
from the compressed gas storage unit.
[0250] For such a reversible turbine to work efficiently, the
airfoil shape of the turbine blades 1442 could be symmetrical with
regard to the left (low pressure) or right (high pressure) side.
Relatively thin airfoils can be made symmetrical to right and left
leading edges owing to their low mass. Blades made of carbon
composite could be strong yet lightweight. They could be rotated at
high RPMs and not tear themselves apart.
[0251] 1a. An apparatus comprising:
[0252] a chamber in selective fluid communication with a compressed
gas storage unit; an element configured to effect gas-liquid heat
exchange with gas expanding within the chamber in an absence of
combustion within the chamber; and
[0253] a turbine rotatable within the chamber to transmit a power
of expanding gas out of the chamber via a mechanical linkage, the
turbine comprising a flexible turbine blade configured to assume a
shape in response to a rotational force.
[0254] 2a. An apparatus as in clause 1a wherein the flexible
turbine blade is also configured to be selectively driven to
compress gas within the turbine.
[0255] 3a. An apparatus as in clause 1a or 1b wherein the chamber
is in selective fluid communication with the compressed gas storage
unit through a counterflow heat exchanger.
[0256] 4a. An apparatus as in clause 1a, 1b, or 1c further
comprising:
[0257] a second chamber in selective fluid communication with a
compressed gas storage unit;
[0258] a second element configured to effect gas-liquid heat
exchange with gas being compressed within the second chamber;
and
[0259] a second turbine configured to be driven by a second
mechanical linkage to rotate within the second chamber to cause a
second flexible turbine blade to compress gas within the second
chamber.
[0260] 5a. An apparatus as in any of clauses 1a-4a wherein the
turbine comprises an axial turbine.
[0261] 6a. An apparatus as in any of clauses 1a-5a wherein the
turbine comprises a centrifugal turbine.
[0262] 7a. An apparatus as in any of clauses 1a-6a wherein the
turbine comprises a unidirectional turbine.
[0263] 8a. An apparatus as in any of clauses 1a-7a wherein the
turbine comprises a bidirectional turbine.
[0264] As discussed at length in the Publication, certain
embodiments of energy storage systems may be in selective
communication with renewable energy sources that are intermittent
in nature, such as a wind turbine or a solar energy harvesting
apparatus (e.g. based upon thermal solar or photovoltaic
principles). In order to meet demand that is continuous (rather
than intermittent) in nature, embodiments may be configured to
selectively operate based upon alternative sources of energy.
[0265] In some embodiments, a reversible compressor/expander (or
dedicated expander) may be configured to operate based upon thermal
energy provided by the combustion of fossil fuels. For example, the
combustion of fossil fuel could be used to heat water that is
injected into a gas for heat exchange. Subsequent expansion of the
heated gas within the reversible compressor/expander, could be used
to drive a generator and provide output power where none is
available from the intermittent energy source or from a stored
supply of compressed gas.
[0266] FIG. 15A shows a simplified view of such an embodiment,
wherein the reversible compressor/expander 1540 is in communication
with a source of compressed gas. The reversible compressor/expander
is also in liquid communication through spray nozzles 1543 with
liquid 1542 (e.g. water) heated from fossil-fuel combustion energy
source 1544. In this manner, the reversible compressor/expander
could thus be selectively configured to operate as a heat
engine.
[0267] Moreover, in certain embodiments the combustion of fossil
fuel could be used to heat water into a gas itself for expansion
(e.g. steam). Such steam could then be introduced directly into the
reversible compressor/expander for expansion.
[0268] FIG. 15B shows a simplified view of such an embodiment,
wherein the reversible compressor/expander 1540 is in selective
fluid communication with input steam 1546, which may result from
heating by fossil-fuel combustion energy source 1544. Such steam
may be generated as part of operation of a steam turbine. In some
embodiments, the steam could be derived from a natural source, for
example geothermal activity.
[0269] While FIGS. 15A-B show the use of an apparatus comprising a
rotating member in the form of a turbine rotor that is configured
to selectively operate based upon steam expansion, this is not
required. Other examples of moveable members which may experience
rotational motion from steam expansion include but are not limited
to screws, lobes, vanes, scrolls, gerotors, and quasi-turbines.
[0270] And while FIGS. 15A-B show the use of an apparatus
comprising a rotating member configured to selectively operate
based upon steam expansion, this is also not required. Alternative
embodiments could comprise a reciprocating member configured to
selectively operate based upon steam expansion.
[0271] Accordingly, FIG. 15C shows a simplified view of such an
embodiment, wherein the chamber 1550 of the reciprocating-type
reversible compressor/expander 1551 is in liquid communication
through spray nozzles 1553 with liquid 1552 heated from fossil-fuel
combustion energy source 1554. In this manner, the reversible
compressor/expander could thus be selectively configured to operate
as a heat engine.
[0272] Moreover, in certain embodiments the combustion of fossil
fuel could be used to heat water into a gas itself for expansion
(e.g. steam). Such steam could then be introduced directly into the
reversible compressor/expander for expansion.
[0273] FIG. 15D shows a simplified view of such an embodiment,
wherein chamber 1560 of reciprocating-type reversible
compressor/expander 1561 is in selective fluid communication with
input steam 1562, which may result from heating by fossil-fuel
combustion energy source 1564. Such steam may be generated as part
of operation of a steam turbine. In some embodiments, the steam
could be derived from a natural source, for example geothermal
activity.
[0274] The selective fluid communication between the steam could be
achieved by operation of valving. In certain embodiments the
valving could comprise a network of two way valves and/or a
multi-way valve. In this manner, the reversible compressor/expander
could be selectively configured to operate as a steam engine.
[0275] It is noted that the specific embodiment of FIG. 15D retains
spray nozzle elements 1563 allowing communication of a liquid to
the chamber. While not employed in the particular operational mode
of FIG. 15D, such nozzles could be used in other operational modes.
In some embodiments the nozzles could be used to communicate a
thermal input from a heat source (not shown in FIG. 15D) in the
form of hot water, causing expansion of gas within the chamber
(and/or reducing a magnitude of a temperature drop experienced by
gas being expanded within the chamber). The nozzles could also be
used to communicate a thermal input from a heat sink to reduce a
magnitude of a temperature change (increase) of gas being
compressed within the chamber.
[0276] 9a. An apparatus comprising:
[0277] a chamber in selective fluid communication with a source of
stored gas, and in selective fluid communication with a source of
steam;
[0278] an element configured to selectively effect gas-liquid heat
exchange with the stored gas expanding within the chamber in an
absence of combustion within the chamber; and
[0279] a member moveable within the chamber to transmit a power of
expanding stored gas or of steam out of the chamber via a
mechanical linkage.
[0280] 10a. An apparatus as in clause 9a wherein the moveable
member is configured to rotate within the chamber.
[0281] 11a. An apparatus as in clause 9a or 10a wherein the
moveable member comprises a turbine rotor.
[0282] 12a. An apparatus as in clause 9a wherein the moveable
member is configured to reciprocate within the chamber.
[0283] 13a. An apparatus as in clause 9a or 12a wherein the
moveable member comprises a solid piston.
[0284] 14a. An apparatus as in any of clauses 9a-13a wherein the
steam source comprises combustion of a fossil fuel.
[0285] 15a. An apparatus as in any of clauses 9a-14a wherein the
steam source comprises a steam turbine.
[0286] 16a. An apparatus as in any of clauses 9a-15a wherein the
chamber is configured to be in fluid communication with the steam
source upon receipt of a signal indicating a loss of power from an
intermittent renewable energy source.
[0287] While certain of the embodiments described above have
related to introduction of a heat exchange liquid as droplets
within a gas, this is not required. Particular embodiments could
employ gas-liquid heat exchange between bubbles of gas within in
the heat exchange liquid. FIGS. 16A-16C show various views of an
embodiment which may be used for this purpose.
[0288] Specifically, FIG. 16A is a simplified top view of a portion
of an embodiment of a reversible Francis turbine 1620 that is
configurable to operate either as a compressor or as an expander.
Francis turbine 1620 comprises rotor 1622 and blades 1624 between a
high pressure liquid side 1626 and a low pressure liquid side
(shown as 1628 in FIGS. 16B-16C). Shaft S is in physical
communication with the rotor 1622, and may be in physical
communication with a generator, motor, or motor-generator (not
shown).
[0289] FIG. 16B is a cross-sectional view along the line A-A' of
FIG. 16A, showing that embodiment configured to operate as a
compressor. In particular, the shaft S is driven to rotate (for
example by a motor or motor-generator), thereby causing rotation of
the rotor and the blades attached thereto. This driven rotation
causes liquid to flow from the low pressure portion to the high
pressure portion.
[0290] Gas is introduced through bubbler(s) 1630 to the liquid in
the low pressure portion. This gas introduction could be passive
via venturi-type action, and/or could be active in combination with
a gas pump (for example to overcome the pressure drop through the
bubblers and the water head). The gas bubbles entrained within the
liquid flowing through the turbine are compressed by rotation of
the blades, with heat exchange between gas and the surrounding
liquid taking place over the large surface area of the
bubble-liquid interface.
[0291] Following this gas compression, the gas and liquid on the
high pressure side are separated in separator 1632, with the gas
being flowed to the compressed gas storage unit 1634. The separated
liquid is in turn flowed through the heat exchanger 1635 to remove
heat, and then to pump/motor 1642 operating as a motor, for liquid
depressurization and recovery of energy therefrom. The
depressurized liquid then flows back to the low pressure side to
again receive bubbles of gas bubbles for compression.
[0292] FIG. 16C is a cross-sectional view along the line A-A' of
FIG. 16A, showing that embodiment configured to operate as an
expander. In particular, compressed gas is introduced through
bubbler(s) 1633 from the compressed gas storage unit as bubbles
into the liquid on the high pressure side. The pressurized air will
drive the Francis turbine, with the pump 1642 supplying some of the
power, since it pressurizes the water to the same pressure as that
of the gas storage.
[0293] The high pressure liquid and gas bubbles entrained
therewith, flows through the Francis turbine in the direction
shown, driving rotation of the blades, attached rotor, and shaft,
in a direction opposite to that during compression. Heat exchange
between the expanding gas and the surrounding liquid takes place
over the large surface area of the bubble-liquid interface.
[0294] Following expansion, the gas and liquid are separated in
separator 1640, with the expanded gas being flowed out of the
system. The separated liquid is in turn pumped by pump/motor 1642
through the heat exchanger to add heat, and then to the high
pressure side to receive further gas bubbles for additional
expansion.
[0295] While this particular embodiment shows the introduction of
gas upstream of the turbine, this is not necessarily required.
According to certain embodiments it may prove beneficial to
introduce the bubbles somewhere directly into the turbine, for
example to minimize bubble coalescence and thereby maintain small
bubbles with lots of surface area for heat exchange. Such bubble
introduction directly into the turbine could be through the housing
and/or through the blades themselves.
[0296] And while the particular embodiment of FIGS. 16A-16C
describes a Francis turbine device exhibiting a centrifugal
orientation, this is not required. Alternative embodiments could
have other orientations, including but not limited to an axial
orientation. Kaplan- or Deriaz-type turbines can be reversible to
operate in compression or expansion.
[0297] Furthermore, while the particular embodiment of FIGS.
16A-16C describes a Francis turbine device that is reversible to be
driven as a pump, this is not required. Alternative embodiments
could employ separate apparatuses dedicated to performing gas
expansion or compression. Dedicated compressors could employ
centrifugal or radial impellers. Dedicated expanders could employ
Pelton wheels.
