U.S. patent application number 12/033604 was filed with the patent office on 2008-11-27 for thermal energy storage systems and methods.
Invention is credited to Brian J. Flynn, Gerald Geiken.
Application Number | 20080289793 12/033604 |
Document ID | / |
Family ID | 40071316 |
Filed Date | 2008-11-27 |
United States Patent
Application |
20080289793 |
Kind Code |
A1 |
Geiken; Gerald ; et
al. |
November 27, 2008 |
THERMAL ENERGY STORAGE SYSTEMS AND METHODS
Abstract
A thermal energy storage apparatus is disclosed. The thermal
energy storage apparatus has a phase change medium, an inner header
having at least one inner feed port, and an outer header having at
least one outer feed port and fluidically coupled to the inner
header. The inner header and the outer header are configured to be
substantially immersed in the phase change medium. Related methods
of constructing and controlling a thermal energy storage system are
also disclosed. A thermal energy power system utilizing a thermal
energy storage apparatus is further disclosed, as is a heat
exchanger for the thermal energy storage system.
Inventors: |
Geiken; Gerald; (Rochester,
NY) ; Flynn; Brian J.; (Churchville, NY) |
Correspondence
Address: |
JAECKLE FLEISCHMANN & MUGEL, LLP
190 Linden Oaks
ROCHESTER
NY
14625-2812
US
|
Family ID: |
40071316 |
Appl. No.: |
12/033604 |
Filed: |
February 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60939426 |
May 22, 2007 |
|
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|
Current U.S.
Class: |
165/10 ;
29/592 |
Current CPC
Class: |
F28F 23/00 20130101;
Y02E 10/40 20130101; Y10T 29/49 20150115; Y02E 60/14 20130101; Y02E
60/142 20130101; F24S 80/20 20180501; F28D 20/028 20130101; F28F
2255/00 20130101; Y02E 60/145 20130101; F28D 2020/0047 20130101;
F28D 20/00 20130101 |
Class at
Publication: |
165/10 ;
29/592 |
International
Class: |
F28D 17/00 20060101
F28D017/00 |
Claims
1. A thermal energy storage apparatus, comprising: a phase change
medium; an inner header having at least one inner feed port; an
outer header having at least one outer feed port and fluidically
coupled to the inner header; and wherein the inner header and the
outer header are configured to be substantially immersed in the
phase change medium.
2. The thermal energy storage apparatus of claim 1, wherein the
phase change medium is selected from the group consisting of a
salt, a salt mixture, a eutectic salt mixture, 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.
3. The thermal energy storage apparatus of claim 1, wherein the
inner header is centered within the outer header.
4. The thermal energy storage apparatus of claim 1, wherein the
inner header and the outer header lie on substantially the same
plane.
5. The thermal energy storage apparatus of claim 1, further
comprising a collection header, and wherein the inner header is
fluidically coupled to the outer header via the collection
header.
6. The thermal energy storage apparatus of claim 5, further
comprising: one or more inner tubes coupled between the inner
header and the collection header; one or more outer tubes coupled
between the outer header and the collection header; and wherein the
inner header is fluidically coupled to the outer header via the one
or more inner tubes, the collection header, and the one or more
outer tubes.
7. The thermal energy storage apparatus of claim 6, further
comprising one or more core heat tubes coupled to the inner
header.
8. The thermal energy storage apparatus of claim 6, wherein at
least one of the one or more inner tubes further comprise a bypass
valve configured to selectably create a hot spot in the phase
change medium.
9. The thermal energy storage apparatus of claim 6, further
comprising a tankless structure configured to contain the phase
change medium such that the inner header and the outer header are
substantially immersed in the phase change medium.
10. The thermal energy storage apparatus of claim 9, wherein the
tankless structure comprises bricks.
11. The thermal energy storage apparatus of claim 10, wherein the
bricks comprise a material selected from the group consisting of
firebrick, refractory material, castable refractories, refractory
brick, mixtures of alumina (Al2O3), silica (SiO2), magnesia (MgO),
zirconia (ZrO2), chromium oxide (Cr2O3), iron oxide (Fe2O3),
calcium oxide (CaO), silicon carbide (SiC), carbon (C); metallic
materials, plain carbon steels; alloy steels, manganese, silicon,
silicon-manganese, nickel, nickel-chromium, molybdenum,
nickel-molybdenum, chromium, chromium-molybdenum,
chromium-molybdenum-cobalt, silicon-molybdenum,
manganese-silicon-molybdenum, nickel-chromium-molybdenum,
silicon-chromium-molybdenum, manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper, and
nickel-chromium-molybdenum.
12. The thermal energy storage apparatus of claim 10, further
comprising at least one layer of insulation substantially
surrounding the bricks.
13. The thermal energy storage apparatus of claim 12, further
comprising at least one band supporting the bricks.
14. The thermal energy storage apparatus of claim 10, wherein the
bricks are configured to have a cooling zone which encourages the
phase change medium to solidify in at least a portion of gaps
defined by the bricks.
15. The thermal energy storage apparatus of claim 9, further
comprising a base which supports the tankless structure.
16. The thermal energy storage apparatus of claim 15, wherein the
base comprises a material selected from the group consisting of
earth, firebrick, refractory material, concrete, castable
refractories, refractory concrete, refractory cement, insulating
refractories, gunning mixes, ramming mixes, refractory plastics,
refractory brick, mixtures of alumina (Al2O3), silica (SiO2),
magnesia (MgO), zirconia (ZrO2), chromium oxide (Cr2O3), iron oxide
(Fe2O3), calcium oxide (CaO), silicon carbide (SiC), carbon (C);
metallic materials, carbon steels; alloy steels, manganese,
silicon, silicon-manganese, nickel, nickel-chromium, molybdenum,
nickel-molybdenum, chromium, chromium-molybdenum,
chromium-molybdenum-cobalt, silicon-molybdenum,
manganese-silicon-molybdenum, nickel-chromium-molybdenum,
silicon-chromium-molybdenum, manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper, and
nickel-chromium-molybdenum.
17. The thermal energy storage apparatus of claim 9, wherein the
outer header has a shape which substantially follows a shape
defined by the tankless structure.
18. The thermal energy storage apparatus of claim 9, wherein the
tankless structure defines a horizontal cross-sectional shape which
is selected from the group consisting of circular, oval, hexagonal,
rectangular, and square.
19. The thermal energy storage apparatus of claim 1, further
comprising: at least one inner valve; at least one outer valve; an
inner pipe which couples the inner valve to the inner feed port;
and an outer pipe which couples the outer valve to the outer feed
port.
20. The thermal energy storage apparatus of claim 19, wherein the
inner pipe and the outer pipe enter the phase change medium
substantially vertically.
21. The thermal energy storage apparatus of claim 19, wherein the
inner pipe and the outer pipe enter the phase change medium
substantially horizontally.
22. The thermal energy storage apparatus of claim 1, wherein the
inner header and the outer header comprise material selected from
the group consisting of plain carbon steels; alloy steels,
manganese, silicon, silicon-manganese, nickel, nickel-chromium,
molybdenum, nickel-molybdenum, chromium, chromium-molybdenum,
chromium-molybdenum-cobalt, silicon-molybdenum,
manganese-silicon-molybdenum, nickel-chromium-molybdenum,
silicon-chromium-molybdenum, manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper, and
nickel-chromium-molybdenum.
