Mechanical-chemical energy storage
11624560 · 2023-04-11
Assignee
Inventors
Cpc classification
C09K5/16
CHEMISTRY; METALLURGY
Y02E60/14
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
F28D20/003
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
F28D17/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
C09K5/16
CHEMISTRY; METALLURGY
Abstract
This invention generally relates to mechanical-chemical energy storage. In particular, the invention relates to a mechanical-chemical energy storage system that stores energy by simultaneously compressing a gas to a higher enthalpy state and recovering the heat of compression by driving a somewhat reversible chemical reaction. The heat energy in the chemical reaction is then recovered while the gas is expanding to a lower enthalpy state.
Claims
1. A method for storing energy comprising the steps of: providing an absorbent reservoir containing a working fluid that is chemically absorbed by an absorbent; desorbing the working fluid from the absorbent in an endothermic process; compressing the working fluid using a reversible turbine; and condensing the working fluid in an exothermic process and transferring the condensed working fluid to a working fluid reservoir under pressure, wherein at least some heat generated during the condensing step is recycled to drive the desorbing step.
2. The method of claim 1, wherein the working fluid comprises carbon dioxide, ammonia, nitrous oxide, air, or water.
3. The method of claim 2, wherein the working fluid comprises carbon dioxide or ammonia.
4. The method of claim 3, wherein the absorbent comprises an organic amine, an inorganic base, an activated carbon, silica gel, a zeolite, a metal organic framework, or any combination thereof.
5. The method of claim 4, wherein the absorbent comprises an organic amine selected from monoethanolamine, piperazine, ammonia, morpholine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, dibutylamine, methyl-diethanolamine, diethylenetriamine, or any combination thereof.
6. The method of claim 2, wherein the working fluid comprises ammonia.
7. The method of claim 6, wherein the absorbent comprises a metal halide salt, a mild acid, water, activated carbon, silica gel, a zeolite, or metal organic framework.
8. The method of claim 2, wherein the working fluid comprises nitrous oxide.
9. The method of claim 8, wherein the absorbent comprises a food oil, silicone oil, activated carbon, silica gel, zeolite, or metal organic framework.
10. The method of claim 1, wherein the at least some heat generated from the condensing step is recycled to drive the desorbing step using a heat exchanger.
11. The method of claim 1, further comprising a step of storing the working fluid in the working fluid reservoir in a liquid state, a critical state, or a trans-critical state.
12. The method of claim 1, wherein the working fluid is compressed to and stored at a pressure of from about 1 bar to about 100 bar.
13. The method of claim 1, further comprising a second compressing step after the compressing step.
14. The method of claim 1, wherein the working fluid is expanded to a pressure of from about 0.1 bar to 10 bar.
15. The method of claim 1, wherein the working fluid is stored at ambient temperature.
16. The method of claim 1, further comprising a step of heating the working fluid using an outside heat source, followed by a step of expanding the working fluid.
17. A method of charging and discharging an energy storage system comprising the steps of: charging the energy storage system comprising the steps of: providing an absorbent storage tank containing a working fluid that is chemically absorbed by an absorbent; desorbing the working fluid from the absorbent in an endothermic process; compressing the working fluid using a reversible turbine; condensing the working fluid in an exothermic process and transferring the condensed working fluid to a working fluid reservoir under pressure; and recycling heat generated during the condensing step to drive the desorbing step; and storing the working fluid in a working fluid reservoir under pressure; and discharging the energy storage system comprising the steps of: expanding the working fluid; chemically absorbing the working fluid with the absorbent in the absorbent storage tank in an exothermic process; recycling heat generated during the chemical absorbing step to drive the expanding step; and storing the absorbent and the absorbed working fluid in the absorbent storage tank.
18. The method of claim 17, wherein the working fluid comprises carbon dioxide, ammonia, nitrous oxide, air, or water.
19. The method of claim 18, wherein the working fluid comprises carbon dioxide.
20. The method of claim 19, wherein the absorbent comprises an organic amine, inorganic base, activated carbon, silica gel, zeolite, or metal organic framework.
21. The method of claim 20, wherein the absorbent comprises an organic amine selected from monoethanolamine, piperazine, ammonia, morpholine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, dibutylamine, methyl-diethanolamine, or diethylenetriamine.
22. The method of claim 18, wherein the working fluid comprises ammonia.
23. The method of claim 22, wherein the absorbent comprises a metal halide salt, mild acid, water, activated carbon, silica gel, zeolite, or metal organic framework.
24. The method of claim 18, wherein the working fluid comprises nitrous oxide.
25. The method of claim 24, wherein the absorbent comprises a food oil, silicone oil, activated carbon, silica gel, zeolite, or metal organic framework.
26. The method of claim 17, wherein the heat generated during the condensing step is recycled drive the desorbing step using a heat exchanger.
27. The method of claim 17, wherein the working fluid is in a liquid state, a critical state, or a trans-critical state when the working fluid is stored in the working fluid reservoir under pressure.
28. The method of claim 17, wherein the working fluid is compressed to and stored at a pressure of from about 1 bar to about 100 bar.
29. The method of claim 27, wherein the compressing step comprises a two-stage compression process.
30. The method of claim 17, wherein the working fluid is expanded to a pressure of from about 0.1 bar to 10 bar.
31. The method of claim 17, wherein the working fluid is stored at ambient temperature.
32. The method of claim 17, further comprising a step of heating the working fluid using an external heat source prior to the expanding step.
33. The method of claim 17, further comprising a step of directing a flow of the working fluid in a first direction during charging, and reversing the flow of the working fluid from the first direction during discharging.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
(27)
(28)
(29)
(30) These figures are provided by way of example and are not intended to limit the scope of the invention.
DETAILED DESCRIPTION
(31) In one aspect, the invention relates to the storage and delivery of energy as mechanical energy. In as much as mechanical and electrical energy are easily interchanged at high efficiencies by motors and generators, the system may also function as a “battery” even though there are no electrochemical reactions involved in the storage of energy by this invention notwithstanding the incidental use of conventional batteries for some system functions.
(32) In another aspect, the invention relates to a chemical and thermodynamic system for energy storage. Energy is stored and released using distinct charge and discharge processes. This system simultaneously compresses a working fluid to a higher enthalpy state and recovers the heat of compression by driving a reversible chemical reaction. The compressed fluid is then expanded to a lower enthalpy state and chemically absorbed, driving the reverse exothermic reaction, from which heat can be supplied to increase the expansion efficiency.
(33) During the discharge process, compressed working fluid (e.g., liquefied or supercritical gas) from a storage tank is expanded through an expansion device such as a turbine, piston, or nozzle, thereby generating power. The expansion results in cooling of the working fluid. The expanded working fluid (gas) exiting the expansion device undergoes a reversible chemical reaction with an absorbent that releases heat (exothermic). The heat is captured, for example by a heat exchanger, and the heat is transferred to the compressed working fluid that has yet to undergo expansion. This transferred heat beneficially increases the enthalpy of the working fluid prior to expansion, thus allowing for greater energy production. The process can continue until the compressed working fluid storage tank is empty.
(34) During the charge process, the absorbed working fluid is desorbed through an endothermic reaction that is driven by a reduction in the pressure of the working fluid and absorbent. Energy is provided to a compression device that compresses the working fluid to a liquid or supercritical state and is stored in a storage tank. Heat from the compression process is captured and transferred to drive the endothermic desorption reaction. The process can continue until all of the working fluid has been desorbed and stored in the storage tank.
(35) The systems and methods of the present invention have some or all of the following properties: High RTE. A high energy density due to high density material forms. A closed cycle device not limited to air or nitrogen as a working fluid. Scalable using existing equipment for power generation and handling of liquefied gases. Energy and power performance specifications can be designed independently of each other. Very low cost. Extremely, long cycle life No self-discharge as heat is never stored as sensible heat but only as chemical potential. Ability to use waste heat or extract heat from the atmosphere to achieve even greater energy conversions.
I. Definitions
(36) For brevity, from hereon we will refer to the “grid” as being any application or solution for which the invention is suitable. We shall also refer to the operation of any of these systems in which energy is put into the device to charge it, as “charging” or “recharging”. Consistent with this definition, when energy is taken out of the device it is referred to as “discharging”. Any cycle of charge (partial or full) and discharge (partial or full) will simply be referred to as a “cycle”.
(37) As used herein, “chemical absorption” refers to absorption using a chemical bond of a covalent pair to form either a solution or compound.
