Fuel Cell Generator with Cryogenic Compression and Co-Generation of Liquefied Air

Abstract

The present invention provides a high efficiency prime mover with phase change energy storage for distributed generation and motor vehicle application. Phase change storage minimizes energy required for refrigerant liquefaction while reducing fuel consumption and emissions.

Claims

1. A fuel cell generator with cryogenic compression and co-generation of liquefied fluid, comprising: a liquefier compressor that compression heats atmospheric air to heated air; an aftercooler in fluid communication with said liquefier compressor such that said liquefier compressor provides the heated air to said aftercooler and wherein said aftercooler cools the heated air to ambient air; a cryo-fluid supply, comprising: a fluid liquefier in fluid communication with said aftercooler such that said aftercooler provides the ambient air to said fluid liquefier and wherein said fluid liquefier liquefies at least a first portion of the ambient air into liquid fluid; a liquid fluid dewar in fluid communication with said fluid liquefier such that said fluid liquefier provides at least a first portion of the liquid fluid to said liquid fluid dewar and wherein said liquid fluid dewar stores at least the first portion of the liquid fluid; and a liquid fluid feed pump in fluid communication with said fluid liquefier and said aftercooler such that said fluid liquefier provides at least a second portion of the liquid fluid to said liquid fluid feed pump and said liquid fluid feed pump pumps at least the second portion of the liquid fluid to said aftercooler; an air pre-heater in fluid communication with said aftercooler such that said aftercooler provides said air pre-heater with cathode intake air and wherein said air pre-heater heats the cathode intake air; a fuel cell generator that generates electricity through chemical reaction, said fuel cell generator comprising: a cathode channel where a cathode reduction reaction occurs and that produces negative oxygen ions, wherein said cathode channel expels oxygen depleted air; an anode channel where an anode oxidation reaction occurs; a solid state electrolyte disposed between said cathode channel and said anode channel, wherein the negative oxygen ions from said cathode channel pass through said solid state electrolyte; and a fuel supply that provides a fuel to said anode channel, wherein said anode channel expels anode steam and residual fuel; wherein said air pre-heater is in further fluid communication with said cathode channel such that said air pre-heater provides the heated cathode intake air to said cathode channel; and means for driving said liquefier compressor.

2. The cryo-compression fuel cell generator as claimed in claim 1, wherein said means comprise a water-steam circuit comprising: a driver that drives said liquefier compressor and expels extraction steam and circulating steam; a condenser in fluid communication with said driver such that said driver provides the circulating steam to said condenser and wherein said condenser condenses the circulating steam into condensate; a water feed pump in fluid communication with said condenser such that said condenser provides the condensate to said water feed pump; a feedwater heater in fluid communication with said driver such that said driver provides the extraction steam to said feedwater heater and in fluid communication with said water feed pump such that said water feed pump pumps the condensate to said feedwater heater, wherein said feedwater heater uses heat from the extraction steam to heat the condensate; a solar evaporator in fluid communication with said feed water heater such that said feedwater heater provides the heated condensate to said solar evaporator and wherein said solar evaporator uses solar radiation to heat the condensate into the circulating steam; a superheater in fluid communication with said solar evaporator such that said solar evaporator provides the circulating steam to said superheater, wherein: said superheater heats the circulating steam; and said superheater is in fluid communication with said driver such that said superheater provides said driver with the heated circulating steam and the driver is driven by the heated circulating steam.

3. The cryo-compression fuel cell generator as claimed in claim 2, wherein: said driver is a hybrid expander electric compressor drive; and said hybrid expander-electric compressor drive is in mechanical communication with said liquefier compressor such that said hybrid expander-electric compressor drive drives said liquefier compressor.

4. The cryo-compression fuel cell generator as claimed in claim 3, further comprising a heat storage unit that stores excess solar insolation.

5. The cryo-compression fuel cell generator as claimed in claim 2, wherein: said driver is a steam turbine generator that generates electricity from the circulating steam; and said steam turbine generator is in electrical communication with said liquefier compressor such that said steam turbine generator drives said liquefier compressor by electricity.

6. The cryo-compression fuel cell generator as claimed in claim 5, wherein said fuel cell generator is also in electrical communication with said liquefier compressor such that said fuel cell generator drives said liquefier compressor by electricity.

7. The cryo-compression fuel cell generator with cryogenic compression and co-generation of liquefied fluid as claimed in claim 1, wherein said means comprise external electricity.