23. A thermal energy power system, comprising: a) a phase change
medium; b) an inner header; c) an outer header; d) a collection
header; e) one or more inner tubes coupled between the inner header
and the collection header; f) one or more outer tubes coupled
between the outer header and the collection header, wherein the
inner header is fluidically coupled to the outer header via the one
or more inner tubes, the collection header, and the one or more
outer tubes; g) a brick structure configured to contain the phase
change medium such that the inner header and the outer header are
substantially immersed in the phase change medium and wherein the
bricks are configured to have a cooling zone which encourages the
phase change medium to solidify in gaps defined by the bricks h) a
base which supports the brick structure; i) a pump; j) a renewable
heat source; k) a turbine plant; and l) wherein the inner header
and the outer header are reversibly connected in a closed loop with
the pump, the renewable heat source, and the turbine plant and
wherein the closed loop carries a heat transfer fluid.
24. The thermal energy power system of claim 23, wherein the
renewable heat source is selected from the group consisting of a
solar parabolic mirror, a solar mirror farm, and a wind
turbine.
25. The thermal energy power system of claim 23, wherein the heat
transfer fluid comprises oil.
26. A method of constructing a thermal energy storage system,
comprising: forming a base; aligning at least one heat exchange
system substantially over the base, the at least one heat exchange
system comprising an inner header and an outer header; dry-laying a
brick wall substantially on the base to surround the at least one
heat exchange system or an area where the at least one heat
exchange system will be aligned; and filling the area defined by
the base and the brick wall with a phase change medium such that
the phase change medium substantially covers the at least one heat
exchange system.
27. The method of claim 26, wherein forming the base further
comprises forming the base on an insulator.
28. The method of claim 26, wherein the brick wall comprises a
material selected from the group consisting of firebrick and
refractory brick.
29. The method of claim 26, further comprising insulating the brick
wall.
30. The method of claim 26, further comprising banding the brick
wall.
31. The method of claim 26, further comprising: heating the phase
change medium so that it transitions to a liquid phase and enters
gaps defined by the dry-laid bricks of the brick wall; and allowing
the phase change medium to cool enough to solidify in at least a
portion of the gaps in order to substantially seal the brick wall
where it meets the phase change medium.
32. A method of controlling a thermal energy storage system,
comprising: a) when a renewable heat source is available: i)
thermally and fluidically coupling the renewable heat source to an
inner header of a heat exchange system which is substantially
immersed in a phase change medium and which is further coupled to
an outer header of the heat exchange system which is also
substantially immersed in the phase change medium; and ii)
thermally and fluidically coupling the outer header to a turbine
plant and then back to the renewable heat source in a closed-loop
heating mode which provides a remaining renewable energy source
heat to the turbine plant; and b) when the renewable heat source is
not available: i) thermally and fluidically coupling the renewable
heat source to the outer header; and ii) thermally and fluidically
coupling the inner header to the turbine plant and then back to the
renewable heat source in a closed-loop cooling mode which provides
a stored heat to the turbine plant.
33. A heat exchanger for a thermal energy storage system,
comprising: an inner header having at least one inner feedport; an
outer header having at least one outer feedport and fluidically
coupled to the inner header; and wherein the inner and outer
feedports are configured to enable a heat transfer fluid to
reversibly flow from the inner header to the outer header when the
inner header and the outer header are substantially immersed in a
phase change medium.
34. The heat exchanger of claim 33, wherein the inner header is
centered within the outer header.
35. The heat exchanger of claim 33, wherein the inner header and
the outer header lie on substantially the same plane.
36. The heat exchanger of claim 33, further comprising a collection
header, and wherein the inner header is fluidically coupled to the
outer header via the collection header.
37. The heat exchanger of claim 36, further comprising: one or more
inner tubes coupled between the inner header and the collection
header; one or more outer tubes coupled between the outer header
and the collection header; and wherein the inner header is
fluidically coupled to the outer header via the one or more inner
tubes, the collection header, and the one or more outer tubes.
38. The heat exchanger of claim 37, further comprising one or more
core heat tubes coupled to the inner header.
39. The heat exchanger of claim 37, wherein at least one of the one
or more inner tubes further comprises a bypass valve.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional patent
application 60/939,426 which was filed on May 22, 2007. U.S.
provisional patent application 60/939,426 is hereby incorporated by
reference in its entirety.
FIELD
[0002] The claimed invention generally relates to energy storage
and, more particularly, to thermal energy storage systems and
methods thereof.
BACKGROUND
[0003] 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.
[0004] 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.
[0005] 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 turned-to
overnight. 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 reusable power
source is unavailable or unable to meet peak demands for
energy.
[0006] 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.
[0007] FIG. 1 illustrates a two-tank direct energy storage system.
Heat transfer fluid is heated by mirrors in a solar field 30 and
stored in a hot oil tank 32. The heat transfer fluid is then pumped
through a steam generator 34 as needed to generate steam and power
a turbine 36 to meet energy demands. Even if the solar field 30 is
not producing newly heated heat transfer fluid for the hot oil tank
32, the hot oil tank 32 has a certain capacity to provide stored
hot transfer fluid to the steam generator 34 for power generation.
After passing though the steam generator 34, the cooled heat
transfer fluid is then pumped into and stored in a cold oil tank
38. When the solar field 30 is active, cooled heat transfer fluid
is pumped from the cold oil tank 38, through the solar field to be
heated-up, and back to the hot oil tank 32 where the process can
begin again. While the two-tank direct energy storage system of
FIG. 1 helps to store energy for non-generation times, it is
unfortunately complex, requires two expensive tanks, and is limited
in the amount energy it can store due to limitations in the heat
storage capacity of the heat transfer fluid.
[0008] FIG. 2 illustrates a two-tank indirect energy storage
system. Relatively cold molten salt is pumped from a cold salt tank
40 out to a heat exchanger 42 where it is heated by proximity to
counter-current running hot heat transfer fluid from the solar
field 44. The newly-heated molten salt is then pumped from the heat
exchanger 42 into a hot salt tank 46 where it is stored until
needed. When energy needs to be reclaimed from the hot salt tank
46, the hot molten salt is pumped out of the hot salt tank 46 and
to a turbine system 48 whereby the heat from the hot molten salt is
used to generate steam to drive the turbine system 48. Relatively
cold molten salt exits the turbine system 48 and is pumped back
into the cold salt tank 40. Alternatively, the hot molten salt from
the hot salt tank 46 may be pumped out of the hot salt tank 46 and
back through the heat exchanger 42 to heat the heat transfer fluid
from the solar field 44 before being pumped back into the cold salt
tank 40. In this alternate setup, the reheated heat transfer fluid
would then be pumped through the turbine system before being
recirculated to the solar field. Taking advantage of the heat
storage capacities of salt in this indirect two-tank system, more
energy may be stored than in the direct system. Unfortunately, this
system still requires two expensive tanks. Furthermore, the system
of FIG. 2 will be subjected-to complexities and issues arising from
the need to pump and transport molten salt. The system may have the
need to keep the salt molten at all times and therefore may require
the addition of heaters not powered by the solar field. If the salt
is allowed to solidify within the transport pipes, the natural
expansion of the salt when transitioning to a solid state may cause
stress cracks in the pipes. Furthermore, if the salt is allowed to
solidify, the system may take an undesirable amount of time to come
on-line as it waits for the salt to liquefy to become pumpable.
