U.S. patent application number 12/842203 was filed with the patent office on 2011-01-27 for thermal energy storage vessel, systems, and methods.
This patent application is currently assigned to BELL INDEPENDENT POWER CORPORATION. Invention is credited to John P. Bell, Joseph M. Bell, Michael S. Bower, Gerard C. Walter.
Application Number | 20110017196 12/842203 |
Document ID | / |
Family ID | 43496193 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110017196 |
Kind Code |
A1 |
Bell; John P. ; et
al. |
January 27, 2011 |
THERMAL ENERGY STORAGE VESSEL, SYSTEMS, AND METHODS
Abstract
A containment vessel for a thermal energy storage system
comprising a bottom wall joined to a surrounding containment side
wall, and a liner comprising a liner bottom disposed upon the
bottom wall of the vessel, the liner bottom having an outer
perimeter and comprising an array of plates, each of the plates
joined at a portion of its perimeter to a portion of the perimeter
of an adjacent plate by a flexible joint; and a liner side wall
joined to the outer perimeter of the liner bottom and disposed
within the containment side wall. A thermal energy storage system
comprising the containment vessel and an array of heat exchangers
is also disclosed. The heat exchangers are disposed in the vessel,
and are each supported by a support frame joined to one of the
plates of the array of plates of the liner.
Inventors: |
Bell; John P.; (Bloomfield,
NY) ; Bell; Joseph M.; (Victor, NY) ; Bower;
Michael S.; (Fillmore, NY) ; Walter; Gerard C.;
(Penfield, NY) |
Correspondence
Address: |
JOHN M. HAMMOND;PATENT INNOVATIONS LLC
150 LUCIUS GORDON DRIVE, SUITE 205
WEST HENRIETTA
NY
14586
US
|
Assignee: |
BELL INDEPENDENT POWER
CORPORATION
Pittsford
NY
|
Family ID: |
43496193 |
Appl. No.: |
12/842203 |
Filed: |
July 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61228351 |
Jul 24, 2009 |
|
|
|
Current U.S.
Class: |
126/400 ;
29/890.06 |
Current CPC
Class: |
F28D 17/02 20130101;
F28F 2265/14 20130101; F24H 1/181 20130101; F28D 20/00 20130101;
B21D 53/02 20130101; Y02E 60/14 20130101; Y02E 60/142 20130101;
Y10T 29/4935 20150115; F24D 11/003 20130101; F28D 20/021 20130101;
Y02B 10/20 20130101; F28F 2270/00 20130101; F24H 1/208 20130101;
Y02E 60/145 20130101; Y10T 29/49394 20150115; F28D 2020/0047
20130101 |
Class at
Publication: |
126/400 ;
29/890.06 |
International
Class: |
F24H 7/00 20060101
F24H007/00; B21D 51/18 20060101 B21D051/18 |
Claims
1. A vessel comprising a bottom wall joined to a surrounding
containment side wall, and a liner comprising: a. a liner bottom
disposed upon the bottom wall of the vessel, the liner bottom
having an outer perimeter and comprising an array of plates, each
of the plates joined at a portion of its perimeter to a portion of
the perimeter of an adjacent plate by a flexible joint; and b. a
liner side wall joined to the outer perimeter of the liner bottom
and disposed within the containment side wall.
2. The vessel of claim 1 wherein the vessel is cylindrical, the
vessel bottom wall is circular, and the array of plates of the
liner bottom is comprised of a plurality of radially arranged
sector-shaped plates.
3. The vessel of claim 2, wherein the array of plates is further
comprised of a central plate bounded by a portion of each of the
radially arranged sector-shaped plates.
4. The vessel of claim 3, wherein the central plate is
circular.
5. The vessel of claim 3, wherein the central plate is a
polygon.
6. The vessel of claim 5, wherein the number of radially arranged
sector-shaped plates is between three and eleven inclusive.
7. The vessel of claim 6, wherein the number of radially arranged
sector-shaped plates is seven.
8. The vessel of claim 5, wherein the number of sides of the
polygon is equal to the number of radially arranged sector-shaped
plates.
9. The vessel of claim 1, wherein each of the flexible joints is
comprised of a first riser joined to the portion of perimeter of a
first plate, and a second riser joined to the portion of perimeter
of a second plate adjacent to the first plate, and wherein the
first riser also joined to the second riser.
10. The vessel of claim 9, wherein the flexible joints are further
comprised of intermediate plates disposed between and joined to the
respective first risers and the second risers.
11. The vessel of claim 1, wherein the liner is made of a material
selected from the group consisting of plain carbon steels; steels
alloyed with copper, manganese, molybdenum, nickel, silicon,
tungsten, titanium, vanadium and chromium chromium-molybdenum alloy
steel, nickel-chromium-molybdenum alloy steel, and stainless
steels.
12. The vessel of claim 1, wherein the liner is made of stainless
steel.
13. The vessel of claim 1, wherein each of the plates of the liner
bottom is joined to the bottom wall of the vessel.
14. The vessel of claim 1, further comprising bottom insulation
disposed between the bottom wall of the vessel and the liner
bottom, and side wall insulation disposed between the containment
side wall of the vessel and the liner side wall.
15. The vessel of claim 14, wherein the side wall insulation is
compressible and expandable.
16. The vessel of claim 1, further comprising an array of heat
exchangers disposed in the vessel, each of the heat exchangers
supported by a support frame joined to one of the plates of the
array of plates of the liner.
17. The vessel of claim 16, wherein pairs of heat exchangers of the
array of heat exchangers are connected in series.
18. A method for making a vessel at a vessel construction site, the
method comprising: a. pre-fabricating modular components of the
vessel at a site other than the construction site, wherein the
modular components include vessel liner components; b. preparing
ground of the construction site to receive the vessel; c.
constructing a bottom wall and a side wall of the vessel; d.
transporting the modular components to the construction site; and
e. assembling the vessel liner components to form a vessel liner
within the vessel, the vessel liner comprising a liner bottom
disposed upon the bottom wall of the vessel, wherein the liner
bottom has an outer perimeter and comprises an array of plates,
each of the plates joined at a portion of its perimeter to a
portion of the perimeter of an adjacent plate by a flexible joint,
and a liner side wall joined to the outer perimeter of the liner
bottom and disposed within the containment side wall.
19. The method of claim 18, further comprising placing heat
exchangers supported by support frames into the vessel.
20. A method for storing thermal energy comprising: a. providing a
vessel comprised of: i. a bottom wall joined to a surrounding
containment side wall; ii. a liner comprising a liner bottom
disposed upon the bottom wall, the liner bottom having an outer
perimeter and comprising an array of plates, each of the plates
joined at a portion of its perimeter to a portion of the perimeter
of an adjacent plate by a flexible joint; and a liner side wall
joined to the outer perimeter of the liner bottom and disposed
within the containment side wall; and iii. an array of heat
exchangers disposed in the vessel; b. filling a portion of the open
volume around the heat exchangers with a thermal storage medium; c.
connecting a heat transfer fluid delivery system to the heat
exchangers; and d. connecting the heat transfer fluid delivery
system to a thermal energy source, thereby transferring thermal
energy into the thermal storage medium.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority from U.S. provisional
patent application Ser. No. 61/228,351, filed Jul. 24, 2009, the
disclosure of which is incorporated herein by reference. This
application is also related to copending commonly owned U.S. patent
application Ser. No. 12/033,604 of Geiken et al., filed Feb. 19,
2008; and to U.S. patent application Ser. No. 12/172,673 of Flynn
et al., filed Jul. 14, 2008. The disclosures of these United States
patent applications are incorporated herein by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The inventions disclosed herein relate generally to energy
storage and, more particularly, to thermal energy storage systems
and methods thereof.
[0004] 2. Description of Related Art
[0005] Worldwide, there are ever-growing demands for electricity
due to increasing populations, technology advancements requiring
the use of electricity, and the proliferation of such technology to
more and more countries around the world. At the same time, there
is an increasing push to harness reusable sources of energy to help
meet these increasing electricity demands and offset and/or replace
traditional carbon-based generators which continue to deplete
natural resources around the world.
[0006] Many solutions have been developed to collect and take
advantage of reusable sources of energy, such as solar cells, solar
mirror arrays, and wind turbines. Solar cells produce direct
current energy from sunlight using semiconductor technology. Solar
mirror arrays focus sunlight on a receiver pipe containing a heat
transfer fluid which absorbs the sun's radiant heat energy. This
heated transfer fluid is then pumped to a turbine which heats water
to produce steam, thereby driving the turbine and generating
electricity. Wind turbines use one or more airfoils to transfer
wind energy into rotational energy which spins a rotor coupled to
an electric generator, thereby producing electricity when the wind
is blowing. All three solutions produce electricity when their
associated reusable power source (sun or wind) is available, and
many communities have benefited from these clean and reusable forms
of power.
[0007] Unfortunately, when the sun or wind is not available, such
solutions are not producing any power. In the case of solar
solutions, non-reusable energy solutions are often employed during
nighttime hours. Similar issues arise for wind turbines during calm
weather. Therefore, some form of energy storage is needed to store
excess energy from the reusable power sources during power
generation times to support energy demands when the renewable power
source is unavailable or unable to meet peak demands for
energy.