8. The cryo-compression fuel cell generator as claimed in claim 1, wherein: said cryo-fluid supply is a cryo-air supply and the liquid fluid is liquid air such that: said fluid liquefier is an air liquefier; said liquid fluid dewar is a liquid air dewar; said liquid fluid feed pump is a liquid air feed pump; said cryo-air supply further comprises a cryo-recuperator, wherein: said cryo-recuperator is in fluid communication with said aftercooler such that said aftercooler provides the ambient air to said cryo-recuperator; said cryo-recuperator further cools the ambient air to sub-ambient air; said cryo-recuperator is in fluid communication with said air liquefier; and said aftercooler provides the ambient air to said air liquefier through said cryo-recuperator such that the ambient air is sub-ambient air; said cryo-air supply further comprises a cryo-compressor, wherein: said cryo-compressor is in fluid communication with said air liquefier such that said air liquefier provides an air vapor portion of the sub-ambient air to said cryo-compressor; said cryo-compressor is in fluid communication with said cryo-recuperator such that said cryo-recuperator provides said cryo-compressor with at least a second portion of the sub-ambient air; said cryo-compressor compression heats a combination of the at least second portion of the liquid air and the at least second portion of sub-ambient air into the cathode intake air; said cryo-compressor is in further fluid communication with said cryo-recuperator such that said cryo-compressor provides the cathode intake air to said cryo-recuperator; said cryo-recuperator heats the cathode intake air; said cryo-recuperator is in further fluid communication with said aftercooler such that said cryo-recuperator provides the heated cathode intake air to said aftercooler; and said fuel cell generator is in electrical communication with said cryo-compressor such that said fuel cell generator provides electricity to said cryo-compressor.

9. The cryo-compression fuel cell generator as claimed in claim 1, wherein: said cryo-fluid supply is a cryo-oxygen/air supply and the liquid fluid is liquid oxygen and liquid air such that: said fluid liquefier is an oxygen/air liquefier; said liquid fluid dewar is a liquid air dewar; said liquid fluid feed pump is a liquid oxygen feed pump; and said aftercooler evaporates the liquid oxygen into oxygen vapor.

10. The cryo-compression fuel cell generator with cryogenic compression and co-generation of liquefied fluid as claimed in claim 1, wherein the fuel of said fuel supply is hydrogen.

11. The cryo-compression fuel cell generator as claimed in claim 1, wherein said means comprise a vehicle deceleration recovery generator in electrical communication with said liquefier compressor such that said vehicle deceleration recovery generator provides electricity to said liquefier compressor.

12. The cryo-compression fuel cell generator as claimed in claim 8, further comprising: a burner, wherein said burner: is in fluid communication with said anode channel such that said anode channel provides the anode steam and residual fuel to said burner, is in fluid communication with said cathode channel such that said cathode channel provides oxygen depleted air to said burner; and burns the residual fuel into combustion product steam; and a gas expander generator that generates electricity from steam and air, wherein said gas expander generator is in: fluid communication with said burner such that said burner provides the anode steam, combustion product steam, and oxygen depleted air to said gas expander generator; and electrical communication with said cryo-compressor of said cryo-air supply such that said gas expander generator provides said cryo-compressor with electricity.

13. The cryo-compression fuel cell generator as claimed in claim 12, wherein said gas expander generator is in further electrical communication with said liquefier compressor such that said gas expander generator provides said liquefier compressor with electricity, such that said gas expander generator is said means.

14. The cryo-compression fuel cell generator as claimed in claim 13, wherein said means further comprise a vehicle deceleration recovery generator in electrical communication with said liquefier compressor such that said vehicle deceleration recovery generator provides electricity to said liquefier compressor.

15. The cryo-compression fuel cell generator with cryogenic compression and co-generation of liquefied fluid as claimed in claim 1, wherein said fuel cell generator is in electrical communication with said liquefier compressor such that said fuel cell generator drives said liquefier compressor by electricity.

16. The cryo-compression fuel cell generator as claimed in claim 13, further comprising an auxiliary fuel supply in fluid communication with said burner such that said auxiliary fuel supply provides auxiliary fuel to said burner burns the auxiliary fuel to produce additional combustion product steam.

17. The cryo-compression fuel cell generator as claimed in claim 16, wherein the auxiliary fuel is a non-carbon liquid fuel.

18. The cryo-compression fuel cell generator as claimed in claim 12, wherein said gas expander generator is in further fluid communication with said air pre-heater such that said gas expander generator provides the anode steam, the combustion product steam, and the oxygen depleted air to said air pre-heater.