[0298] 17a. An apparatus comprising:
[0299] a chamber in selective fluid communication with a liquid
circuit comprising a liquid; a bubbler configured to introduce
bubbles of gas from a compressed gas storage unit into the liquid;
and
[0300] a first moveable member rotatable to transmit out of the
chamber via a mechanical linkage, a power of the gas bubbles
expanding within the liquid,
[0301] wherein a gas-liquid separator of the liquid circuit is
configured to receive a gas-liquid mixture from the chamber.
[0302] 18a. An apparatus as in clause 17a wherein the first
moveable member comprises a liquid turbine.
[0303] 19a. An apparatus as in clause 18a wherein the liquid
turbine comprises a centrifugal turbine.
[0304] 20a. An apparatus as in clause 17a wherein the liquid
turbine comprises a reversible turbine.
[0305] 21a. An apparatus as in clause 20a wherein the liquid
turbine comprises a Francis turbine.
[0306] 22a. An apparatus as in any of clauses 17a-21a wherein the
liquid turbine comprises a dedicated turbine, the apparatus further
comprising a dedicated compressor.
[0307] 23a. An apparatus as in clause 22a wherein the dedicated
compressor comprises a second bubbler configured to introduce gas
bubbles for compression by a second moveable member within a second
chamber.
[0308] 24a. An apparatus as in any of clauses 17a-23a wherein the
first moveable member comprises a propeller.
[0309] 25a. An apparatus as in any of clauses 17a-23a wherein the
first moveable member comprises a bucket.
[0310] 26a. An apparatus as in clause 18a wherein the liquid
turbine comprises an axial turbine.
[0311] As described above, elements of compressed gas systems
according to the present invention may be in communication with
other structures through one or more linkages, as generically
depicted in FIG. 17. Such linkages between a compressed gas energy
system 1700 and external elements can include physical linkages
1702 such as mechanical linkages, hydraulic linkages, magnetic
linkages, electro-magnetic linkages, electric linkages, or
pneumatic linkages.
[0312] Other possible types of linkages between embodiments of
systems according to the present invention include thermal linkages
1704, which may comprise conduits for liquid, gaseous, or solid
materials, conduits, pumps, valves, switches, regenerators, and
heat exchangers, including cross-flow heat exchangers.
[0313] As further shown in FIG. 17, other possible types of
linkages between embodiments of systems according to the present
invention and outside elements, include fluidic linkages 1706, and
communications linkages 1708. Examples of the former include flows
of material in the gas or liquid phase, and may include conduits,
valves, pumps, reservoirs, accumulators, bottles, sprayers, and
other structures.
[0314] Examples of communications linkages include wired or optical
fiber linkages 1710a and wireless communications networks 1710b,
that are locally active or which operate over a wide area. Examples
of communications networks which may be suited for use by
embodiments in accordance with the present invention include, but
are not limited to, Ethernet, CAN, WiFi, Bluetooth, DSL, dedicated
microwave links, SCADA protocols, DOE's NASPInet, DoD's SIPRNet,
IEEE 802.11, IEEE 802.15.4, Frame Relay, Asynchronous Transfer Mode
(ATM), IEC 14908, IEC 61780, IEC 61850, IEC 61970/61968, IEC 61334,
IEC 62056, ITU-T G.hn, SONET, IPv6, SNMP, TCP/IP, UDP/IP, advanced
metering infrastructure, and Smart Grid protocols.
[0315] An amount of stored work that is present in a volume of air
at a given pressure, and hence an amount of work that is stored in
system 1700 of FIG. 17, may be calculated as follows.
[0316] The quantity
W V 0 ##EQU00001##
represents the amount of work stored per unit volume in a storage
vessel. This is the storage energy density. This energy density can
be determined utilizing the following formula:
W V 0 = P a [ 1 + ( P 0 P a ) [ ln ( P 0 P a ) - 1 ] ] ;
##EQU00002##
where: W=stored work; V.sub.0=volume of the storage unit; and
P.sub.a=ambient pressure in an open system, or the low pressure in
a closed system; and P.sub.0=pressure in the tank.
[0317] Expression of this energy density from volume in units of
liters (L) and from pressure in units of atmospheres (atm),
requires the use of a conversion factor:
W V 0 = 101.325 P a [ 1 + ( P 0 P a ) [ ln ( P 0 P a ) - 1 ] ] (
Joule L ) , ##EQU00003##
where: W=stored work (Joule); V.sub.0=volume of storage unit (L);
P.sub.a=ambient pressure in an open system, or low pressure for a
closed system (atm); and P.sub.0=pressure in the tank (atm).
[0318] So, under standard conditions where:
V.sub.0=1 L;
[0319] P.sub.a=1 atm; and
P 0 P a .ident. r : W / V 0 = 101.325 [ 1 + r ( ln r - 1 ) ] (
Joule L ) , or ##EQU00004## W / V 0 = 0.101325 [ 1 + r ( ln r - 1 )
] ( kJoule L ) ##EQU00004.2##
[0320] The inverse of W/V.sub.0 represents the volume of a tank
required to store a given amount of energy. This formula may be
expressed in units of L/kWhaccording to the following:
V 0 / W ( L kW h ) = 3600 / ( W / V 0 ) , ##EQU00005##
where:
1 Joule=1 Ws;
3600 Joule=1 Wh; and
[0321] 3600 kJoule=1 kWh
[0322] This yields the following results at the given exemplary
pressures:
TABLE-US-00001 P.sub.0 W / V 0 ( kJoule L ) ##EQU00006## V 0 / W (
L kW h ) ##EQU00007## 300 atm 143 25.16 310 bar 146.5 24.57 10 atm
1.42 2533 8 atm 0.976 3687
[0323] Consideration of efficiency results in alteration of the
above equation as follows:
W V 0 = 101.325 P a [ 1 + ( P 0 P a ) [ ln ( P 0 P a ) - 1 ] ] e (
kJoule L ) , ##EQU00008##
where: e=one-way efficiency of the system.
[0324] So in a system recovering compressed air to a final pressure
(P.sub.a) of 1 atm from a storage pressure (P.sub.0) of 300 atm
with an efficiency (e) of 0.8, the quantity
V 0 / W = 31.45 ( L kW h ) . ##EQU00009##
[0325] The ability of systems according to embodiments of the
present invention, to rapidly recover energy stored in the form of
compressed gas, may render such systems potentially suitable for a
variety of roles. Several such roles involve the energy system's
placement within the network responsible for providing electrical
power to one or more end-users. Such a network is also referred to
hereafter as a power grid.
[0326] Incorporated by reference in its entirety herein for all
purposes, is the following document: "Energy Storage for the
Electricity Grid: Benefits and Market Potential Assessment Guide: A
Study for the DOE Energy Storage Systems Program", Jim Eyer &
Garth Corey, Report No. SAND2010-0815, Sandia National Laboratories
(February 2010).
[0327] FIG. 18 presents a generic description of an embodiment of a
network for the generation, transmission, distribution, and
consumption of electrical power. The embodiment shown in FIG. 18
represents a substantial simplification of an actual power network,
and should not be understood as limiting the present invention.
[0328] Power distribution network 1801 comprises a generation layer
1802 that is in electrical communication with a transmission layer
1804. Power from the transmission layer is flowed through
distribution layer 1805 to reach the individual end users 1806 of
the consumption layer 1808. Each of these layers of the power
distribution network are now described in turn.
[0329] Generation layer 1802 comprises a plurality of individual
generation assets 1810a, 1810b that are responsible for producing
electrical power in bulk quantities onto the network. Examples of
such generation assets 1810a, 1810b can include conventional power
plants that burn fossil fuels, such as coal-, natural gas-, or
oil-fired power plants. Other examples of conventional power plants
include hydroelectric, and nuclear power plants that do not consume
fossil fuels. Still other examples of generation assets include
alternative energy sources, for example those exploiting natural
temperature differences (such as geothermal and ocean depth
temperature gradients), wind turbines, or solar energy harvesting
installations (such as photovoltaic (PV) arrays and thermal solar
plants).
[0330] The assets of the generation layer generally deliver
electrical power in the form of alternating current at relatively
low voltages (<50 kV) compared to the transmission layer. This
electrical power is then fed to the transmission layer for routing.
Specifically, the interface between a generation asset and the
transmission layer is hereafter referred to as a busbar 1812.
[0331] The transmission layer comprises respective transformer
elements 1820a and 1820b that are positioned at various points
along a transmission line 1822. The step-up transformer 1820a is
located proximate to the generation assets and corresponding
busbars, and serves to increase the voltage of the electricity for
efficient communication over the transmission line. Examples of
voltages in the transmission layer may be on the order of hundreds
of kV.
[0332] At the other end of the transmission line, a step-down
transformer 1820b serves to reduce the voltage for distribution,
ultimately to individual end users. Power output by step-down
transformers of the transmission layer may be in the voltage range
of low tens of kV.
[0333] FIG. 18 presents the transmission layer in a highly
simplified form, and transmission of power may actually take place
utilizing several stages at different voltages, with the stages
demarcated by transmission substation(s) 1865. Such a transmission
substation may be present at the point of interface between
transmission line 1822 and second transmission line 1863.
[0334] The distribution layer receives the power from the
transmission layer, and then delivers this power to the end users.
Some end users 1806a receive relatively high voltages directly from
primary substation 1830a. The primary substation serves to further
reduce the voltage to a primary distribution voltage, for example
12,000 V.
[0335] Other end users receive lower voltages from the secondary
substations 1830b. Feeder lines 1832 connect the primary substation
with the secondary substation, which further reduces the primary
distribution voltage to the final voltage delivered to end users at
a meter 1834. An example of such a final voltage is 120 V.
[0336] FIG. 18 provides a general description of the physical
elements of a power network which may be used in the generation,
transmission, distribution, and consumption of electric power.
Because it forms a vital part of the public infrastructure, and
requires cooperation from a multitude of distinct geographic and
political entities, such power networks are highly regulated at
many levels (local, national, international).
[0337] FIG. 18 thus also provides a framework for classifying the
regulation of various network elements by different regulatory
agencies. For example, an element of the power network may be
regulated based upon its classification as an asset of the
generation layer, transmission layer, distribution layer, or
consumption layer, of the power network. Such regulatory
classification can play an important role in determining properties
of an energy storage system that is integrated within a power
network.
[0338] According to certain embodiments of the present invention, a
compressed gas system may be incorporated within a generation layer
of a power supply network. In certain embodiments energy recovered
from the compressed gas may supply stable electricity over a short
term period of time. According to some embodiments, energy
recovered from the compressed gas may supply electricity to smooth
or levelize variable output from a generation asset comprising a
renewable energy source, for example a wind farm.
[0339] The various assets of the generation layer of the power
network of FIG. 18, may be categorized in terms of the types of
power that are to be produced. For example, baseload generation
assets typically comprise apparatuses that are configured to
produce energy at the cheapest price. Such baseload power
generation assets are generally operated continuously at full power
in order to afford a highest efficiency and economy. Examples of
typical baseload generation assets include large power plants, such
as nuclear, coal, or oil-fired plants.
[0340] Load following generation assets generally comprise
apparatuses that are more capable of responding to changes in
demand over time, for example by being turned on/off or operating
at enhanced or diminished capacities. Examples of such load
following generation assets include but are not limited to steam
turbines and hydroelectric power plants.
[0341] A load following generation asset may be called upon to
provide additional power to meet shifting demand, with as little
advance notice as 30 minutes. Because load following generation
assets typically do not operate continuously at full capacity, they
function less efficiently and their power is in general more
expensive than that available from baseline generation assets.