(38) As used herein, the term “tank” and “reservoir” are used interchangeably to refer to a storage chamber.
(39) As used herein, “desorption” is a process that is the inverse of absorption whereby some, or all, of an absorbed substance is released. Specifically, desorption is the process by which the molecules of a covalent pair are separated from each other in order to form, or reconstitute the original, prior to absorption, covalent pair.
(40) For brevity, embodiments of the invention may be described as involving either an “absorption” or “adsorption” process. It will be understood to the reader that either process may be used in the embodiments of the invention depending on the choice of materials. Similarly, the terms “absorption agent”, “absorbent”, or “sorbent” are used interchangeably and may each refer to either a liquid or a solid agent that can absorb or adsorb a fluid, respectively.
(41) As used herein, “round trip efficiency” or “RTE” is calculated as the power produced during expansion divided by the power required for compression.
(42) As used herein, “activated carbon” is a form of carbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions.
(43) As used herein, the term “metal organic framework” refers to crystalline compounds consisting of metal ions or clusters coordinated to organic molecules to form one-, two-, or three-dimensional structures. In some cases, the structures are porous and the pores are stable during elimination of the guest molecules (often solvents) and can be used for the storage of gases.
(44) As used herein, the term “food oil” refers to oils commonly used in cooking and food preparation including olive oil, palm oil, soybean oil, canola oil (rapeseed oil), pumpkin seed oil, corn oil, sunflower oil, safflower oil, peanut oil, grape seed oil, sesame oil, argan oil, rice bran oil and other vegetable oils.
(45) As used herein, the term “silicone oil” refers to any liquid polymerized siloxane with organic side chains. Examples of silicone include are hexamethyldisiloxane and simethicone.
(46) As used herein, the terms “first” and/or “second” do not refer to order or denote relative positions in space or time, but these terms are used to distinguish between two different elements or components. For example, a first component does not necessarily proceed a second component in time or space; however, the first component is not the second component and vice versa. Although it is possible for a first component to precede a second component in space or time, it is equally possible that a second component precedes a first component in space or time.
II. Systems
(47) Referring to
(48) In this embodiment, the system undergoes charging or recharging when desorbed working fluid (e.g., working fluid in a liquid physical state) is channeled from the absorbent tank or reservoir to the compressor (e.g., a piston cylinder) along flow pathway 1 where the working fluid is compressed. From the compressor, the compressed working fluid is channeled along flow pathway 2 to a heat exchanger that cools and/or condenses the compressed working fluid. The cooled and/or condensed working fluid is channeled along flow pathway 3 to the working fluid tank where it is stored until the system discharges energy. During the charging process, heat may be transferred in a closed loop, along flow pathways 4 and 5, from the compressor to the absorbent tank to enhance the efficiency of the system.
(49) In this embodiment, the system undergoes discharging when desorbed working fluid is channeled from the working fluid tank, along flow pathways 6 and 7, to one or more heat exchangers that transfer heat to the working fluid. From the one or more heat exchangers, the heated working fluid is channeled, along flow pathway 8, to the expander wherein the working fluid undergoes volumetric expansion. Energy is discharged from system from the expander that may be coupled with a generator for producing electrical energy. The expanded working fluid, i.e., working fluid in a gaseous physical state, is channeled, along flow pathways 9 and 10, to the absorbent tank, wherein the working fluid is mixed or dissolved in the absorbent. In some embodiments, heat flows, along flow pathway 11, from one or more heat exchangers to the condensed working fluid before the fluid is expanded. After the working fluid is expanded, the one or more heat exchangers can transfer heat, along flow pathway 12, away from absorbent tank where heat is generated during the dissolution of the working fluid in the absorbent.
(50) Alternatively, the system of the present invention may undergo discharging when desorbed working fluid having a liquid physical state is channeled, along flow pathway 13, to an expander wherein the liquid working fluid is transformed into an expanded vapor. The expanded vapor is channeled, along flow pathways 14 and 15, to one or more heat exchangers that transfer heat to or from the expanded vapor. The working fluid is then channeled, along flow pathway 16, to the working fluid tank, where it is stored until the system undergoes charging or recharging.
(51) The system may undergo charging when desorbed working fluid is channeled, along flow pathways 17 and 18, from the working fluid tank to one or more heat exchangers and, along flow pathway 19, to the compressor, wherein the working fluid is compressed. From the compressor, compressed working fluid is channeled to one or more heat exchangers, along flow pathways 20-22, to the absorbent tank wherein the working fluid is mixed or dissolved in the absorbent.
(52) Another aspect of the present invention relates to an energy storage system comprising: a working fluid reservoir containing compressed working fluid; an expander that fluidly communicates with the working fluid reservoir and is configured to expand the working fluid; an absorbent storage reservoir containing an absorbent, wherein the absorbent reservoir fluidly communicates with the expander and is configured to receive and absorb the expanded working fluid; a first heat exchanger that thermally communicates with the absorbent reservoir and is configured to transfer heat generated by the absorption of the working fluid by the absorbent to the working fluid during the discharge of the system; a pressure release mechanism configured to reduce pressure in the absorbent reservoir; a compressor that fluidly communicates with the absorbent reservoir and fluidly communicates with the working fluid reservoir and is configured to compress the working fluid that desorbs from the absorbent; and a second heat exchanger in thermal communication with the working fluid in the compressor, in thermal communication with the absorbent and working fluid in the absorbent storage tank, and configured to transfer heat that is generated by the compression of the working fluid, to the absorbent and working fluid in the absorbent storage tank.
(53) In some embodiments, the working fluid comprises carbon dioxide, freon, methane, ammonia, nitrous oxide, air, or water.
(54) In some embodiments, the working fluid comprises carbon dioxide.
(55) In some embodiments, the absorbent comprises an organic amine, inorganic base, activated carbon, silica gel, zeolite, or metal organic framework.
(56) In some embodiments, the absorbent comprises an organic amine selected from monoethanolamine, piperazine, ammonia, morpholine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, dibutylamine, methyl-diethanolamine, or diethylenetriamine. For example, the absorbent comprises monoethanolamine (MEA). In some embodiments the absorbent comprises a mixture of MEA and water.
(57) In some embodiments, the working fluid comprises ammonia.
(58) In some embodiments, the absorbent comprises a metal halide salt (e.g. MgCl.sub.2 or CaCl.sub.2), mild acid, water, activated carbon, silica gel, zeolite, or metal organic framework.
(59) In some embodiments, the working fluid comprises nitrous oxide.
(60) In some embodiments, the absorbent comprises a food oil, silicone oil, activated carbon, silica gel, zeolite, or metal organic framework.
(61) In some embodiments, the compressor and expander comprise a reversible turbine.
(62) In some embodiments, the compressor comprises a turbine, piston, radial reaction turbine.
(63) In some embodiments, the expander comprises a turbine, piston, or turbo-expander.
(64) In some embodiments, the system further comprises an electrical generator connected to the expander.
(65) In some embodiments, the system further comprises a motor connected to the compressor.
(66) In some embodiments, the system further comprises an external heat source, in thermal communication with the expanded working fluid.
(67) In some embodiments, the system further comprises a controller connected to the compressor (motor), expander (generator), pressure release mechanism, absorbent storage tank, working fluid storage tank, or any combination thereof.
(68) In some embodiments, the first heat exchanger and second heat exchanger each comprise high surface area fin-shaped structures within the absorbent storage tank.
(69) In some embodiments, the system further comprises one or more additional compressors, fluidly connected to and positioned between the first compressor and the working fluid storage tank.
(70) In some embodiments, the system further comprises one or more additional expanders, fluidly connected to and positioned between the first expander and the absorbent storage tank.
(71) In some embodiments, the pressure release mechanism is a valve.
(72) In some embodiments, the system further comprises a pump that fluidly communicates with the absorbent storage tank and a sprayer in fluid communication with the pump and the absorbent storage tank. For example, the pump pumps the absorbent and absorbed working fluid to the sprayer and the sprayer sprays the fluid back into the absorbent storage tank. In some embodiments, the sprayer atomizes the fluid to small droplets. In some embodiments the sprayer sprays the absorbent over the heat exchanger with high surface area fin-shaped structures within the absorbent storage tank.
(73) In some embodiments, the system further comprises a separator that fluidly communicates with the absorbent storage tank and the compressor. In some embodiments the separator is a centrifugal or cyclonic separator. In other embodiments the separator is a demister or a filter.
