U.S. patent number RE34,542 [Application Number 07/691,360] was granted by the patent office on 1994-02-15 for chemical energy storage system.
This patent grant is currently assigned to Rocky Research. Invention is credited to Uwe Rockenfeller.
United States Patent |
RE34,542 |
Rockenfeller |
February 15, 1994 |
Chemical energy storage system
Abstract
A system for storing chemical energy comprises first and second
vessels, the first containing a liquid solution of an alkali or
alkaline earth metal hydroxide, halide, or thiocyanate, or ammonium
halide or thiocynate at an initial concentration of between about
30% to abotu 80%, by weight, the second vessel containing liquid, a
space about the liquid in each vessel and a conduit communicating
between the spaces having a valve for selectively allowing liquid
vapor to pass between the spaces, means for heating the solution to
a temperature above about 80.degree. F., means for cooling the
liquid to a temperature below about 55.degree. F., and heat
exchange means for transferring heat from the heated solution and
for transferring heat to the cooled liquid. Water is the preferred
liquid although ammonia, lower alcohols, and polyols such as
glycerol, glycols, polyglycols, glycol ethers, lower aliphatic
amines and alkanol amines, and mixtures thereof, may be used.
Inventors: |
Rockenfeller; Uwe (Boulder
City, NV) |
Assignee: |
Rocky Research (Boulder City,
NV)
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Family
ID: |
21899294 |
Appl.
No.: |
07/691,360 |
Filed: |
April 25, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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38323 |
Apr 14, 1987 |
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Reissue of: |
215204 |
Jul 5, 1988 |
04823864 |
Apr 25, 1989 |
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Current U.S.
Class: |
165/104.12;
62/106; 62/478; 62/481; 62/494; 62/484; 62/112; 62/477 |
Current CPC
Class: |
F25B
17/02 (20130101); F28D 20/003 (20130101); F28D
5/02 (20130101); Y02E 60/142 (20130101); Y02E
60/14 (20130101) |
Current International
Class: |
F28D
20/00 (20060101); F25B 17/02 (20060101); F25B
17/00 (20060101); F25B 017/02 () |
Field of
Search: |
;165/104.12
;62/478,477,481,484,494,112,106,485,482,480 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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117745 |
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Jul 1982 |
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JP |
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612 |
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Mar 1981 |
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WO |
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Primary Examiner: Davis, Jr.; Albert W.
Attorney, Agent or Firm: Seiler; Jerry R.
Parent Case Text
This application is a continuation-in-part of specification Ser.
No. 038,323 filed Apr. 14, 1987 now abandoned.
Claims
I claim:
1. Apparatus for .[.transferring heat.]. .Iadd.alternately charging
and discharging thermal energy .Iaddend.comprising
a first vessel containing a liquid solution of a compound selected
from the group consisting of alkali and alkaline earth metal
hydroxide, halide and thiocyanate, ammonium halide, .Iadd.ammonium
metal halide .Iaddend.and thiocyanate, and mixtures thereof, said
solution having an initial concentration of between about 30% and
about 80% by weight of said compound, said liquid selected from the
group consisting of water, ammonia, an alcohol having between 1 and
8 carbon atoms, glycerol, glycols, polyglycols, glycol ethers,
aliphatic amines and alkanol amines having between 1 and about 6
carbon atoms, and mixtures thereof, and a first space above the
level of said liquid solution and means for pumping said liquid
solution to distribution means for directing said liquid solution
into said first space,
a second vessel containing said liquid without said compound
therein, and a second space above the level of said liquid and
means for pumping said liquid to distribution means for directing
said liquid solution into said second space,
both said first and second vessels being closed to atmosphere and
capable of holding a vacuum,
conduit means communicating between said first space and second
space for allowing liquid vapor and pressure changes to pass
therebetween, and valve means cooperating with said conduit means
for terminating communication between said spaces,
heating means .[.for.]. .Iadd.capable of .Iaddend.heating said
solution to a temperature of above about
.Badd..[.90.degree..]..Baddend. .Iadd.85.degree. .Iaddend.F., and
cooling means .[.for.]. .Iadd.capable of .Iaddend.cooling said
liquid to a temperature below about 55.degree. F. .Iadd.during said
charging .Iaddend.,
first heat exchange means cooperating with said first vessel for
transferring heat from heated solution therein, and second heat
exchange means cooperating with said second vessel for transferring
heat to liquid therein .Iadd.during said discharging. .Iaddend.