[0342] A third type of generation asset are the peak generation
assets. Peak generation assets are utilized on an intermittent
basis to meet the highest levels of demand. Peak generation assets
are capable of operating on relatively short notice, but with
reduced efficiency and correspondingly greater expense. A natural
gas turbine, is one example of an apparatus that is typically
employed as a peak generation asset. Another is a diesel
generator.
[0343] While they are capable of providing power on relatively
short notice, even peak generation assets require some lead time
before they are able to produce power of the quantity and quality
necessary to meet the requirements of the power network. Examples
of such power quality requirements include stability of voltage
within a given tolerance range, and the necessity of synchronizing
frequency of output with the frequency that is already extant on
the network.
[0344] One potential feature of compressed gas energy storage and
recovery systems, is their availability on short notice, to provide
energy stored in relatively stable form. Specifically, the
compressed gas may be maintained at an elevated pressure within a
storage unit having a large volume. Examples of such storage
structures include but are not limited to man-made structures such
as tanks or abandoned mines or oil wells, or naturally-occurring
geological formations such as caverns, salt domes, or other porous
features.
[0345] Upon demand, the energy stored in the form of compressed gas
may be accessed by actuating a gas flow valve to provide fluid
communication between the storage unit and an expander apparatus.
This simple valve actuation allows rapid conversion of the energy
in the compressed gas into mechanical or electrical form.
[0346] For example, as described below expansion of the compressed
gas within a chamber may serve to drive a turbine blade also
disposed therein. A shaft associated with a rotor of the turbine
may be in mechanical communication with a generator to create the
electricity. Such a configuration allows for stable power to be
rapidly generated because no warm-up period characteristic of a
combustion engine is required. The energy in the air is available
immediately, and need only overcome the system's inertia in order
to deliver full power. A few seconds is sufficient.
[0347] Such ready availability of energy stored in the form of
compressed gas, stands in marked contrast to combustion-type
apparatuses, where stable power output may only be achieved upon
regulation of multiple flows of material. For example, stable
operation of a natural gas turbine may only occur by exercising
precise control over flows of air and natural gas, the mixing of
these flows, and the ignition of the mixture under substantially
unvarying conditions. Operation of a gas turbine to produce stable,
reliable output also requires careful management of the heat
resulting from the combustion, to produce expanding gas that is
converted to mechanical energy in the form of spinning turbine
blades.
[0348] Depending upon the particular role upon which it is called
upon to perform, a generation asset may operate with certain
performance characteristics. Certain such characteristics are
described in the table of FIG. 19.
[0349] According to certain embodiments, the compressed gas energy
storage and recovery system may be physically co-situated with the
generation asset, and may be in electrical communication with the
power network through a common busbar. Alternatively, the
generation asset and the energy storage and recovery system may be
in electrical communication with the power network through a same
transmission line.
[0350] Compressed gas energy storage and recovery systems according
to the present invention, may be incorporated into the generation
layer of a power network to levelize output of renewable energy
sources that are variable in nature. For example, the output of a
wind turbine is tied to the amount of wind that is blowing. Wind
speed can rise or fall over relatively short periods, resulting in
a corresponding rise and fall in the power output. Similarly, the
output of a solar energy harvesting apparatus is tied to the amount
of available sunshine, which can change over relatively short
periods depending upon such factors as cloud cover.
[0351] Conventionally however, power networks have relied upon
energy sources such as fossil fuel power plants, that exhibit an
output that is substantially constant and controllable over time.
This difference between renewable energy sources and those
traditionally relied upon by power networks, may pose a barrier to
the adoption renewable energy sources such as solar and wind power
that are intermittent and/or variable in nature.
[0352] Accordingly, embodiments of compressed gas energy storage
and recovery systems of the present invention may be coupled with
renewable energy sources, in order to levelize their output onto
the power network. FIG. 20 shows a simplified view of such a
levelizing function.
[0353] For example, over the time period A shown in FIG. 20, the
compressed gas energy storage and recovery system provides
sufficient output to make up for differences between the variable
output of the renewable alternative energy resource and a fixed
value Z. This fixed value may be determined, for example, based
upon terms of a contract between the owner of the generation asset
and the network operator.
[0354] Moreover, at the time period starting at point B in FIG. 20,
the energy provided by the renewable generation asset falls off
precipitously, for example based upon a complete loss of wind or an
approaching storm front. Under such circumstances, the compressed
gas energy storage and recovery system may be configured to supply
energy over a time period following B, until another generation
asset can be ramped up to replacement energy coverage over the
longer term.
[0355] Accordingly, certain embodiments compressed gas energy
storage and recovery systems may be utilized to provide stable
electrical power over a short term period, thereby covering the
time period required to ramp-up a power generation asset. In a
particular embodiment, a compressed gas energy storage and recovery
system may supply stable power with advance notice of ten minutes
or less, to cover a ramp-up period of one hour to two hours or less
of a gas turbine peak generation asset.
[0356] The following provides a listing the characteristic time
constants in which a generation asset is required to act under
various circumstances. These times, in reality are a function of
the desired service required, as well as the characteristics of the
specific generator, and thus should be considered as guidelines
rather than binding limitations. The capacities and outputs are
situational, and can vary from hundreds of kw to tens of Mw with
time durations ranging from minutes to hours.
[0357] Peak [0358] Time to Ramp--1+ hour [0359] Output--Situational
1-100 Mw [0360] Capacity--2-200 Mwh
[0361] Load Following [0362] Time to ramp--continuous in steps of
1-5 seconds [0363] Output--1 to 100 Mw [0364] Capacity--0.5 to 50
Mwh
[0365] Spinning Reserve [0366] Time to ramp--1 to 10 minutes [0367]
Output--10 to 100 Mw [0368] Capacity--20 to 500 Mwh
[0369] Standby Non-Spinning Reserve [0370] Time to ramp--1 hour
[0371] Output--10 to 100 Mw [0372] Capacity--20 to 500 Mwh
[0373] According to certain embodiments, electricity recovered from
the storage of compressed gas, may be used to supply stable
electrical power to cover the period required for a generation
asset to ramp-up. Accordingly, close proximity between the energy
storage system and the generation asset may help to facilitate a
seamless transition from electricity being output onto the network
from the storage system, to electricity being output onto the
network from the generation asset.
[0374] While desirable under certain circumstances, it is not
required that the compressed gas energy storage system according to
the present invention be physically co-situated with a power
generation asset. In particular, the increased reliability of
communication over wide area networks such as the internet, or
utility Supervisory Control and Acquisition (SCADA) systems, has
reduced the need for close proximity between different elements of
the network.
[0375] In certain embodiments, the compressed gas energy storage
and recovery system could be configured to transmit a message to
the replacement generation asset to begin the ramp-up process. Such
a message could be carried by a wide area network such as the
internet or a smart grid, where the compressed gas energy storage
and recovery system is not physically co-situated with the
replacement generation asset.
[0376] Specifically, incorporation of embodiments of compressed gas
storage and recovery systems into a power network, is also shown in
FIG. 18. According to certain embodiments, a compressed gas energy
storage and recovery system 1840b may be incorporated in the
generation layer located along the same transmission line as a
power generation asset 1810a or 1810b. In other embodiments, a
compressed gas energy storage and recovery system 1840a according
to the present invention may be physically co-situated with the
power generation asset, possibly behind the same busbar.
[0377] Locating a compressed gas energy storage and recovery system
with a power generation asset, may confer certain benefits. One
such potential benefit is a cost advantage afforded by allowing
more efficient operation.
[0378] For example, in certain embodiments the compressor element
of the compressed gas energy storage and recovery system could be
in physical communication with a moving member of a power
generation asset through a physical linkage 1841. Thus, as
described above, in a particular embodiment, the spinning blades of
a gas or wind turbine could be in physical communication with the
compressor of a compressed gas energy storage system through a
mechanical, hydraulic, or pneumatic linkage.
[0379] The direct physical communication afforded by such a linkage
may allow power to be transferred more efficiently between these
elements, thereby avoiding losses associated with having to convert
the power into electrical form. In this manner, power from an
operating gas or wind turbine could be utilized to store compressed
gas for later recovery in an output levelizing or ramp-up coverage
role.
[0380] Moreover, co-situation of the compressed gas storage and
recovery system with a generation asset, may allow efficient
communication between them of other forms of energy flows. For
example, certain embodiments of an energy storage system may be in
thermal communication through a thermal link 1842, with a
co-situated generation asset. Thus in some embodiments, an
efficiency of expansion of compressed gas by the compressed gas
energy storage system, could be enhanced utilizing heat that is
communicated from the generation asset.
[0381] In this manner, waste heat from a thermal solar power plant
could be leveraged to enhance gas expansion in the chamber of an
energy storage system. Under certain circumstances, the system and
thermal solar plant could be co-situated. In other embodiments, the
compressed gas could be brought to the generation asset through an
elongated conduit.
[0382] Siting of an energy storage system with a generation asset
may also afford actual fluid communication between these elements
through a fluid link 1844. For example, where an energy storage
system is co-situated with a gas turbine generator, the fluid link
could allow compressed gas stored by the system to be flowed
directly to such a gas turbine for combustion, thereby enhancing
the efficiency of operation of the gas turbine.
[0383] Another possible benefit which may be realized by
co-situation of the energy storage system with a power generation
asset, is the ability to leverage off of existing equipment. For
example, an existing generation asset typically already includes a
generator for converting mechanical energy into electrical power. A
compressed gas energy storage and recovery system according to the
present invention could utilize the same generator element to
convert motion from gas expansion into electrical power. Similarly,
a compressed gas energy storage and recovery system could utilize a
power generation asset's existing interface with the network
(busbar), in order to communicate power to the network.
[0384] Yet another possible benefit which may be realized by
locating an energy storage system behind the busbar in the
network's generation layer, is the resulting form of regulatory
oversight. As part of the generation layer, an energy storage
system's contact with the network is relatively simple and limited.
In particular, the energy storage system would contact the network
through a single interface, and the magnitude and direction of
flows of power through the interface would be based upon expected
operation of the generator and the energy storage system.
[0385] Co-situation of the energy storage system with a power
generation asset, may further enhance coordinated action between
the two elements. In particular, the communication link 1850
between the compressed gas energy storage system 1840a and the
co-situated generation asset may be local in nature, and hence
potentially faster and more reliable than a larger area
network.
[0386] Such close proximity between the energy storage system and
the generation asset may help to facilitate a seamless transition
between power being output onto the network from the storage
system, to power being output onto the network from the generation
asset. In the output levelizing role, close proximity between the
energy storage system and the alternative source of intermittent
energy may facilitate rapid and smooth intervention by the storage
system to produce power in the face of rapidly changing
conditions.
[0387] While desirable under certain circumstances, it is not
required that the compressed gas energy storage and recovery system
according to the present invention be physically co-situated with a
power generation asset. In particular, the increased reliability of
communication over wide area networks such as the internet, has
reduced the need for close proximity between different elements of
the network.
[0388] Accordingly, FIG. 18 also shows an embodiment of a
compressed gas energy storage and recovery system 1840b that is
located along the same transmission line as a power generation
asset 1810a. System 1840b and power generation asset 1810a may
effectively communicate over wired or wireless network link
1857.
[0389] For example, one potential role for a compressed gas energy
storage and recovery system according to embodiments of the present
invention, is to provide a governor response mechanism that may
otherwise be lacking from certain forms of alternative energy
sources. Specifically, conventional power generators involving the
flows of fluids (such as steam turbines), include a governor device
linking measured speed of the generator with a fluid flow valve.