Corrosion is also an issue when pumping molten salt.
[0009] FIG. 3 illustrates a single-tank thermocline energy storage
system. The thermocline tank 50 holds a hot molten salt on the top
of the tank 50 and a relatively cool molten salt in the bottom of
the tank 50. When the solar field 52 is active, a hot heat transfer
fluid is pumped from the solar field to a heat exchanger 54. The
relatively cool molten salt is pumped out of the bottom of the
thermocline tank 50 out to the heat exchanger 54 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 50. When the solar field 52 is not active, the
flow to and from the thermocline tank 50 is reversed. Heated molten
salt is pumped out of the top of the thermocline tank 50 to the
heat exchanger 54, where it transfers its heat to the heat transfer
fluid. The heat transfer fluid is pumped to a turbine system 56 for
generating electricity. The molten salt which gave up some of its
heat in the heat exchanger 54 is then returned to the bottom of the
thermocline tank 50. While this system takes advantage of a
vertical temperature gradient within the thermocline tank to move
down to a single tank, the tank itself may still be expensive when
properly sized for industrial and/or community demands, and the
system continues to have the corrosion and solidification concerns
mentioned above when pumping molten salt.
[0010] Therefore, there is a need for a thermal energy storage
system which can take advantage of the high energy storage
capacities of phase change media, such as salts, while avoiding
corrosion and solidification issues in an inexpensive,
easy-to-construct, control, and maintain fashion.
SUMMARY
[0011] A thermal energy storage apparatus is disclosed. The thermal
energy storage apparatus has a phase change medium, an inner header
having at least one inner feed port, and an outer header having at
least one outer feed port and fluidically coupled to the inner
header. The inner header and the outer header are configured to be
substantially immersed in the phase change medium.
[0012] A thermal energy power system is also disclosed. The thermal
energy power system has a phase change medium, an inner header, an
outer header, and a collection header. The thermal energy power
system also has one or more inner tubes coupled between the inner
header and the collection header. The thermal energy power system
further has one or more outer tubes coupled between the outer
header and the collection header, wherein the inner header is
fluidically coupled to the outer header via the one or more inner
tubes, the collection header, and the one or more outer tubes. The
thermal energy power system also has a brick structure configured
to contain the phase change medium such that the inner header and
the outer header are substantially immersed in the phase change
medium and wherein the bricks are configured to have a cooling zone
which encourages the phase change medium to solidify in gaps
defined by the bricks. The thermal energy power system also has a
base which supports the brick structure, a pump, a renewable heat
collector, and a turbine plant. The inner header and the outer
header are reversibly connected in a series closed loop with the
pump, the renewable heat source, and the turbine plant. The closed
loop carries a thermal fluid.
[0013] A method of constructing a thermal energy storage system is
also disclosed. A base is formed. At least one heat exchange system
is substantially aligned over the base, the at least one heat
exchange system comprising an inner header and an outer header. A
brick wall is dry-laid substantially on the base to surround the at
least one heat exchange system. An area defined by the base and the
brick wall is filled with a phase change medium such that the phase
change medium substantially covers the at least one heat exchange
system.
[0014] A method of controlling a thermal energy storage system is
also disclosed. When a renewable heat source is available: i) the
renewable heat source is thermally and fluidically coupled to an
inner header of a heat exchange system which is substantially
immersed in a phase change medium and which is further coupled to
an outer header of the heat exchange system which is also
substantially immersed in the phase change medium; and ii) the
outer header is thermally and fluidically coupled to a turbine
plant and then back to the renewable heat source in a closed-loop
heating mode which provides a remaining renewable energy source
heat to the turbine plant. When the renewable heat source is not
available: i) the renewable heat source is thermally and
fluidically coupled to the outer header; and ii) the inner header
is thermally and fluidically coupled to the turbine plant and then
back to the renewable heat source in a closed-loop cooling mode
which provides a stored heat to the turbine plant. A heat exchanger
for a thermal energy storage system is also disclosed. The heat
exchanger has
[0015] an inner header having at least one inner feedport. The heat
exchanger also has an outer header having at least one outer
feedport and fluidically coupled to the inner header. The inner and
outer feedports are configured to enable a heat transfer fluid to
reversibly flow from the inner header to the outer header when the
inner header and the outer header are substantially immersed in a
phase change medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates a prior art embodiment of a direct
two-tank thermal energy storage system.
[0017] FIG. 2 illustrates a prior art embodiment of an indirect
two-tank thermal energy storage system.
[0018] FIG. 3 illustrates a prior art embodiment of a single tank
thermocline energy storage system.
[0019] FIG. 4 schematically illustrates a side cross-sectional view
of one embodiment of a heat exchanger for use in an energy storage
system.
[0020] FIG. 5 schematically illustrates a top view of the embodied
heat exchanger of FIG. 4.
[0021] FIG. 6 schematically illustrates a side cross-sectional view
of another embodiment of a heat exchanger for use in an energy
storage system.
[0022] FIG. 7 schematically illustrates a side cross-sectional view
of another embodiment of a heat exchanger for use in an energy
storage system.
[0023] FIG. 8 schematically illustrates a side cross-sectional view
of a further embodiment of a heat exchanger for use in an energy
storage system.
[0024] FIG. 9 schematically illustrates one embodiment of a thermal
energy storage apparatus.
[0025] FIG. 10A schematically illustrates another embodiment of a
thermal energy storage apparatus.
[0026] FIG. 10B schematically illustrates a further embodiment of a
thermal energy storage apparatus.
[0027] FIG. 11 illustrates an embodiment of a method for
constructing a thermal energy storage system.
[0028] FIG. 12A schematically illustrates a side cross-sectional
view of another embodiment of a thermal energy storage system.
[0029] FIG. 12B schematically illustrates a cross-sectional view of
the embodied thermal energy storage system shown in FIG. 12A taken
along lines 2-2.
[0030] FIG. 12C schematically illustrates a cross-sectional view of
the embodied thermal energy storage system shown in FIG. 12A taken
along lines 3-3.
[0031] FIG. 12D schematically illustrates flow through the embodied
thermal energy storage system of FIG. 12A during heating to store
energy.
[0032] FIG. 12E schematically illustrates flow through the embodied
thermal energy storage system of FIG. 12A during cooling to deliver
energy.
[0033] FIG. 13 schematically illustrates an embodiment of a thermal
energy power system.
[0034] FIG. 14 schematically illustrates flow through the embodied
thermal energy power system of FIG. 13 during a heating mode.
[0035] FIG. 15 schematically illustrates flow through the embodied
thermal energy power system of FIG. 13 during a cooling mode.
[0036] FIG. 16 illustrates an embodiment of a method for
controlling a thermal energy storage system.
[0037] It will be appreciated that for purposes of clarity and
where deemed appropriate, reference numerals have been repeated in
the figures to indicate corresponding features, and that the
various elements in the drawings have not necessarily been drawn to
scale in order to better show the features.