2. Apparatus of claim said first and second vessels comprise first
and second chambers in a divided tank, respectively.
3. Apparatus of claim 2 wherein said conduit means comprises port
means communicating between said first and second spaces, and
wherein said valve means opens and closes said port means
4. Apparatus of claim 1 including first pipe means and first pump
means for directing said solution between said first vessel and
said first heat exchange means, and second pipe means and second
pump means for directing said liquid between said second vessel and
said second heat exchange means.
5. Apparatus of claim 4 wherein said first heat exchange means
comprises a heat pump condenser, and said second heat exchange
means comprises a heat pump evaporator.
6. Apparatus of claim 4 wherein said .[.first heat exchanger.].
.Iadd.heating .Iaddend.means comprises waste heat or solar heat
means.
7. Apparatus of claim 1 wherein said first heat exchange means
includes a first heat exchange pipe exposed in said first space and
wherein said distribution means directs said solution over the
first heat exchange pipe in said first space.
8. Apparatus of claim 7 including spray means for spraying said
solution over said first heat exchange pipe.
9. Apparatus of claim 7 wherein said first heat exchange pipe
comprises a condenser coil.
10. Apparatus of claim 1 wherein said second heat exchange means
includes a second heat exchange pipe exposed in said second space
and wherein said distribution means directs said liquid over said
second heat exchange pipe.
11. Apparatus of claim 10 including spray means for spraying said
liquid over said second heat exchange pipe.
12. Apparatus of claim 10 wherein said second heat exchange pipe
comprises an evaporator coil. .[.
13. Apparatus of claim 1 wherein said first heat exchange means
include evaporative or air to air cooling means and first
supplemental heat transfer means comprising a first conduit loop
having heat transfer liquid therein and a pump cooperating
therewith for pumping said heat transfer liquid through said first
conduit loop, said first conduit loop extending between said first
space and said evaporative or air to air cooling means..].
14. Apparatus of claim .[.13.]. .Iadd.15 .Iaddend.including spray
means for spraying said solution over said first conduit loop in
said first space.
15. Apparatus for .[.of claim 13.]. .Iadd.alternately charging and
discharging thermal energy comprising
a first vessel containing a liquid solution of a compound selected
from the group consisting of alkali and alkaline earth metal
hydroxide, halide and thiocyanate, ammonium halide, metal halide
and thiocyanate, and mixtures thereof, said solution having an
initial concentration of between about 30% and about 80%, by weight
of said compound, said liquid selected from the group consisting of
water, ammonia, an alcohol having between 1 and 8 carbon atoms,
glycerol, glycols, polyglycols, glycol ethers, aliphatic amines and
alkanol amines having between 1 and about 6 carbon atoms, and
mixtures thereof, and a first space above the level of said liquid
solution and means for pumping said liquid to distribution means
for directing said liquid into said first space,
a second vessel containing said liquid without said compound
therein, and a second space above the level of said liquid and
means for pumping said liquid to distribution means for directing
said liquid into said second space,
both said first and second vessels being closed to atmosphere and
capable of holding a vacuum,
conduit means communicating between said first space and said
second space for allowing liquid vapor and pressure changes to pass
therebetween, and valve means cooperating with said conduit means
for terminating communication between said spaces,
heating means capable of heating said solution to temperature of
above about 85.degree. F., and cooling means capable of cooling
said liquid to a temperature below about 55.degree. F., during said
charging,
first heat exchange means cooperating with said first vessel for
transferring heat from heated solution therein, and second heat
exchange means cooperating with said second vessel for transferring
heat to liquid therein during said discharging,
wherein said first heat exchange means include evaporative or air
to air cooling means and first supplemental heat transfer means
comprising a first conduit loop having heat transfer liquid therein
and a pump cooperating therewith for pumping said heat transfer
liquid through said first conduit loop, said first conduit loop
extending between said first space and said evaporative or air to
air cooling means, and.Iaddend.
wherein said second heat exchange means includes a heat pump
evaporator and second supplemental heat transfer means comprising a
second conduit loop having a heat transfer liquid therein and a
pump cooperating therewith for pumping said heat transfer liquid
through said second conduit loop said second conduit loop extending
between said second space and said evaporator.
16. Apparatus of claim 15 including spray means for spraying said
liquid over said second conduit loop in said second space.