19. The cryo-compression fuel cell generator with cryogenic compression and co-generation of liquefied fluid as claimed in claim 1, wherein said solid state electrolyte is yttria stabilized zirconia.

20. The cryo-compression fuel cell generator as claimed in claim 3, wherein: said cryo-fluid supply is a cryo-air supply and the liquid fluid is liquid air such that: said fluid liquefier is an air liquefier; said liquid fluid dewar is a liquid air dewar; said liquid fluid pump is a liquid air feed pump; said cryo-air supply further comprises a cryo-recuperator, wherein: said cryo-recuperator is in fluid communication with said aftercooler such that said aftercooler provides the ambient air to said cryo-recuperator; said cryo-recuperator further cools the ambient air to sub-ambient air; said cryo-recuperator is in fluid communication with said air liquefier; and said aftercooler provides the ambient air to said air liquefier through said cryo-recuperator such that the ambient air is sub-ambient air; said cryo-air supply further comprises a cryo-compressor, wherein: said cryo-compressor is in fluid communication with said air liquefier such that said air liquefier provides an air vapor portion of the sub-ambient air to said cryo-compressor; said cryo-compressor is in fluid communication with said cryo-recuperator such that said cryo-recuperator provides said cryo-compressor with at least a second portion of sub-ambient air; said cryo-compressor compression heats a combination of the at least second portion of the liquid air and the at least second portion of sub-ambient air into the cathode intake air; said cryo-compressor is in further fluid communication with said cryo-recuperator such that said cryo-compressor provides the cathode intake air to said cryo-recuperator; said cryo-recuperator heats the cathode intake air; said cryo-recuperator is in further fluid communication with said aftercooler such that said cryo-recuperator provides the heated cathode intake air to said aftercooler; and said fuel cell generator is in electrical communication with said cryo-compressor such that said fuel cell generator provides electricity to said cryo-compressor; said cryo-compression fuel cell with expansion engine further comprises: a burner, wherein said burner: is in fluid communication with said anode channel such that said anode channel provides the anode steam and residual fuel to said burner; is in fluid communication with said cathode channel such that said cathode channel provides oxygen depleted air to said burner; and burns the residual fuel into combustion product steam; and a gas expander generator that generates electricity from steam and air, wherein said gas expander generator is in: fluid communication with said burner such that said burner provides at least a first portion of the anode steam, the combustion product steam, and the oxygen depleted air to said gas expander generator; fluid communication with said superheater of said water-steam circuit such that said gas expander generator provides the anode steam, the combustion product steam, and the oxygen depleted air to said superheater; and electrical communication with said cryo-compressor such that said gas expander generator provides said cryo-compressor with electricity.

21. The cryo-compression fuel cell generator as claimed in claim 9, wherein: said anode channel is in further fluid communication with said air pre-heater such that said anode channel provides the anode steam and the residual fuel to said air pre-heater; and said cryo-compression fuel cell generator further comprises: a cathode exhaust circulator in fluid communication with said cathode channel of said fuel cell generator such that said cathode channel provides the oxygen depleted air to said cathode exhaust circulator and wherein said cathode exhaust circulator circulates the oxygen depleted air; an anode exhaust drive in fluid communication with said air pre-heater such that said air pre-heater provides the anode steam and the residual fuel to said anode exhaust drive and wherein said anode exhaust drive condenses the anode steam into anode condensate; and a fuel separator in fluid communication with said anode exhaust drive such that said anode exhaust drive provides the anode condensate and residual fuel to said fuel separator, wherein: said fuel separator separates the anode condensate from the residual fuel; said fuel separator is in fluid communication with said fuel supply of said fuel cell generator such that said fuel separator provides the residual fuel to said fuel supply; said fuel separator expels the anode condensate; and said fuel supply further supplies the residual fuel to said anode channel.