(74) Another embodiment of the present invention, illustrated in
(75)
(76)
(77) In
(78) There are several suitable expansion type devices available to recover the energy from expanding gases. These can be of any design and include both turbines and piston type motors. In general, the turbines, when used in this application, are commonly called “turbo-expanders”. In some embodiments, the expander or turbo-expander obtains conversion efficiency in excess of about 80% of the energy in the expanding gas. In other embodiments, the turbo-expander obtains about 90% efficiency. In some embodiments, the expander is a radial reaction turbine (RRT). And, in some embodiments, the RRT is configured to run with supercritical working fluids, such as CO.sub.2, to achieve high efficiencies. To use an RRT, the absorbent(s) are selected that match the pressure range of the output of the RRT in the system.
(79) The critical temperature of CO.sub.2 is 31° C. At this temperature, the pressure of the CO.sub.2 is 56 bar. In some instances, the pressures in the RRT vary between about 50 bar and about 120 bar. If a solid absorbent is paired with a supercritical working fluid (e.g., CO.sub.2), the heat transfer associated with the solid absorbent will be improved because supercritical fluids are efficient heat transfer agents.
(80) As illustrated in
(81) In systems of the present invention, heat exchangers can possess any suitable configuration.
(82) Referring to
(83) The working fluid travels along flow paths 44, 130, and 138 to a compressor. Electrical energy runs motor 106 that compresses or increases the pressure of the working fluid. The motor may operate compressor 108 or the motor may reverse the operation of turbo-expander so that the turbo-expander functions to compress the working fluid. Any suitable compressor can be used to complete this step. The pressurized work fluid is channeled along flow path 128, 134, and 136 to the working fluid storage tank, where it is stored until a discharge cycle begins.
(84) As illustrated in
(85) Depending on how much pressure change is desired in the cycle, the compressor may be one or more (e.g., 1, 2, 3, 4, or more) stages. The choice of pressure range is governed by design choices based on absorbent properties and the desired energy density. Energy density is related to the operating pressure since, as can be seen by
(86) As shown in
(87) In some embodiments, the vacuum action of the intake side of the compressor will be sufficient to allow working fluid (e.g., CO.sub.2) to be released from the absorbent. In these embodiments, this is an endothermic reaction and the absorbent will cool. However, the action of compressing the working fluid will generate heat. In some embodiments, this heat is removed to maintain efficiencies. Further, the absorbent cannot cool indefinitely, so as the absorbent cools, heat generated in the compressor heats the absorbent. The heat going to the absorbent may drive the endothermic reaction and facilitate the release of additional working fluid (e.g., CO.sub.2) for compression. This continues until the working fluid (e.g., CO.sub.2) tank is full or until it is desired to stop the recharging process.
(88) Accordingly, systems of the present invention may be charged or discharged and reversed at any part of the cycle. These systems may also be run at any power level even its maximum power right to the very end of the cycle. It may be discharged to 100% depth of discharge as often as desired and at full power as well with no detrimental effects to the system.
(89) In some embodiments, during the recharge cycle, as the working fluid (e.g., CO.sub.2) is being released from the absorbent, some absorbent may become entrained in the working fluid. Should this be the case, an optional separator 24 may be placed between the absorbent reservoir and the intake to the expander (e.g., turbo-expander). In some embodiments, such as the embodiment illustrated in
(90) Another embodiment of the mechanical-chemical energy storage system is described in the schematic diagram shown in
(91) In one loop, the expanded working fluid (e.g., CO.sub.2) or exhaust from the expansion device travels through heat exchanger (Hx3). Later, this low-pressure working fluid (e.g., CO.sub.2 gas) labeled “low pressure CO.sub.2” is compressed by one or more compressors C1-C5 returning to higher pressure carbon dioxide phase. During the compression of the carbon dioxide gas, which is an exothermic process, heat is captured by one or more heat exchangers H.sub.x4-H.sub.x7.
(92) In another loop, the expanded working fluid or exhaust from the expansion device reacts with an absorber (e.g., aqueous ammonia (˜36% solution)) in an exothermic reaction that generates heat while absorbing the working fluid (e.g., CO.sub.2). Thus, this additional energy increases the enthalpy of the working fluid allowing for a greater energy production from this part of the cycle. Since the temperature of the absorbent is higher than the temperature of the cooling working fluid, energy will naturally flow in the desired direction shown by the arrow in the discharge portion of
(93) In another loop, the low concentration liquid working fluid and absorbent solution (e.g., CO.sub.2 and ammonia solution) exiting the reboiler is circulated into the chamber containing Hx1 and Hx2 heat exchangers. Working fluid gas (e.g., CO.sub.2 gas) is further separated from absorbent (e.g., ammonia) in this chamber and circulated via heat exchanger Hx3 into compressors C1-C5. Thus, the working fluid (e.g., CO.sub.2) gas enters into the next cycle.
(94) Another embodiment of the mechanical-chemical energy storage system is described in the schematic diagrams shown in
(95) Working Fluids
(96) All suitable working fluids are within the scope of the invention. Suitable working fluids can be expanded and compressed and can be absorbed by an absorbent. Exemplary working fluids include fluids that can be compressed to a liquid, critical, or trans-critical state at the desired operating pressures and temperatures. For example, the desired temperature may be ambient temperature (about 20 to 25° C.) and the desired pressure range may be from about 40 to 60 bar, thus, exemplary working fluids would be in a liquid, critical, or trans-critical state at those conditions. Some exemplary working fluids will be absorbed by the absorbent in a reversible and/or exothermic process. Some specific exemplary working fluids include carbon dioxide (CO.sub.2), ammonia (NH.sub.3), nitrous oxide (N.sub.2O), air, and water.
(97) Examples of suitable working fluids are described in Table 1.
(98) TABLE-US-00001 TABLE 1 Working fluids. Latent Melting Heat of Point Working Fluid Additive Fusion (J/g) (° C.) Fatty Acids Hexadecane Na Mont- 126 — morillonite Fatty acids Surfactants 191 — Oleic acid CuO — — Myristic acid palmitic acid 190 61 Capric acid — 170 36 Capric acid Nanotubes 75 36 Lauric acid — 188 49 Myristic acid — 201 61 Palmitic acid — 185-220 67 Stearic acid — 220 73 Dodecanoic acid — 190 42 Lauric acid/stearic — 131 33 acid Stearic acid Bentonite 84 73 Paraffins Paraffin — 173 64 Paraffin waxes Nanotubes — 60 Paraffin Graphite 180 40 Paraffin SiO.sub.2 110 — Paraffin Fe.sub.2O.sub.3 — 47 Paraffin Siloxane 160 35 Nonacosane — 240 64 Hexacosane — 257 56 Organics Tetrabutylammonium — 200 — clathrates Tetradecanol Graphite 220 36 Naphthalene — 148 80 Erytritol — 340 118 Camphene — 238 50 1,3-ditetradecanoyl — 126 48 thiourea Salt Hydrates Glauber's salt polyacrylomide 270 32 (Na.sub.2SO.sub.4 *10H.sub.2O) Glauber's salt Gelatin 248 — (Na.sub.2SO.sub.4 *10H.sub.2O) Hydrate salts — 103 21 CaCl.sub.2/MgCl.sub.2 + SrCl.sub.2 Na.sub.2CO.sub.3*10H.sub.2O — 247 33-36 NaHPO.sub.4*7H.sub.2O — 135-170 48 MgSO.sub.4*7H.sub.2O — 202 49 Ba(OH).sub.2*8H.sub.2O — 265-280 78 CH.sub.3COONa*3H.sub.2O — 270-290 58 CH.sub.3COONa*3H.sub.2O Graphite — — NaOH*H.sub.2O — 272 58 Eutectic Mixtures Naphthalene + Benzoic — 123 67 acid AlCl.sub.3 + NaCl + ZrCl.sub.2 — 234 68 Long Chain Polymers PEO carbon black 120-170 60 PEO Graphite 130-160 60 PEO carbon fibers 140-180 60 PEO Fullerenes 160-180 60 PEO SWCNT 150-180 60 PEO Cellulose 40-130 60 PEO Starch 47-97 60 PEG Chitosan 140 ~50 PEG Cellulose 60 ~50 PEG 35,000 — 167 68 PEG 35,000 lauric acid 186 43-56 PEG 3400 lauric acid 188 43-54 Dissolved Gases.sup.1 SO.sub.3 — 331 62 CO.sub.2 — — — NH.sub.3 — — — N.sub.2O — — — halons — — — alcohol vapor — — — gaseous hydrocarbons — — — freons — — — Molten Salts Na.sub.2SO4*10H.sub.2O — — 32.4 Solid PCM Pentaglycerin — 192 81 2-amino-2-methyl- — 264 78 1,3-propanediol Misc. Materials oleochemical — 144-227 from −6 to 47 carbonates .sup.1Possible solvents for freons, hydrocarbons and Nitrous oxide include butanediammine, 2-diethylamino ethanol, aqueous Na glycinate solution, diethanolamine, olive oil, aqueous hydroxide solution, dodecane, ammonia water, amine based solvent (e.g., Stonvent), vegetable oil, paraffins, or any combination thereof.