17. A .[.heat exchange.]. process .Iadd.for alternately storing and
discharging thermal energy .Iaddend.utilizing the apparatus of
claim 1 comprising:
(a) opening said valve means,
(b) heating said solution in said first vessel to a temperature of
above about 85.degree. F. .Iadd.by exposing said solution to said
heating means .Iaddend.and evaporating liquid therefrom, directing
the liquid vapor from the space in said first vessel to the space
in said second vessel through said conduit means,
concurrently cooling the liquid in said second vessel to a
temperature below about 55.degree. F, .Iadd.by exposing said liquid
to said cooling means .Iaddend.and condensing the .[.water.].
.Iadd.liquid .Iaddend.vapor in the space therein and continuing
said heating and cooling until the concentration of said material
in said first vessel is between about 6% and about 25% greater than
said initial concentration,
(c) terminating said heating of said solution and said cooling of
said liquid and closing said valve means thereby closing
communication between said spaces in said first and second
vessels,
(d) selectively opening said valve whereby liquid therein is
evaporated thereby cooling said liquid in said second vessel as
liquid vapor pressure differential between said first and second
vessel is eliminated,
(e) exposing said liquid in said second vessel to heat exchange
means and pumping said liquid to said distribution means and
spraying said pumped liquid into said second space .[.;.]..Iadd.,
.Iaddend.and
(f) concurrently with step (e) exposing said solution in said first
vessel to heat exchange means and pumping said solution to said
distribution means and spraying said pumped solution into said
first space.
18. Process of claim 17 wherein said solution is heated to above
.Badd..[.80.degree..]..Baddend. .Iadd.85.degree. .Iaddend.F. in
step (b) by directing said solution to a heat pump condenser or
solar or waste heat source and exposing said solution to heated
elements thereof.
19. Process of claim 18 wherein said liquid is cooled below about
55.degree. F. by directing said liquid to a heat pump .Iadd.or air
conditioning .Iaddend.evaporator and exposing said liquid to cooled
elements thereof.
20. Process of claim 17 wherein said liquid is cooled to below
about 55.degree. F. in step (b) by directing said liquid to a heat
pump .Iadd.or air conditioning .Iaddend.evaporator and exposing
said liquid to cooled elements thereof.
21. Process of claim 20 wherein said cooled liquid from step (e) is
directed to a heat exchange evaporator for cooling elements
thereof.
22. Process of claim 17 comprising providing elements of said first
heat exchange means in said first space and providing elements of
said second heat exchange means in said second space and spraying
said liquid over said elements of said second heat exchange means
in step (e) and spraying said solution over said elements of said
first exchange means in step (f).
23. Process of claim 22 comprising providing said heat exchange
elements in said second space and spraying said elements with said
liquid. .Iadd.
24. Apparatus of claim 1 wherein said liquid comprises water or a
mixture of water and ammonia, and said compound is selected from
the group consisting of an alkali and alkaline earth metal
hydroxide, calcium chloride, calcium bromide, and mixtures thereof.
.Iaddend. .Iadd.25. Apparatus of claim 1 wherein said cooling means
for cooling said liquid to a temperature below about 55.degree. F.
comprises a heat pump or air conditioning evaporator. .Iaddend.
.Iadd.26. Apparatus of claim 1 wherein said liquid comprises
ammonia, and wherein said compound is selected from the group
consisting of ammonium halide, ammonium metal halide and
ammonium thiocyanate. .Iadd.27. Apparatus for alternately charging
and discharging thermal energy comprising:
a first vessel containing a liquid solution of a compound selected
from the group consisting of alkali and alkaline earth metal
hydroxide, halide and thiocyanate, ammonium halide and thiocyanate,
and mixtures thereof, said solution having an initial concentration
of between about 30% and about 80%, by weight of said compound,
said liquid selected from the group consisting of water, ammonia,
an alcohol having between 1 and 8 carbon atoms, glycerol, glycols,
polyglycols, glycol ethers, aliphatic amines and alkanol amines
having between 1 and about 6 carbon atoms, and mixtures thereof,
and a first space above the level of said liquid solution and means
for pumping said liquid solution to distribution means for
directing said liquid solution into said first space,
a second vessel containing said liquid without said compound
therein, and a second space above the level of said liquid and
means for pumping said liquid to distribution means for directing
said liquid into said second space,
both said first and second vessels being closed to atmosphere and
capable of holding a vacuum,
conduit means communicating between said first space and said
second space for allowing liquid vapor and pressure changes to pass
therebetween, and valve means cooperating with said conduit means
for terminating communication between said spaces,
means for charging said thermal energy comprising heating means
capable of heating said solution to a temperature of above about
85.degree. F., and cooling means capable of cooling said liquid to
a temperature below about 35.degree. F.,
means for discharging said thermal energy comprising first heat
exchange means cooperating with said first vessel for transferring
heat from heated solution therein, and
second heat exchange means cooperating with said second vessel for
utilizing the thermal energy benefit of the cooled liquid o provide
cooling to air conditioner or heat pump cooling heat exchange means
during
said discharging. .Iaddend. .Iadd.28. Apparatus of claim 27 wherein
said cooling means comprises a heat pump or refrigeration system
evaporator.