[0008] Solar mirror arrays generate and transfer heat as an
inherent part of their operation. Solar cells and wind turbines
which typically generate electricity can also selectively be used
to drive heaters to generate heat and/or transfer heat from
windings to a heat transfer fluid. Several solutions have been
developed to store heat from these renewable energy sources for use
in non-energy-generating times. In particular, one or more large
vessels of a liquid may be used to temporarily contain the sensible
heat contained by oil heated in a solar field, and delivered to the
liquid in the vessels by heat exchangers disposed therein. Hot oil
is delivered to heat exchangers in a vessel containing relatively
cold liquid, and the liquid in contact with the heat exchangers is
heated up. The liquid may initially be in solid form, with some
portion of the energy transfer being in the latent heat of fusion
in the solid liquid transition.
[0009] During nighttime, or on overcast days when the solar field
is down, the flow through the heat exchangers in the thermal energy
storage vessel is directed to a steam generator which drives a
turbine, which in turn is connected to an electrical generator.
Heat is transferred from the heated liquid back into the oil in the
heat exchangers, which is pumped to the steam turbine, to drive the
turbine and generate electrical power.
[0010] One suitable energy storage medium is a molten inorganic
salt, with a liquid phase temperature range from about 400 to 750
degrees Fahrenheit (.degree. F.). This temperature range is
effective for providing high pressure steam to drive large scale
steam turbines for electrical power generation. Additionally,
inorganic salts typically have a substantially higher specific
gravity than water or organic heat transfer oils, in the range of
about two to about four times that of water. On a volumetric basis,
a molten inorganic salt can contain more sensible heat than an
equal volume of a typical organic heat transfer oil, and is thus
preferred in this regard.
[0011] Thermal energy storage systems which use molten salt are
known, such as the "Solar Two" system which was built near Barstow,
Calif., and was operational from about 1994 to 1999. This system
used molten salt comprised of a combination of about 60% sodium
nitrate and about 40% potassium nitrate as an energy storage
medium, which was circulated from a cold storage tank, through the
solar field where it was heated, to a hot storage tank. A summary
of a similar system is described and shown in FIG. 2 of the
aforementioned copending U.S. patent application Ser. No.
12/033,604 of Geiken et al.
[0012] Another known thermal energy storage system is the
single-tank thermocline energy storage system, which is also
described in the aforementioned patent application Ser. No.
12/033,604 of Geiken et al., and shown in FIG. 3 thereof. The
thermocline tank of this system contains a hot molten salt in the
top portion thereof and a relatively cool molten salt in the bottom
portion thereof. When the solar field 52 is active, a hot heat
transfer fluid is pumped from the solar field to a heat exchanger.
The relatively cool molten salt is pumped from the bottom of the
thermocline tank out to the heat exchanger where it is heated by
proximity to the hot heat transfer fluid from the solar field. The
heated molten salt is then returned to the top of the thermocline
tank. When the solar field is not active, the flow to and from the
thermocline tank is reversed. Heated molten salt is pumped out of
the top of the thermocline tank to the heat exchanger, where it
transfers its heat to the heat transfer fluid. The heat transfer
fluid is pumped to a steam turbine system for generating
electricity. The molten salt which gave up some of its heat in the
heat exchanger is then returned to the bottom of the thermocline
tank. While this system takes advantage of a vertical temperature
gradient within the thermocline tank to enable simplification to a
single tank, challenges with respect to the pumping, valving, and
delivery of molten salt through a complex network of piping to the
solar field, and to the power generator remain present.
[0013] It is therefore preferable to have a thermal energy storage
system in which the molten salt is simply contained within a vessel
as the thermal storage medium, and not pumped throughout the
overall system. Instead, the thermal energy is transferred from the
solar field to the vessel of molten salt by the circulation of a
heat transfer fluid, such as an organic heat transfer oil, from the
solar field through one or more heat exchangers immersed in the
molten salt in the vessel. In like manner, during nighttime or
overcast days, the thermal energy is transferred from the vessel of
molten salt to the power generator by the circulation of the heat
transfer fluid therebetween. The handling of heat transfer fluid by
standard pumps, valves and piping is much simpler than the
equivalent handling of a molten inorganic salt, which is corrosive,
and which is abrasive if some portion of solid phase salt
(crystals) is present, and which can solidify in the pumps, valves,
and piping at temperatures lower than 400.degree. F., thus
requiring a disruptive thawing process step to restart the
system.
[0014] By using a heat transfer fluid to perform the energy
transfer from the solar field to the thermal storage vessel, and
from the vessel to the power generator, the problems to be
addressed are simplified to those relating to containment of the
molten salt, and heat transfer to and from the molten salt. This
simplification notwithstanding, the problems of containing the
molten salt, and transferring thermal energy to and from it are
significant, particularly at the scale needed by a public utility
for an economically viable thermal energy storage process. The main
problems are summarized briefly as follows: [0015] 1. The
containment vessel is of economic necessity quite large, and the
molten salt contained therein is quite dense, on the order of two
to four times the density (or specific gravity) of water.
Consequently, the structural loads on the vessel bottom and side
wall are very high. [0016] 2. The molten salt within the vessel may
reach temperatures of up to about 750.degree. F. Therefore, the
containment vessel bottom and side walls must retain the required
structural strength to contain the molten salt at temperatures much
higher than the ambient environment. [0017] 3. The containment
vessel will undergo repeated thermal expansion and contraction, and
must be able to accommodate such extreme thermal cycling. During
system fabrication, the vessel is constructed at substantially
ambient temperature, and is then cycled up to as high as
750.degree. F. during startup and operation. The vessel is then
cycled between its minimum operating temperature (about 400.degree.
F. to about 500.degree. F.) to its maximum operating temperature of
about 750.degree. F. on a daily basis when in operation. The vessel
may also be occasionally cycled back down to ambient temperature of
between about 0.degree. F. and about 90.degree. F. during process
shutdowns. Given the requisite size of the containment vessel (on
the order of 25 feet in diameter by 30 feet high in one
embodiment), the dimensional changes of the vessel (and any
insulation contained therein or applied thereto) over the full
temperature range is significant, and must be accommodated.
Accordingly, the repeated cycles of thermal expansion and
contraction must occur without any structural failures of the
vessel, which could result in leaks of the molten salt therefrom
and/or collapse of the vessel. [0018] 4. The heat exchangers
contained within the vessel must also be able to withstand the
above-described thermal cycling, and must remain securely fixed
within the vessel during such cycling. [0019] 5. Many environments
where a thermal energy storage system may be located are
seismically active. Accordingly, the containment vessel and heat
exchangers must be able to withstand seismic events such as
earthquakes without significant damage, and without any leakage of
the molten salt. [0020] 6. A high degree of serviceability is
preferred in operation of the system. For example, it is desirable
that if a single heat exchanger develops a problem, such as a leak,
that the heat exchanger can be removed and replaced without
shutting down the overall system, thus incurring costly downtime.
[0021] 7. Modularity of the system is preferred. In construction of
the vessel and overall thermal energy storage system, a system that
is of a modular design is more cost effective. In a modular system,
a major portion of the system components can be fabricated in a
shop environment, which is better equipped and controlled, and then
shipped to the job site. Final construction and assembly can then
be done on the job site.
[0022] It is further noted that at minimum, for any thermal energy
storage system that comprises a molten inorganic salt as a thermal
storage medium, the above problems 1-4 must be simultaneously
addressed or otherwise rendered inconsequential by the features and
capabilities of the system. A system that further addresses
problems 5, 6, and/or 7 will be further advantageous.
SUMMARY
[0023] In accordance with the present disclosure, the problem of
containing a large mass of molten salt, which undergoes repeated
extreme thermal cycling in a thermal energy storage system is
solved by providing a containment vessel comprising a bottom wall
joined to a surrounding containment side wall, and a liner
comprising a liner bottom disposed upon the bottom wall of the
vessel, the liner bottom having an outer perimeter and comprising
an array of plates, each of the plates joined at a portion of its
perimeter to a portion of the perimeter of an adjacent plate by a
flexible joint; and a liner side wall joined to the outer perimeter
of the liner bottom and disposed within the containment side wall.
The vessel may be cylindrical, with the bottom wall of the vessel
correspondingly being circular.
[0024] The liner contained within the vessel is constructed so as
to be able to expand and contract under the loading thereof with
the molten salt, and in particular, due to the thermal expansion
and contraction caused by contact with the molten salt at
temperatures up to about 750.degree. F. In one embodiment, the
array of plates of the liner bottom is comprised of a plurality of
radially arranged sector-shaped plates. Such an array of plates may
be further comprised of a central plate, bounded by a portion of
each of the radially arranged sector-shaped plates. The central
plate may be circular, or the central plate may be a polygon. The
central plate may be square. The number of radially arranged
sector-shaped plates may be between three and eleven, or more,
depending upon the number and size of the heat exchangers of the
thermal energy storage system to be disposed within the vessel and
supported by the plates. In some embodiments, the number of sides
of the polygon of the central plate may be equal to the number of
radially arranged sector-shaped plates. In one embodiment, the
number of radially arranged sector-shaped plates is seven; along
with a central plate, the resulting eight total plates support
eight heat exchangers. Each of the plates of the liner bottom may
be joined to the bottom wall of the vessel.
[0025] A flexible joint which joins a plate at a portion of its
perimeter to a portion of the perimeter of an adjacent plate may be
comprised of a first riser joined to the portion of perimeter of
the first adjacent plate, and a second riser joined to the portion
of perimeter of the second adjacent plate, the first riser also
being joined to the second riser. The flexible joint may be further
comprised of an intermediate plate disposed between and joined to
the first riser and the second riser.