(99) Absorbents
(100) All suitable absorbents are within the scope of the invention. Suitable absorbents agents are capable of chemically absorbing a working fluid. Exemplary absorbents will absorb the working fluid in a reversible and/or endothermic process. Some specific exemplary absorbents include: absorbents of carbon dioxide, such as organic amines (e.g., monoethanolamine (MEA), piperazine, ammonia, morpholine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, dibutylamine, methyl-diethanolamine, or diethylenetriamine), inorganic bases (e.g., potassium carbonate, ammonium carbonate), activated carbon, silica gel, zeolites, and metal organic frameworks; absorbents of ammonia, such as salts that form ammonates, halide salts (e.g., magnesium chloride (MgCl.sub.2), calcium chloride (CaCl.sub.2)), mild acids, water, activated carbon, silica gel, zeolites, and metal organic frameworks; absorbents of nitrous oxide, such as oils that dissolve nitrous oxide (e.g., food oils, silicone oils), activated carbon, silica gel, zeolites, and metal organic frameworks; and absorbents of air such as activated carbon and zeolites. The terms “absorption agent”, “absorbent”, and “sorbent” are used interchangeably and may each refer to either a liquid or a solid agent that can absorb or adsorb a fluid, respectively.
(101) Examples of pairs of absorbents and working fluids suitable for use in the present invention are described in Table 2
(102) TABLE-US-00002 TABLE 2 Working fluids and absorbents. Working H.sub.ads, Fluid Absorbent (kJ/mole) Pressure CO.sub.2 CO.sub.2 silicas ~5-15 — CO.sub.2 organic and inorganic ~1-40 — carbonates CO.sub.2 absorbent carbons ~5-15 — CO.sub.2 clays ~5-5 — CO.sub.2 aluminas ~5-15 — CO.sub.2 zeolites ~5-15 — CO.sub.2 amine and methyl <5 ~1 bar substituted MOF CO.sub.2 various coals ~12-13 up to 200 bar CO.sub.2 MOF ~16-20 — CO.sub.2 carborane based MOF ~22 up to 10 bars CO.sub.2 DABCO based MOF ~20-24 up to 25 bars CO.sub.2 MOF ~22-24 — CO.sub.2 Au in range of — 22-26 CO.sub.2 zeolitic imidazolate ~21-30 — CO.sub.2 modified MOF ~26 — CO.sub.2 MOF BTC framework 27-37 — CO.sub.2 carbon sorbent 28-25.7 ~1 bar CO.sub.2 Cr-phthalate ~30 up to 30 bar CO.sub.2 Zeolite 13X ~31 ~2 bar CO.sub.2 MOF ~33, ~22 up to ~5 bar CO.sub.2 chabazite ~35 — CO.sub.2 fluoro-functionalized ~45 — metal oxide framework decreasing to ~30 CO.sub.2 metal oxide framework ranges from 1-50 bar 16-41 CO.sub.2 silica foam 43 up to 1 bar CO.sub.2 unsaturated metal 22, 32, 45, — centers 47-52, 44-54 CO.sub.2 zeolite 13X and 46 and 41 1 bar Mg.sub.2(dobdc) respectively CO.sub.2 molecular porous ~47 — material CO.sub.2 benzene-dicarboxylate 30-50 — CO.sub.2 methyl diethanolamine ~50-58 — (aq) CO.sub.2 ionic liquids 80 2-3 bar CO.sub.2 chabazite zeolites — up to ~10 bar CO.sub.2 hydromagnesite — — CO.sub.2 imidazolium based ionic — up to ~20 bar liquids CO.sub.2 MOF — 0-5 bar CO.sub.2 Zn(II) -cyclen — — CO.sub.2 silicon nitride — — CO.sub.2 TBAB (aq) — — CO.sub.2 Triethylbutylammonium — — Acetate CO.sub.2 porous organic — — polymers CO.sub.2 clathrate hydrates — — CO.sub.2 aminosilicates — — CO.sub.2 Hydrated salts — — CO.sub.2 MOF 177 — up to 20 bar CO.sub.2 Triethylbutyl — — ammonium acetate CH.sub.4 CH.sub.4 various carbons ~10-11 — CH.sub.4 various coals ~10-11 — CH.sub.4 MOF ~11-12 — CH.sub.4 zeolites ~14 90 bar decreasing to ~6 CH.sub.4 carborane based MOF ~15 20 bar CH.sub.4 zeolite 13X 15 ~2 bar CH.sub.4 DABCO based MOF ~14 to ~18 25 bar CH.sub.4 zeolite templated carbon 16-20 — CH.sub.4 MOF ~21, ~18 up to ~5 bar NH.sub.3 NH.sub.3 salt ammonates 5-45 — (CaCl.sub.2*6NH.sub.3) NH.sub.3 thiocyanate — — NH.sub.3 ammonia borane — 1-4 bars NH.sub.3 CaCl.sub.2 - vermiculite ~40 up to 4 bar NH.sub.3 SrCl.sub.2 - amine ~33 ~2 bar NH.sub.3 MgCl.sub.2 55-87 5 bar NO.sub.2 NO.sub.2 biochar 20-27 for ~1 bar biochar, ~10 for Al.sub.2O.sub.3, Fe.sub.2O.sub.3 and peat CO CO DABCO based MOF ~10 to ~12 25 bar CO MOF ~45, ~23 up to ~5 bar CO Ni or Fe powder — — CO CO complexes — — Ar, N.sub.2, O.sub.2 Ar, N.sub.2, O.sub.2 carbon sorbent 16-17 ~1 bar H.sub.2 H.sub.2 zeolite 3.5 and — higher Ne Ne chabazite ~5 — Ar Ar chabazite ~15 — Ar various coals ~14-16 — ethylene + ethylene + NaX zeolite 28-40 — ethane ethane N.sub.2 N.sub.2 various coals ~8 — freons, freons, various carbons ~8 — halons halons freons, various silicas ~8 — halons freons, various zeolites ~8 — halons freons, various clays ~8 — halons freons, various MOF's ~8 — halons freons, various aluminas ~8 — halons freons, graphene ~8 — halons freons, graphite oxide ~8 — halons freons, various MOF's ~8 — halons freons, various MOF's ~8 — halons NO NO NO complexes ~10-20 — H.sub.2O H.sub.2O salt hydrates 5 to 45 — H.sub.2O silcas 5 to 45 — H.sub.2O zeolites 5 to 45 — H.sub.2O aluminas 5 to 45 — H.sub.2O various MOF'scarbons 5 to 45 — H.sub.2O inorganic and organic 5 to 45 — oxide-hydroxides both
III. Mechanical Chemical Energy Storage Methods
(103) One aspect of the invention relates to a method for storing energy comprising: providing an absorbent reservoir containing a working fluid that is chemically absorbed by an absorbent; desorbing the working fluid from the absorbent in an endothermic process; and condensing the working fluid in an exothermic process and transferring the condensed working fluid to a working fluid reservoir under pressure wherein at least some of the heat generated during the condensing step is recycled to drive the desorbing step.
(104) In some implementations, the working fluid comprises carbon dioxide, ammonia, nitrous oxide, air, or water.
(105) In some implementations, the working fluid comprises carbon dioxide or ammonia.
(106) In some implementations, the absorbent comprises an organic amine, an inorganic base, an activated carbon, silica gel, a zeolite, a metal organic framework, or any combination thereof.
(107) In some implementations, the absorbent comprises an organic amine selected from monoethanolamine, piperazine, ammonia, morpholine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, dibutylamine, methyl-diethanolamine, diethylenetriamine, or any combination thereof. For example, the absorbent comprises monoethanolamine (MEA).
(108) In some implementations the absorbent comprises a mixture of MEA and water.
(109) In some implementations, the working fluid comprises ammonia.