.Iaddend. .Iadd.29. A method for utilizing the apparatus of claim
27 comprising:
charging thermal energy to said apparatus at night or during period
of reduced demand for electrical power by opening said valve means,
heating said solution in said first vessel to a temperature of
above about 85.degree. F. and evaporating liquid therefrom,
directing the liquid vapor from the space in said first vessel to
the space in said second vessel through said conduit means,
concurrently cooling the liquid in said second vessel to a
temperature below about 55.degree. F. and condensing the water
vapor in the space therein,
terminating said heating of said solution and said cooling of said
liquid and closing said valve means thereby closing communication
between said spaces in said first and second vessels;
discharging thermal energy from said apparatus during the day or
period of higher demand of electrical power by exposing said cooled
liquid in said second vessel to air conditioner or heat pump
cooling heat exchange means whereby said cooled liquid becomes
heated by said exposure, and
pumping said liquid to said distribution means and spraying said
pumped liquid into said second space and opening said valve whereby
heated liquid therein is evaporated thereby cooling said liquid in
said second vessel as liquid vapor pressure differential between
said first and second vessels is eliminated, exposing said solution
in said first vessel to heat exchange means and pumping said
solution to said distribution means and spraying said pumped
solution into said first space. .Iaddend. .Iadd.30. Method of claim
29 wherein said liquid is cooled to a temperature of below about
35.degree. F. during said charging. .Iaddend. .Iadd.31. Method of
claim 30 wherein said solution is heated to between about
85.degree. F. and about 130.degree. F. during said charging.
.Iaddend. .Iadd.32. Method of claim 31 wherein heating said
solution during said charging is carried out by exposing said
solution to a heat exchanger of a heat pump or refrigeration
apparatus condenser. .Iaddend. .Iadd.33. Method of claim 31 wherein
said cooling said liquid during said charging is carried out by
exposing said liquid to a heat exchanger of an evaporator of a heat
pump or air conditioning system. .Iaddend. .Iadd.34. Method of
claim 31 including continuing said heating and cooling during said
charging until the concentration of said compound in said first
vessel is between about 6% and about 25% greater than said initial
concentration. .Iaddend.
.Iadd. 5. Apparatus alternately storing and discharging thermal
energy comprising
a first vessel containing a liquid solution of a compound selected
from the group consisting of alkali and alkaline earth metal
hydroxide, halide and thiocyanate, ammonium halide, metal halide
and thiocyanate, and mixtures thereof, said solution having an
initial concentration of between about 30% and about 80%, by weight
of said compound, said liquid selected from the group consisting of
water, ammonia, an alcohol having between 1 and 8 carbon atoms,
glycerol, glycols, polyglycols, glycol ethers, aliphatic amines and
alkanol amines having between 1 and about 6 carbon atoms, and
mixtures thereof, and a first space above the level of said liquid
solution and means for pumping said liquid solution to distribution
into said first space, a second vessel containing said liquid
without said compound therein, and
a second space above the level of said liquid and means for pumping
said liquid to distribution means for directing said liquid into
said second space,
both said first and second vessel being closed to atmosphere and
capable of holding a vacuum,
conduit means communicating between said first space and said
second space for allowing liquid vapor and pressure changes to pass
therebetween, and valve means cooperating with said conduit means
for terminating communication between said spaces,
heating means for heating said solution to a temperature of above
about 85.degree. F., and cooling means comprising a heat pump or
air conditioning system evaporator for cooling said liquid to a
temperature below about 55.degree. F.,
first heat exchange means cooperating with said first vessel for
transferring heat from heated solution therein, and second heat
exchange means cooperating with said second vessel for transferring
heat to liquid therein. .Iaddend.