The governor may be operated in a manner to provide negative
feedback, for example opening the valve to promote fluid flow when
operational speed is too low, and closing the valve to restrict
fluid flow when operational speed is too high.
[0390] Such generators may be designed to have Automatic Generation
Control (AGC) capability. Where additional power is needed to
stabilize frequency, voltage, or for other ancillary purposes, AGC
allows a message from the system operator requesting an increase or
decrease in output to be forwarded directly to the governor. This
signal takes precedence over the governor's own determination of
speed and other conditions.
[0391] However, certain power generation assets lack inherent AGC
capability. For example, the amount of power output by a wind
turbine is based upon a speed of rotation of the turbine blades by
the wind. Such rotation cannot be accelerated in the conventional
manner by action of a governor, in order to provide additional
voltage.
[0392] Certain forms of solar energy may also lack an intrinsic
governor response mechanism. For example, the amount of energy
available from an array of photovoltaic cells or thermal solar
system is typically dictated by sunshine, and may not necessarily
be readily augmented in order to meet a demand for additional
power.
[0393] Accordingly, some embodiments of compressed gas energy
storage and recovery systems according to the present invention may
be coupled with such non-governor generation assets of the power
network. Such a storage system could essentially take the place of
a governor, endowing the generation asset with AGC capability, and
automatically outputting more power on short notice in response to
a request for voltage stabilization by the system operator. Such a
configuration would facilitate integration of an alternative energy
source within the existing power grid infrastructure, and would not
necessarily require physical co-situation of the energy storage
system with alternative power generation asset.
[0394] Such positioning of the energy storage system in a location
different from the generation asset, may be beneficial under
certain circumstances. For example, the site of a renewable energy
source is largely dictated by the availability of natural resources
such as wind or sunlight. As a result, such alternative generation
assets may be situated in remote areas, increasing the expense of
inspection and maintenance of any co-situated elements such as a
compressed gas energy storage and recovery system. Additional costs
may be associated with transmitting the power from a remote area to
where it is needed. Accordingly, providing the energy storage
system in a more accessible location may improve the cost
effectiveness of its operation.
[0395] Positioning a compressed gas energy storage and recovery
system in a different location than a generation asset, may also
endow it with greater flexibility. Specifically, operation of such
a remotely located energy storage system would not necessarily be
tied to any particular generation asset. Thus, the compressed gas
energy storage and recovery system 1840b of FIG. 18 could readily
supply power onto the network in order to provide coverage over the
ramp-up period for generation asset 1810a, generation asset 1810b,
or both of these.
[0396] FIG. 21 shows a simplified block diagram of one embodiment
of a compressed gas storage and recovery system in accordance with
an embodiment of the present invention.
[0397] In particular, compressed gas storage and recovery system
2101 comprises compressor/expander (C/E) 2102 in fluid
communication with gas inlet 2105, and in fluid communication with
compressed gas storage unit 2103.
[0398] FIG. 21 shows that compressor/expander 2102 is in selective
physical communication with/generator (M/G) 2104 through linkage
2107. In a first mode of operation, motor/generator 2104 operates
as a motor to allow energy to be stored in the form of a compressed
gas (for example air). Motor/generator 2104 receives power from an
external source, and communicates that power to cause
compressor/expander 2102 to function as a compressor. One possible
source of power for the motor/generator 2104 is the meter 2180 that
is in electrical communication through line 2181 with substation
2182 of the distribution layer of the power grid 2114. As described
further in detail below, the power grid 2114 may be a smart grid
containing information in addition to power.
[0399] In compression, motor/generator 2104 in turn communicates
power to compressor/expander 2102 through linkage 2107, allowing
compressor/expander 2102 to function as a compressor.
Compressor/expander 2102 receives the gas from inlet 2105,
compresses the gas, and flows the compressed gas to the storage
unit 2103.
[0400] FIG. 21 also shows that the system 2101 may also be
configured to receive energy from a first (variable) alternative
source 2110 such as a wind turbine. Here, the compressor/expander
2102 is shown as being in physical communication with the wind
turbine 2110 through a linkage 2120. This linkage may be
mechanical, hydraulic, or pneumatic in nature.
[0401] The direct communication between the rotating blades of the
wind turbine and the compressor/expander, afforded by linkage 2120,
may allow for the efficient storage of energy as compressed gas
with little energy loss. Embodiments of a combined wind
turbine-compressed gas storage system are described in the
co-pending U.S. Nonprovisional patent application Ser. No.
12/730,549, which is incorporated by reference in its entirety
herein for all purposes. In certain embodiments, the energy storage
system and the alternative energy source may share a common
generator, as indicated by the physical linkage 2121.
[0402] In certain embodiments, the alternative energy storage
source may include a separate generator and provide energy in
electrical form through linkage 2183 to power motor/generator 2104
that is functioning as a motor. In certain embodiments a separate
generator in the wind turbine may be in electrical communication
with motor/generator 2104 through linkage 2183.
[0403] FIG. 21 further shows that the compressed gas energy storage
and recovery system 2101 may also be configured to receive energy
from a second (dispatchable) source 2150, such as a pipeline of oil
or natural gas. The system may draw upon this dispatchable energy
source 2150 to meet contractual commitments to supply power, for
example where previous operation has exhausted the stored
compressed gas supply.
[0404] In particular, the energy from the dispatchable source 2150
may be consumed by an element 2164 such as a natural gas turbine,
diesel motor, or gas motor, to drive motor/generator 2104 through
linkage 2122 to operate as a generator, and thereby produce
electricity for output onto the grid (for example during peak
demand periods). Energy from the alternative energy source 2150 may
also be consumed by element 2164 to drive compressor/expander 2102
through linkage 2185 to operate as a compressor, and thereby
compress gas for energy recovery, for example during off-peak
demand periods.
[0405] The element 2164 may also be in thermal communication with a
heat source 2162 through heat exchanger 2160. In this manner,
thermal energy resulting from operation of element 2164 may improve
the efficiency of expansion during recovery of energy from
compressed gas.
[0406] Where element 2164 is a turbine (such as a gas turbine), in
certain embodiments it may utilize expansion of compressed gas from
the storage unit during a combustion process. Accordingly, FIG. 21
shows element 2164 in selective fluid communication with compressed
gas storage unit 2103 through a fluid conduit 2176 and a valve
2178. Utilizing the compressed gas for combustion in this manner
may allow high efficiency recovery of the energy stored in that
compressed gas.
[0407] In certain embodiments compressor/expander 2102 may comprise
a separate compressor and a separate expander that are configurable
to be arranged to operate together as a heat engine. In such an
embodiment, heat from heat source 2162 may be used to drive
motor/generator 2104 even after gas storage unit 2103 has been
depleted.
[0408] In certain embodiments, the energy storage and recovery
system 2101 may also be co-situated with another facility 2170,
which may be a large consumer of electricity. Examples of such
facilities include but are not limited to, manufacturing centers
such as factories (including semiconductor fabrication facilities),
data centers, hospitals, ports, airports, and/or large retail
facilities such as shopping malls.
[0409] The facility 2170 and the energy storage and recovery system
2101 may share a common interface (such as a meter) with the power
grid, although power may be routed between system 2101 and facility
2170 through a separate channel 2174. Power may be communicated
directly from the energy storage and recovery system to the
facility through channel 2174 to serve as an uninterruptible power
supply (UPS), or to allow the facility to satisfy objectives
including but not limited to peak shaving, load leveling, and/or
demand response. Other links (not shown here), such as thermal,
fluidic, and/or communication, may exist between the facility and
the energy storage system, for example to allow temperature
control.
[0410] In a second mode of operation, energy stored in the
compressed gas is recovered, and compressor/expander 2102 operates
as an expander. Compressor/expander 2102 receives the compressed
gas and allows this compressed gas to expand, driving a moveable
member in communication through linkage 2107 with motor/generator
2104 that is functioning as a generator. The resulting power from
the motor/generator may be output onto the power grid via the
busbar 2172 and the transmission line 2112 for consumption.
[0411] As previously described, gas undergoing compression or
expansion will tend to experience some temperature change. In
particular, gas will tend to increase in temperature as it is
compressed, and gas will tend to decrease in temperature as it
expands.
[0412] The processes of compressing and decompressing the gas as
described above, may experience some thermal and mechanical losses.
However, these processes will occur with reduced thermal loss if
they proceed at near-isothermal conditions with a minimum change in
temperature. Such near-isothermal compression and/or expansion may
be achieved utilizing one or more techniques, including but not
limited to injection of liquid to perform heat exchange.
[0413] Accordingly, the compressor/expander apparatus 2102 of the
system 2101 is in fluid communication with one or more heat
exchanger(s) 2160 that may be selectively in thermal communication
with a heat sink or a heat source 2162. In a compression mode of
operation, the heat exchanger is placed into thermal communication
with a heat sink, for example the atmosphere, where a fan that
blows air to cool the heat exchanger. In an expansion mode of
operation, the heat exchanger is placed into thermal communication
with a heat source, for example an environmental air temperature or
a source of waste heat. The heat source may be a structure such as
a pond that is configured to receive and store heat generated by
element 2164 drawing upon energy source 2150.
[0414] While the particular embodiment of FIG. 21 shows an energy
storage and recovery system in the form of a system utilizing
compressed gas, the present invention is not limited to such a
system. Alternative embodiments of the present invention could
utilize other forms of energy storage and recovery systems located
behind the same busbar, or in communication with the same
transmission line, as a generation asset of a power supply network.
Examples of such other types of energy storage and recovery systems
include but are not limited to: pumped hydroelectric, flywheels,
batteries, ultracapacitors, thermal storage, chemical storage,
osmotic pressure storage, or superconducting rings.
[0415] The various elements of the system 2101 are in communication
with a central controller or processor 2196, that is in turn in
electronic communication with a computer-readable storage medium
2194. The central controller or processor 2196 may also be in
communication with a power grid 2114 (for example a smart grid)
through a wired connection 2116 and/or a wireless link between
nodes 2118 and 2128. The central controller or processor 2196 may
also be communication with other sources of information, for
example the internet 2122.
[0416] Based upon instructions in the form of computer code stored
on computer-readable storage medium 2194, the controller or
processor 2196 may operate to control various elements of the
system 2101. This control may be based upon data received from
various sensors in the system, values calculated from that data,
and/or information received by the controller or processor 2196
from various sources, including co-situated sources or external
sources.
[0417] In certain embodiments, the controller of the system may be
configured to commence operation based upon an instruction received
from a generation asset. For example, a compressed gas storage and
recovery system may be engaged to provide power to levelize
intermittent output from a renewable energy generation asset. In
such circumstances, the controller could then be configured to
receive a signal indicating the variable or intermittent output
from the renewable energy generation asset, and in response
generate a sufficient amount of power.
[0418] In certain embodiments, the compressed gas energy storage
and recovery system may transmit signals to a generation asset. For
example, a system engaged in the levelizing function may receive an
indication of long term loss of output from a renewable energy
generation asset (due to cloudiness or of loss of wind). Upon
detection of such an event, the system controller could be
configured to transmit a signal instructing another generation
asset to provide sufficient power coverage over longer time
frame.
[0419] FIG. 21A is a simplified block diagram showing the various
system parameters of operation of a combination
compression/expansion system in accordance with an embodiment. FIG.