(110) In some implementations, the absorbent comprises a metal halide salt, a mild acid, water, activated carbon, silica gel, a zeolite, or metal organic framework.
(111) In some implementations, the working fluid comprises nitrous oxide.
(112) In some implementations, the absorbent comprises a food oil, silicone oil, activated carbon, silica gel, zeolite, or metal organic framework.
(113) In some implementations, the heat generated from the condensing step is recycled to drive the desorbing step using a heat exchanger.
(114) In some implementations, the method further comprises compressing the working fluid using a reversible turbine.
(115) In some implementations, the method further comprises compressing the working fluid and storing the working fluid in the working fluid reservoir in a liquid state, a critical state, or a trans-critical state.
(116) In some implementations, the working fluid is compressed to and stored at a pressure of from about 1 bar to about 200 bar (e.g. 10 bar to 100 bar, or about 50 bar).
(117) In some implementations, the method further comprises a second compression stage after the first compression.
(118) In some implementations, the working fluid is expanded to a pressure of from about 0.1 bar to 10 bar (e.g., about 0.5 bar to about 5 bar, or about 1 bar).
(119) In some implementations, the working fluid is stored at ambient temperature.
(120) In some implementations, the method further comprises heating the working fluid prior to expansion using an outside heat source.
(121) Another aspect of the invention relates to a method of charging and discharging an energy storage system comprising: (1) charging the system comprising: providing an absorbent storage tank containing a working fluid that is chemically absorbed by an absorbent; desorbing the working fluid from the absorbent in an endothermic process; condensing the working fluid in an exothermic process and transferring the condensed working fluid to a working fluid reservoir under pressure; and recycling heat generated during the condensing step to drive the desorbing step; and storing the working fluid in a working fluid reservoir under pressure; and (2) discharging the system comprising: expanding the working fluid; chemically absorbing the working fluid with the absorbent in the absorbent reservoir in an exothermic process; recycling heat generated during the absorption reaction to drive the expanding step; and storing the absorbent and the absorbed working fluid in the absorbent reservoir.
(122) In some implementations, the working fluid comprises carbon dioxide, ammonia, nitrous oxide, air, or water.
(123) In some implementations, the working fluid comprises carbon dioxide.
(124) In some implementations, the absorbent comprises an organic amine, inorganic base, activated carbon, silica gel, zeolite, or metal organic framework.
(125) In some implementations, the absorbent comprises an organic amine selected from monoethanolamine, piperazine, ammonia, morpholine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, dibutylamine, methyl-diethanolamine, or diethylenetriamine. For example, the absorbent comprises monoethanolamine (MEA). In some implementations the absorbent comprises a mixture of MEA and water.
(126) In some implementations, the working fluid comprises ammonia.
(127) In some implementations, the absorbent comprises a metal halide salt (e.g., MgCl.sub.2, CaCl.sub.2), mild acid, water, activated carbon, silica gel, zeolite, or metal organic framework.
(128) In some implementations, the working fluid comprises nitrous oxide.
(129) In some implementations, the absorbent comprises a food oil, silicone oil, activated carbon, silica gel, zeolite, or metal organic framework.
(130) In some implementations, the heat generated during the condensing step is recycled drive the desorbing step using a heat exchanger.
(131) In some implementations, the working fluid is compressed by a reversible turbine.
(132) In some implementations, the method further comprises compressing the working fluid and storing the working fluid in the working fluid reservoir in a liquid state, a critical state, or a trans-critical state.
(133) In some implementations, the working fluid is compressed to and stored at a pressure of from about 1 bar to about 100 bar, (e.g. from about 10 bar to about 100 bar, from about 20 bar to about 80 bar, or about 50 bar).
(134) In some implementations, the compressing step comprises a two-stage compression process.
(135) In some implementations, the working fluid is expanded to a pressure of from about 0.1 bar to 10 bar (e.g. about 1 bar).
(136) In some implementations, the working fluid is stored at ambient temperature.
(137) In some implementations, the method further comprises beating the working fluid prior to expansion using an external heat source.
(138) In some implementations, the method further comprises directing the flow of the working fluid a first direction during charging, and reversing the flow of the direction of the working fluid during discharging.
(139) Another aspect of the mechanical-chemical energy storage systems of the present invention are illustrated in
(140) When it is desired to recharge the system, the reverse process is shown in the charge portion of
(141) Another aspect of the present invention provides a method of storing energy using mechanical-chemical energy storage system is described in
(142) Some implementations further include discharging energy from the mechanical-chemical energy storage system. Discharging energy from this system comprises expanding the working fluid through expanders (e.g., turbines, turbo-expanders, pistons, or any combination thereof) E10-E30. One or more heat exchangers Hx80, Hx10, and Hx20 transfer heat to the working fluid. The one or more heat exchangers are arranged to input heat to the working fluid between successive expansions. In some instances, the heat exchangers are arranged along the working fluid flow path between expanders. Alternatively, a single heat exchanger can input heat to the working fluid between successive expansions.
IV. Examples
Example 1: Ammonia and Magnesium Chloride
(143) Magnesium chloride can form ammonates. MgCl.sub.2 can absorb up to 6 molecules of ammonia to form MgCl.sub.2*6NH.sub.3.
(144) The pressure of the ammonia over the MgCl.sub.2 varies as more or less ammonia is incorporated into the molecular structure. Since the salt and its ammonate are solid, the heat generated from the reaction needs to be allowed to move to the cooling ammonia by either packing the salt on one side of a heat exchanger and having the ammonia on the other side of the same heat exchanger or by having an intermediate heat transfer fluid carry the heat away from the salt and deliver it to the ammonia.
(145) Simplified chemical equations representing these reactions include:
MgCl.sub.2+NH.sub.3==>MgCl.sub.2*NH.sub.3 (1)
MgCl.sub.2*NH.sub.3+NH.sub.3==>MgCl.sub.2*2NH.sub.3 (2)
MgCl.sub.2*2NH.sub.3+NH==>MgCl.sub.2*3NH.sub.3 (3)
MgCl.sub.2*3NH.sub.3+NH.sub.3==>MgCl.sub.2*4NH.sub.3 (4)
MgCl.sub.2*4NH.sub.3+NH.sub.3==>MgCl.sub.2*5NH.sub.3 (5)
MgCl.sub.2*5NH.sub.3+NH.sub.3==>MgCl.sub.2*6NH.sub.3 (6)
(146) As NH.sub.3 pressure is increased all of the above reactions will go to completion (to the right). This is the case as the system is discharging.
(147) These are also all exothermic reactions. Thus, the heat that is released can be used to expand the ammonia to get addition energy from the system. Note that this heat energy is generated when and as the system discharges. It is not stored as heat but used right away to create more energy and increase the efficiency of the system.
(148) Further, removing ammonia during the recharge step will drive the reactions to the left and create a source of cold to help with the liquefaction of ammonia. Again this cold is not stored as a cold material but is generated as the recharging process takes place.
(149) In this case, the vacuum at the intake of the compression device could be sufficient to start removing ammonia from the MgCl.sub.2*NH.sub.3 and drive the recharge reaction. The additional heat from the compression of the ammonia can also drive the release of the ammonia until the recharging is complete.
Example 2: Carbon Dioxide and Monoethanolamine
(150) Monoethanolamine (MEA), usually as a 30% solution in water, has been used for many years for removal of CO.sub.2 from natural gas.
(151) The simplified chemical equations representing these reactions include:
CO.sub.2+H.sub.2O==>HCO.sub.3.sup.−+H.sub.+ (7)
MEA+HCO.sub.3.sup.−==>MEAHCO.sub.2.sup.−+H.sub.2O (8)
(152) These reactions are exothermic and give off heat as CO.sub.2 is absorbed. These are essentially simple acid-base reactions that are easily reversible since they are not too exothermic.
(153) The fact that a gas is part of the equilibrium helps the reaction be driven in either direction by change of gas pressure. This allows for the storage of energy as chemical potential and allows for the control of this reaction by pressure and temperature.
(154) Thus, as CO.sub.2 exits the turbo-expander, the equilibrium in reaction 7 is pushed to the right, which also pushes reaction 8 to the right, releasing heat energy as needed to expand the CO.sub.2 further.