DETAILED DESCRIPTION
[0038] FIG. 4 schematically illustrates a side cross-sectional view
of one embodiment of a heat exchanger 58 for use in an energy
storage system. The heat exchanger 58 has an inner header 60 with
an inner feedport 62. The heat exchanger 58 also has an outer
header 64 with an outer feedport 66. The inner feedport 62 and the
outer feedport 66 do not have to project out from the inner and
outer headers 60, 64. The inner and outer feedports 62, 66 may
optionally be openings which provide access for fluid delivery via
external piping which can be attached to inner and outer feedports
62, 66. Such external piping may enter vertically, horizontally, or
at any desired angle. The outer header 64 is fluidically coupled to
the inner header 60, in this embodiment via outer tubes 68, 70 and
inner tube 72. Other embodiments may have differing numbers of
inner tubes and/or outer tubes. In this embodiment, the inner
header 60 and the outer header 64 have a circular cross-sectional
shape. In other embodiments, the inner header and the outer header
may have other cross-sectional shapes, such as, but not limited to
oval, square, triangular, and hexagonal. The inner header 60 and
the outer header 64 do not have to have the same cross-sectional
shape or size. Certain cross-sectional shapes may provide more or
less surface area for heat transfer or may assist with ease of
manufacturing and may be chosen to fit certain heat transfer and
assembly goals by those skilled in the art depending on the
embodiment.
[0039] In this embodiment, the inner header 60 and the outer header
64 lie in substantially the same plane. In other embodiments, the
inner header 60 may be on a lower plane than the outer header 64 or
visa versa. Furthermore, in this embodiment, the inner header 60 is
centered within the outer header 64. In other embodiments, the
inner header 60 may be off-center in comparison with the outer
header 64.
[0040] The inner header 60 and the outer header 64 may be
constructed of a variety of materials, for example, but not limited
to plain carbon steels; alloy steels, manganese, silicon,
silicon-manganese, nickel, nickel-chromium, molybdenum,
nickel-molybdenum, chromium, chromium-molybdenum,
chromium-molybdenum-cobalt, silicon-molybdenum,
manganese-silicon-molybdenum, nickel-chromium-molybdenum,
silicon-chromium-molybdenum, manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper,
nickel-chromium-molybdenum, and any combination thereof.
[0041] The inner feedport 62 is configured to allow a heat transfer
fluid to flow into the inner header 60, down through inner tube 72,
back up outer tubes 68, 70, into the outer header 64, and back out
the outer feedport 66. This flow path through the heat exchanger 58
may also be reversed. Suitable examples of a heat transfer fluid
include, but are not limited to mineral oil and other types of oil.
The heat exchanger 58 is designed to be substantially immersed in a
phase change medium (not shown in this view) and should preferably
be manufactured from a material which is compatible with the phase
change medium.
[0042] Suitable examples of materials which the heat exchanger 58
may be manufactured from include, but are not limited to plain
carbon steels; alloy steels, manganese, silicon, silicon-manganese,
nickel, nickel-chromium, molybdenum, nickel-molybdenum, chromium,
chromium-molybdenum, chromium-molybdenum-cobalt,
silicon-molybdenum, manganese-silicon-molybdenum,
nickel-chromium-molybdenum, silicon-chromium-molybdenum,
manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper,
nickel-chromium-molybdenum, and any combination thereof.
[0043] FIG. 5 schematically illustrates a top view of the embodied
heat exchanger 58 of FIG. 4. In this embodiment, the outer header
64 has a partial circular shape when viewed from the top. In other
embodiments, the shape of the outer header when viewed from the top
may include, but is not limited to a complete circle, an oval, a
partial oval, a square, a partial square, a rectangle, a partial
rectangle, a triangle, a partial triangle, a hexagon, a partial
hexagon, and combinations thereof. This top-view shape may be
chosen to fit within a design-constrained space or may be chosen to
mirror the shape of a structure which will house the heat exchanger
58. In this embodiment, the inner header 60 has a capsule shape
when viewed from the top. In other embodiments, the shape of the
inner header when viewed from the top may include, but is not
limited to a circle, an oval, a square, a rectangle, a loop, a
triangle, and a hexagon.
[0044] FIG. 6 schematically illustrates a side cross-sectional view
of another embodiment of a heat exchanger 74 for use in an energy
storage system. The heat exchanger 74 has an inner header 60 with
an inner feedport 62. The heat exchanger 74 also has an outer
header 64 with an outer feedport 66. The heat exchanger 74 further
has a collection header 76 which is fluidically coupled to the
inner header 60 via one or more inner tubes 78 and to the outer
header 64 via one or more outer tubes 80. The collection header 76
may facilitate the use of a plurality of inner tubes 78 and/or a
plurality of outer tubes 80 by providing a common connection
point.
[0045] In this embodiment, the collection header 76 lies in a plane
below the inner header 60 and the outer header 64, but in other
embodiments, the collection header 76 could lie in a plane above
the inner header 60 and the outer header 64, in a plane above the
inner header 60 and below the outer header 64, in a plane below the
inner header 60 and above the outer header 64, or in substantially
the same plane as the inner header 60 and the outer header 64.
Furthermore, although the collection header 76 is illustrated as
centered in this embodiment, other embodiments need not be so.
[0046] In this embodiment, the collection header 76 has a circular
cross-sectional shape. In other embodiments, the inner header and
the outer header may have other cross-sectional shapes, such as,
but not limited to oval, square, triangular, and hexagonal. Certain
cross-sectional shapes may provide more or less surface area for
heat transfer or may assist with ease of manufacturing and may be
chosen to fit certain heat transfer and assembly goals by those
skilled in the art depending on the embodiment.
[0047] FIG. 7 schematically illustrates a side cross-sectional view
of another embodiment of a heat exchanger 82 for use in an energy
storage system. Similar to the embodiment of FIG. 4, the embodiment
of FIG. 7 has an inner header 60 having an inner feedport 62 and an
outer header 64 having an outer feedport 66, the features of which
have been discussed above. The outer header 64 is fluidically
coupled to the inner header 60, in this embodiment via outer tubes
84, 86 and inner tube 88. Other embodiments may have differing
numbers of inner tubes and/or outer tubes, and may also include a
collection header as previously discussed.
[0048] As with all of the embodiments of the heat exchangers, this
heat exchanger 82 is also designed to be substantially immersed in
a phase change medium (not shown in this view). Unlike other
thermal energy storage systems which use phase change medium, the
current embodiments and their equivalents do not have to maintain
the phase change medium in a liquid state because the phase change
media is not being pumped anywhere. Instead, the heat exchangers
are designed to be immersed in the phase change medium. This offers
several benefits, including a simpler, less expensive design and
the ability to take advantage of the latent heat of fusion which
may still be present in a given phase change medium after it has
solidified, thereby increasing the energy storage capacity of
thermal energy systems using this design over prior art
systems.
[0049] One of the considerations when operating a heat exchanger
submersed in a phase change medium is how the heat exchanger will
initially liquefy the phase change medium. Surprisingly, it has
been discovered that if the phase change medium is heated too
slowly, there can be too much expansion of the phase change medium
because of an insufficient vent path through the phase change
medium. This can put undesired stress on a container holding the
phase change medium and even cause phase change medium to leak from
the container. In order to assist the phase change medium to heat
quickly, some embodiments of heat exchangers, such as the heat
exchanger 82 in FIG. 7, may have one or more core heat tubes 90
which are directly or indirectly coupled to the inner header 60.