21A shows that under compression, motor/generator 2104 receives
power from an external source, and communicates that power
(W.sub.in) to cause compressor/expander 2102 to function as a
compressor. Compressor/expander 2102 receives uncompressed gas at
an inlet pressure (P.sub.in), compresses the gas to a greater
pressure for storage (P.sub.st) in a chamber utilizing a moveable
element such as a piston, and flows the compressed gas to the
storage unit 2103.
[0420] FIG. 21A also shows that in a second mode of operation,
energy stored in the compressed gas is recovered, and
compressor-expander 2102 operates as an expander.
Compressor/expander 2102 receives the compressed gas at the stored
pressure P.sub.st from the storage unit 2103, and then allows the
compressed gas to expand to a lower outlet pressure P.sub.out in
the chamber. This expansion drives a moveable member which is in
communication with motor/generator 2104 that is functioning as a
generator. Power output (W.sub.out) from the compressor/expander
and communicated to the motor/generator 2104, can in turn be input
onto a power grid and consumed.
[0421] FIG. 21A also shows the existence of possible physical,
fluidic, communications, and/or thermal linkages between the
compressed gas storage and recovery system, and other elements.
[0422] While FIGS. 21 and 21A have shown an embodiment of a
compressed gas storage and recovery system having a combined
compressor/expander (C/E) and a combined motor/generator (M/G),
this is not required by the present invention. FIG. 21B shows an
alternative embodiment which utilizes separate, dedicated
compressor and expander elements 2186 and 2188, respectively, that
are in communication with separate, dedicated motor and generator
elements 2187 and 2189 respectively. In certain embodiments these
elements may be in physical communication through a single common
linkage. In other embodiments, these elements may be in physical
communication through a plurality of linkages. In still other
embodiments, motor 2187 and generator 2189 may be combined into a
single motor/generator unit.
[0423] In this embodiment as well as others, energy recovered from
expansion of compressed gas need not be routed out of the system as
electrical energy. In certain modes of operation the full amount of
the energy derived from expanding gas may be consumed for other
purposes, for example temperature control (such as heating or
cooling) and/or the compression of more gas by a compressor.
[0424] FIG. 21C shows a simplified block diagram of an alternative
embodiment of a compressed gas storage and recovery system in
accordance with an embodiment of the present invention. In the
embodiment of FIG. 21C, the dedicated compressor (C) 2186, the
dedicated expander (E) 2188, a dedicated motor (M) 2187, and a
dedicated generator (G) 2189, are all in selective physical
communication with one another through a multi-node gear system
2199. An embodiment of such a gear system is a planetary gear
system described in U.S. Nonprovisional patent application Ser. No.
12/730,549, which is incorporated by reference herein for all
purposes.
[0425] A multi-node gearing system such as a planetary gear system
may permit movement of all of the linkages at the same time, in a
subtractive or additive manner. For example where the wind is
blowing, energy from the turbine linkage may be distributed to
drive both the linkage to a generator and the linkage to a
compressor. In another example, where the wind is blowing and
demand for energy is high, the planetary gear system permits output
of the wind turbine linkage to be combined with output of an
expander linkage, to drive the linkage to the generator.
[0426] Moreover, a multi-node gear system may also be configured to
accommodate movement of fewer than all of the linkages. For
example, rotation of shaft 2241 in FIGS. 22-22A may result in the
rotation of shaft 2262 or vice-versa, where shaft 2268 is prevented
from rotating. Similarly, rotation of shaft 2241 may result in the
rotation of only shaft 2268 and vice-versa, or rotation of shaft
2262 may result in the rotation of only shaft 2268 and vice-versa.
This configuration allows for mechanical energy to be selectively
communicated between only two elements of the system, for example
where the wind turbine is stationary and it is desired to operate a
compressor based upon output of a motor.
[0427] Certain embodiments of the present invention may favorably
employ a planetary gear system to allow the transfer of mechanical
energy between different elements of the system. In particular,
such a planetary gear system may offer the flexibility to
accommodate different relative motions between the linkages in the
various modes of operation.
[0428] While FIG. 21C shows an embodiment having a multi-node gear
system, this is not required by the present invention. In
alternative embodiments, various elements of the system could be in
physical communication with each other through individual physical
linkage or through physical linkages shared with fewer than all of
the other elements.
[0429] In certain embodiments, a compressed gas energy storage and
recovery system may utilize injection of liquid to facilitate heat
exchange during compression and/or expansion. Such heat exchange
may allow temperature controlled (such as near-isothermal)
conditions to be maintained during the compression and/or expansion
processes, thereby improving efficiency of the corresponding
storage and recovery of energy.
[0430] Incorporation of compressed gas energy storage and recovery
systems into the generation layer of a power network, may allow
existing generation assets to be utilized in roles from which they
might otherwise be precluded by virtue of their ramp-up times. For
example, a potential role for generation assets may be to sell
power onto energy markets.
[0431] One such market is for the sale of energy to balance supply
with demand over time frames of greater than one hour. Such an
embodiment may dispatch power from storage systems in near-real
time in order to allow an existing generation asset to meet
short-term fluctuation in demand. These fluctuations can result
from natural causes, for example a change in an amount of power
supplied by a variable renewable energy source (such as a wind
farm). The fluctuations can also be of an artificial origin, for
example changes in rate scheduling by energy markets.
[0432] Certain embodiments of compressed gas energy storage and
recovery systems may be configured to facilitate the ramp-up of
generation assets to sell power onto wholesale energy markets over
longer time frames, for example within a day. Thus another
potential role for energy storage systems of the present invention,
may be to facilitate bulk intraday arbitrage by a generation
asset.
[0433] In such a role, a generation asset would function to ramp-up
and provide energy for sale when wholesale power is expensive. The
presence of a compressed gas energy storage system would allow a
generation asset to respond on short notice to opportunities for
such bulk intraday arbitrage.
[0434] Power from the storage system (and later replaced by power
from the generation asset after ramp-up), could be sold onto the
wholesale energy market. Such a compressed gas energy storage and
recovery system could be owned and operated by an Independent Power
Producer (IPP), a generation utility, or some other Load Serving
Entity (LSE).
[0435] Another potential role for generation assets whose ramp-up
is covered by compressed gas energy storage and recovery systems,
may be to perform diurnal renewable levelizing. Specifically, the
fast response time of such a generation asset would allow demand to
quickly be shifted from variable renewable energy sources in order
to better match load and transmission availability. For example,
where winds die down, energy from compressed gas could tide over
the power network until a gas turbine is ramped-up to cover the
loss of the renewable supply. This would increase the reliability,
and hence value, of the renewable energy.
[0436] While the above description has related to systems
classified as belonging to the generation layer whose recovered
power is sold onto wholesale energy markets, the present invention
is not limited to performing such roles. In accordance with
alternative embodiments, energy storage and recovery systems could
sell energy to other types of markets and remain within the scope
of the present invention.
[0437] An example of such an alternative market for selling power
recovered from compressed gas, is the ancillary services (A/S)
market. Broadly speaking, the ancillary services market generally
represents the sale of electrical power to the network for purposes
other than consumption by end users. Such purposes include
maintaining integrity and stability of the network, and the quality
of the power provided thereon.
[0438] The ability (capacity) to provide energy to the ancillary
services market, is usually sold for periods of less than one day,
at a market price. The Independent System Operator (ISO) pays the
capacity cost for reserving such capacity.
[0439] The actual energy itself, is sold in response to a call from
the network to provide the power for a duration. When this happens,
the owner of the system would be paid the market value of the
energy sold.
[0440] One ancillary market exists for maintaining the capacity to
provide necessary reserves needed to operate the network. That is,
the operator of the network is required to be able to supply an
amount of power above and beyond an existing demand, in order to
ensure that the network is able to meet future demand. Such
reserves are typically calculated as a percentage in excess of a
supply.
[0441] One form of reserves are contingency reserves. Contingency
reserves are summoned by the power network at relatively short
notice in response to certain events (contingencies) that are
unexpected but need to be planned for. Examples of such possible
contingencies include the failure of an element of the transmission
layer (such as a transmission line), an unanticipated surge in
demand, or the need to shut down or reduce output of a generation
element on short notice.
[0442] One form of contingency reserves are spinning reserves. Such
spinning reserves are typically available on extremely short
notice. Spinning reserves have traditionally taken the form of an
increase in output from generating units that are operating at less
than capacity, or by interruption of service to certain customers.
Such reserve is referred to as "spinning" because in order to
satisfy the demand on short notice, the generation asset may
already be on-line and operating in a synchronous manner
("spinning") with the rest of the network.
[0443] Another form of contingency reserves are standing reserves.
Standing reserves are available with a longer lead time than
spinning reserves, as the generation element is not yet
synchronously on-line. Standing reserves may also take the form of
an interruption of service to certain customers, with a
correspondingly longer notice period.
[0444] In certain embodiments, existing generation assets whose
ramp-up times are covered by compressed gas energy storage and
recovery systems according to the present invention, may be able to
function to provide contingency reserves. Such generation assets
would have the capacity to provide the necessary amount of
contingency power for a duration required by the service provider.
Various possible roles for ramp-up coverage are summarized
above.
[0445] A compressed gas energy storage and recovery system may be
incorporated within a power supply network, with an end user behind
the meter. Such an energy storage and recovery system could
function in power supply and/or temperature control roles. In
certain embodiments, the energy recovered from expansion of
compressed gas may be utilized to cool an end user. According to
some embodiments, heat generated from compression of the gas could
be utilized for heating. In functioning as a power supply, the
compressed gas energy storage and recovery system could serve as an
uninterruptible power supply (UPS) for the end-user, and/or could
function to provide power to allow the end user to perform peak
shaving and/or participate in demand response programs.
[0446] According to embodiments of the present invention, a
compressed gas energy storage and recovery system may be
incorporated within a power supply network behind the meter of an
end user. In certain embodiments energy produced by compression of
the gas, or energy recovered from expansion of the gas (and
possibly supplemented from other heat sources), may be utilized to
provide temperature control (for example cooling and/or heating) of
the end user.
[0447] Examples of some parameters for such temperature control
roles are listed in the table shown as FIG. 23.
[0448] In certain embodiments, compressed gas energy storage
systems that are located within the consumption layer, may provide
a supply of power to meet the full or partial needs of the end
user. Examples of such power supply roles include but are not
limited to functioning as an uninterruptible power supply (UPS), as
a power supply allowing the end user to engage in daily arbitrage
(i.e. the daily purchase of power from the network at times of
lower price), as a power supply allowing the end user to
participate in demand response programs, as a power supply allowing
the end user to reduce consumption below historic peak levels,
and/or as a power supply furnishing power during periods of varying
or intermittent supply from a renewable energy source, such as a
wind turbine or photovoltaic (PV) array.
[0449] Examples of some parameters for such power supply roles are
listed in the table shown as FIG. 19.
[0450] An example of a small end user includes an individual
residence or a small business. Examples of a medium-sized end users
include those with greater demands for power and/or temperature
control, for example hospitals, office buildings, large stores,
factories, or data storage centers. A large end user may include
ones made up of a plurality of individual entities, for example a
shopping mall, a residential subdivision, an academic or
administrative campus, or a transportation node such as an airport,
port, or rail line.
[0451] FIG. 18 shows incorporation of various embodiments of
compressed gas storage systems into a power network. FIG. 18 shows
that in certain embodiments, a compressed gas energy storage and
recovery system 1840a may be incorporated in the consumption layer
behind a meter 1834a with an end user 1806a. In such a
configuration, a plurality of different types of linkages 1850
(including but not limited to physical, thermal, electrical,
fluidic, and/or communication) may be present between the end user
and the energy storage and recovery system.