(155)
(156)
(157) These relationships, shown in
(158) As an example, a system may have a vacuum side of the compressor that will operate at 100 pascals and will charge the MEA up to 100,000 pascals. The amount of CO.sub.2 can then be calculated by finding those two points on the graph where the line crosses and reading down to how much CO.sub.2 is absorbed by the MEA at those pressures. In this case, when charging at 100,000 pascals, the mole ratio is about 0.6 moles of CO.sub.2 per mole of MEA. Down at the lower pressure the ratio is about 0.2 to 1. These two ratios are subtracted and it is determined that the capacity of the MEA operation between these pressures will cycle at about 0.4 moles of CO.sub.2 per mole of amine. It should be noted that these curves are at a single temperature.
(159)
(160)
(161)
Example 3: Process Simulation No. 1—(CO.SUB.2./MEA)
(162) In order to simulate an exemplary process, a CHEMCAD simulation software package was used. The process was simulated in sections rather than in a single simulation to allow for the use of different models for the fluid properties in certain segments of the process. Initial simulations were performed assuming a constant CO.sub.2 mass flow rate (1 lb/sec) and assuming negligible carryover of any impurities or sorbents through the expansion/contraction steps. It is also assumed that the heat of solution of the CO.sub.2 and sorbent is capable of heating the solution to the fixed set point temperature for the calculation. Therefore, it must be noted that the highest temperatures in the simulations below may not be achievable without additional heat input (this will be discussed further).
(163) Using a single stage expander,
(164) Referring to
(165) In order to improve the performance of compressors and expanders, multiple stages are often employed. For example, in the calculations used in
(166) For the two-stage process, the first stage pressurized the 80° F. working fluid from 200-425 psia; the compression caused the fluid to warm, so a heat exchanger is used to reduce the temperature to 80° F. Then the second stage is run to pressurize from 425-900 psia.
(167) For the three-stage process, the first stage pressurized the 80° F. working fluid from 200-330 psia; the compression caused the fluid to warm, so a heat exchanger is used to reduce the temperature to 80° F. Then the second stage is run to pressurize from 330-550 psia. Again, the compression heated working fluid is cooled to 80° F. and then enters the third stage where it achieves a final pressure of 900 psia.
(168) As can be seen in
(169) Of particular interest in evaluating the process will be the percentage of the recharge power that can be delivered in discharge mode; this will be referred to as the Round Trip Efficiency (RTE). The minimum acceptable value for this process is 0.6 (60%).
(170) One method to improve power output is to pressurize the liquid CO.sub.2 with a standard pump when it leaves the storage tank, and then add heat to move the working fluid into a supercritical state. This approach works because the power required to pressurize a liquid is significantly lower than the power output that can be gained from the expander (assuming a heat source is available, of course).
(171) Up to this point, the sorbent has not been considered in the analysis. All of the above calculations look at CO.sub.2, and the power generated or consumed during discharge or recharge steps. The choice of sorbent is important for the system design. Of particular interest for the preceding analysis is the heat of solution. It has been assumed that the energy needed to heat the working fluid is available. One sorbent of interest is monoethanolamine (MEA). It has a high heat of solution with CO.sub.2. Using the CHEMCAD AMINE model, it is possible to calculate the temperature of CO.sub.2/MEA mixed solutions. One simulation looked at mixing 100% pure MEA with CO.sub.2, and it was found that ˜17 wt % CO.sub.2 was dissolved and the final solution temperature achieved 330° F. Using this heated sorbent as the heat supply for the CO.sub.2 heat exchanger prior to the expander, we found that it was possible to heat the CO.sub.2 to 280° F. in two expansion stages. The outgoing sorbent stream still retained a significant amount of heat, as the outlet temperature was ˜290° F. after heating the CO.sub.2.
(172) In order to achieve a high sorbent temperature, the MEA sorbent must dissolve a significant amount of CO.sub.2.
Example 4: Process Simulation No. 2
(173) Another exemplary process was simulated using the software package described above. The following assumptions were made: 1) All streams can be heated or cooled to 80° F. from the atmosphere, whether heating or cooling. All phase change energy is supplied from the atmosphere. Energy to run the air blowers is neglected. 2) Working fluid liquid inlet condition is set at 70° F., where the fluid is a liquid at its vapor pressure. 3) Pressure is set between 100-856 psia and 200-856 psia. 4) Piston work is calculated as PdV. A simple curve fit of Pressure to Volume information was used for the integration. 5) Piston heat is calculated as TdS. 6) Assumed inefficiencies remained the same as with isentropic process—85% for expansion, 75% for compression. Lost energy is not accounted for in the simulation. 7) RTE is calculated as the power produced during piston expansion divided by the power required by the piston compression.
(174) A schematic of the process used for the simulation is shown in
(175) TABLE-US-00003 TABLE 3 Discharge Sorption T = 160 F. Streams Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 856 A +68.5 Air 2 80 856 B +28.1 System 3 150 856 C 35.2 −55.0 Exp. Cooling 4 150 200 D +55.0 System 5 160 200 E +2.4 System Recharge Desorption T = 60 F. Unit Ops T (F) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 200 A −61.3 Air 2 70 856 B 47.6 +56.2 Comp Heat 3 70 856 C −56.2 System H.sup.ads 85.5 kJ/sec 8.3 kJ/mol RTE 0.74
(176) TABLE-US-00004 Discharge Sorption T = 160 F. Streams Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 856 A +68.5 Air 2 80 856 B +28.1 System 3 150 856 C 54.5 −81.3 Exp. Cooling 4 150 100 D +81.3 System 5 160 100 E +2.3 System Recharge Desorption T = 60 F. Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 100 A −61.3 Air 2 70 856 B 78.2 +83.0 Comp Heat 3 70 856 C −83.0 System H.sup.ads 111.7 kJ/sec 10.8 kJ/mol RTE 0.70
(177) To balance a system, such as the system described in this example or the other embodiments described herein, calculation of the minimum heat and maximum temperature of the absorber may be useful. Two criteria should be met. The first is the minimum heat of reaction required for the absorber. This is calculated by dividing the amount of energy required to reverse the chemical reaction of the working fluid with the absorber (the ‘B’ unit op column Q in the recharge cycle above) by the number of moles of working fluid needed to create a given amount of energy, which in this model is set at 1 #/sec. Thus, for CO.sub.2 in this case is 10.32 moles.
(178) So in the example above Q=56.2 kJ this divided by 10.32 moles=5.45 kJ/mole as a minimum reaction energy (delta G) for each mole of working fluid that reacts with each mole of absorber. The order of magnitude of this energy is actually very low compared to most chemical reactions. While it is good to have a delta G larger than the minimum it also needs to be reversible at a temperature that is available from the heat of compression. In general the higher the delta G the higher the temperature (and or pressure differential) that will be required to reverse the reaction. There is no exact formula that relates delta G to the temperature so each system has to be considered to make sure that it is reversible. Zeolites and activated carbons have delta G values of about 5 to about 20 kJ/mole for CO.sub.2 and NH.sub.3 working fluids. Another example is water and CO.sub.2 going to HCO.sub.3.sup.−, which has a delta G of about 12 kJ/mole. Many of these compounds can easily be desorbed by allowing the pressure to decrease on them.
(179) In the case of a solid absorbent, a secondary heat transfer loop using an inert heat transfer liquid may also be used. Heat exchange could also be accomplished by injecting an inert heat exchange fluid (such as silicone oil) into the expander and/or compressor as opposed to the external heat exchangers discussed herein.
Example 5: Process Simulation No. 3
(180) Another exemplary process was simulated using the computer software package described above. The following assumptions were made: 1) All streams can be heated or cooled to 80° F. from the atmosphere, whether heating or cooling. All phase change energy is supplied from the atmosphere. Energy to run the air blowers is neglected. 2) Working fluid (CO.sub.2) liquid inlet condition is set at 70° F., where the fluid is a liquid at its vapor pressure. 3) Pressure is set between 200-856 psia. 4) Desorption conditions not accounted for—assumed to happen at any T, P set. No pressure or temperature swing has been included. 5) Work is calculated as isentropic. 6) Assumed inefficiencies based mechanical losses (BNI)—98% for expansion, 96% for compression. Lost energy is not accounted for in the simulation. 7) RTE is calculated as the power produced during piston expansion divided by the power required by the piston compression.