22. The cryo-compression fuel cell generator as claimed in claim 21, wherein: said means comprise a water-steam circuit comprising: a steam turbine generator that drives said liquefier compressor, expels extraction steam and circulating steam, and generates electricity from the circulating steam; a condenser in fluid communication with said driver such that said steam turbine generator provides the circulating steam to said condenser and wherein said condenser condenses the circulating steam into condensate; a water feed pump in fluid communication with said condenser such that said condenser provides the condensate to said water feed pump; a feedwater heater in fluid communication with said steam turbine generator such that said steam turbine generator provides the extraction steam to said feedwater heater and in fluid communication with said water feed pump such that said water feed pump pumps the condensate to said feedwater heater, wherein said feedwater heater uses heat from the extraction steam to heat the condensate; a solar evaporator in fluid communication with said feedwater heater such that said feedwater heater provides the heated condensate to said solar evaporator and wherein said solar evaporator uses solar radiation to heat the condensate into the circulating steam; a superheater in fluid communication with said solar evaporator such that said solar evaporator provides the circulating steam to said superheater, wherein: said superheater heats the circulating steam; and said superheater is in fluid communication with said steam turbine generator such that said superheater provides said steam turbine generator with the heated circulating steam and said steam turbine generator is driven by the heated circulating steam; wherein said steam turbine generator is in electrical communication with said liquefier compressor such that said steam turbine generator drives said liquefier compressor by electricity; said cathode exhaust circulator is in further fluid communication with said superheater of said water-steam circuit such that said cathode exhaust circulator provides oxygen depleted air to said superheater; and said cryo-compression fuel cell generator further comprises an oxygen mixing junction, in fluid communication with: said superheater such that said superheater provides oxygen depleted air to said oxygen mixing junction; said aftercooler such that said aftercooler provides the oxygen vapor to said oxygen mixing junction, wherein said oxygen mixing junction mixes the oxygen depleted air and the oxygen vapor to create cathode intake air; and said air pre-heater such that said aftercooler provides said air pre-heater with cathode intake air through said oxygen mixing junction.

23. A method for operating a fuel cell system with co-generation means, said method comprising the steps of: maintaining constant electricity generation in the fuel cell; determining a time of reduced demand for the electricity generated in said maintaining step; providing excess generated electricity generated in said maintaining step during the time of reduced demand determined in said determining step to a fluid liquefier; and producing liquid fluid.

24. The method as claimed in claim 23, wherein: said step of providing excess generated electricity generated in said maintaining step during the time of reduced demand determined in said determining step to a fluid liquefier comprises providing excess generated electricity generated in said maintaining step during the time of reduced demand determined in said determining step to an air liquefier; and said step of producing liquid fluid comprises producing liquid air.

25. The method as claimed in claim 23, wherein: said step of providing excess generated electricity generated in said maintaining step during the time of reduced demand determined in said determining step to a fluid liquefier comprises providing excess generated electricity generated in said maintaining step during the time of reduced demand determined in said determining step to an air/oxygen liquefier; and said step of producing liquid fluid comprises producing liquid air/oxygen.

26. The cryo-compression fuel cell generator as claimed in claim 7, wherein said means further comprise a water-steam circuit comprising: driver that drives said liquefier compressor and expels extraction steam and circulating steam; a condenser in fluid communication with said driver such that said driver provides the circulating steam to said condenser and wherein said condenser condenses the circulating steam into condensate; a water feed pump in fluid communication with said condenser such that said condenser provides the condensate to said water feed pump; a feedwater heater in fluid communication with said driver such that said driver provides the extraction steam to said feedwater heater and in fluid communication with said water feed pump such that said water feed pump pumps the condensate to said feedwater heater, wherein said feedwater heater uses heat from the extraction steam to heat the condensate; a solar evaporator in fluid communication with said feedwater heater such that said feedwater heater provides the heated condensate to said solar evaporator and wherein said solar evaporator uses solar radiation to heat the condensate into the circulating steam; a superheater in fluid communication with said solar evaporator such that said solar evaporator provides the circulating steam to said superheater, wherein: said superheater heats the circulating steam; and said superheater is in fluid communication with said driver such that said superheater provides said driver with the heated circulating steam and the driver is driven by the heated circulating steam.

27. The cryo-compression fuel cell generator as claimed in claim 26, wherein: said driver is a hybrid expander electric compressor drive; and said hybrid expander-electric compressor drive is in mechanical communication with said liquefier compressor such that said hybrid expander-electric compressor drive drives said liquefier compressor.

28. The cryo-compression fuel cell generator as claimed in claim 27, further comprising a heat storage unit that stores excess solar insolation.

29. The cryo-compression fuel cell generator as claimed in claim 26, wherein: said driver is a steam turbine generator that generates electricity from the circulating steam; and said steam turbine generator is in electrical communication with said liquefier compressor such that said steam turbine generator drives said liquefier compressor by electricity.

30. The cryo-compression fuel cell generator as claimed in claim 29, wherein said fuel cell generator is also in electrical communication with said liquefier compressor such that said fuel cell generator drives said liquefier compressor by electricity.