[0452] FIG. 18 also shows that in other embodiments, a compressed
gas energy storage and recovery system 1840b according to the
present invention may be co-situated behind a meter 1834b with both
the end user 1806b and with one or more local power sources 1855.
Examples of such local power sources include but are not limited to
wind turbines and solar energy harvesting apparatuses such as a
rooftop photovoltaic (PV) arrays and/or thermal solar systems. In
such a configuration, a plurality of different types of linkages
1850 (including but not limited to physical, electronic,
communication, thermal, and/or fluidic) may be present between the
end user and the energy storage and recovery system, between the
end user and the local generator, and/or between the energy storage
and recovery system and the local power source.
[0453] FIG. 24 shows a simplified block diagram of one embodiment
of a compressed gas storage and recovery system in accordance with
an embodiment of the present invention. In particular, compressed
gas storage and recovery system 2401 comprises a motor/generator
(M/G) 2404 configured to be in electrical communication with an end
user 2450 and with a meter 2492.
[0454] Motor/generator (M/G) 2404 is in selective physical
communication with dedicated compressor (C) 2402 through physical
linkage 2421 and clutch 2422. Motor/generator (M/G) 2404 is also in
selective physical communication with dedicated expander (E) 2405
through linkage 2423 and clutch 2424.
[0455] The dedicated compressor (C) 2402 is in selective fluid
communication with gas inlet 2403. A gas outlet 2447 of the
dedicated compressor is in selective fluid communication with
compressed gas storage unit 2432 through counterflow heat exchanger
2428 and one-way valve 2409.
[0456] In certain embodiments, the compressed gas storage unit 2432
may be in selective communication with a heat source. For example,
the compressed gas storage unit could be positioned in thermal
communication with the sun, such that during the daylight hours it
absorbs solar energy. In certain embodiments the storage unit could
be coated with a material that promotes the absorption of thermal
energy, for example a dark colored paint.
[0457] In certain embodiments the compressed gas storage unit could
be positioned in thermal communication with the sun behind an
optically transparent barrier, such as glass. The barrier could
serve to trap infrared (IR) radiation from the sun's rays, thereby
further enhancing heating of the compressed gas during daylight
hours.
[0458] A gas inlet 2449 of the dedicated expander (E) is in
selective fluid communication with compressed gas storage unit 2432
through the counterflow heat exchanger 2428 and one-way valve 2411.
The dedicated expander is in selective fluid communication with gas
outlet 2407.
[0459] As mentioned above, embodiments of the present invention
employ heat exchange with introduced liquid to achieve efficient
energy storage and recovery utilizing gas compression and expansion
under conditions of controlled temperature change. In certain
embodiments, these controlled temperature conditions may result in
near-isothermal gas compression or expansion.
[0460] Thermal energies extant within the system may be
communicated through a variety of thermal linkages. A thermal
linkage according to embodiments of the present invention may
comprise one or more elements configured in various combinations to
allow the transfer of thermal energy from one physical location to
another. Examples of possible elements of a thermal linkage include
but are not limited to, liquid flow conduits, gas flow conduits,
heat pipes, heat exchangers, loop heat pipes, and
thermosiphons.
[0461] For example, the dedicated compressor may be in selective
thermal communication with thermal sink 2462 through a thermal
linkage 2461. This thermal linkage may allow the transfer of
thermal energy in the form of heat from the compressed gas.
[0462] The dedicated expander may be in selective thermal
communication with thermal source 2488 through thermal linkage
2464. This thermal linkage may allow the transfer of thermal energy
in the form of coolness from the expanded gas.
[0463] The dedicated compressor includes a thermal linkage 2463
that is configured to communicate thermal energy in the form of
heat from the compressed gas. This thermal energy in the form of
heat may be selectively flowed through switch 2484 out of the
system, or through thermal linkage 2482 to the end user. In certain
embodiments, thermal linkage 2482 may convey heat in the form of
the compressed gas itself. In certain embodiments, the thermal
linkage may convey the heat in the form of a fluid that has
exchanged heat with the compressed gas.
[0464] The dedicated expander includes a thermal linkage 2473 that
is configured to communicate thermal energy in the form of coolness
from the expanded gas. This thermal energy in the form of coolness
may be selectively flowed through switch 2481 either out of the
system, or through thermal linkage 2480 to the end user. In certain
embodiments, thermal linkage 2473 may convey coolness in the form
of the expanded gas itself. In certain embodiments, the thermal
linkage may convey the coolness in the form of a fluid that has
exchanged heat with the expanded gas.
[0465] In certain embodiments, the thermal links 2480 and 2482 may
be configured to interface with an existing Heating, Ventilation,
and Air-Conditioning (HVAC) system in the end user. Examples of
such standard HVAC systems include but are not limited to available
from the following manufacturers: AAON, Addison Products Company,
Allied Thermal Systems, American Standard, Armstrong, Bard,
Burnham, Carrier, Coleman, Comfortmaker, Goodman, Heil, Lennox,
Nordyne, Peake Industries Limited, Rheem, Trane, and York
International.
[0466] Exemplary types of residential HVAC systems may comprise air
conditioners, heat pumps, packaged gas electric, packaged heat
pumps, packaged air conditioners, packaged dual fuel, air handlers,
and furnaces. Exemplary types of commercial HVAC systems may
comprise packaged outdoor units, including packaged rooftop units
using Puron.RTM. refrigerant, packaged rooftop units using R-22
refrigerant, and 100% Dedicated outdoor air units. Commercial HVAC
systems packaged indoors include indoor self-contained units, water
source heat pumps, and packaged terminal air conditioners.
Commercial HVAC systems may also be in the form of packaged
split-systems.
[0467] Examples include split systems (6 to 130 tons), split
systems (1.5 to 5 tons), condensers, duct free systems, furnaces,
and coils.
[0468] Examples of chillers include but are not limited to
air-cooled chillers, water-cooled chillers, condenserless chillers,
and may include condensers and other chiller components.
[0469] Airside equipment may include but is not limited to air
handlers, air terminal coils, fan coils, heat/energy recovery
units, induction units, underfloor air distribution systems and
unit ventilators. Examples of heating equipment include but are not
limited to boilers and furnaces.
[0470] In many embodiments the thermal linkages may comprise
fluidic conduits that are part of a loop or circuit of fluid flow.
In certain embodiments, fluid(s) cooled by direct or indirect
heating of the end user (or heated by direct or indirect cooling of
the end user) may be returned to the system.
[0471] Thus in certain embodiments, heated liquid outlet from the
compressor, may be circulated back to the compressor after exposure
to a heat sink (which may be an end user requiring heating).
Similarly, cooled liquid outlet from the expander may be circulated
back to the expander after exposure to a heat source (which may be
an end user requiring cooling). In both cases, the thermal exposure
could occur through one or more heat exchanger structures.
[0472] In certain embodiments, cooled gas outlet from the expander,
may be circulated back to the compressor after exposure to a heat
source in the form of an end user requiring cooling. Similarly,
heated gas outlet from the compressor may be circulated back to the
expander after exposure to a heat sink in the form of an end user
requiring heating. In such cases, the thermal exposure could occur
through one or more heat exchanger structures.
[0473] Again, the thermal linkages need not comprise a single
element. Thermal energy could be transferred from a liquid flowing
through a liquid conduit, to a gas flowing through a gas conduit
(and vice-versa), utilizing heat exchangers of various types. Such
heat exchangers may be positioned in a variety of different
locations, ranging from the site of the original heat exchange, to
inside of the end user. In certain embodiments, one or more
components of a thermal linkage could comprise a heat pipe, in
which a fluid changes phase between gas and liquid.
[0474] Operation of an embodiment of a system according to the
present invention with a power grid could be coordinated by a
central processor receiving inputs and producing outputs based upon
a control algorithm. An example of such operation is now described
in connection with FIGS. 25-25A.
[0475] FIG. 25 plots power output over time, of various elements of
a power supply network. A first element is a renewable energy
source (such as wind farm), whose output is variable depending upon
natural forces. A second element is a system according to an
embodiment of the present invention.
[0476] A third element whose power output is shown in FIG. 25, is a
short-term generation asset. Such a short-term generation asset may
be configured to provide power on short notice, but at low
efficiency and/or relatively high cost. An example of such a
short-term generation asset is a diesel generator, or even another
energy storage apparatus.
[0477] A fourth element whose power output is shown in FIG. 25, is
a longer-term generation asset. Such a longer-term generation asset
may be configured to provide efficient power at relatively low
cost, but requiring longer term notice. An example of such a
longer-term generation asset is a natural gas turbine.
[0478] Operation of these various elements may be coordinated by a
central processor, in order to maintain a stable supply of power on
the network while ensuring efficient utilization of available
resources. FIG. 25A shows a simplified view of an example of a
system 2500 comprising a processor 2502 in electronic communication
with a power supply network and with an energy storage apparatus,
the system further comprising a computer-readable storage medium
2504 in electronic communication with the processor and having
stored thereon code configured to cause the processor to:
[0479] receive an input 2506 relating to a predicted change in a
load of the power supply network, or a change in generation
capacity available to the power supply network,
[0480] process the input according to a control algorithm,
[0481] communicate a first signal 2508 either automatically causing
the energy storage apparatus to operate to output electrical power,
or recommending a human operator to instruct the energy storage
apparatus to operate to output electrical power, and
[0482] communicate a second signal 2510 either automatically
causing ramp-up of a generation asset of the power supply network,
or recommending the human operator to instruct ramp-up of a
generation asset of the power supply network.
[0483] According to certain embodiments, the input may originate
from the power supply network, for example a demand response
command). In some embodiments, the input may originate from the
meter, for example indicating consumption approaching or exceeding
a historic peak.
[0484] In certain embodiments, the input may be a predicted change
in wind or solar energy at a renewable generation asset of the
power supply network. The input may comprise an environmental
temperature change indicative of the changed load, or may comprise
a weather disturbance predictive of disruption of the power supply
network.
[0485] In certain embodiments, the energy storage apparatus may be
configured to output the electrical power directly to a consumer
located behind a meter of the power supply network. According to
particular embodiments, the energy storage apparatus may be
configured to output the electrical power onto the power supply
network, for example to a distribution or transmission layer
through a transformer, or to a generation layer through a
busbar.
[0486] In certain embodiments the energy storage system may store
energy in electrical form, for example a battery or capacitor bank.
In some embodiments, the energy storage apparatus is configured to
generate the electrical power from expansion of compressed gas in a
presence of a liquid to drive a physical linkage such as a
crankshaft. Particular embodiments may introduce the liquid by
spraying with a rotational motion followed by impingement upon a
deflection surface.
[0487] According to some embodiments, the computer readable storage
medium may further include code stored thereon to cause the
processor to communicate a signal 2512 either automatically halting
operation of the energy storage apparatus, or recommending the
human operator to instruct halting of operation of the energy
storage apparatus, in response to a signal 2514 indicating
completion of the ramp-up of the generation asset.
[0488] A system according to particular embodiments may have the
computer readable storage medium further including code stored
thereon to communicate a signal 2516 either automatically causing
replenishment of the energy storage apparatus, or recommending the
human operator to instruct replenishment of the energy storage
apparatus.
[0489] Returning to the particular example shown in FIG. 25, over
the time interval A the renewable energy source provides a power
output that varies within an expected range R. Over this same time
interval A, the system according to an embodiment provides
sufficient power to compensate for this variable power output and
thereby maintain power at a level Z. Here, Z may represent the
total power on the grid, or a portion of that total power (for
example a power commitment from the wind farm established by
contract). Accordingly, over the time period A neither the
short-term nor the long-term generation assets are required to be
used.