[0026] Depending upon the particular molten salt, the liner may be
made of a material selected from, but not limited to, plain carbon
steels; steels alloyed with copper, manganese, molybdenum, nickel,
silicon, tungsten, titanium, vanadium and chromium, individually or
in any combination thereof such as chromium-molybdenum, or
nickel-chromium-molybdenum; and stainless steels. In one
embodiment, the liner is made of 316 stainless steel.
[0027] The bottom wall and containment side wall of the vessel may
be made of concrete, and preferably, steel-reinforced concrete. The
bottom wall of the vessel may be formed so as to decrease in
thickness from the central region thereof to the perimeter region
thereof. The vessel may be further comprised of bottom thermal
insulation disposed between the bottom wall of the vessel and the
liner bottom, and side wall insulation disposed between the
containment side wall of the vessel and the liner side wall. The
side wall insulation may compressible and expandable, so as to
accommodate the radial thermal expansion and contraction of the
liner over the range of operating temperatures of the salt
contained in the vessel.
[0028] A thermal energy storage system may include the instant
containment vessel comprising a bottom wall joined to a surrounding
containment side wall, and a liner comprising a liner bottom
disposed upon the bottom wall of the vessel, the liner bottom
having an outer perimeter and comprising an array of plates, each
of the plates joined at a portion of its perimeter to a portion of
the perimeter of an adjacent plate by a flexible joint; and a liner
side wall joined to the outer perimeter of the liner bottom and
disposed within the containment side wall; and an array of heat
exchangers disposed in the vessel, each of the heat exchangers
supported by a support frame joined to one of the plates of the
array of plates of the liner. The heat exchangers may operate in
parallel, or pairs of heat exchangers of the array of heat
exchangers may be connected in series.
[0029] The roof truss assembly may be disposed on a top surface of
the containment side wall. Each of the support frames of the heat
exchangers may be joined to the roof truss assembly. For seismic
stability, each of the heat exchangers and frames may be
constrained to prevent movement in the horizontal direction;
simultaneously, the heat exchangers and frames must be permitted to
expand and contract in the vertical direction due to their exposure
to the range of operating temperatures of the salt contained in the
vessel. The problem of constraining a heat exchanger and its
support frame in the horizontal direction while permitting it to
move in the vertical direction is solved by providing a fastening
arrangement at the upper portion of the frame which joins the heat
exchanger frame to the roof truss assembly in a manner that fixes
the horizontal location of the upper portion of the frame with
respect to the truss assembly, while permitting the upper portion
of the frame to translate vertically up and down with respect to
the truss assembly.
[0030] The roof truss assembly may be comprised of a plurality of
radially disposed roof trusses. The roof truss assembly may further
include a central cage joined to each of the roof trusses. The roof
truss assembly may be radially expandable with respect to the
containment side wall of the vessel.
[0031] In accordance with the invention, a method for making a
thermal energy storage system is also provided. One aspect of the
method is that because the system is of a modular design, a large
share of the system components may be fabricated in a shop of
factory environment in a better equipped and controlled environment
and then shipped to the thermal system construction site. The
modular components include the heat exchangers, heat exchanger
support frames, vessel liner, heat transfer fluid delivery system,
and roof trusses and center cage of the roof truss assembly. This
may be done in parallel while the excavation and grading of the
site is performed. If the containment vessel is to be partially
below grade, a containment pit may be dug. The containment vessel
bottom wall and side wall may then be constructed while the modular
components are shipped to the construction site. The thermal
insulation may then be applied to the vessel bottom and/or vessel
side wall. The liner may then be fabricated from modular
components. The pre-fabricated modular heat exchanger support
frames and heat exchangers may then be placed in the containment
vessel, and the roof truss assembly may be assembled from
pre-fabricated trusses and a central cage. The heat transfer fluid
delivery system may then be constructed and connected to the heat
exchangers, the solar field, and the electrical generation station.
The thermal energy storage system may then be started up, and used
for storing and releasing thermal energy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The present disclosure will be provided with reference to
the following drawings, in which like numerals refer to like
elements, and in which:
[0033] FIG. 1 is a schematic illustration of a thermal storage
system and method in accordance with the present disclosure;
[0034] FIG. 2A is a side elevation cross-sectional of a containment
vessel and heat exchangers of the thermal storage system;
[0035] FIG. 2B is a plan view of the containment vessel, and heat
exchangers of the thermal storage system;
[0036] FIG. 2C is a perspective cutaway view of the containment
vessel and heat exchangers of the thermal storage system;
[0037] FIG. 3 is a cross-sectional view of the containment vessel
of the thermal storage system;
[0038] FIG. 4A is a plan view of the containment vessel of FIG. 3,
depicting one arrangement of an array of heat exchangers contained
therein;
[0039] FIG. 4B is a detailed cross sectional view of a plate for
supporting a heat exchanger on the bottom of the containment
vessel;
[0040] FIG. 5A is a perspective cutaway view of a liner of the
containment vessel of FIG. 3;
[0041] FIG. 5B is a plan view of the bottom of the liner of FIG.
5A;
[0042] FIG. 5C is a detailed plan view of a central plate of the
liner bottom of FIG. 5B;
[0043] FIG. 5D is a detailed plan view of a radial flexible joint
at its intersection with the central plate of the liner bottom of
FIG. 5B;
[0044] FIG. 5E is a detailed cross-sectional view of a flexible
joint of the liner bottom, taken along the line 5E-5E of FIG.
5D;
[0045] FIG. 5F is a detailed cross-sectional view of an outer end
of a flexible joint of the liner bottom, taken along the line 5E-5E
of FIG. 5B;
[0046] FIG. 5G is a detailed cross-sectional view of a joining of
the liner bottom to the liner side wall, taken along the line 5G-5G
of FIG. 5B;
[0047] FIG. 6A is a cross-sectional view of the containment vessel
of the thermal storage system, showing the thermal insulation
contained therein;
[0048] FIG. 6B is a detailed cross-sectional view of the thermal
insulation at the upper side wall of the containment vessel;
[0049] FIG. 6C is a detailed cross-sectional view of the thermal
insulation at the bottom and lower side wall of the containment
vessel;
[0050] FIG. 7A is a plan view of a roof truss assembly disposed on
the top of the containment vessel;
[0051] FIG. 7B is a side elevation view of a portion of the roof
truss assembly of FIG. 7A;
[0052] FIG. 7C is a detailed side elevation view of a bearing
support plate for supporting the roof truss assembly at the top of
the side wall of the containment vessel;
[0053] FIG. 7D is a top view of the bearing support plate of FIG.
7C, taken along line 7D-7D of FIG. 7C and shown supporting a roof
truss;
[0054] FIG. 8 is a perspective view of a heat exchanger of the
thermal energy storage system;
[0055] FIG. 9 is a perspective view of a support frame for a heat
exchanger of FIG. 8;
[0056] FIG. 10 is a perspective view of the support frame of FIG. 9
assembled with the heat exchanger of FIG. 8;
[0057] FIG. 11A is a plan view of a locating frame of the roof
truss assembly that is used to support the heat exchanger assembly
of FIG. 10;
[0058] FIG. 11B and FIG. 11C are orthogonal views of a joint of the
locating frame of FIG. 11A; and
[0059] FIG. 12 is a flow chart depicting a method of making the
applicants' thermal energy storage system.
[0060] The present invention will be described in connection with a
preferred embodiment, however, it will be understood that there is
no intent to limit the invention to the embodiment described. On
the contrary, the intent is to cover all alternatives,
modifications, and equivalents as may be included within the spirit
and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION
[0061] For a general understanding of the present invention,
reference is made to the drawings. In the drawings, like reference
numerals have been used throughout to designate identical
elements.
[0062] FIG. 1 is a schematic illustration of a thermal storage
system and method in accordance with the present disclosure. The
thermal energy storage system 100 is comprised of a containment
vessel 101, which contains a heat exchanger or an array 500 of heat
exchangers immersed in a molten salt. The system 100 is further
comprised of a liquid transfer unit 600 (that may be of a modular
design), which circulates a heat transfer fluid through the heat
exchangers during operation of the system 100. The liquid transfer
unit 600 is comprised of liquid piping, various switching and
control valves, a pump 602, and a pressure relief tank 604. The
liquid transfer unit 600 may further include a heater loop 630
comprising an oil heater 632 and an expansion tank 634 for heating
and circulating heat transfer fluid through the heat exchanger
array 500 when the system 100 is not online.
[0063] In daytime operation of the system 100, the control valves
of the liquid transfer unit 600 are positioned such that heat
transfer oil is recirculated by the pump 602 from the solar field
10, through the heat exchanger array 500 in the vessel 101, and
back out to the solar field 10. In the solar field 10, the heat
transfer fluid passes through piping in the solar collectors, which
collect and concentrate the solar radiation by suitable means such
as mirrors and/or lenses onto the piping. The heat transfer fluid
passing therethrough is heated to a high temperature of as much as
800.degree. F. This hot heat transfer fluid is then pumped through
the heat exchanger array 500 in the containment vessel 101. Heat
from the hot heat transfer fluid is transferred into the molten
salt contained in the vessel 101, and the heat transfer oil is
cooled. The relatively cold heat transfer oil is recirculated back
to the solar field for reheating. During a startup condition, the
solid salt in the vessel is heated and melted into a liquid
(molten) state, and is then further heated up beyond its melting
point. The molten salt thus contains energy in the form of the
latent heat of fusion of the salt, as well as the sensible heat of
the heated liquid. It is also noted that during the delivery of hot
oil from the solar field 10 to the system 100, some portion of the
hot oil may be routed directly to a power generating station 20 by
pumps, piping, and valving (not shown) for driving the power
generating station 20.