31. The cryo-compression fuel cell generator as claimed in claim 7, wherein: said cryo-fluid supply is a cryo-air supply and the liquid fluid is liquid air such that: said fluid liquefier is an air liquefier; said liquid fluid dewar is a liquid air dewar; said liquid fluid feed pump is a liquid air feed pump; said cryo-air supply further comprises a cryo-recuperator, wherein: said cryo-recuperator is in fluid communication with said aftercooler such that said aftercooler provides the ambient air to said cryo-recuperator; said aftercooler provides the ambient air to said cryo-recuperator; said cryo-recuperator further cools the ambient air to sub-ambient air; said cryo-recuperator is in fluid communication with said air liquefier; and said aftercooler provides the ambient air to said air liquefier through said cryo-recuperator such that the ambient air is sub-ambient air; said cryo-air supply further comprises a cryo-compressor, wherein: said cryo-compressor is in fluid communication with said air liquefier such that said air liquefier provides an air vapor portion of the sub-ambient air to said cryo-compressor; said cryo-compressor is in fluid communication with said cryo-recuperator such that said cryo-recuperator provides said cryo-compressor with at least a second portion of the sub-ambient air; said cryo-compressor compression heats a combination of the at least second portion of the liquid air and the at least second portion of sub-ambient air into the cathode intake air; said cryo-compressor is in further fluid communication with said cryo-recuperator such that said cryo-compressor provides the cathode intake air to said cryo-recuperator; said cryo-recuperator heats the cathode intake air; said cryo-recuperator is in further fluid communication with said aftercooler such that said cryo-recuperator provides the heated cathode intake air to said aftercooler; and said fuel cell generator is in electrical communication with said cryo-compressor such that said fuel cell generator provides electricity to said cryo-compressor.

32. The cryo-compression fuel cell generator as claimed in claim 31, further comprising: a burner, wherein said burner: is in fluid communication with said anode channel such that said anode channel provides the anode steam and residual fuel to said burner; is in fluid communication with said cathode channel such that said cathode channel provides oxygen depleted air to said burner; and burns the residual fuel into combustion product steam; and a gas expander generator that generates electricity from steam and air, wherein said gas expander generator is in: fluid communication with said burner such that said burner provides the anode steam, combustion product steam, and oxygen depleted air to said gas expander generator; and electrical communication with said cryo-compressor of said cryo-air supply such that said gas expander generator provides said cryo-compressor with electricity.

33. the cryo-compression fuel cell generator as claimed in claim 32, wherein said gas expander generator is in further electrical communication with said liquefier compressor such that said gas expander generator provides said liquefier compressor with electricity, such that said gas expander generator is also said means.

34. The cryo-compression fuel cell generator as claimed in claim 33, wherein said means further comprise a vehicle deceleration recovery generator in electrical communication with said liquefier compressor such that said vehicle decleration recovery generator provides electricity to said liquefier compressor.

35. The cryo-compression fuel cell generator as claimed in claim 33, further comprising an auxiliary fuel supply in fluid communication with said burner such that said auxiliary fuel supply provides auxiliary fuel to said burner burns the auxiliary fuel to produce additional combustion product steam.

36. The cryo-compression fuel cell generator as claimed in claim 35, wherein the auxiliary fuel is a non-carbon liquid fuel.

37. The cryo-compression fuel cell generator as claimed in claim 32, wherein said gas expander generator is in further fluid communication with said air pre-heater such that said gas expander generator provides the anode steam, the combustion product steam, and the oxygen depleted air to said air pre-heater.

38. The cryo-compression fuel cell generator with cryogenic compression and co-generation of liquefied fluid as claimed in claim 1, wherein load shifting via electrical communication occurs from said fuel cell generator to said liquefier compressor.

Description

DRAWING FIGURES

[0047] FIG. 1 is a schematic illustrating a combined fuel cell and gas expander prime mover with a liquid air heat sink and a steam-electric driven air liquefier.

[0048] FIG. 2 is a schematic illustrating a fuel cell prime mover with heat recovery, a liquid oxygen heat sink, and an electric-driven oxygen/air liquefier.

[0049] FIG. 3 is a schematic illustrating a combined fuel cell and gas expander prime mover with a liquid air heat sink, an all-electric driven air liquefier, and an auxiliary fuel supply.

[0050] FIG. 4 is a flow chart depicting the steps of the method of the present invention.