Description
BACKGROUND OF THE INVENTION
With the high cost of electrical energy required to operate air
conditioners or heat pumps for cooling buildings, and particularly
with the heavy demands for commercial building cooling systems at
peak use hours, attention has been directed to various types of
thermal energy storage systems. Such energy storage is advantageous
since the building cooling and/or heating and process cooling may
be generated and stored during off-peak hours at night when most
businesses are normally closed, with the ambient outside
temperatures being cooler and municipal power requirements
reduced.
Most state of the art thermal energy storage systems are based on a
solid to liquid phase change using energy storage in a narrow
temperature range. Water based systems using ice storage are
especially desirable because of low fluid costs and availability.
However, the disadvantages of such systems include low evaporator
temperature requirements because thermal gradient forces evaporator
temperatures to a level far below 32.degree. F., also reducing the
chiller efficiency, incomplete or low phase change, often in the
order of about 50% to 55%, and low overall energy density of 80
BTU/lb. However, due to the exceptional environmental acceptability
qualities and large availability, water is preferred above more
corrosive, volatile, expensive and less readily available energy
storage materials.
SUMMARY OF THE INVENTION
The present invention is directed to an energy storage system
utilizing the advantages of a phase change of gaseous and liquid
water. The energy density of such a phase change is in excess of
1000 BTU/lb. with no solidification or crystallization required.
Moreover, the present system utilizes relatively low cost and
simple apparatus for taking advantage of the energy storage
combined with state of the art heat exchange equipment normally
found in modern residential and commercial buildings. These as well
as other advantages will be evident from the following description
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional view of a first embodiment of the
system of the invention used in direct heat transfer;
FIG. 2 is a schematic sectional view of the system of the invention
using a direct expansion system; and
FIG. 3 is a schematic sectional elevation illustrating a system for
use in an indirect heat transfer system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The basic invention comprises charging the energy storage system by
heating an aqeuous salt solution and cooling water in separate
vessels to a liquid temperature differential of at least 30.degree.
F., and preferably 50.degree. F. or more up to about 180.degree. F.
differential. The vessels are separated although the space above
each liquid in the respective vessels are in communication until
the desired vapor mass transfer is completed. Thereafter the
spatial communication is terminated until it is desired to
discharge the energy stored in the system as will be described
hereinafter.
In FIG. 1 there is shown an illustration of a first embodiment of
the chemical thermal storage system of the invention. The apparatus
illustrated schematically comprises a container 10 having two
cavities or vessels 12 and 14 separated by a baffle or wall 24. The
container must be air-tight so that the two cells or cavities can
selectively maintain different vapor pressures. It will be
appreciated that although a single container 10 is shown having the
two vessels, different containers may be used, the important
consideration being that two vessels or cavities are required for
holding two different liquids of the system with means for
transferring water vapor and communicating vapor pressure
differentials between the vessels.
In the preferred embodiment shown, a valve 26 communicates between
the spaces of the two vessels above the liquid levels. The valve,
conveniently located in wall 24, is preferably a butterfly valve
with an orifice of several inches and associated with convenient
means for opening and closing the valve. A first liquid composition
16 is located in first vessel 12 and fills the cavity only
partially leaving a space 20 above the liquid level. Similarly, in
second vessel 14, liquid 18 only partially fills the cavity leaving
a second space 22 above the liquid level. It is the spaces 20 and
22 which are in communication via valve 26 which can be selectively
opened or closed to allow for water vapor to pass between the two
spaces thereby maintaining vapor pressure differential
between-the-two-vessels when the valve is closed.
In the first vessel 12 is a liquid solution of a n ammonium halide
or thiocyanate, alkali or alkaline earth metal halide, hydroxide or
thiocyanate, or mixtures thereof, having initial concentrations of
between about 30 and about 80%, and preferably between about 30 and
about 80%, and preferably between about 40% and 75%, by weight. In
the second vessel 14 is liquid 18. The preferred solvent in vessel
12 and liquid in vessel 14 is water although ammonia and
ammonia/water mixtures may be used for low temperature
applications. In addition, lower aliphatic amines, lower alkanol
amines, alcohols, glycerol, glycols, polyglycols, alkylene glycol
ethers and aqueous solutions or mixtures thereof may also be used
in combination with water or ammonia. Useful alcohols are those
having between 1 and 12 carbon atoms. Lower aliphatic amines and
alkanol amines are those of from 1 to about 6 carbon atoms.