Such core heat tubes 90 may trap hot incoming heat transfer fluid
supplied to the inner header 60 and create a hot spot within the
phase change medium that the exchanger will be placed within. The
one or more core heat tubes 90 may be preferably placed near or in
the central portion of the heat exchanger to quickly heat the
middle of the phase change medium and create a vent path which
helps to alleviate outward expansion of the phase change
medium.
[0050] FIG. 8 schematically illustrates a side cross-sectional view
of a further embodiment of a heat exchanger 92 for use in an energy
storage system. Similar to the embodiment of FIG. 4, the embodiment
of FIG. 8 has an inner header 60 having an inner feedport 62 and an
outer header 64 having an outer feedport 66, the features of which
have been discussed above. The outer header 64 is fluidically
coupled to the inner header 60, in this embodiment via outer tubes
94, 96 and inner tubes 98, 100. Other embodiments may have
differing numbers of inner tubes and/or outer tubes, and may also
include a collection header as previously discussed. In this
embodiment, at least one of the one or more inner tubes 100 has a
bypass valve 102 which may be opened or closed by a mechanical,
electromechanical, hydraulic, or pneumatic activator. In normal
operation, if the bypass valve 102 is opened, the inner tube 100
operates like other inner tubes 98 which do not have a bypass
valve, allowing hot heat transfer fluid to flow through. If it is
desired to create a hot spot around the inner tubes, however, the
bypass valve 102 may be fully or partially closed. As discussed
above, the creation of a hot spot can assist the formation of a
vent path to alleviate unwanted outward expansion.
[0051] FIG. 9 schematically illustrates one embodiment of a thermal
energy storage apparatus 104. The thermal energy storage apparatus
104 has a heat exchanger 106 such as the heat exchangers which have
been discussed above. The illustrated heat exchanger 106 in FIG. 9
has an inner header 60 having at least one inner feed port 62 and
an outer header 64 having at least one outer feed port 66, the
features of which have been discussed above. The outer header 64 is
fluidically coupled to the inner header 60, in this embodiment via
outer tubes 108, 110 and inner tubes 112. Other embodiments may
have differing numbers of inner tubes and/or outer tubes, and may
also include a collection header and/or one or more core heat tubes
and/or one or more inner tubes with a bypass valve as previously
discussed. The inner header 60 and the outer header 64 are
substantially immersed in a phase change medium 114.
[0052] The phase change medium 114 may be selected based on
operating temperature considerations. Other considerations for the
selection of the phase change medium 114 are chemical stability,
non-toxicity, corrosiveness, and thermal properties, such as heat
of fusion, thermal conductivity, and heat capacity. Suitable
examples of phase change medium 114 may include, but are not
limited to salt, a salt mixture, a eutectic salt mixture, 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,
zinc chloride, and any combination thereof.
[0053] FIG. 10A schematically illustrates a side cross-sectional
view of another embodiment of a thermal energy storage apparatus
116. The thermal energy storage apparatus 116 has a heat exchanger
118 similar to the heat exchangers which have been discussed above.
The illustrated heat exchanger 118 in FIG. 10A has an inner header
60 having at least one inner feed port 62 and an outer header 64
having at least one outer feed port 66, the features of which have
been discussed above. The heat exchanger 118 further has a
collection header 76 which is fluidically coupled to the inner
header 60 via one or more inner tubes 78 and to the outer header 64
via one or more outer tubes 80. The features of the one or more
inner tubes 78, the collection header 76, and the one or more outer
tubes 80 have been discussed previously. Other embodiments may have
differing numbers of inner tubes and/or outer tubes, and may also
include one or more core heat tubes and/or one or more inner tubes
with a bypass valve as previously discussed.
[0054] The thermal energy storage apparatus 116 also has a tankless
structure 120 which is configured to contain the phase change
medium 114 such that the inner header 60 and the outer header 64
are substantially immersed in the phase change medium 114. In this
embodiment, the tankless structure 120 is constructed of
dry-stacked bricks 122. Since the bricks 122 are dry-stacked, they
will have inherent small gaps and spaces between them. These spaces
124 have been exaggerated in the drawing to facilitate discussion
of the thermal energy storage apparatus 116.
[0055] Suitable examples of materials which the bricks 122 may be
constructed from include, but are not limited to firebrick,
refractory material, castable refractories, refractory brick,
mixtures of alumina (Al2O3), silica (SiO2), magnesia (MgO),
zirconia (ZrO2), chromium oxide (Cr2O3), iron oxide (Fe2O3),
calcium oxide (CaO), silicon carbide (SiC), carbon (C); metallic
materials, plain carbon steels; alloy steels, manganese, silicon,
silicon-manganese, nickel, nickel-chromium, molybdenum,
nickel-molybdenum, chromium, chromium-molybdenum,
chromium-molybdenum-cobalt, silicon-molybdenum,
manganese-silicon-molybdenum, nickel-chromium-molybdenum,
silicon-chromium-molybdenum, manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper,
nickel-chromium-molybdenum, and any combination thereof.
[0056] Since the thermal energy storage apparatus 116 has a
tankless structure 120, the phase change medium 114 will tend to
leak through the gaps 124 in the bricks 122 when it is in a liquid
state. For this reason, it is preferred to size the bricks 122 such
that they have a cooling zone 126 which encourages the phase change
medium 114 to solidify 128 in at least a portion of the gaps 124
defined by the bricks 122. Thus, when the phase change medium 114
is first liquefied, it can seep into the gaps 124 and then cool at
some point within the gaps 124 to substantially seal itself 128 to
prevent leakage of the phase change medium 114 from the tankless
structure 120. The tankless structure 120 does not have the
corrosive concerns of typical single or multiple tank systems, it
will last longer, it is less expensive to construct, and it is
easily scalable. The tankless structure 120 is also suitable for
use in seismic regions because it remains flexible due to its
dry-stacked and self-sealing nature. Although the illustrated
embodiment shows a single layer of bricks 122, other embodiments
may utilize multiple layers of bricks 122.
[0057] The tankless structure 120 may define a variety of
horizontal cross-sectional shapes, such as, but not limited to
circular, oval, hexagonal, rectangular, and square. However, since
the heat exchanger 118 is configured to take advantage of radial
heat differences within the tankless structure 120, a circular
horizontal cross-sectional shape defined by the tankless structure
120 is preferred for even heat distribution. A tankless structure
120 which defines a circular horizontal cross-sectional shape will
also have reduced mechanical stresses since it will not have
corners.
[0058] Although the outer header 64 may have many configurations as
discussed above, it is preferred that the outer header 64 have a
horizontal cross-sectional shape which substantially follows the
horizontal cross-sectional shape defined by the tankless structure
120. Such a configuration enables the routing of the outer tubes 80
near to the tankless structure where the temperature of the phase
change medium 114 will be at a minimum.