DETAILED DESCRIPTION

[0051] As a preface, it should be noted that all physical components are referred to with an even reference number and all fluid compounds that move amongst the physical components are referred to with an odd reference number. Components with heat exchange properties are depicted as bisected boxes, generally depicting hot and cold sides. It will be understood from the description that these components gain heat from one fluid and provide that heat to another fluid, where the fluids are not likely to mix. Lines indicating an electrical communication are included between relevant components and do not include reference numbers. This is as opposed to lines between components where an arrow is labeled with a reference number, which indicates a specific fluid and that fluid's direction. Finally, it is noted that when a specific model or distributor of a system component is included, this inclusion is merely exemplary and comparable components may be substituted. In addition, one of at least ordinary skill in the art will recognize that alternate fluids may be substituted.

[0052] Referring first to FIG. 1, a schematic illustrating a preferred embodiment of the present invention of a fuel cell/gas expander system 100 is provided. System 100 is the preferred version of the first embodiment, discussed above. System 100 includes combined electrical output in conjunction with steam-electric driven air liquefaction. A fuel cell generator 102 generates electricity by chemical reaction while additional electric output is generated from pressurized fuel cell exhaust at high temperature via a positive displacement gas expander generator 108, such as a piston engine.

[0053] System 100 includes a fuel cell generator 102 with an anode channel 104 and a cathode channel 106; a gas expander generator 108; a cryo-air supply 110; a fuel supply 112; an air pre-heater 114; a hydrogen burner 116; and a water-steam circuit 118. Gas expander generator 108 provides heat to water-steam circuit 118. Water-steam circuit 118 includes a superheater 120 with a heat storage unit 122; a hybrid expander electric compressor drive 124; a condenser 126; a water feed pump 128; a solar evaporator 130; and a feedwater heater 132. Cryo-air supply 110 includes a cryo-compressor 134; a cryo-recuperator 136; a liquefier compressor 138, with steam expansion and supplemental electric motor drive; an aftercooler 140; and an air liquefier 142 with a liquid air feed pump 144, a liquid air dewar 146, and a liquid air extraction valve 148.

[0054] Composition of the fuel cell working fluid varies through system 100 from atmospheric intake air 101 to exhaust 103. Circulation of air, fuel, and products of reaction is described, as follows. Intake air 101 is compression heated in compressor 138 and then cooled to ambient in aftercooler 140, which recovers heat to pre-heat cathode intake air 105, which is air that will be used as a reagent in cathode channel 106. As used herein, it is understood that “cathode intake air” is air that will be used as a reagent in cathode channel 106 and is labeled differently only to distinguish from air in different forms that may be present in other parts of the system of the present invention, such as atmospheric air 105, liquid air 109, surplus air 111, sub-ambient air 107, etc. Air 101 is further cooled to sub-ambient air 107 in cryo-recuperator 136. Sub-ambient air 107 enters air liquefier 142. Air liquefier 142 delivers liquid air 109 via liquid air feed pump 144 and an air vapor portion 157 of sub-ambient air 107 to cryo-compressor 134, while surplus air 111 discharges to atmosphere. Liquid air 109 also enters cryo-compressor 134. This combination emerges from cryo-compressor 134 as cathode intake air 105, which gains heat in cryo-recuperator 136 and then in aftercooler 140, while providing cooling of atmospheric air 101. Cathode intake air 105 continues from aftercooler 140, further increasing in temperature due, in turn, to transfer of heat in pre-heater 114 and fuel cell reaction in fuel cell generator 102.

[0055] In the fuel cell generator 102, negative oxygen ions 113, generated by reduction reaction with a ceramic cathode in cathode channel 106, pass through a solid state electrolyte 115, such as yttria stabilized zirconia. The electrolyte 115 is disposed between anode channel 104 and cathode channel 106, enabling the fuel cell generator 102 to operate with a combustible fuel, most commonly supply hydrogen 117 from fuel supply 112. Anode steam 119 and residual hydrogen 121 from anode channel 104 and oxygen depleted air 123 from cathode channel 106 then enter burner 116, producing an exhaust that includes combustion product steam 127, steam 119, and depleted air 123. This exhaust combination 119, 127, 123 expands through expander generator 108. Finally, heat of exhaust combination 119, 127, 123 is recovered, in turn, to circulating steam 125 in superheater 120 and to air 105 in pre-heater 114. Exhaust 103 discharges to atmosphere. Air 123 may be captured for further oxygen separation, as required.

[0056] In water-steam circuit 118, condensate 129 is circulated by feed pump 128 and heated, in turn, in feedwater heater 132, solar evaporator 130, and superheater 120. Steam 125, superheated above saturation, is then expanded to provide power from compressor drive 124 to liquefier compressor 138. Extraction steam 131 provides feedwater heating in heater 132. Steam 131 is also condensed into condensate 129 in condenser 126 by cooling water 133. Excess solar insolation is stored in heat storage unit 122, as required.