(181) A schematic of the process used for the simulation is shown in
(182) TABLE-US-00005 TABLE 4 Carbon Dioxide - Isentropic, Single Stage. Discharge Sorption T = 210 F. Streams Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 856 A +68.5 Air 2 80 856 B 31.0 3 150 856 C +17.7 Air 4 4.1 200 D +28.5 System 5 80 200 E +2.4 System 6 200 200 F +43.8 System Recharge Desorption T = 70 F. Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 20 A −68.6 Air 2 286 856 B 40.7 3 80 856 C 4 70 856 D −68.9 System H.sup.ads 68.9 kJ/sec 6.7 kJ/mol Heat from Absorber RTE 0.76
Carbon Dioxide—Isentropic, Two-Stage Expansion/Three-Stage Compression
(183) TABLE-US-00006 Discharge Sorption T = 210 F. Streams Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 856 A +68.5 Air 2 80 856 B 35.8 System 3 150 856 C +17.7 Air 4 102.5 200 D +28.5 System 5 80 200 E +2.4 System 6 200 200 F +43.8 System Recharge Desorption T = 70 F. Unit Ops T (F.) P (psi) W (kJ/sec) Q (kJ/sec) Heat Source 1 70 200 A −68.7 Air 2 135.8 856 B 39.5 −38.0 System 3 80 856 C 4 70 856 D −23.2 System H.sup.ads 79.6 kJ/sec 7.7 kJ/mol Heat from absorber RTE 0.906
Example 6: Use of Air as Working Fluid and Half-Systems
(184) One issue with conventional compressed air energy storage is the low energy density of the compressed gas. However, zeolite type absorbents will absorb air and have acceptable delta G values. If air were to be compressed into an insulated tank of zeolites, and then simply discharged to the atmosphere (no absorption on discharge) this would increase both the RTE of compressed air energy storage as well as the energy density.
(185) This would operate conceptually as a half-system with only a single storage tank and that is not a closed cycle. However, it is an improvement over ordinary CAES. Both the heat of compression and the absorption energy will be stored and available for discharge. Although activated carbon also absorbs air, there should be a warning that high pressure air could ignite certain carbons and this would be a limit on those particular absorbents.
Example 7: Three-Loop Carbon Dioxide and Aqueous Ammonia System
(186) The absorption of carbon dioxide in aqueous ammonia solution leads to a number of products including ammonium carbamate, bicarbonate, and carbonate. The ratio of these reaction products are a function of the carbon dioxide loading, solution pH, and the concentration of ammonia in the aqueous media.
(187) Simplified chemical equations representing these reactions include:
NH.sub.2COONH.sub.4(q)+H.sub.2O.Math.NH.sub.4HCO.sub.3(aq)+NH.sub.3(aq) ΔH.sub.rx=8.06 kJ/mol (9)
2NH.sub.4HCO.sub.3(aq).Math.(NH.sub.4).sub.2CO.sub.3(aq)+CO.sub.2(g)+H.sub.2O ΔH.sub.rx=26.88 kJ/mol (10)
NH.sub.4HCO.sub.3(aq).Math.NH.sub.3(aq)+CO.sub.2(g)+H.sub.2O ΔH.sub.rx=64.26 kJ/mol (11)
NH.sub.2COONH.sub.4(aq).Math.2NH.sub.3(aq)+CO.sub.2(g) ΔH.sub.rx=72.32 kJ/mol (12)
(NH.sub.4).sub.2CO.sub.3(aq).Math.2NH.sub.3(aq)+CO.sub.2(g)+H.sub.2O ΔH.sub.rx=101.22 kJ/mol (13)
(188) The schematic flow diagram for the process is shown in
(189) The operating parameters for the initial feasibility evaluation are:
(190) 1) Absorption vessel conditions are 150° F. and 257 psi (˜66° C. and 1.77 Mpa);
(191) 2) Desorption vessel conditions are 180° F. and 257 psi (˜82° C.);
(192) 3) Ammonia concentration level of 36% was maintained;
(193) 4) Total flow rate of working fluid equal to 142.6 kg/s;
(194) 5) Expansion efficiency: 88%;
(195) 6) Compressor efficiency: 84%;
(196) 7) Heat exchanger efficiency: 2%;
(197) 8) The molar ratios of carbon dioxide to ammonia in solution are between 0.35 to 0.60;
(198) 9) The reversible heat of reaction: 80 kJ/mol; and
(199) 10) Thermodynamic and transport properties estimated with using the National Institute of Standards and Technology (NIST) standard reference program.
(200) All state functions, for each location, as shown in
(201) TABLE-US-00007 TABLE 5 Physical parameters data at various locations. Temperature Pressure Density Enthalpy Entropy Location.sup.3 (.sup.° K) (Mpa) (kg/m.sup.3) (kJ/kg) (kJ/kg .sup.° K) 901 333.15 6.63 143.66 476.09 1.9083 903 333.15 3.76 69.441 506.26 2.0852 904 299.82 2.3442 47.202 484.33 2.0935 905 333.15 2.32 40.213 518.9 2.2043 906 298.71 1.77 34.596 489.59 2.1581 915 305.37 2.28 44.562 490.84 2.1193 916 333.71 3.17 56.84 512.2 2.1311 917 305.37 3.14 64.921 481.07 2.0351 918 333.15 4.316 81.984 500.96 2.0469 919 305.37 4.275 96.472 466.34 1.9401 920 334.26 5.9 120.76 486.74 1.9568 921 358.71 2.31 36.386 544.63 2.2795 934 333.15 1.74 29.28 523.73 2.2703 934(l)* 333.15 1.74 937 333.15 1.77 30.01 523.41 2.2653 940 339.93 6.63 136.34 486.23 1.9384 941 355.37 1.73 27.09 545.31 2.333 942 352.59 1.73 27.339 542.61 2.3254 943(l)* 330.37 1.77 945(l)* 355.37 1.73 946(l)* 352.59 1.73 .sup.3Locations are shown in FIG. 13. *Assuming that heat capacity (C.sub.p) of the solution (both rich and lean) containing CO.sub.2/NH.sub.3/H.sub.2O is equal to 1 cal/g .sup.° C.
(202) All calculations and thermodynamic state function are normalized to 1 kg of carbon dioxide of working fluid. The assumed value for heat capacity (C.sub.p), for the carbon dioxide/ammonia/water solution is equal to 1 cal/g° C. The assumed density for the carbon dioxide/ammonia/water solution is equal to 1 g/cm.sup.3. The sensible heat requirements: 29.9 kJ/kg carbon dioxide and stripping heat is zero.
(203) The value for each expansion and compression work is calculated as follows: E1 is calculated by referring to Table 5 above and
(204) TABLE-US-00008 TABLE 6 Multi-Stage Expanders. Expansion Heat Stages.sup.4 Work, kJ/kg CO.sub.2 Exchangers Q kJ/kg CO.sub.2 E1 −24.39 H.sub.x1 54.56 E2 −21.93 H.sub.x2 34.57 E3 −29.31 H.sub.x3 33.82 Total −75.65 122.95 .sup.4Expansion stages E1, E2 and E3 are shown in FIG. 13.
(205) TABLE-US-00009 TABLE 7 Multi-Stage Compressors. Compression Heat Stages.sup.3 Work, kJ/kg CO.sub.2 Exchangers Q kJ/kg CO.sub.2 C1 20.90 H.sub.x4 −53.79 C2 21.36 H.sub.x5 −31.13 C3 19.89 H.sub.x6 −34.62 C4 20.40 C5 −.61 Total: 82.55 −119.54 .sup.3 Compression stages C1, C2, C3, C4 and C5 are shown in FIG. 13.
(206) Estimation of Sensible Heat:
(207) The sensible heat is defined as the amount of energy required to raise the temperature of the solution to the temperature of regeneration, which while not recovered in this flow chart, may allow for partial recovery. Assuming 36% by weight of ammonia concentration in water and maintaining the molar ratio of carbon dioxide to ammonia in the solution between 0.35 to 0.6 during absorption and desorption cycle, the reaction heat is:
(Q.sub.absorption+Q.sub.desorption)/2=(122.95+119.54)/2=121.3 kJ/kg CO.sub.2
Since the total ΔQ for desorption and absorption is essentially equal.
(208) Accepting reaction heat 80 kJ/mol, as reported in the literature
80×[(1000×0.36)(0.6−0.35)/17]=424 kJ/kg of solution
The ΔT is the temperature difference between stream 43 and reboiler 180-135° F.=25° C. Sensible (Q.sub.sensible) heat is equal to
Q.sub.sensible=(121.3×25×4.18)/424=29.9 kJ/kg CO.sub.2
(209) The System Efficiency:
Efficiency (RTE)=[(Work out)/(Work in+Sensible Heat)]×100
RTE=[75.65/(82.55+29.9)]×100=67.2%
Example 8: Process Simulation No. 4
(210) The system illustrated in
(211) This simulation calculates the thermodynamic efficiency of CO.sub.2 working fluid as it completes a full charge-discharge cycle. Note that this simulation does not show a specific absorption reaction. It assumes that heat is put into a given reaction during charging/compression and withdrawn from the reverse of that reaction during the discharge/expansion thru the heat exchangers. The data generated in this simulation is presented in Tables 8-15, below.