[0490] At a time B, the central processor receives information
indicative of a long term loss of power from the renewable
generation asset. For example, the renewable generation asset may
communicate information indicating a pattern of changed wind
velocity conforming to historical trends of substantial wind loss.
Such historical trends may also be influenced by other factors,
such as the time of year, the time of day, the particular
geographic location of the wind turbine, and meteorological models
of current and future weather activity. One possible source of
predictive wind modeling is True Wind Solutions LLC of Albany,
N.Y.
[0491] Accordingly, at time B the processor sends a signal to the
short-term generation asset, instructing its ramp-up to begin to
supply power replacing that of the renewable generation asset. As
such ramp-up is not instantaneous, the processor also notifies the
compressed gas storage system to expect to maintain or even
increase its output in order to cover the ramp-up period of the
short-term generation asset.
[0492] As predicted at time C the wind velocity drops below a
threshold T, below which no power is generated from the wind
turbine. At this point C the compressed gas energy storage system
assumes the entire load Z.
[0493] The ability of the system according to an embodiment of the
present invention to provide power, may ultimately be limited by
one or more factors, including the size of its generator, the size
of its storage capacity, and the current state of its existing
storage capacity. In addition, the system may provide power at a
certain cost that may be higher than that available from the
long-term generation asset. These pieces of information are
available as inputs to the processor. In response, at time C the
central processor notifies the longer-term generation asset to
prepare to come on-line to meet the load over the longer term.
[0494] At time D the short-term generation asset has warmed up and
comes on-line, and rapidly begins to generate power to meet the
full demand by time E. Over the period from D to E, the compressed
gas storage system correspondingly ramps down its output.
[0495] By time F, the prolonged ramp-up period for the long-term
generation asset has been reached, and that asset also now comes
on-line and begins to provide increasing power to meet the load.
Over the period from F to G, the short-term generation asset
correspondingly ramps down its output.
[0496] The transition of FIG. 25 (from the grid receiving power
primarily from the renewable energy source, to its receiving power
from a longer-term generation asset), is coordinated by the central
processor based upon information received from various sources.
This transition is accomplished with desirable efficiency from
available resources, without imperiling the stability of power on
the network.
[0497] The particular transition shown in FIG. 25, represents a
highly simplified case. For example, at any given time multiple
generation assets of different types (i.e. variable (renewable),
baseline, peak, load following) would be contributing power to meet
demand. Moreover, multiple storage apparatuses would be deployed at
different points in the network, with more than one storage
apparatus being used to satisfy demand at any given point in
time.
[0498] The specific scenario shown in FIG. 25 is also simplified in
that it shows only the activation of resources to meet demand. In a
variant of these events, the wind speed could unexpectedly pick
back up in a manner indicating continued dependable supply. In such
a scenario, based upon this newly received information the
processor could instruct/recommend suspension of ramp-up of
generation assets, or other steps accommodating the now-available
dependable supply of renewable energy.
[0499] The scenario shown in FIG. 25 is simplified in that the
overall load is shown as unchanging. In reality, the load on the
grid will experience changes over time in ways that are both
predictable (e.g. daily patterns, scheduled maintenance) and
unpredictable (storm damage, unscheduled maintenance). The ability
of the processor to rapidly respond to such changing conditions (in
the form of varying inputs), can aid a human operator in the
decision-making process.
[0500] The scenario of FIG. 25 is simplified in that it presents
only one particular chain of events (loss of generation capacity
available from a renewable resource). A myriad of other events is
of course possible, influenced by factors including but not limited
to:
[0501] weather patterns;
[0502] demand patterns;
[0503] energy pricing structures/agreements;
[0504] availability of transmission and/or distribution assets;
[0505] conditions of other interconnected power grids.
[0506] Of course, the present invention is not limited to use with
renewable energy sources, or with particular energy storage
systems. Rather, embodiments of the present invention could employ
a central processor to control (or recommend control decisions to a
human user) various assets of a power supply network to coordinate
activity with different types of energy storage, of which
compressed gas is only one example. Thus according to alternative
embodiments, a central processor could execute a control algorithm
to integrate a storage system comprising a battery, with
non-renewable generation assets of a grid, for example to meet
changing demands.
[0507] Examples of inputs to such a control algorithm executed by a
central processor, include but are not limited to:
[0508] existing/expected future load;
[0509] price of power from generation asset;
[0510] ramp-up time of generation asset;
[0511] available storage capacity;
[0512] storage recharge requirements;
[0513] status of generation asset (i.e. spinning, stand-by);
[0514] market (wholesale, A/S) price for power;
[0515] status of renewable power sources (i.e. current/future
meteorological conditions);
[0516] transmission capacity.
[0517] Examples of decisions made or recommended to a human
operator based upon inputs to a control algorithm, include but are
not limited to:
[0518] activating/de-activating generation assets;
[0519] discharging/charging storage apparatuses;
[0520] altering transmission/distribution pathways; and
[0521] purchasing power from wholesale or ancillary services
markets.
[0522] reducing/shifting demand;
[0523] In connection with reducing/shifting of demand, an energy
storage apparatus could perform this function without actually
outputting electricity onto the network through a busbar or
transformer. Specifically, an energy storage apparatus positioned
behind a meter with an end user, could output power (in electrical
or other forms) directly to that end user. Such power output from
the storage device would effectively replace the electricity drawn
by the consumer from the grid, thereby reducing the load on the
power supply network.
[0524] Embodiments of apparatuses, methods, and systems according
to the present invention may allow the conversion between different
forms of energy. For example, FIGS. 26A-B show views of an
embodiment of a system. FIG. 26A shows the input 2600 of different
energy types to an system 2602 having one or more characteristics
as described herein. FIG. 26A also shows the corresponding output
2604 of energy in various forms, from the system. FIG. 26A further
shows the optional storage of compressed gas in storage unit 2605,
between the input and the output.
[0525] Particular embodiments of compression/expansion systems
according to the present invention, have previously been shown and
described. FIG. 26B shows a generalized depiction of such a system
2602 (including the optional compressed gas storage 2605), in
communication with an energy source 2610 and with an energy
destination 2612.
[0526] Specifically, energy source 2610, system 2602, and energy
destination 14412 are in thermal communication with thermal network
2650. Such a network transmits thermal energy, and may comprise
elements such as liquid flow conduits, gas flow conduits, heat
pipes, insulated vessels, heat exchangers (including counterflow
heat exchangers), loop heat pipes, thermosiphons, heat sources, and
heat sinks. FIG. 26B particularly shows the thermal network as
including heat source 2652 and heat sink 2654, which comprise a
source of low grade heat and the external environment,
respectively.
[0527] FIG. 26B also shows energy source 2610, system 2602, and
energy destination 2612, as being in communication with fluidic
network 2660. Such a network transmits fluids including gases,
liquid, and/or mixtures thereof, and may comprise elements such as
tanks or reservoirs, liquid flow conduits, gas flow conduits,
pumps, vents, liquid flow valves, gas flow valves, switches, liquid
sprayers, gas spargers, mixers, accumulators, and separators.
[0528] Various types of separators have been mentioned above.
Gas-liquid separators and/or liquid-liquid separators may be
employed, depending upon the particular embodiments. Examples of
gas-liquid separator designs include vertical type, horizontal
type, and spherical type. A liquid collector section of a separator
may include elements such as inlet diverters including diverter
baffles, tangential baffles, centrifugal, elbows, wave breakers,
vortex breakers, defoaming plates, stilling wells, and mist
extractors.
[0529] FIG. 26B further shows energy source 2610, system 2602, and
energy destination 2612 as being in communication with physical
network 2670. Such a network transmits physical energy, and may
comprise mechanical elements configured to convert linear motion
to/from rotational motion, such as shafts (including crankshafts).
Other examples of mechanical components of physical networks
include screws, pistons, gears (including multi-node gearing
systems such as planetary gears), and motors.
[0530] Physical networks may also comprise hydraulic or pneumatic
elements, including pistons, accumulators, gas chambers liquid
chambers, gas conduits, liquid conduits, hydraulic motors,
hydraulic transformers, pneumatic motors, and others known in the
art.
[0531] FIG. 26B finally shows energy source 2610, system 2602, and
energy destination 2612 as being in communication with electrical
network 2680. Such a network transmits electrical energy, and may
comprise elements such as resistors, transistors, capacitors,
inductors, transformers, batteries, insulators, diodes, amplifiers,
power sources, bus lines, meters, busbars, filters, power
conditioning equipment, and any of the other myriad of electrical
components as are known in the art.
[0532] FIG. 27A shows a simplified schematic diagram of an
embodiment of an apparatus in accordance with the present
invention, that may be arranged in various configurations to
provide different functions. In particular, FIG. 27A shows a system
2700 comprising two chambers 2702, 2704 housing rotors and blades
connected to shaft(s) coupled to a motor/generator 2760.
[0533] According to certain embodiments (e.g. where the rotation of
the rotors is in the same direction for compression and for
expansion), the shafts may be a common shaft. Alternatively, the
shafts may be separate, and be connected to the motor/generator via
one or more intermediate linkages 2799. Examples of such
intermediate linkages include but are not limited to clutches,
multi-node gear systems, and mechanical reversing linkages (e.g.
where rotation of the rotors is in the opposite direction for
compression and expansion).
[0534] FIG. 27A shows each chamber having respective ports 2770,
2772, 2774, 2776, through which gas is flowed to/from the chamber
via a gas/liquid flow network 2798 that may comprise elements
including but not limited to such as gas flow conduits, liquid flow
conduits, valves, pumps, accumulators, heat exchangers, pulsation
dampener bottles, condensers, gas-liquid mixing chambers, and
gas-liquid separators. Gas-liquid separators of the gas/liquid flow
network may be in thermal communication with respective gas-gas
heat exchangers 2716, 2720, and in fluid communication with a
respective chamber to accomplish gas-liquid heat exchange
therein.
[0535] FIG. 27A further shows the chambers as being in selective
fluid communication with each other, with the storage tank, and
with various ports to the system, through a network of gas conduits
and multi-way valves 2706, 2708, 2710, and 2712. Operation of such
multi-way valves, in addition to operation of the gas/liquid flow
network and 2798 and component valves thereof, may be coordinated
by a central processor 2790 based upon code present in
computer-readable storage medium 2792.
[0536] FIG. 27A further shows various thermal nodes 2725, 2728,
2730, 2732, 2734, 2736, and 2740. Such thermal nodes can comprise
one or more external heat sources, or one or more external heat
sinks. Examples of such possible such external heat sources include
but are not limited to, thermal solar configurations, geothermal
phenomena, and proximate heat-emitting industrial processes.
Examples of such possible such external heat sinks include but are
not limited to, the environment (particularly at high altitudes
and/or latitudes), and geothermal phenomena (such as snow or water
depth thermal gradients). Thermal energy communicated to/from the
system at these various thermal nodes, can affect the operation of
the system.
[0537] The following table shows different configurations of the
apparatus of FIG. 27A.