[0057] Innovative features of system 100 include feed of liquid air 109 into cryo-compressor 134; steam power to liquefier compressor-138 by recovered heat; and steady state fuel cell generator 102 output by load shift to compressor 138. Liquid air 109 in cryo-compressor 134 increases effectiveness of cryo-recuperator 136 by decreased terminal temperature difference, while providing least work quasi-isothermal compression of air 109, 157 in cryo-compressor 134. Steam to drive compressor 138 is generated, in turn, by evaporation in solar evaporator 130, and then superheating by recovered fuel cell exhaust heat in superheater 120. Shifting of fuel cell electric load to the air liquefier during reduced fuel cell electric demand maintains relatively constant fuel cell output to extend the fuel cell life via reduced thermal transients and associated stresses. Electric power to compressor 134 is from output of fuel cell generator 102 and expander generator 108. Supplemental electric power to compressor 134 may also be from external sources, as available and/or as needed.

[0058] The hydrogen fueled hybrid fuel cell/steam expander system exemplifies design point performance of a prime mover as shown in FIG. 1. Fuel consumption is reduced, as compared to a typical solid oxide fuel cell with heat recovery and ambient compression, due to combined effect of low cryo-compression work with heat recovery and solar evaporation. Based on 40% oxygen reacting with electrolyte and 10% unreacted residual hydrogen, the combined fuel cell and gas expander delivers 26.5 kWh/kg (12.0 kWh/lb) hydrogen with a fuel efficiency of about 80%. Operating conditions are: fuel cell pressure=10 atm. at discharge temperature=1000° C. (1832° F.), gas expander pressure ratio=10 at inlet temperature=1100° C. (2012° F.) with temperature increase due to combustion of residual hydrogen. Cryo-compressor inlet temperature is −173° C. (−280° F.). Cryo-compression reduces fuel cell compression work to about 8% of total generating capacity, as compared to 25% with ambient air at excess air ratio of 4.0. Baseline power to the liquefier compressor is from recovered heat of air expander exhaust, providing 100% liquid air for cryo-compression of working fluid in system 100. Supplemental power sources to the liquefier compressor are off-peak load shifting plus solar insolation and wind, as available. Highly variable liquid air production due to load shifting is estimated at one-third of system electric output, providing twice the liquid air for export as fuel cell baseline. Fuel consumption in motor vehicles using the export liquid air is estimated at five times higher than fuel consumption to maintain steady state fuel cell electric output. Estimated liquid air production due to solar generated steam and wind drive of the liquefier is potentially more than double as with load shifting, depending on location, collection area, tracking, and conversion efficiency.

[0059] FIG. 2 is a schematic illustrating an alternate preferred embodiment of the present invention of a fuel cell/steam expander system 200. System 200 is the preferred version of the second embodiment, discussed above. The fuel cell generator 202 generates electricity by chemical reaction. Additional electric output is generated from recovered heat of pressurized oxygen depleted air 223 discharging from cathode channel 206 at high temperature via a steam turbine generator 260. Combined electric output drives liquefaction of oxygen and air for fuel cell reaction and for export, respectively.

[0060] System 200 includes a fuel cell generator 202 with an anode channel 204 and a cathode channel 206; a cathode exhaust circulator 250 with an anode exhaust drive 252; a fuel supply 212; an air pre-heater 214; a residual hydrogen separator 254; and an oxygen mixing junction 256. System 200 also includes the following sub-systems: a cryo-oxygen/air supply 258 and a water-steam circuit 218. Cathode channel 206 provides exhaust heat to water steam circuit 218 via exchange of heat in superheater 220 following pressure drop in circulator 250. A circulator is used instead of a compressor to recirculate air back to the cathode with minimal pressure loss. Water-steam circuit 218 includes a superheater 220; a steam turbine generator 260; a condenser 226; a water feed pump 228; a solar evaporator 230; and a feedwater heater 232. Cryo-oxygen/air supply 258 includes a liquefier motor compressor 262; an aftercooler 240; an oxygen/air liquefier 264 with a liquid oxygen feed pump 266; a liquid air dewar 246; a liquid air extraction valve 248; and an external oxygen valve 268.