[0064] On overcast days and during nighttime, this sensible and
latent heat is available to be transferred back into the heat
transfer oil, and delivered to an electrical power generating
station or "power block" 20. During this portion of the operation,
the control valves of the liquid transfer unit 600 are positioned
such that heat transfer oil is recirculated by the pump 602 from
the power block 20, through the heat exchanger array 500 in the
vessel 101, and back out to the power block 20. In the power block
20, the heat transfer fluid passes through a steam generator, which
produces high pressure steam that is used to drive a turbine, which
drives an electrical generator. The heat transfer fluid passing
therethrough is cooled substantially as its thermal energy is
transferred to produce steam. This relatively cold heat transfer
fluid is then pumped through the heat exchanger array 500 in the
containment vessel 101, where it is reheated and delivered back to
the power block 20. This cycle may continue, with the thermal
energy contained in the molten salt that was transferred from the
solar field being used to generate electrical power during
nighttime or overcast days, for as long as the molten salt contains
enough thermal energy to heat the heat transfer fluid to a
temperature suitable for producing steam in the steam turbines of
the power block 20.
[0065] The salt used for thermal energy storage may be a salt
mixture, or a eutectic salt mixture. Suitable salts include,
without limitation, lithium nitrate, potassium nitrate, sodium
nitrate, sodium nitrite, calcium nitrate, lithium carbonate,
potassium carbonate, sodium carbonate, rubidium carbonate,
magnesium carbonate, lithium hydroxide, lithium fluoride, beryllium
fluoride, potassium fluoride, sodium fluoride, calcium sulfate,
barium sulfate, lithium sulfate, lithium chloride, potassium
chloride, sodium chloride, iron chloride, tin chloride, and zinc
chloride, and mixtures and solutions thereof.
[0066] A thermal energy storage system containing a molten salt
will be particularly useful in the commercial generation of
electrical power if it can contain a minimum of 3,400 MMBTU
(million British Thermal Units) for transfer to the power block 20
during nighttime or overcast days. Such a system would have the
capacity to maintain generating operation of a 50 megawatt power
block for about 6 hours.
[0067] This need for large thermal capacity in a thermal energy
storage system results in the previously recited problems of vessel
size, related structural loads, high operating temperatures, and
repeated thermal cycling. These problems are solved in the thermal
energy storage system, containment vessel, heat exchanger array,
and related support frames. The containment vessel is comprised of
a bottom wall joined to a surrounding containment side wall, and an
expandable liner. The expandable liner includes a liner bottom
disposed upon the bottom wall of the vessel, the liner bottom
having an array of plates. Each of the plates is joined at a
portion of its perimeter to a portion of the perimeter of an
adjacent plate by a flexible joint. The side wall of the liner is
joined to the outer perimeter of the liner bottom and disposed
within the containment side wall. An array of heat exchangers is
contained within the vessel. The heat exchangers are held within
support frames, which are joined to the bottom wall of the vessel,
and to a roof truss assembly disposed upon the top of the vessel.
In the following disclosure, the containment vessel of the thermal
energy storage system 100 will be described first, followed by
descriptions of the expandable liner, the thermal insulation of the
vessel, the roof truss assembly, and the heat exchanger array. The
respective relationships between these components and
sub-assemblies to form the overall thermal storage system 100, and
methods for making and assembling the system 100, vessel, liner,
and heat exchanger will also be provided.
[0068] Turning first to FIGS. 2A-2C, a portion of the thermal
energy system 100 is shown. The system 100 is comprised of a
containment vessel 101 including a liner 200 and thermal insulation
300, a roof truss assembly 400, a heat exchanger array 500, and a
liquid transfer unit 600 (FIG. 1). For the sake of simplicity of
illustration in the cross-sectional view of FIG. 2A, only two heat
exchangers of the heat exchanger array 500, and only a portion of
the roof truss assembly 400 are shown. The system 100 is also shown
with a vertical portion having been cut away; the height of the
vessel 101, liner 200, insulation 300, and heat exchanger array 500
may be greater relative to the diameter of the vessel 101 than
shown in FIG. 2A.
[0069] Referring to FIGS. 3 and 4A, in one embodiment, the
containment vessel 101 is cylindrical, with the bottom wall of the
vessel correspondingly being circular, although other vessel shapes
may be employed. The vessel 101 is comprised of a bottom wall 110
joined to a surrounding containment side wall 160. The bottom wall
110 and containment side wall 160 of the vessel may be made of
concrete, and preferably, steel-reinforced concrete comprised of
steel rebar embedded in the concrete. The bottom wall 110 of the
vessel 101 may be formed so as to decrease in thickness from the
central region 112 thereof to the perimeter region 114 thereof. The
steel rebar 116 in the bottom wall 110 may be arranged in a layered
crossed pattern, with some portion of the rebar 118 positioned
proximate to the lower surface 120 of the bottom wall 110, and some
portion of the rebar 122 positioned proximate to the upper surface
124 of the bottom wall 110.
[0070] The containment side wall 160 may be comprised of vertical
rebar 162 and horizontal rebar 164. In construction of the
containment vessel 101, the bottom wall 110 is constructed first,
followed by the side wall 160. The side wall 160 is joined to the
bottom wall 110. In one embodiment, this may be accomplished by
embedding a circular ring of L-shaped rebar 126, which protrudes
upwardly from the upper surface 124 of the bottom wall 110. When
the side wall 160 is poured, the exposed portion of the L-shaped
rebar 126 becomes embedded in the side wall 160, thereby joining
the side wall 160 to the bottom wall 110. In one embodiment, the
side wall 160 may be comprised of an lower section 166 and an upper
section 168, with the concrete of the lower section 166 being
poured first, followed by the pouring of concrete of the upper
section 168. Some vertical rebar 167 may extend from the lower
section 166 upwardly, and become embedded in the upper section 168
when it is poured, thereby joining the lower section 166 to the
upper section 168. In order to withstand the higher fluid pressure
from the molten salt at the bottom of the vessel 110, the
distribution of rebar in the lower section 166 may be "denser" than
in the upper section 168, with the lowest portion 169 of the lower
section 166 being of greatest density, as shown in FIG. 3.
[0071] To further provide strength to the vessel 110 to withstand
the higher fluid pressure from the molten salt at the bottom
thereof, the vessel 110 may be constructed such that the bottom
wall 110 and the lower section 166 of the sidewall 160 are "below
grade," i.e., buried in the surrounding ground. To construct the
vessel in this manner, a pit may be dug in the ground, and the
bottom wall 110 and lower section 166 of the side wall 160
constructed as described above. Referring again to FIG. 3, the
bottom wall 110 and lower section 166 of the side wall 160 are then
buried with backfill. In one embodiment, a layer of "engineered
fill" 40 may be filled in along most of the lower section 166 of
the side wall 110 of the vessel 101. The engineered fill 40 may be
uniformly packed such that it exerts a more uniform pressure
against the lower section 166 of the side wall 110. The remaining
portion of backfilling is accomplished with the local soil 42 that
is available on site. In one embodiment, a layer of geotextile 44
may be disposed between the outer limit of the engineered fill 40
and the backfilled soil 42. To seal the bottom wall 110 to the
sidewall 160, thereby preventing water vapor or liquid from
entering the containment vessel 101, a seal 128 between them may be
made by applying a suitable sealing material around the entire
perimeter of the vessel 101 at the outer junction of the bottom
wall 110 and side wall 160. In one embodiment, the seal 128 may be
made of rods of bentonite clay formed to the junction.
[0072] Details of one exemplary design of the applicants' thermal
energy storage system and containment vessel will now be provided.
These details are to be considered as exemplary only, and not
limiting. May other designs of the system and vessel are possible,
and are within the scope of the present invention. In this
embodiment, the side wall 160 of the vessel may be about 26 feet in
diameter and about 31 feet high, with a wall thickness of about 1.5
feet. The bottom wall of the vessel has a central region 112 of
about 3.5 feet in diameter and 5 feet thick, tapering
proportionately in the radial direction as shown in FIG. 3 to a
thickness of about 2.5 feet in the outer region 114. The bottom
wall 110 and side wall 160 may be reinforced with #6 rebar ASTM A
615 Grade 60 distributed substantially as shown in FIG. 3. The
concrete used in the bottom wall 110 may be 5000 psi (pounds per
square inch) concrete, and the concrete used in the side wall 160
may be 4000 psi (pounds per square inch) concrete. The geotextile
may be MIRAFI.RTM. 500.times. sold by the TenCate Geosynthetics
Corporation of Pendergrass, Ga., USA. The engineered fill may be
naturally occurring material or crushed stone with a gradation of
100% less than 6 inches in size, 70-100% less than 3 inches,
50-100% less than number 4 sieve, and 50% less than number 200
sieve, compacted to 95% per ASTM standard D698.
[0073] The liner 200 of the containment vessel 101 will now be
described. The liner is characterized as being able to expand and
contract under the loading thereof with molten salt, and in
particular, due to the thermal expansion and contraction caused by
contact with the molten salt at temperatures up to about
750.degree. F., during the repeated high-temperature thermal
cycling of the vessel 101 as previously described herein. The
construction and structure of the liner 200 is best understood with
reference to FIGS. 5A-5G. The liner 200 is comprised of a liner
bottom 210 disposed upon the bottom wall 110 of the vessel, and a
liner side wall 260 joined to the outer perimeter of the liner
bottom 210. The liner 200 is disposed within the containment vessel
side wall 160, and covers substantially the entire inner surface of
the side wall 160 and the vessel bottom wall 110. The liner 200 is
separated from the containment vessel walls 110 and 160 by thermal
insulation, as will be explained subsequently herein.