[0059] The thermal energy storage apparatus 116 also has a base 130
which supports the tankless structure 120. Although the base 130 is
illustrated as being smooth and level, the base 130 in other
embodiments may have other profiles. The base 130 may be earth or
some structure which is stacked, formed, poured, set, filled or
otherwise constructed in place to support the tankless structure
120. Suitable materials for the base 130 include, but are not
limited to earth, firebrick, refractory material, concrete,
castable refractories, refractory concrete, refractory cement,
insulating refractories, gunning mixes, ramming mixes, refractory
plastics, refractory brick, mixtures of alumina (Al2O3), silica
(SiO2), magnesia (MgO), zirconia (ZrO2), chromium oxide (Cr2O3),
iron oxide (Fe2O3), calcium oxide (CaO), silicon carbide (SiC),
carbon (C); metallic materials, carbon steels; alloy steels,
manganese, silicon, silicon-manganese, nickel, nickel-chromium,
molybdenum, nickel-molybdenum, chromium, chromium-molybdenum,
chromium-molybdenum-cobalt, silicon-molybdenum,
manganese-silicon-molybdenum, nickel-chromium-molybdenum,
silicon-chromium-molybdenum, manganese-chromium-molybdenum,
manganese-silicon-chromium-molybdenum, vanadium, chromium-vanadium,
silicon-chromium-vanadium, manganese-silicon-chromium-vanadium,
chromium-vanadium-molybdenum,
manganese-silicon-chromium-vanadium-molybdenum, chromium-tungsten,
chromium-tungsten-molybdenum, chromium-tungsten-vanadium,
chromium-vanadium-tungsten-molybdenum,
chromium-vanadium-tungsten-cobalt,
chromium-vanadium-tungsten-molybdenum-cobalt; stainless steels,
austenitic, ferritic, martensitic, duplex, precipitation-hardening,
superaustenitic, superferritic; nickel alloys,
nickel-chromium-iron, nickel-chromium-iron-aluminum,
nickel-chromium-iron-aluminum-titanium,
nickel-chromium-iron-aluminum-titanium-niobium,
nickel-chromium-iron-cobalt-molybdenum,
nickel-chromium-iron-niobium,
nickel-chromium-iron-molybdenum-niobium,
nickel-chromium-iron-molybdenum-niobium-titanium-aluminum,
nickel-chromium-molybdenum-iron-tungsten,
nickel-chromium-iron-molybdenum-copper-titanium,
nickel-chromium-iron-molybdenum-titanium,
nickel-iron-cobalt-aluminum-titanium-niobium, nickel-copper,
nickel-copper-aluminum-titanium, nickel-molybdenum-chromium-iron,
nickel-chromium-molybdenum-copper,
nickel-chromium-molybdenum-iron-tungsten-copper,
nickel-chromium-molybdenum, and any combination thereof.
[0060] A support 132 may be provided to support the heat exchanger
118 on the base 130.
[0061] FIG. 10B schematically illustrates a side cross-sectional
view of a further embodiment of a thermal energy storage apparatus
134. This embodiment of a thermal energy storage apparatus 134 has
all the features of the apparatus in FIG. 10A with some added
features. At least one layer of insulation 136 may be provided to
substantially surround the bricks 122 of the tankless structure 120
thereby helping to reduce heat loss and prolong the energy storage
time of the thermal energy storage apparatus 134. Care should be
taken that the insulation 136 is not so thick that it prevents the
bricks 122 from having a cooling zone 126, otherwise the phase
change medium 114 may leak out of the tankless structure 120.
Additionally or optionally, a top layer of insulation 138 may be
placed over the tankless structure 120. One or more bands 140 may
be placed around the tankless structure 120 and the insulation 136
to support the bricks 122.
[0062] FIG. 11 illustrates an embodiment of a method for
constructing a thermal energy storage system. A base is formed 142.
This can include clearing or defining a space on the earth, or it
can include forming, laying, pouring, setting, or otherwise
building or defining the base on or above a surface. The base may
optionally be formed on an insulator. At least one heat exchange
system is aligned 144 substantially over the base. The at least one
heat exchange system has an inner header and an outer header.
Suitable example embodiments of heat exchangers have been discussed
herein. A brick wall is dry-laid 146 substantially on the base to
surround the at least one heat exchange system or an area where the
at least one heat exchange system will be aligned. This takes into
account construction methods which first align the heat exchange
system over the base and then dry-lay the brick wall around the
heat exchange system as well as construction methods which first
dry-lay the brick wall and then align the heat exchange system over
the base within the brick wall. The area defined by the base and
the brick wall are then filled 148 with a phase change medium such
that the phase change medium substantially covers the at least one
heat exchange system. The brick wall may optionally be insulated
150. The brick wall may optionally be banded 152 for added strength
and stability.
[0063] Since the thermal energy storage system is a tankless
system, the phase change medium may optionally be heated 154 so
that it transitions to a liquid phase and enters gaps defined by
the dry-laid bricks of the brick wall. Then, the phase change
medium may optionally be allowed 156 to cool enough to solidify in
at least a portion of the gaps in order to substantially seal the
brick wall where it meets the phase change medium.
[0064] Another embodiment of a thermal energy storage system 158 is
illustrated and discussed with regard to FIGS. 12A-12E. The
embodied thermal energy storage system 158, as well as the
previously discussed embodiments and their equivalents are designed
to be easily scalable from about 50 kilowatt-hours (kWhr) to about
30 MWhr of storage capacity, by way of example. The thermal energy
storage system is easily configured to optimize ease of changing
fluid temperatures (since this can be different at different
installations), phase change medium makeup (since different phase
change media have optimum characteristics at the different
operating temperatures), and heat transfer fluids (these also vary
at installations). Heat exchanger tube spacing, the number of rows,
and the number of tubes in each row can be separately adjusted for
the outer tubes 160 connecting the outer header 162 to the
collection header 164, and the inner tubes 166 connecting the
collection header 164 to the inner header 168 to optimize heat
transfer, to minimize external heat losses, and to account for
thermal conductivity differences between solid phase change media
and molten phase change media.
[0065] By way of example only, one embodiment of a thermal energy
storage system 158 is described below. The design criteria for this
thermal energy storage system 158 includes: (1) a phase change
medium including a eutectic salt mixture with a melting point a
minimum of 75.degree. F. below a maximum oil outlet temperature at
the particular solar field the thermal energy storage system 158 is
proposed to be used at (This particular field has the lowest
operating temperature expected for this thermal energy storage
system); (2) a minimum storage capacity of 150 btu/lbm of salt; (3)
a minimum storage efficiency of 75%; (4) the ability to transfer 20
btu/lbm of salt when heating the salt and transfer as low as 9
btu/lbm when removing heat from the salt; (5) acceptable material
performance for the heat exchange, piping and containment vessel;
(6) providing access to the heat exchanger for repairs; (7) an
effective containment system for integrity, structural capability
and heat retention; (8) a design life of a minimum of 20 years with
daily cycles from minimum temperature to maximum temperature; (9)
the ability to maintain relatively constant oil (heat transfer
fluid) outlet temperature throughout repeated 24 hour cycles; and
(10) the ability to utilize the same oil (heat transfer fluid) as
the solar field.
[0066] The embodied thermal energy storage system 158 includes the
containment structure 170 or system, the heat exchanger 172, an oil
circulating system, the salt 174 or other phase change media, and
an inert gas control system, if required, although the thermal
energy storage system 158 could include other types and numbers of
components, devices, and systems in other configurations. For
example, other embodiments of the thermal energy storage system 158
may include instrumentation to collect data and to control the
thermal energy storage system. In some embodiments, the oil
circulating system may include a nitrogen overpressure system, a
surge tank, (a heater capable of heating the oil to operating
temperatures for mock-up purposes only), circulating pump, (a
cooler capable of cooling the oil at a constant rate for mock-up
purposes only), a bypass throttle valve, reversing valves, and
interconnecting piping, although the oil circulating system could
include other types and numbers of components, devices, and systems
in other configurations.