(212) TABLE-US-00010 TABLE 8 Expander Efficiency: 85%, Compressor Effic.: 84% Different Compressor Temperature Out. E30(P) = C10(P); C40(T, P) = E10(T, P); E30(T) NOT = C10(T) Final Heater Final Pr. Temp Temp Power Out Out Out MW E10 35.00 72.17 110 2.81 E10 in T/P: E20 15.00 51.20 100 4.38 115 deg C./61 bar E30 6.00 41.60 4.80 11.99 Final Cooler Final Pr. Temp Temp Power Out Out Out MW C10 14.94 100 69 6.90 C10 in T/P: C20 21.03 100 62 2.58 18 deg C./5.6 bar C30 35.46 110 63 3.82 C40 61.51 115 3.81 17.12 TRUE RTE 70.06
(213) TABLE-US-00011 TABLE 9 Expander Efficiency: 85%, Compressor Effic.: 84% Different Compressor Temperature Out. E30(P) = C10(P); C40(T, P) = E10(T, P); E30(T) NOT = C10(T) Final Heater Final Pr. Temp Temp Power Out Out Out MW E10 35.00 72.17 110 2.81 E10 in T/P: E20 15.00 51.20 100 4.38 115 deg C./61 bar E30 6.00 41.60 4.80 11.99 Final Cooler Final Pr. Temp Temp Power Out Out Out MW C10 13.80 103 69 6.38 C10 in T/P: C20 21.02 103 62 3.17 28 deg C./5.7 bar C30 35.44 110 63 3.82 C40 61.47 115 3.81 17.19 TRUE RTE 69.78
(214) TABLE-US-00012 TABLE 10 Expander Efficiency: 85%, Compressor Effic.: 84% Different Compressor Temperature Out. E30(P) = C10(P); C40(T, P) = E10(T, P); E30(T) NOT = C10(T) Final Heater Final Pr. Temp Temp Power Out Out Out MW E10 35.00 77.01 120 2.87 E10 in T/P: E20 15.00 60.49 105 4.53 120 deg C./61 bar E30 6.00 46.12 4.88 12.28 Final Cooler Final Pr. Temp Temp Power Out Out Out MW C10 12.25 101 64 5.48 C10 in T/P: C20 19.43 104.5 62 3.49 37 deg C./5.8 bar C30 33.89 112 61 4.10 C40 61.39 117 4.12 17.20 TRUE RTE 71.42
(215) TABLE-US-00013 TABLE 11 Expander Efficiency: 85%, Compressor Effic.: 84% Different Compressor Temperature Out. E30(P) = C10(P); C40(T, P) = E10(T, P); E30(T) NOT = C10(T) Final Heater Final Pr. Temp Temp Power Out Out Out MW E10 35.00 72.17 110 2.81 E10 in T/P: E20 15.00 51.20 100 4.38 115 deg C./61 bar E30 6.00 41.60 4.80 11.99 Final Cooler Final Pr. Temp Temp Power Out Out Out MW C10 12.70 102 69 5.73 C10 in T/P: C20 20.01 105 62 3.45 35 deg C./5.8 bar C30 34.13 111 63 3.93 C40 61.20 116 4.04 17.15 TRUE RTE 69.94
(216) TABLE-US-00014 TABLE 12 Expander Efficiency: 85%, Compressor Effic.: 84% Different Compressor Temperature Out. E30(P) = C10(P); C40(T, P) = E10(T, P); E30(T) NOT = C10(T) Final Heater Final Pr. Temp Temp Power Out Out Out MW E10 35.00 77.01 120 2.87 E10 in T/P: E20 15.00 60.49 105 4.53 120 deg C./61 bar E30 6.00 46.12 4.88 12.28 Final Cooler Final Pr. Temp Temp Power Out Out Out MW C10 12.48 102 64 5.58 C10 in T/P: C20 19.68 105 62 3.54 35 deg C./5.7 bar C30 33.57 111 61 4.10 C40 61.10 116 4.12 17.33 TRUE RTE 70.85
(217) TABLE-US-00015 TABLE 13 Std Ideal Mass Liq Vol Vapor/ Molar Pressure Temp. Flow Flow Phase Enthalpy Location [bar] [C.] [kg/s] [m3/h] Fraction [kJ/kgmole] 1921 14.93721229 100 100 436.1865066 1 −391267.0048 1915 14.93721229 69 100 436.1865065 1 −392586.3377 1916 21.03372089 100 100 436.1865066 1 −391449.4834 1917 21.03372089 62 100 436.1865066 1 −393111.4838 1918 35.46339734 110 100 436.1865066 1 −391429.8615 1919 35.46339734 63 100 436.1865066 1 −393637.51 1940 61.51466519 115 100 436.1805066 1 −391959.8495 1934 5.6 18 100 436.1865066 1 −394303.7714 1909 35 72.1652056 100 436.1865066 1 −393181.8818 1903 35 110 100 436.1865066 1 −391416.2255 1904 15 51.19538871 100 436.1865066 1 −393342.6754 1905 15 100 100 436.1865066 1 −391268.8689 1906 6 41.60482521 100 436.1865066 1 −393382.2592 1941-2 61 22 100 436.1865066 0 −404047.2745 1900 61 115 100 436.1865066 1 −391944.4882 1941 61.51466519 22 100 436.1865066 0 −404077.447
(218) TABLE-US-00016 TABLE 14 Hx40 Hx50 Hx60 Hx70 Duty [kJ/h] 10792163.03 13595187.4 18058597.24 9.9E+07 Pressure Drop 0 0 0 0 [kPa]
(219) TABLE-US-00017 TABLE 15 C10 C20 C30 C40 Compressor Speed [rpm] Power [kW] 6900.221073 2583.190312 3821.02624 3812.02 Capacity (act feed vol flow) 34174.65632 14743.26663 9951.324512 5550.81 [ACT_m3/h] Adiabatic Efficiency 84 84 84 84 Polytropic Efficiency 85.57271157 84.58712734 84.90616828 84.988 Compressor Volume [m3] 0 0 0 0 Delta T [C] 82 31 48 52 Delta P [kPa] 933.7212287 609.6508608 1442.967645 2605.13 Polytropic Head [m] 6021.124725 2228.127363 3308.252024 3303.64 Adiabatic Head [m] 5910.464533 2212.661675 3272.944422 3265.23 Dynamic Head [m] 6021.124725 2228.127363 3308.252024 3303.64 Polytropic Fluid Head [kJ/kg] 59.04706278 21.8504652 32.44286971 32.3976 Adiabatic Fluid Head [kJ/kg] 57.96185701 21.69879862 32.09662041 32.021 Dynamic Fluid Head [kJ/kg] 59.04706278 21.8504652 32.44286971 32.3976 Polytropic Head Factor 1.00068214 1.00002664 0.999848205 0.99913 Polytropic Exponent 1.327392038 1.328738561 1.333983706 1.36064 Isentropic Exponent 1.266002311 1.261753035 1.266416427 1.2885 Dynamic Delta P RC-Typical Design Speed RC-Volumetric Efficiency PD Number of Cylinders 0 0 0 0 PD Bore [m] PD Stroke [m] PD Piston Rod Diameter [m] PD Const Volmetric Efficiency Loss [%] Transient Rotational Power 0 0 0 0 [kW] Friction Loss Power [kW] 0 0 0 0 Fluid Power [kW] 6900.221073 2583.190312 3821.02624 3812.02 Total Rotor Torque [N-m] Transient Rotational Torque [N-m] Friction Loss Torque [N-m] Fluid Torque [N-m] Duty [kJ/h] 24840795.86 9299485.123 13755694.46 1.4E+07
OTHER EMBODIMENTS
(220) All publications and patents referred to in this disclosure are incorporated herein by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Should the meaning of the terms in any of the patents or publications incorporated by reference conflict with the meaning of the terms used in this disclosure, the meaning of the terms in this disclosure are intended to be controlling. Furthermore, the foregoing discussion discloses and describes merely example embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.