[0074] The liner bottom 210 is comprised of an array of plates.
Each of the plates serves to support the bottom of a heat exchanger
frame, which in turn supports a heat exchanger disposed within the
containment vessel 101, as will be described subsequently herein.
In the exemplary embodiment described and shown in the drawings
herein, the heat exchanger support frames have a square-shaped
bottom, and hence the respective "footprints" 201-208 of the heat
exchanger support frame bottoms are shown in dotted line in FIG.
5B.
[0075] The plates of the liner bottom 210 and the side wall 260 of
the liner 200 are preferably made of metal, which provides
sufficient structural strength at high temperatures, and which is
joinable at the job site by suitable means such as welding. The
particular metal must also be resistant to corrosion by the molten
salt. Suitable metals include stainless steel, titanium, and other
metals and metal alloys previously cited herein with regard to the
liner. In one embodiment, the liner 200 may be made of 316
stainless steel.
[0076] In an embodiment in which the containment vessel 101 and the
liner 200 are cylindrical in shape, as depicted in FIGS. 2A, 3A,
and 5A, the liner bottom 210 is substantially circular. In such an
embodiment, the array of plates of the liner bottom 210 may be
comprised of a plurality of radially arranged sector-shaped plates
201-217. Such an array of plates 211-217 may be further comprised
of a central plate 218, which is bounded by a portion of each of
the radially arranged sector-shaped plates 211-217. In the
embodiment depicted in FIGS. 5A-5C, the central plate 218 is
square, dimensioned to substantially match the footprint 208 of the
central heat exchanger support frame bottom. Alternatively, the
central plate 218 may be a polygon. For example, in the embodiment
depicted in FIGS. 5B and 5C, the central plate may be a heptagon,
with the sides of the heptagon being adjacent to a corresponding
portion of the perimeter of each of the respective
radially-arranged sector plates 211-217. In another embodiment, the
central plate 218 may be circular, as indicated by the inner dotted
line circle 219 of FIG. 5C.
[0077] The number of radially arranged sector-shaped plates may be
between three and eleven, or more, depending upon the number and
size of the heat exchangers of the thermal energy storage system to
be disposed within the vessel and supported by the plates. In some
embodiments, the number of sides of the polygon of the central
plate 218 may be equal to the number of radially arranged
sector-shaped plates. In the embodiment depicted in FIGS. 5A-5C,
the number of radially arranged sector-shaped plates is seven;
along with the central plate 218, the resulting eight total plates
support an array of eight heat exchangers 501-508, as depicted in
FIG. 1.
[0078] It is preferable for the heat exchangers to be firmly
supported and located within the containment vessel 101,
particularly if a seismic event such as an earthquake occurs. To
achieve this, the bottoms of each of the support stands of the heat
exchangers is firmly joined to the bottom wall 110 of the
containment vessel 101. Since this joining is made through the
liner bottom 210, each of the plates 211-218 of the liner bottom
210 is also joined to the bottom wall 110 of the containment vessel
at the location of its respective heat exchanger 501-508 that it
supports. With each of the plates 211-218 thus fixed in location in
the bottom of the containment vessel 101, when the salt contained
therein is heated from ambient temperature to a molten state at up
to about 750.degree. F., each of the plates 211-218 undergoes a
substantial thermal expansion radially outwardly from its
respective heat exchanger footprint, as indicated by arrows 299 for
plate 213. If the liner bottom 210 does not have provisions to
accommodate this thermal expansion, a problem arises in that the
expansion puts the liner bottom under very high stresses, which can
cause the liner bottom to warp and/or buckle. With repeated thermal
cycling, the liner 200 is prone to cracking and failure.
[0079] This problem is solved by providing a liner bottom 210
wherein each of the plates 211-218 is joined at a portion of its
perimeter to a portion of the perimeter of an adjacent plate by a
flexible joint. Referring again to FIGS. 5B and 5C, sectoral plates
211 and 212 are joined at a radial flexible joint 231. In like
manner, successive pairs of sector plates from plates 212-217 are
joined by radial flexible joints 232-237. The perimeter of the
central plate 218 is joined to the respective inner ends of the
sector plates 211-217 at flexible joints 221-224 disposed around
such perimeter. In another embodiment (not shown) the central plate
218 may have a heptagonal perimeter, which is joined to the
respective inner ends of the sector plates 211-217 at seven
flexible joints. In another embodiment, the central plate 218 may
have a circular perimeter 219, with the respective inner ends of
the sector plates 211-217 joined thereto at a circular flexible
joint 220.
[0080] FIG. 5D is a detailed plan view of an exemplary radial
flexible joint 233 between sector plates 213 and 214, at its
intersection with the flexible joint 222 along the perimeter of the
central plate 218 of the liner bottom 210. FIG. 5E is a detailed
cross-sectional view of one embodiment of a flexible joint of the
liner bottom, taken along the line 5E-5E of FIG. 5D. Referring
FIGS. 5D and 5E, and in one embodiment depicted therein, a flexible
radial joint such as joint 233 (or a plate perimeter joint such as
joint 222) may be made by pre-forming a sheet of metal into a first
flange 241, a first riser 242, a second riser 243, and a second
flange 244. The first flange 241 is joined to the perimeter region
246 of sector plate 213 by weld 247, and the second flange 244 is
joined to the perimeter region 248 of sector plate 214 by weld
249.
[0081] When the plates 213 and 214 expand and contract due to the
contact with the cyclically heated and cooled molten salt as
indicated by bidirectional arrows 298, the first and second risers
242 and 243 of the flexible joint 233 move correspondingly as
indicated by bidirectional arrows 297. The respective perimeter
edges 226 and 228 of the sector plates 213 and 214 are sufficiently
separated such that they do not contact each other when the thermal
cycling occurs. In that manner, the respective plates are free to
expand and contract relative to adjacent plates, without
introducing high stresses into the liner bottom 210.
[0082] Referring again to FIG. 5E, and in one embodiment, the
exemplary flexible joint 233 may be further comprised of an
intermediate plate 245 that is formed between the first and second
risers 242 and 243. In another embodiment (not shown), an upwardly
directed arched transition region may be provided between the first
and second risers 242 and 243. Referring again to FIG. 5D, at the
intersection of a radial flexible joint such as joint 233, and a
center plate perimeter flexible joint such as joint 222, the two
joints are joined and sealed to each other by welding.
[0083] The flexible joints may be made by suitable forming means
such as a sheet metal brake, or by stamping with a die. The
flexible joints may be made of the same material as the sector
plates 211-217 and the central plate 218.
[0084] FIG. 5F is a detailed cross-sectional view of an outer end
of an exemplary flexible joint 233 of the liner bottom 210, taken
along the line 5E-5E of FIG. 5B.
[0085] The outer end 227 of the flexible joint 233 may be sealed
with an end cap or plug 229 that is welded in place. In another
embodiment, the outer end 227 of the flexible joint 233 may include
a curvilinear transition region 238 that is formed to intersect and
be welded and sealed to the arcuate corner 250 of the liner bottom.
In another embodiment (not shown) a flat beveled corner may be
provided instead of an arcuate corner. In another embodiment (not
shown), a perimeter flexible joint may be provided around the outer
perimeter edges of the sector plates 211-217.
[0086] One aspect of the liner 200 of the containment vessel 101 is
that it may be designed in a modular manner, i.e. such that the
various pieces of the liner bottom 210 and liner side wall 260 may
be cut and formed in a workshop or factory, and then transported to
the job site to be assembled. The side wall 260 may be formed from
upper and lower arcuate panels that are pre-formed in a shop and
welded together at the job site. In one embodiment, the lower
panels may be thicker than the upper panels to contain the higher
fluid pressures near the bottom of the containment vessel 101. The
respective sector plates 211-217, center plate 218, radial flexible
joints 231-237, and center plate perimeter joints 221-224 may also
all be pre-cut and formed in a shop. The arcuate corner 250 may be
made in pieces by forming a suitable length of tubing into a circle
of the diameter of the liner, and cutting it axially into quarters,
and then into shorter sections. The side wall 260 may be formed in
chords for welding into the cylindrical side wall shape at the job
site.
[0087] Other configurations of the sectoral portions of the liner
bottom 210 are also possible. In one embodiment, the sectoral
portions may be formed by suitable means such as by stamping, with
a radial flexible joint running through the middle region thereof.
In such an instance, the welded seams between them may intersect
the heat exchanger support plate locations. In another embodiment,
each sectoral section could be provided with a flexible joint
formed along one radial edge, with the other radial edge being a
simple straight edge. In that manner, when the sectoral plates are
joined together, a flexible joint is provided between each of them.
Additionally, the center plate 218 could be formed with its
perimeter flexible joints integrally formed therein. Many other
configurations are possible, with the operative requirement being
that the respective adjacent plates are separated by flexible
joints to accommodate the expansion and contraction during thermal
cycling.
[0088] Details of one exemplary design of the applicants' liner 200
for a containment vessel 101 will now be provided. These details
are to be considered as exemplary only, and not limiting. May other
designs of the liner 200 are possible, and are within the scope of
the present invention. In this embodiment, the liner 200 is
dimensioned to match the previously described exemplary design of
the containment vessel 101. The side wall 260 of the liner 200 may
be about 22.5 feet in diameter and about 31 feet high. All panels
of the exemplary liner are of 316 stainless steel. Lower panels of
the liner preferably may have a minimum wall thickness of about 1/4
inch, and upper panels of the wall have a minimum thickness of
about 1/8 inch. The seven sectoral plates 211-217 and center plate
218 of the liner 200 have a minimum thickness of about 1/8
inch.