[0067] In this particular example, the thermal energy storage
system 158 is using standard heat exchanger sized tubes. In this
embodiment, a minimum of four tubes are utilized (two inner tubes
166 and two outer tubes 160), with an OD of 3/4'', although the
type, number, configuration, and dimensions of these and other
tubes or piping, the holes or openings, and the connections
throughout can vary. This establishes the minimum size requirement
of all components when applying the heat transfer criteria listed
above. Additionally the thermal energy storage system 158 is sized
to store a minimum of 200 kW-hours of storage, although other
amounts of energy could be stored. It is assumed for this
particular example that the heat is added to the thermal energy
storage system 158 over eight hours, but for sizing it may
optionally be assumed that heat is added at a constant rate over 6
hours to account for non-linearity in the heat rate. Therefore, the
heat exchanger is sized for a Q of 34 kW, or 0.125 mmbtu/hr,
although the heat exchanger could have other sizing for other
applications.
[0068] As FIGS. 12A, 12B, and 12C illustrate, the heat exchanger
172 comprises a rolled outer header 162, a collection or
intermediate header 164, and an inner header 168, although the heat
exchanger 172 can comprise other types and numbers of components,
devices, and systems in other configurations. The three headers
162, 164, and 168 are connected by tubing sized for the proper heat
transfer surface area. The design temperature is 750.degree. F. and
design pressure is 250 psig in this particular example, although
the thermal energy storage system 172 could be designed for other
temperatures, pressures, and characteristics.
[0069] The outer header 162 in this embodiment is 3'' nominal
piping, 12' long, rolled on a 22.5'' radius capped on both ends,
although the type, number, configuration, and dimensions of these
and other tubes or piping, the holes or openings, and the
connections throughout can vary. An oil supply inlet (outer
feedport) 176 of 11/2'' piping enters at the top center of the
header. Thirty-eight (38)3/4'' outer tubes 160 exit the bottom of
the outer header 162 through holes spaced to maintain the tubes
parallel to each other, 13/4'' center to center. The outer header
162 is supported solely by the outer tubes 160 and connecting inlet
piping 176, and `floats` approximately 1 foot below the top of the
salt 174 or other phase change media. A tie-rod may be used to
connect the capped ends of the outer header 162. All connections to
the outer header 162 are by fillet weld of equal size to the
smaller material thickness, although other types of connections
could be used.
[0070] The collection header 164 is 6'' nominal piping, 4' long
with one end with a bolted flange 178, and the opposite end weld
capped 180, although the type, number, configuration, and
dimensions of these and other tubes or piping, the holes or
openings, and the connections throughout can vary. The collection
header 164 is supported on chair legs 182, 6'' off the base 184 of
the thermal energy storage system 158, on the approximate
centerline of the thermal energy storage system 158. The flanged
end 178 butts against one side of the thermal energy storage system
158. Nineteen (19)3/4'' holes are located on each side (38 total);
located and spaced 13/4'' center to center to accept connecting
outer tubes 160 from the outer header 162. At forty-five degrees
from the top of the collection header 164 on each side, nineteen
(19)3/4'' holes spaced 13/4'' center to center are drilled for the
inner tubes 166 (total of 383/4'' holes). All tubes are fillet
welded to the collection header 164, although other types of
connections could be used.
[0071] The inner header 168 is 4'' nominal piping, 42'' long, with
welded caps on each end, although the type, number, configuration,
and dimensions of these and other tubes or piping, the holes or
openings, and the connections throughout can vary. Nineteen
(19)3/4'' holes are located 45 degrees off the bottom center of the
inner header 168 in each direction spaced 13/4'' center-to-center
(38 holes total) to accept the inner tubes 166 from the collection
header 164. A 11/2'' oil pipe connection (inner feedport) 186 is
provided at the top center of the inner header 168. All tubes are
fillet welded to the inner header 168, although other types of
connections could be used.
[0072] The interconnecting tubes are 3/4'' carbon steel tubing,
nominal wall thickness of 0.060'', although the number,
configuration, and dimensions of these and other tubes or piping
and also the holes or openings described throughout can vary. The
connecting tubing from the outer header 162 to the collection
header 164 is bent to 90 degrees, 351/4'' from one end, 38 total
tubes, nineteen per side of the collection header. The connecting
tubing from the collection header 164 to the inner header 168 is
351/4'' long, bent at 45 degrees 6'' from one end and 51/4'' from
the other end, thirty-eight (38) total. Overall tube length is
271.6 feet or approximately 270 feet for heat transfer
purposes.
[0073] One embodiment of an oil circulating system (heat transfer
fluid circulating system) which can be used with the thermal energy
storage system 158 may include a nitrogen overpressure system,
surge tank, (heater capable of heating the oil to operating
temperatures for testing purposes only), circulating pump, (a
cooler capable of cooling the oil at a constant rate for testing
purposes only), a bypass throttle valve, reversing valves, and
interconnecting piping, although the oil circulating system and
each of its components as described herein could include other
types and numbers of components, devices, and systems in other
configurations. The oil system may be designed for a nominal
pumping rate of 20 gpm, a temperature of 750.degree. F. and 250
psig, although the system can be designed for other pumping rates,
temperatures, pressures, and other characteristics. The total
required volume of oil is approximately 55 gallons plus that
required by the field and any turbine heat exchanger configuration
coupled to the thermal energy storage system 158. The
interconnecting piping is 11/2'' carbon steel schedule 40 and is
insulated. The throttle bypass valve is a nominal 3/4'' valve, with
a turndown of 50 and is designed to be controlled by a temperature
controller. The intent of this valve is to control downstream
temperature at a fixed value. This embodiment of a thermal energy
storage system 158 requires four reversing valves which are quarter
turn ball valves, although other types of valves can be used. The
reversing valves are 11/2'' inch nominal. The oil cooler is sized
to remove heat from the oil at a maximum rate of 60,000 BTU/our and
is air cooled.
[0074] Temperature measurements are required on the oil system at
the heater inlet and outlet, storage outlet, storage collection
header, and cooler inlet and outlet. Four thermocouples will also
be embedded in the salt bath. Surface temperatures on the tankless
structure can be taken by hand-held instruments. Oil flow through
the heater and bypass are required. Oil pressure at the expansion
tank, pump discharge, tank inlet and outlet are required.
[0075] One of the advantages of the thermal energy storage system
158 is that the containment of the phase change media 174 is
tankless. The molten salt 174 is contained in a structure made of
refractory 188 (bricks or castable), which contains both the phase
change media 174 and the heat exchanger 172.
[0076] Unique aspects of this embodiment of a thermal energy
storage system 158 include having the inner and outer headers 162,
168 located at the top of the system 158 just below the top of the
phase change media 174. This design minimizes the number of
penetrations at the molten salt/atmosphere interface where
corrosion is a concern. Another unique aspect is that the outer
header 162 is a toroid in this embodiment allowing the outer tubes
160 (cooler fluid) to be circumferentially located in close
proximity to the tankless structure 170 to minimize heat losses
through the exterior of the containment, thereby improving system
efficiency. Another unique aspect is that a large diameter
intermediate/collection header 164 is located near the bottom of
the containment with a flange 178 abutting one wall of the
containment structure. This allows the outer tubing 160 to not only
be located near the outer wall (as described above), but also to be
located near the bottom of the containment to minimize heat losses
through the base 184. The collection header 164 design also allows
for ease of serviceability of the heat exchanger because it can be
accessed without removal of the majority of the phase change media
174 by removing nearby bricks 188 and burrowing in to the flange
178.