Examples of the amines are methylamine, ethylamine, etc. while
ethanolamine and propanolamine are examples of alkanol amines.
Preferred glycols are ethylene glycol and propylene glycol while
suitable glycol ethers include ethylene glycol dimethyl ether,
diethylene glycol diethyl ether, etc.
Most preferred salts in aqueous systems are the alkali or alkaline
earth metal hydroxides especially those of sodium, potassium,
cesium, magnesium, lithium, strontium and calcium. Lithium or
calcium chloride or bromide are also preferred. Mixtures of the
hydroxides may also be used together with lithium chloride or
lithium bromide or calcium chloride as well as nitrate salts of
those metals as corrosion suppressing additives, in systems where
corrosion may be a problem. For ammonium solvent systems, preferred
salts include ammonium halides such as ammonium bromide and
ammonium chloride, ammonium thiocyanate as well as ammonium metal
halide salts, for example NH.sub.4 AlCl.sub.4, (NH.sub.4).sub.2
Z.sub.n Cl.sub.4 and (NH.sub.4).sub.3 Zn Cl.sub.5. The above
described organic additives may be used to increase the sorption
rates and to increase the differential pressure, as well as to
serve as freeze point suppressants in aqueous systems in vessels 12
and 14. For this purpose, plastic vessels or containers which are
resistant to the aqueous hydroxide solutions are to be used as 13
are plastic tubing or conduits. Other materials that are lined or
coated with compositions which are not susceptible to corrosion
when exposed to the strong hydroxide compositions may be used.
The apparatus also includes suitable conduits, pumps and spray
nozzle systems for handling the liquids in the respective cavities.
Thus, conduits 30 and 32, and pump 34 direct aqueous solution 16
from vessel 12 to a heat exchanger, for example, a condenser of a
heat pump or chiller or a waste heat source (not shown) for heating
the solution to a desired temperature of at least 30.degree. F. and
preferably at least 50.degree. F. higher than the temperature of
water in second vessel 14. Preferred solution temperatures are
between about 85.degree. and about 130.degree. F. although higher
temperatures may be used. The heated solution is then directed to
first space 20. A preferred method of returning the heated aqueous
solution to the first vessel incorporates a nozzle or spray nozzle
system 36 which simply sprays the heated aqueous composition in the
form of droplets or a fine mist into first space 20 above the
surface of liquid 16 in vessel 12. Any suitable spray nozzle means
may be used for this purpose. Similarly, in second vessel 14, water
18 is pumped to a heat exchanger by pump 44 via line 42 where it is
cooled, for example, by an air conditioning or heat pump
evaporator, cooling tower or other evaporative cooling means or an
air to air means after which the cooled water is directed via pipe
40 to second space 22 above the water level using a spray nozzle
means 46.
In operating the above-described apparatus in a storage system of
the invention, preferably, during the night, or otherwise at
relatively low ambient temperature conditions and when area or
municipal use loads are at below peak or high requirements, aqueous
solution 16 is heated with condenser heat from a building heat pump
system, or otherwise heated conveniently to a temperature of above
about 85.degree. F. up to about 130.degree. F. At the same time,
water 18 is cooled to a temperature of below about 55.degree. F.,
and preferably below 35.degree. F., using an evaporator from a
building heat pump or air conditioning system. Because the vapor
pressure of the aqueous solution, for example 42% NaOH, by weight,
at 120.degree. F. is higher than the vapor pressure of water at
34.degree. F., the solution will desorb water in the form of water
vapor via open valve 26 into second space 22 which condenses into
the liquid water 18. This process continues until a solution
concentration of approximately 52% of NaOH, by weight, is achieved.
At this point, the system is charged, and valve 26 is closed to
separate the first and second spaces in the two vessels and
maintain vapor pressure differential which thereby allows the
charged system to remain stored for an indefinite period of
time.
When it is desired to utilize the stored energy in the system
created by the above-described charging process, the cold water is
circulated to a heat exchanger for the building, for example,
passed through a cooling coil in an air handler for cooling the
building. During this discharge period, again, the water is pumped
via pipe 42 using pump 44 to the building air handler or other heat
exchange cooling means, and returned via pipe 40 to second vessel
14 using the spray nozzle device 46. The water thus becomes heated
as it absorbs or picks up building heat through the heat transfer
system during this discharge phase. Concurrently, hot aqueous
solution 16 is pumped via pipe 32 and pump 34 to outside air heat
exchangers or coolers such as evaporative coolers, cooling towers
and the like thereby cooling the aqueous solution which is then
returned via pipe 30 and discharged into first space 20 using a
spray apparatus 36.