[0089] The flexible joints of the liner are formed from 14 gauge
316 stainless steel, with a flange 1/2 inches wide, a riser height
of 21/4 inches, and an intermediate plate width of 1/2 inch. The
radial flexible joints are made about 10% to 11 feet long as needed
to match the lengths of the radial edges of the sector plates
211-217. The center plate 218 is a square of about 4 feet on a
side, with the center plate flexible joints of corresponding
length; although as noted previously, the center plate may be
circular or polygonal, so long as it is large enough to place a
heat exchanger frame thereupon. The radius of the edge transition
250 between the liner bottom 210 and the liner side wall 260 is
about 4 inches, and may be made from a circularly formed 8-inch
diameter stainless steel pipe that is cut into shorter lengths and
sectioned lengthwise in quarters. In fabrication, all exposed
intersections and/or overlaps between adjacent components are fully
welded, in order to provide a maximum structural strength and
leak-free liner 200 within the containment vessel 101.
[0090] It is further noted that the liner of the instant
containment vessel is not limited to a use in which each of the
bottom plates is fixed to a supporting surface beneath them. In
other applications, the liner bottom may be supported by a
supporting surface without the plates being joined to the surface,
or the liner itself may serve as a vessel in which the expandable
bottom serves to reduce stresses from thermal expansion and
contraction, and/or mechanical loading from the liquid contained
therein.
[0091] The thermal insulation 300 of the containment vessel 101
will now be described. The insulation 300 is characterized in that
the inner portion of the side wall insulation is compressible and
expandable, so as to accommodate the radial thermal expansion and
contraction of the liner over the range of operating temperatures
of the salt contained in the vessel as previously described herein.
The construction and structure of the thermal insulation 300 is
best understood with reference to FIGS. 6A-6C, and FIGS. 4A-4B.
[0092] Referring first to FIG. 6A, the vessel 101 may be provided
with a layer of bottom thermal insulation 310. The bottom
insulation 310 may be a castable refractory insulation that is
poured and leveled on the bottom slab 110 of the vessel 101.
Suitable castable refractory insulations include, without
limitation, materials containing a combination of titanium oxide,
magnesium oxide, calcium oxide, iron (III) oxide, (cristobalite)
silica dioxide, aluminum dioxide, and (tridymite) silicon dioxide.
Referring also to FIG. 4A, when the refractory insulation is
poured, a set of support plates 131-138 may be embedded in the
upper surface 312 of the cast insulation. FIG. 4B is a detailed
cross sectional view of one exemplary support plate 131 for
supporting a heat exchanger on the bottom of the containment vessel
101, taken along line 4B-4B of FIG. 4A. The support plate 131 may
be further comprised of an array of anchor studs 141 which extend
downwardly from the lower surface 142 thereof. The anchor studs 141
may be arranged in rows and columns. In fabrication of the vessel
101, before the bottom refractory insulation 310 is poured, the
various support plates 131-138 may be placed in the desired
locations to receive and support the array of heat exchangers. Each
of the support plates 131-138 may be placed upon sets of support
stands 143, which temporarily hold the support plates 131-138 in
place until the bottom insulation 310 is poured and cured. The
support stands 143 may be made of metal sheet or wire. After the
insulation 310 is cured, the anchor studs 141 are embedded in the
insulation 310, and the top surfaces of the support plates 131-138
and the top surface 312 of the insulation are substantially flush,
i.e. coplanar. The anchor studs 133 serve to firmly secure the
support plates 131-138 in place in the bottom insulation 310, which
in turn secure the lower portion of the respective heat exchangers
and support frames in place. This aspect is beneficial in
preventing the heat exchangers from moving substantially during a
seismic event. In the event that a layer of bottom insulation 310
is not provided, the heat exchanger support plates 131-138 may be
embedded directly into the vessel bottom 110 in a similar
manner.
[0093] In the embodiment depicted in FIG. 4B, the liner bottom 210
is also shown being disposed on the layer of bottom insulation 310.
One or more layers of thermal cloth insulation may also be provided
between the liner bottom 210 and the bottom insulation 310. These
layer(s) of thermal cloth provide a reduced-friction surface for
the liner bottom 210 to expand and contract along during thermal
cycling.
[0094] Referring now to FIGS. 6B and 6C, the thermal insulation 300
of the vessel 101 is further comprised of side wall insulation 360.
In one embodiment, the side wall insulation may be comprised of a
first, outer layer of batt insulation 362 disposed on the side wall
160 of the vessel 101. In construction, the batt insulation 362 is
temporarily adhered to the side wall 160. Alternatively, a
temporary form may be constructed and a layer of side wall
refractory insulation 364 may be cast. Following the pouring and
curing of the side wall refractory insulation 364, a second, inner
layer 366 of batt insulation may be applied to the inner surface
368 of the side wall refractory insulation 364. To complete the
side wall refractory insulation 364, a cap 370 may be poured at the
top portion thereof.
[0095] The liner 200 may then be constructed within the vessel 101
as previously described herein. The liner bottom 210 is
substantially contiguous with the bottom insulation 310, with a
thermal cloth 314 optionally disposed therebetween. The liner side
wall 260 is substantially contiguous with the side wall insulation
360. During construction of the liner, additional batt insulation
372 may be disposed in the corner formed between the bottom
insulation 310, the side wall insulation 360, and the liner wall
transition 250.
[0096] One aspect of the combination of the liner 200 and the
vessel insulation 300 is that the inner side wall insulation 366 is
compressible and expandable, so as to accommodate the radial
thermal expansion and contraction of the liner 200, and the
resulting motion of the liner side wall 260 over the range of
operating temperatures of the salt contained in the vessel 101.
Referring to FIGS. 6B and 6C, it can be seen that the liner side
wall 260 moves radially inwardly and outwardly during repeated
thermal cycling, and is followed by the side wall insulation 366,
as indicated by bidirectional arrows 399. Another aspect of the
liner 200 is that the upper edge 262 of the liner side wall 260
moves vertically as indicated by bidirectional arrow 296 of FIG. 6B
as the liner side wall 260 expands and contracts during the thermal
cycling.
[0097] To accommodate this movement, during construction of the
liner 200 at ambient temperature, the upper edge 262 of the liner
side wall 260 is terminated at a distance below the upper edge 374
of the insulation cap 370. In that manner, the upper edge 262 of
the liner side wall 260 can be displaced to the extent indicated at
262E, without contacting and binding against any objects disposed
at the top of the vessel 101.
[0098] Details of one exemplary design of the applicants' thermal
insulation 300 for a containment vessel 101 will now be provided.
These details are to be considered as exemplary only, and not
limiting. May other designs of the thermal insulation 300 are
possible, and are within the scope of the present invention. In
this embodiment, the thermal insulation 300 is dimensioned to match
the previously described exemplary design of the containment vessel
101. In this embodiment, the bottom insulation 310 may be an
aluminum-silicate cement bonded castable refractory insulation,
such as, for example, "RESCOCAST 6," manufactured and sold by Resco
Products Inc., of Pittsburgh Pa., USA. The bottom insulation 310
may be about 9% inches thick. The castable side wall insulation 364
may be of the same material at a thickness of about 6 inches. In
construction, the side wall insulation 260 may be built up
vertically in several sequences of application of outer batt
insulation 362, poured cast insulation 364, and inner batt
insulation 366. The side wall batt insulation 262 and 266 may be
made of alumina, zirconia, and silica spun ceramic fibers formed
into a blanket, such as, for example, DURABLANKET.RTM. S insulation
manufactured and sold by Unifrax LLC of Niagara Falls, N.Y., USA.
The layers 362 and 366 of side wall batt insulation may be about 1
inch thick as applied, with it being understood that the outer batt
insulation layer 362 may be compressed to some extent by the poured
side wall insulation 364, and the inner batt insulation layer is
compressed during thermal expansion of the liner 200. The thermal
cloth 314 may be a refractory silica cloth, such as, for example,
REFRASIL.RTM. C-Series cloth manufactured and sold by Hitco Carbon
Composites, Inc. of Gardena, Calif., USA.
[0099] The roof truss assembly 400 of the thermal storage system
100 and containment vessel 101 will now be described. One aspect of
the roof truss assembly 400 is that it provides a structure for
covering the containment vessel 101, thereby retaining the heat
energy therein, and protecting the contents thereof from exposure
to weather and/or to unauthorized access. Another aspect of the
roof truss assembly 400 is that it provides lateral support to the
heat exchanger support frames, while permitting such frames to
expand vertically due to thermal expansion. The roof truss assembly
400 is best understood with reference to FIG. 2A, and FIGS. 7A-7D.
Referring first to FIG. 2A, which depicts a portion of the
assembly, the roof truss assembly 400 is comprised of a plurality
of radially disposed roof trusses 410. The roof truss assembly may
further include a central cage 480 joined to each of the roof
trusses 410.
[0100] Referring now to FIG. 7A, and in the embodiment depicted
therein, the roof truss assembly 400 may be comprised of radially
disposed roof trusses 411-417.
[0101] In one embodiment, the roof truss assembly may include seven
roof trusses, and seven linkages provided therebetween, for
providing support to the seven heat exchangers 501-507 (see FIG.