[0077] Additionally, this design improves mixing of the fluid phase
change medium 174 to promote thermal consistency. Differing designs
between inner outer tubing to account for differences in heat
transfer characteristics between the phase change media in the
upper center of the containment from the periphery.
[0078] Another advantage of this embodiment of a thermal energy
storage system 158 is that it may be designed with a valve control
system including both reversing valves and temperature control
valves. The reversing valves allow for flow to enter the heat
exchange system 172 through the inner header 168 (See FIG. 12D)
when heating the phase change media 174, and conversely to enter
the heat exchanger 172 through the outer header 162 (See FIG. 12E)
when cooling the system. This keeps the cooler oil (heat transfer
fluid) always on the outside of the containment, minimizing heat
losses through the exterior. The constant temperature control
valves maintain oil temperature to the turbine supply heat
exchanger to operate at a constant temperature whether or not the
thermal energy storage system is being heated or cooled (i.e.
energy added or removed). This allows a turbine to be designed to
operate at peak efficiency because a single inlet condition is
maintained.
[0079] FIG. 13 schematically illustrates an embodiment of a thermal
energy power system 190. The thermal energy power system 190 has a
thermal energy storage apparatus 116, the features of which have
been discussed above with regard to FIG. 10A. Other embodiments of
thermal energy power systems may have other embodiments of thermal
energy storage apparati as have also been discussed above with
numerous examples and their equivalents. The thermal energy power
system 190 has at least one inner valve 192 which may be used to
selectably and fluidically couple the inner header 60 to either a
renewable heat source 194 or a pump 196. Suitable examples of a
renewable heat source 194 include, but are not limited to solar
cells, solar mirror arrays, and wind turbines. Other non-limiting
examples of renewable heat sources 194 may include industrial stack
heat and/or excess heat which is the by-product of industrial,
municipal, institutional, individual, or other activity. For
example, a manufacturing plant which operates during the day may
generate heat which can be stored to supply power for other
activities at a later time. Heat transfer fluid is preferably used
to remove heat from the renewable heat source 194 and transfer it
throughout the system when moved by the pump 196. The thermal
energy power system 190 also has at least one outer valve 198 which
may be used to selectably and fluidically couple the outer header
64 to either the renewable heat source 194 or the pump 196. The
inner header 60 and the outer header 64 are reversibly connected in
a closed loop with the pump 196, the renewable heat source 194, and
a turbine plant 200. The reversible connection can be made possible
by a variety of valve devices, the illustrated inner and outer
selection valves 192, 198 being only one example. The turbine plant
200 uses heat delivered to it by the pump from the renewable heat
source 194 or the thermal energy storage apparatus 116 to generate
steam which drives generators to make electricity.
[0080] FIG. 14 schematically illustrates flow through the embodied
thermal energy power system of FIG. 13 during a heating mode.
During this heating mode, the renewable energy source 194 is
available (producing heat), for example, when the sun is shining on
a solar array. The inner selection valve 192 is set to a first
position (position A in the drawing) which couples heated heat
transfer fluid 202 from the renewable heat source 194 to the inner
header 60 of the thermal energy storage apparatus 116. The outer
selection valve 198 is set to a second position (position B in the
drawing) which fluidically couples the outer header 64 to the
turbine plant 200. In this embodiment, the pump 196 is in the fluid
path from the outer header 64 to the turbine plant 200 to provide
the force to move the thermal transfer fluid through the power
system. Other embodiments may place the pump in different locations
or use more than one pump. Thermal transfer fluid from the turbine
plant 200 is then coupled back to the renewable heat source
194.
[0081] During operation, the heat transfer fluid 202 which is
heated by the renewable heat source passes into 204 the inner
header and down 206 through one or more inner tubes within the
approximate center of the phase change media. Heat from the heat
transfer fluid is transferred to and stored by the phase change
media. The heat transfer fluid then passes 208 through the
collection header, up the one or more outer tubes, and into the
outer header. The heat transfer fluid, having given-up some of its
heat to the phase change media may then be pushed 210 to the
turbine plant 200 if it still has enough heat to generate steam.
Alternatively, the heat transfer fluid may be routed back to the
renewable heat source or augmented with a separate line of hot heat
transfer fluid from the renewable heat source before being sent to
the turbine plant. The cooled heat transfer fluid leaving the
turbine plant is returned 212 to the renewable heat source for
further heating.
[0082] FIG. 15 schematically illustrates flow through the embodied
thermal energy power system of FIG. 13 during a cooling mode.
During this cooling mode, the renewable energy source 194 is not
available (not producing heat), for example, when the sun is not
shining on a solar array. The outer selection valve 198 is set to a
first position (position A in the drawing) which fluidically
couples the outer header 64 to the renewable heat source which is
currently not generating heat. The inner selection valve 192 is set
to a second position (position B in the drawing) which couples
heated heat transfer fluid (heated by the phase change media 114)
from the inner header 60 of the thermal energy storage apparatus
116 to the to the turbine plant 200. In this embodiment, the pump
196 is in the fluid path from the inner header 60 to the turbine
plant 200 to provide the force to move the thermal transfer fluid
through the power system. Other embodiments may have the pump in
different locations or use more than one pump. Thermal transfer
fluid from the turbine plant 200 is then coupled back to the
renewable heat source 194.
[0083] During operation, the heat transfer fluid which is heated by
the phase change medium passes 214 from the collection header up
into the inner header and is pushed 216 to the turbine plant for
generating steam. The heat transfer fluid is cooled after leaving
the turbine plant and is recirculated 218 back to the renewable
heat source (which is currently not producing heat). The heat
transfer fluid is then moved 220 into the outer header and down 222
through the one or more outer tubes and back into the collection
header where the heat transfer fluid may be heated again to power
the turbine plant. In alternate embodiments, the cooled heat
transfer fluid which leaves the turbine plant may be routed to
circumvent the renewable heat source, which is not producing heat,
directly back into the outer header.
[0084] FIG. 16 illustrates an embodiment of a method for
controlling a thermal energy storage system. A determination is
made 224 as to whether a renewable heat source is available. When a
renewable heat source is available 226: i) the renewable heat
source is thermally and fluidically coupled 228 to an inner header
of a heat exchange system which is substantially immersed in a
phase change medium and which is further coupled to an outer header
of the heat exchange system which is also substantially immersed in
the phase change medium; and ii) the outer header is thermally and
fluidically coupled 230 to a turbine plant and then back to the
renewable heat source in a closed-loop heating mode which provides
a remaining renewable energy source heat to the turbine plant. When
the renewable heat source is not available 232: i) the renewable
heat source is thermally and fluidically coupled 234 to the outer
header; and ii) the inner header is thermally and fluidically
coupled 236 to the turbine plant and then back to the renewable
heat source in a closed-loop cooling mode which provides a stored
heat to the turbine plant.
[0085] Having thus described several embodiments of the claimed
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 the scope of the
claimed invention. Additionally, the recited order of the
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. Accordingly, the claimed invention is limited only by the
following claims and equivalents thereto.
* * * * *