TABLE-US-00002 Config. ID 1 2 3 4 Description Energy Energy Heat
Engine Heat Engine Storage Delivery Storage to storage from storage
No storage No storage Gas Flow Open Open System; Closed Open
System; FIG. 27BB; Circuit; System; FIG. 27BA; downward FIG. 27BC;
FIG. 27BD upward to from storage storage Chamber No. 2702
Compressor Expander Compressor Compressor 2704 Compressor Expander
Expander Expander Valve No. 2706 b c d b Connection: 2708 c b d d
Port a - port 2710 b c d d 2712 c b d b
[0538] FIGS. 27BA-BF are highly simplified depictions of the flow
of gases through the apparatus of FIG. 27A in various
configurations. For example, in configuration 1, (FIG. 27BB) both
chambers act as compressors. Gas is sucked in from ambient, a tank,
or another, lower pressure stage. Gas is then compressed
near-isothermally by spraying a liquid into the air during or
before compression. An amount of liquid introduced into the
chambers controls the discharge temperature of compressed gas. Heat
can be extracted from the heated compressed gas before or after it
enters the tank or a second stage.
[0539] In configuration 2 (FIG. 27BB), both chambers act as
expanders. Compressed gas is fed into the chambers from a tank
and/or another source of compressed gas (such as a higher-pressure
stage). Pressure of the compressed gas drives the physical linkages
and/or electrical generator in communication therewith. This
process produces cold gas and cool liquid that can be used,
directly or indirectly, for air-conditioning, refrigeration, or
cooling.
[0540] In configuration 3 (FIG. 27BC), one chamber acts as a
compressor and the other acts as an expander. The working gas is in
a closed loop. Gas is compressed in the compressor, producing hot
gas and hot liquid. The compressed gas is then fed into the
expander. The liquid sprayed into the expander, or the compressed
gas, can be preheated by external heat sources to generate a net
deliverable mechanical energy. Expander produces the power required
to derive the compressor, and to generate energy in various forms
(e.g. electrical/mechanical/hydraulic/pneumatic energy).
[0541] In configuration 3, gas may be flowed through a counter flow
heat exchanger. The counter flow heat exchanger may be used to
preheat the compressed gas and cool down the expanded gas.
[0542] In configuration 4 (FIG. 27BD), one chamber acts as a
compressor and the other acts as an expander. Gas is sucked in from
ambient, a tank, or another stage. The gas is then compressed
near-isothermally. Heat may be extracted from the heated compressed
gas, or additional heat may be added to the gas stream before it is
fed into the expander. The liquid sprayed into the expander may be
preheated with an external heat source. The expander produces the
power required to derive the compressor, and to generate output
energy in one or more forms (e.g.
electrical/mechanical/hydraulic/pneumatic energy).
[0543] Certain embodiments may operate in any of the above
configurations continuously, or may switch between configurations
intermittently. For example, such intermittent operation between
configurations could entail electronic control over the states of
the multi-way valves, for example such that gas is flowed to and/or
from the storage unit at particular times.
[0544] Moreover, systems according to embodiments could be operated
in a combination of the above configurations. For example, FIG.
27BE shows a simplified view of the flow of gases through the
system of FIG. 27A, in an alternative configuration combining
compressor and heat engine functions.
[0545] In certain such combined configurations, the multi-way
valves may be configured to combine multiple inputs, or to provide
multiple outputs. In the combined configuration of FIG. 27BE, one
of the multi-way valves outputs compressed gas not only to the
(right-hand) chamber acting as an expander, but also to the storage
tank.
[0546] FIG. 27BF shows a simplified view of the flow of gases
through the system of FIG. 27A, in an alternative configuration
combining expander and heat engine functions. In this
configuration, one of the multi-way valves receives compressed gas
not only from the (left-hand) chamber acting as a compressor, but
also from the storage tank. The right hand chamber recovers energy
from expansion of this combined amount of compressed gas.
[0547] While FIGS. 27BE-BF show combinations of configurations
where the gas flow path is open, embodiments of the present
invention are not limited to this approach. Alternative embodiments
could employ the flow of compressed gas to/from storage, in
combination with gas flow within a closed circuit, as in the manner
of FIG. 27BC.
[0548] In certain embodiments of configurations, a starter may be
used to initiate the action of the compressor.
[0549] Embodiments of the present invention are not limited to
expansion of compressed gas to atmospheric pressure, and under
certain circumstances the gas may be expanded to above or below
atmospheric. Moreover embodiments of the present invention are not
limited to compressing gas from ambient temperature, and under some
circumstances the inlet gas for compression may be above or below
ambient temperature.
[0550] Furthermore, the present invention is not limited to the
particular apparatus shown in FIG. 27A, and variations are
possible. For example, in some embodiments a system could be
operated with additional heat exchanger(s), or without heat
exchanger(s). In particular embodiments, the system could be
operated in parallel or series with one or more similar
systems.
[0551] Connection of embodiments of a system to one or more of the
various different networks, allows flows of energy between various
sources and destinations to be converted into different forms. The
tables of FIGS. 27C-EB show examples of the processes and pathways
of such energy conversion.
[0552] Embodiments of the present invention operating as heat
engines and receiving input in the form of thermal energy, may be
used to substitute or supplement conventional regimes relying upon
the Rankine cycle. For example, an embodiment according to the
present invention may be incorporated within a combustion- or
nuclear-based power plant in lieu of, or in supplement to, a
Rankine cycle steam turbine.
[0553] The system is not limited to receiving or outputting energy
in any single form. Instead, the system may include an ability to
combine different forms of input energy, and/or to apportion output
energy into a multitude of different forms. Such apportioning is
depicted in simplified form in FIG. 28.
[0554] Specifically, inputs in the form of compressed gas, heated
gas/liquid, cooled gas/liquid, physical energy, and/or electrical
energy, may be combined as shown to ultimately produce energy in
the form of compressed gas. Optionally, this compressed gas may be
stored for later recovery.
[0555] Upon expansion of the compressed gas (whether immediately or
following storage for some period of time), the energy released
therefrom may be apportioned between multiple forms of output. For
example, apportioning may occur between energy released in thermal
form versus non-thermal form. Such apportioning may be determined
by controlling the magnitude of the temperature change experienced
by the expanding gas, for example by an amount of liquid that is
injected.
[0556] Under certain circumstances (such as a heat wave), a large
amount of energy in thermal form may be desirable. Compressed gas
could thus be expanded in a substantially non-isothermal manner,
with the resulting cooled gas being used to absorb heat from a
user. Such non-isothermal expansion could be realized by
controlling an amount of liquid that is introduced into the
expansion chamber for heat exchange.
[0557] Conversely, where a large amount of non-thermal output is
desired, expansion could take place under isothermal or
near-isothermal conditions. Such energy recovery would result in
energy recovery at high efficiency. The transfer of heat between
gas and injected liquid, would allow thermal energy to be output in
the form of the liquid.
[0558] Still another apportioning is of the non-thermal energy. As
shown in FIG. 28, the non-thermal energy may be apportioned between
output in electrical form and in mechanical/hydraulic/pneumatic
form. For example, a rotating shaft or other physical linkage may
be in communication with a gearing system (for example a multi-node
gearing system such as a planetary gear system) allowing some of
the non-thermal output energy to drive an electrical generator to
produce electricity.
[0559] FIG. 28 shows still another apportioning, here of the
thermal energy. In particular, this thermal energy from the
expanding gas may be apportioned between heated gas and/or liquid
and/or cooled gas and/or liquid. Apportioning of energy resulting
from gas expansion between different outputs, may be accomplished
with reference to the various pathways presented in connection with
FIGS. 27BA-EB.
[0560] While certain aspects of the above description have
emphasized the storage, generation, and conversion of power, the
primary emphasis of a system according to embodiments of the
present invention could be on temperature control, with the added
benefit of reduced consumption of power from the grid. Such savings
could be achieved by 1) harnessing the cooling/heating power of the
gas and/or separated liquid, and/or 2) time-shifting the storage
and expansion of the gas to leverage economic factors such as price
and demand.
[0561] Depending upon the particular embodiment, a reversible
compressor/expander apparatus incorporated within an energy storage
system, could provide a number of potential benefits. For example,
the electrical power generated by expansion of compressed gas could
serve to firm the output of an intermittent renewable energy source
to the grid. That is, compressed gas could be expanded to allow the
generation of electricity when natural conditions are not conducive
to the generation of power (e.g. the wind is not blowing, or clouds
interfere with solar collection).
[0562] As mentioned above in connection with FIG. 13, a reversible
compressor/expander apparatus may be employed in conjunction with a
power source having an existing electrical generator. In certain
embodiments, use of a reversible compressor/expander apparatus may
also serve to reduce a size and hence cost of an electrical
generation resource and/or transmission resource associated with a
renewable energy source.
[0563] For example FIG. 29 shows a schematic view of incorporation
of an embodiment of an energy storage system 2900 with generation
resources 2902 and transmission resources 2904 of a power supply
network 2906. As shown in FIG. 29, the availability of energy
storage allows a wind turbine 2908 having a maximum power output of
1 MW but a capacity factor of only 1/3, to utilize a generator of
having an operating output of 1/3 MW to provide power to the grid
over a continuous period. Such a smaller generator may be cheaper
to purchase and more cost-effective to operate and maintain.
[0564] Moreover, the reduced size of the generator relative to the
peak power output of the renewable resource, may allow reduced
consumption of (potentially precious) transmission assets. For
example, a size of the transmission lines leading to/from the
busbar 2910 could be reduced, and/or an excess transmission
capacity freed up for allocation to other uses.
[0565] The use of a reversible compressor/expander apparatus may
also serve to improve an efficiency of operation of a generation
asset. For example, a generation asset such as a combined cycle
turbine typically operates at a highest efficiency when providing a
fixed power output.
[0566] By contrast, as discussed in the Publication a reversible
compressor/expander operating as part of an energy storage system,
may be throttleable based at least upon an amount of gas introduced
to the chamber for compression, or an amount of compressed gas
admitted to the chamber for expansion. Thus as shown in FIG. 30 a
combined cycle generation asset may be operated at peak efficiency
to provide baseline power to meet a load while a reversible
compressor/expander of a compressed gas energy storage system
throttles up or down to provide sufficient additional power to meet
changes in load attributable to fluctuation in demand.
[0567] When the load in fact actually falls below the baseline load
(e.g. T'>time>T), excess power output by the combined cycle
generation asset may be harnessed to operate the compressor to
store compressed gas for future expansion. Again, the
throttleability of the energy storage system, allows this
compression to occur with the combined cycle power plant continuing
to maintain the baseline power output.
[0568] 27a. An apparatus comprising:
[0569] an element configured to effect gas-liquid heat exchange
with gas inside a chamber; and
[0570] a mechanical linkage selectively configured to transmit
power into the chamber to cause a rotatable member to compress gas
within the chamber, the mechanical linkage configured to be in
selective communication with a baseline generation asset when a
load falls below a baseline.
[0571] 28a. An apparatus as in clause 27a wherein when the load
rises above the baseline:
[0572] the chamber is configured to be in selective fluid
communication with a compressed gas storage unit; and
[0573] the mechanical linkage is configured to transmit out of the
chamber to an electrical generator, a power of gas expanding within
the chamber.
[0574] 29a. An apparatus as in clause 27a or 28a wherein the
mechanical linkage is in selective communication with an
intermittent renewable energy source to cause the rotatable member
to compress gas within the chamber.
[0575] 30a. An apparatus as in clause 27a, 28a, or 29a wherein the
rotatable member comprises a turbine.
[0576] 31a. An apparatus as in clause 30a wherein the turbine
comprises a gas turbine.
[0577] 32a. An apparatus as in clause 30a wherein the turbine
comprises a liquid turbine.
[0578] 33a. An apparatus as in clause 29a wherein the rotatable
member comprises a blade.
* * * * *