1). Referring also to FIG. 7B, an exemplary roof truss 411 is
comprised of a framework 420 of members, including an upper member
421, a lower member 422, a proximal upright member 423, a distal
upright member 424, upright support struts 425 and 426, and
diagonal support struts 427 and 428. The various members may be
made of tubing, angle (L), channel, I-beam or other structural
shapes. The members may be made of a metal, such as steel or
aluminum. The members are joined to each other by suitable means
such as by brackets and fasteners, or by welding.
[0102] Referring to FIGS. 2 and 7A, the central cage 480 of the
roof truss assembly 400 is comprised of an upper ring 482, a lower
ring 484, and a plurality of vertical struts 486 joined to the
upper ring 482 and the lower ring 484. Each of the proximal upright
members 423 of the roof trusses 411-417 is joined to the upper ring
482 and the lower ring 484 of the central cage 480.
[0103] A network of structural members is provided between each of
the respective pairs of roof trusses. For example, referring again
to FIG. 7A, a network 430 of structural members is provided between
roof trusses 411 and 417. The network 430 is comprised of an inner
tangential member 431, an outer tangential member 432, and first,
second, third, and fourth radial members 433-436. The network 430
of structural members serves to join the respective pairs of roof
trusses to each other, and to an outer circumferential ring 438.
Additionally, the inner and outer tangential members 431 and 432,
and the first and second radial members 433 and 434 are dimensioned
and positioned so as to form a structural frame 440 for supporting
a heat exchanger. Details of this structural frame 440 will be
provided subsequently herein with reference to FIGS. 11A-11C.
[0104] The third and fourth radial members 435 and 436 of network
430 are joined to the outer circumferential ring 438. The ends of
the inner and outer tangential members 431 and 432 may be joined to
the respective lower members 422 of the roof trusses 411 and 417.
Additionally, second upper networks (not shown) of structural
members that are similar to the first network 430, and comprise
inner and outer tangential members, radial members, and an outer
ring member may be provided, wherein each of the upper networks are
joined to the respective upper members 421 of adjacent pairs of
roof trusses. The various members of the networks 430 may be made
of tubing, angle (L), channel, I-beam or other structural shapes.
The members may be made of a metal, such as steel or aluminum. The
members are joined to each other by suitable means such as by
brackets and fasteners, or by welding.
[0105] The roof truss assembly 400 may also be provided with a top
sheet covering (not shown) disposed upon the upper members 421 of
the roof trusses, and extending out to overhang the outer ring 438;
and a side covering (not shown) around the outer ends of the roof
trusses. In that manner, the components of the thermal storage
system 100 contained therein are protected from exposure to weather
and/or to unauthorized access. The top sheet covering and side
coverings may be provided in multiple pieces, which are joined and
sealed to each other, and to the roof truss assembly at the job
site. Referring again to FIG. 2A, the roof truss assembly may also
be provided with a bottom sheet covering 442 which is joined to the
lower members 422 of the roof trusses. The bottom sheet 442
provides a protective barrier to prevent personnel from falling
into the containment vessel during inspection and service, and also
provides a structural support, upon which thermal insulation can be
disposed, to further conserve the heat energy contained within the
vessel 101. Referring again to FIG. 7A, the roof truss assembly 400
may be further provided with a salt fill port 447, which extends
downwardly through the bottom sheet 442. The salt fill port 442 may
be provided with a removable cap (not shown). In that manner, the
vessel 101 can be filled with granular solid salt through the fill
port 442 at the time of startup of the thermal storage system
100.
[0106] The roof truss assembly 400 is supported by the upper edge
of the vessel side wall 160. The roof truss assembly may be
configured and supported so as to be radially expandable with
respect to the containment side wall of the vessel. Referring again
to FIG. 4A, the vessel side wall 160 is provided with a plurality
of truss bearing plates joined to the top surface 161 thereof. In
the embodiment of the thermal storage system 100 depicted in FIGS.
4A and 7A-7D, the upper surface 161 is provided with seven bearing
plates 171-177 positioned to receive and support corresponding
bearing plates provided on each of the roof trusses 411-417.
[0107] FIG. 7C is a detailed side elevation view of an exemplary
bearing support plate 171 for supporting a roof truss at the top
surface 161 of the side wall 160 of the containment vessel 101; and
FIG. 7D is a top view of the bearing support plate 171 of FIG. 7C,
taken along line 7D-7D of FIG. 7C, and shown supporting a roof
truss 411. The bearing support plate 171 may be bonded to the upper
surface 161 of the side wall 160 by grout 178. A threaded rod 179
may be embedded in the side wall 160 and extend upwardly through
the support plate 171, to which it may be joined, and beyond above
the support plate 171. Two threaded rods 179 and 180 may be so
provided. The lower member 422 of the roof truss 411 is provided
with a corresponding bearing support plate 446 that rests upon
bearing support plate 171.
[0108] In the embodiment depicted in FIGS. 7C and 7D, the lower
member 422 is comprised of first and second back-to-back angle L
pieces 448 and 449, which are provided with slots 450 and 451
formed therein. Threaded rods 179 and 180 extend upwardly through
respective slots 450 and 451. When the thermal energy system 100 is
in operation and contains hot molten salt, the roof truss assembly
400 is heated due to its proximity to the molten salt. The roof
truss assembly 400 undergoes thermal expansion and contraction
during the thermal cycling, with each of the roof trusses such as
roof truss 420 expanding and contracting. The lower member 422 is
free to expand and contract as indicated by bidirectional arrows
499, with the slots 450 and 451 permitting such motion with respect
to the respective threaded rods 179 and 180 which are embedded in
the vessel side wall 160. The mated bearing support plates 171 and
446 may be provided with a suitable lubricant to facilitate the
sliding action between them. In one embodiment, the bearing plates
are provided with a fluoropolymer coating such as TEFLON.RTM..
Other anti-friction coatings may be used. The threaded rods 179 and
180 may also be provided with retaining nuts (not shown), which are
loosely disposed above the respective angle L pieces 448 and
449.
[0109] One aspect of the roof truss assembly 400 is that it may be
of modular construction. The roof trusses 411-417, the central cage
480, the various pieces of the networks between the roof trusses,
and the top, bottom, and side protective sheets may all be
fabricated in a shop or factory and shipped to the job site for
simple and quick assembly.
[0110] The heat exchanger array 500 of the thermal storage system
will now be described. The heat exchanger array 500 is shown
schematically in FIG. 1, and in elevation, plan and cutaway
perspective views in FIGS. 2A, 2B, and 2C. For the sake of
simplicity of illustration, only two heat exchangers are shown in
FIG. 2A; and the roof truss assembly 400 is not shown in FIGS. 2B
and 2C. The heat exchanger array 500 is comprised of a plurality of
heat exchangers disposed in the containment vessel 101, and a
plurality of heat transfer fluid delivery and exit pipes, which are
connected to the heat transfer fluid supply unit 600. In the
embodiment depicted in FIGS. 1-2C, the heat transfer array is
comprised of eight heat exchangers disposed in a circular
arrangement of seven heat exchangers 501-507, with the eighth heat
exchanger 508 being disposed in the center of the arrangement.
Pairs of the heat exchangers may be connected in series, such as
exchangers 501 and 507, 502 and 503, 508 and 504, and 506 and 505.
Heat transfer fluid is supplied to the pairs of heat exchangers
through respective delivery pipes 511-514 and withdrawn from the
pairs of heat exchangers through respective exit pipes 516-519.
Other arrangements of more or fewer heat exchangers, and other
connection arrangements with or without connections in series may
be suitable.
[0111] Each of the heat exchangers 501-508 may be supported by a
support frame, which may be joined at the bottom thereof to the
liner bottom 210, and at the top thereof to the roof truss assembly
400. FIGS. 8 and 9 are perspective views of an exemplary heat
exchanger 501 and support frame 540. The heat exchanger 501 is
comprised of a plurality of heat exchanger tubes 520, which are
sealed by welding, for example, to a header plate 522. The tubes
520 may be U-tubes, i.e., formed into U-shapes, and joined at their
respective ends to the header plate 522. The tubes may be supported
and aligned along their lengths by several tube alignment sheets
524, 526, and 528. A cap 530 is joined to the header plate 522, and
is provided with an inlet port 532, and outlet port 534, and
internal passageways to direct the heat transfer fluid into and out
of the U-tubes 520. In operation, heat transfer fluid is delivered
into inlet port 532, through the inlets of the respective U-tubes
520 that are jointed to the header plate 522, through the outlets
of the U-tubes 520, and out the outlet port 534.
[0112] The heat exchangers 501-508 may be constructed of a variety
of materials, for example, but not limited to plain carbon steels;
steels alloyed with copper, manganese, molybdenum, nickel, silicon,
tungsten, titanium, vanadium and chromium, individually or in any
combination thereof such as chromium-molybdenum, or
nickel-chromium-molybdenum; and stainless steels.
[0113] Referring now to FIG. 9, a support frame 540 is provided for
receiving and supporting the heat exchanger 501. The support frame
540 is comprised of a base plate 541, and a plurality of upright
support columns 542-548, which are joined to each other by a
network of diagonal cross struts 550 and horizontal cross struts
552. In the embodiment depicted in FIG. 9, the support plate 541 is
square, and four upright support columns 542-548 are provided.
Other shapes of base plate 541 and arrangements of support columns
542 et seq. and cross struts 550/552 are possible.