During this discharge cycle, valve 26 must be opened and because of
the difference in vapor pressure between the first and second
spaces, 20 and 22 respectively, water is evaporated in second space
22 to provide substantial cooling of the liquid in second vessel
14. At the same time, the evaporated water is passed into first
space 20 where it is absorbed into solution 16, which causes a heat
of condensation and solutions in first vessel 12, which heat is
again exchanged by the outside cooling means (not shown) previously
discussed. Alternatively, the heat of condensation and solutions in
first vessel 12 may be used for heating purposes, for example in a
dual temperature storage capability for building heating and
cooling.
In FIG. 2 there is illustrated another variation or embodiment of a
system according to the invention in which a coolant, such as a
refrigerant may be directly cooled or condensed at low temperature
during discharge of the energy storage system of the invention.
Again, a container 10 having two vessels or cavities as illustrated
in FIG. 1 may be used with a divider 24 separating the two
cavities. The liquid solution 16 and water 18 in the respective
containers are substantially like that previously described as is
the change of vapor pressure and exchange of water vapor between
the cavities 20 and 22, respectively, through valve 26, in both the
charging and discharging phases of the operation of the system. In
this embodiment, the water is cooled during the charging phase by
direct exposure to evaporator coils of an air conditioning system
evaporator. For example, the air conditioning system of the
building may utilize a cooling conduit 66 which is exposed directly
in second cavity 22 through which cold refrigerant is directed
during the charging phase. At that time, water 19 will be pumped
via pump 60 and conduit 58 and sprayed through spray nozzle
apparatus 46 over the cold pipe or coil 66 to be cooled.
Concurrently, with valve 26 open during the charging phase, aqueous
solution 16 is heated by pumping the solution via pump 54 and
conduit 52 through spray nozzle apparatus 36 over heated pipe or
coils 56 from a condenser 75 or other heating means including a
heat exchanger of the HVAC (heating ventilation air conditioning)
equipment condensing the refrigerant. In that case, hot refrigerant
may be directed into pipe or coil 56 via pump 74 from the heat
exchanger 75. Once the vapor mass transfer between the liquid
solution 16 and water 1 is achieved during this charge phase,
further heating and cooling, respectively is terminated and valve
26 is closed thereby again maintaining the energy charged in the
respective liquids stored until its use is desired.
During discharge, valve 26 is opened, and the respective liquids
are pumped through their respective nozzle sprayers over the heat
exchange conduits present in the spaces in the respective vessel.
Refrigerant directed via conduit or coil 66 is cooled by
evaporation of water as water is sprayed over the coil in space 22,
the water gradually becoming heated as it picks up heat as it cools
the refrigerant from heat exchanger 72. Similarly, in this
discharge phase of operation, heat from solution 16 is removed by
heat exchanger 75 which similarly pumps a coolant via coil 56
present in space 20.
A third apparatus configuration utilizing an indirect heat transfer
system is illustrated in FIG. 3. In this apparatus, substantially
like that described in FIG. 2, a heat exchanger 76 is used for
directly heating and cooling liquid 16 in the charge and discharge
phases, respectively of the operation of the system by pumping a
heat transfer fluid with pump 74. The heat exchanger illustrated
utilizing water with the system is somewhat different in that pump
77 will direct a heat transfer material such as water, ammonia,
methanol, glycol-water mixtures, and the like through remote heat
exchanger 71, 73 and 79 at various locations throughout a building
in which the system is to operate. Pump 77 simply pumps the
secondary cooling material via pipe 70 to the respective heat
exchangers, with the pipe 70 being exposed in space 22 over which
water is sprayed as previously discussed regarding the apparatus
shown in FIG. 2.
The specific types of heat exchangers and apparatus used within the
purview of the scope of the systems described herein are not so
important and other types of systems may be used to achieve the
same purpose. Thus, the specific design of the systems shown and
described herein are for the purpose of illustration only and the
invention is not to be necessarily limited thereto. These as well
as other modifications, variations and advantages of the system
within the purview of the invention will be evident to those
skilled in the art.
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