[0114] Referring also to FIG. 4B, the base plate 541 is provided
with a plurality of mounting holes 554, through which mounting
studs 556 extend. The mounting studs 556 are joined to the heat
exchanger support plate 131, and to the liner bottom 210. When the
heat exchanger 501 and heat exchanger support frame 540 are placed
in operating position in the containment vessel 101, nuts 558 are
used to secure them in place. FIG. 10 is a perspective view of the
heat exchanger 501 assembled to the support frame 551. The heat
exchanger 501 and the support frame 540 are modular in that they
can be separately fabricated and then joined to each other. The
heat exchanger 501 and the support frame 540 can be fabricated in a
shop and then joined to each other to be shipped to the job site.
The entire assembly can then be placed in the containment vessel;
or they can be separated, and the support frame 540 first installed
in the containment vessel, followed by the placement of the heat
exchanger 501 into the support frame 540. The cap 530 of the heat
exchanger 501 may be provided with a lug (not shown) for engagement
with a lifting hook for such placement purposes.
[0115] In the embodiment depicted in FIGS. 8-10, the heat exchanger
is provided with engagement sleeves 556 which are joined to the
underside of the header plate 522 proximate to the corners thereof.
When the heat exchanger 501 is lowered into the support frame 540,
the upper ends of the support columns 542-548 are received in the
engagement sleeves 556. The support columns 542-548 may be further
secured therein by bolts (not shown) which pass through the
engagement sleeves 556 and upper ends of the support columns
542-548.
[0116] One aspect of the combination of the heat exchangers
501-508, heat exchanger support frames 540 and the roof truss
assembly 400 is that for seismic stability, each of the heat
exchangers frames may be constrained to prevent movement in the
horizontal direction by the roof truss assembly 400, while
simultaneously being permitted to expand and contract in the
vertical direction due to their exposure to the range of operating
temperatures of the salt contained in the vessel 101. The
constraining of a heat exchanger and its support frame in the
horizontal direction while permitting it to move in the vertical
direction is enabled by providing a fastening arrangement at the
heat exchanger header plate which joins the heat exchanger and
support frame to the roof truss assembly in a manner that fixes the
horizontal location of the upper portion of the heat exchanger and
frame with respect to the truss assembly, while permitting the heat
exchanger header plate and upper portion of the frame to translate
vertically up and down with respect to the truss assembly.
[0117] This is best understood with reference to FIGS. 7A, 10, and
11A-11C. As was described previously with reference to FIG. 7A, a
network 430 of structural members is provided between adjacent roof
trusses, such as network 430 between roof trusses 411 and 417. A
frame 440 is formed by and within network 430 and dimensioned to
substantially match the perimeter of the heat exchanger header
plate 522.
[0118] Referring in particular to FIGS. 11A-11C, the heat exchanger
header plate 522 is provided with a plurality of brackets 560
joined proximate to the perimeter thereof by suitable means such as
welding. The brackets 560 may be L-shaped, with a vertical leg 561
and a horizontal leg 562. The vertical legs 561 of the brackets 560
are provided with elongated slots 563, which transition into relief
slots 564 that are formed in the horizontal legs 562. The brackets
560 are joined to the four members 431-434 of the frame 440 that is
formed in the network 430 of structural members by bolts 565 and
nuts 566. The shanks 567 of the bolts 565 (both shown in dotted
line in FIG. 11B) are disposed in the elongated slots 563 of the
brackets 560. When the salt in the thermal energy storage system is
heated to a molten state from ambient temperature, the support
frame 540 of the heat exchanger expands upwardly, which raises the
header plate 522 of the heat exchanger 501; and subsequently,
during thermal cycling, the header plate 522 rises and falls with
the vertical expansion and contraction of the support frame 540.
This rising and falling of the header plate 522 of the heat
exchanger 501 is permitted by the sliding motion of the bolts 565
in the vertical slots 563 of the brackets 560, as indicated by
bidirectional arrow 599. Simultaneously, the heat exchanger 501 and
its support frame 540 are prevented from horizontal motion in the
event of a seismic disturbance. It is to be understood that the
heat exchangers 502-507 are supported in substantially the same
manner; and that a frame similar to frame 440 is provided within
the central cage 480 to support the central heat exchanger 508 in
substantially the same manner.
[0119] Details of one exemplary design of a suitable heat exchanger
and support frame of the applicants' thermal energy storage system
and containment vessel will now be provided. These details are to
be considered as exemplary only, and not limiting. Many other
designs of the system and heat exchangers are possible, and are
within the scope of the present invention. This exemplary
embodiment is designed to match the previously described exemplary
designs of the containment vessel 101, liner 200, insulation 300,
and roof truss assembly 400. The U-tubes 520 and tube alignment
sheets 524/526/528 of the heat exchanger 501, and the columns
542-548, cross struts 550/552, and base plate 541 of the support
frame 540 are made of "21/4 Cr-1 Mo alloy," (also known as ASME
SA-213-T22 tubing), a steel alloy containing molybdenum and
chromium, which is particularly suitable for high temperature
pressure vessels in corrosive environment. The heat exchanger cap
530, header plate 532, and engagement sleeves 556 are made of SA
516 GR 70 carbon steel.
[0120] The heat exchanger 501 is about 32 feet long from the top of
the cap 530 to the distal ends of the U-tubes 520. The U-tubes are
made of 21/4 Cr-1 Mo alloy tubing having an outside diameter of 3/4
inch and a wall thickness of 0.083 inch and have lengths between
about 28 to about 30 feet. The header plate 522 is a square having
a side of about 41 inches long and a thickness of about 23/8
inches. The heat exchanger comprises about 336 U-tubes having a
total combined length of about 20,000 feet. The heat exchanger is
designed per the ASME Boiler and Pressure Vessel Code, Section
VIII, Division 1, 2007 Edition, to operate at a maximum allowed
working pressure of 250 pounds per square inch. Following
fabrication of a heat exchanger or various components thereof, such
as the cap 530 and header plate 522, the heat exchanger or
components may be heat treated to relieve residual stresses at
various welds, tube bends, and other locations. In one embodiment,
the heat exchanger cap and header plate are heat treated at
1100.degree. F. for about one hour per inch of thickness of the
header plate (i.e. about 2 hours and 22 minutes for the above
exemplary heat exchanger cap 530 and header plate 522). In one
embodiment, the heat exchanger tubes are heat treated at about
1250.degree. F. for about one hour per inch of diameter of the
tubes (i.e. about 3/4 hour for the above exemplary heat exchanger
tubes).
[0121] The support frame base plate 541 is a square having a side
of about 36 inches long and a thickness of about 3/4 inch. The
columns 542-548 are of ANSI 3 inch NPS (nominal pipe size) pipe
having a wall thickness of about 0.300 inches, and the cross struts
550 and 552 are of ANSI 1 inch NPS pipe having a wall thickness of
about 0.179 inches.
[0122] Referring to FIG. 2A, when the placement and assembly of the
heat exchangers 501-508 and support frames, and the assembly of the
roof truss assembly 400 are complete, a layer of batt insulation
470 is applied to the upper surface of the bottom sheet of the roof
truss assembly 400, and the caps 530 of the heat exchangers
501-508.
[0123] FIG. 12 is a flow chart depicting a method of making the
applicants' thermal energy storage system. It is to be understood
that although the steps of the method 700 of FIG. 12 are
illustrated in a serial order, the method is not limited to being
done in the order depicted in FIG. 12. Certain steps of the method
700 may be performed in parallel, and/or in orders other than
depicted in FIG. 12.
[0124] One aspect of the method is that because the system is of a
modular design, a large share of the system components may be
fabricated in a shop of factory environment. In step 710, the
modular components including the heat exchangers 501-508, heat
exchanger support frames 540, vessel liner 200, and roof trusses
411-418, networks 430 and center cage 480 of the roof truss
assembly 400, and the heat transfer fluid delivery system 600 are
fabricated. This may be done in parallel while the excavation and
grading 720 of the site is performed. If the containment vessel 101
is to be partially below grade, a containment pit may be dug. The
containment vessel bottom wall 110 and side wall 160 may then be
constructed in step 740 while the modular components are shipped to
the construction site in step 730. The thermal insulation 300 may
then be applied to the vessel bottom 110 and/or vessel side wall
160 in step 750. The liner 200 may then be fabricated from the
pre-fabricated bottom plates, flexible joints, and side wall
sections in step 760. The pre-fabricated modular heat exchanger
support frames 540 and heat exchangers 501-508 may then be placed
in the containment vessel in step 770, and the roof truss assembly
may be assembled from pre-fabricated trusses and a central cage in
step 780. The heat transfer fluid delivery system may then be
constructed and connected to the heat exchangers in step 790. The
thermal energy storage system 100 may then be connected to the
solar field 10 and the electrical generation station 20, and
started up in step 800. The system 100 may be used to store thermal
energy from the solar field 10, and release thermal energy to the
electrical generation station 20.
[0125] It is, therefore, apparent that there has been provided, in
accordance with the present invention, a vessel for containing a
thermal energy storage liquid, a thermal energy storage system
comprising such vessel, and methods for making and using the vessel
and thermal energy storage system. Having thus described the basic
concept of the invention, it will be rather apparent to those
skilled in the art that the foregoing detailed disclosure is
intended to be presented by way of example only, and is not
limiting. Various alterations, improvements, and modifications will
occur and are intended to those skilled in the art, though not
expressly stated herein. These alterations, improvements, and
modifications are intended to be suggested hereby, and are within
the spirit and scope of the invention. Additionally, the recited
order of processing elements or sequences, or the use of numbers,
letters, or other designations therefore, is not intended to limit
the claimed processes to any order except as may be specified in
the claims.
* * * * *