[0061] Composition of the fuel cell working fluid varies through system 200 downstream of atmospheric intake air 201 and supplied fuel 217. Hydrogen 217, recirculated residual hydrogen 221, and cathode intake air 205 enter fuel cell generator 202, while oxygen depleted air 223 is recirculated and anode product condensate 235 is discharged to atmosphere.

[0062] Atmospheric intake air 201 is compression heated in motor compressor 262 and then cooled to ambient in aftercooler 240, which recovers heat to evaporate liquid oxygen 237 to oxygen vapor 239. Then in oxygen/air liquefier 264, atmospheric air 201 is separated into liquid oxygen 237 that will be delivered to fuel cell generator 202 and liquid air 209 that will be stored in liquid air dewar 246 before export. Any surplus air 211 portion is discharged to atmosphere.

[0063] Oxygen 241 from an external source may be added via valve 268 and pumped into cryo-oxygen/air supply 258 through feed pump 266. Product liquid air 209 is stored for export in dewar 246 under control of valve 248. Liquid oxygen 237 from feed pump 266 is first evaporated in aftercooler 240. The evaporated oxygen 239 is then combined with oxygen depleted air 223 in mixing junction 256. This mixing forms cathode intake air 205, which is preheated by anode steam 219 and residual hydrogen 221 in pre-heater 214, before entering cathode channel 206.

[0064] In the fuel cell generator 202, negative oxygen ions 213, generated by reduction reaction with a ceramic cathode, pass through a solid state electrolyte 215, such as yttria stabilized zirconia. The electrolyte 215 is disposed between anode channel 204 and cathode channel 206, enabling the fuel cell generator 202 to operate with a combustible fuel, which is most commonly supply hydrogen 217. Finally, oxygen depleted air 223 discharging from cathode channel 206 is circulated, in turn, through superheater 220, mixing junction 256, and pre-heater 214 by circulator 250. Anode steam 219 and residual hydrogen 221 from air pre-heater 214 are provided to anode exhaust drive 252 and then to fuel separator 254. Anode exhaust drive 252 is driven by anode steam 219 and residual hydrogen fuel 221 from air-pre-heater 214. Anode exhaust drive 252 and cathode exhaust circulator 250 are in mechanical communication, so that anode steam 219 and residual hydrogen fuel 221 also indirectly drive cathode exhaust circulator 250. Anode exhaust drive 252 is in electrical communication with fuel cell generator 202, which provides electricity to anode exhaust drive 252. Fuel separator 254 is preferably a hydrogen separator that separates anode steam 219 from the residual hydrogen fuel 221. The anode steam 219 is expelled in the form of anode condensate 235 and the separated hydrogen fuel 221 is provided back to the hydrogen fuel supply 212.

[0065] In water-steam circuit 218, condensate 229, from feed pump 228, is heated in turn, in feedwater heater 232, solar evaporator 230, and superheater 220. Circulating steam 225, superheated above saturation, then expands to deliver electrical output from steam turbine generator 260. Extraction steam 231 from turbine generator 260 provides feedwater heating in heater 232 before combining with condensate 229 from condenser 226 to enter feed pump 228. Cooling water 233 provides condensation of steam 225 from turbine generator 260.

[0066] Innovative features of system 200 include recovery turbine 260 for minimal electric output within limited rotational speed; re-oxygenation of depleted air 223 while recirculating intake air 205; fuel cell heat recovery with solar evaporation; and shifting of fuel cell electric load to the liquefier motor compressor 262 during reduced fuel cell electric demand to maintain relatively constant fuel cell output to extend fuel cell life via reduced thermal transients and associated stresses.

[0067] The hydrogen fueled fuel cell/steam expander system exemplifies design point performance of a prime mover as shown in FIG. 2, capable of efficient fuel cell heat recovery as low as 2 kWe. Fuel consumption is reduced, as compared to a typical solid oxide fuel cell with heat recovery and ambient compression, due to combined effect of minimal compression work, heat recovery and solar evaporation. Exhaust recirculation is enabled by operation at minimal fuel cell inlet temperature of 350° C. (662° F). The combined fuel cell (3.0 kWe) and steam turbine (1.5 kWe) delivers 24.3 kWh/kg (11.0 kWh/lb) hydrogen with a fuel efficiency of about 75%, based on 40% oxygen reacting with electrolyte and 10% recycled residual hydrogen. Operating conditions are: fuel cell pressure=10 atm. at fuel cell discharge temperature=700° C. (1292° F.), and steam turbine pressure ratio to vacuum=50 at turbine inlet temperature=680° C. (1250° F.). Cryo-compressor inlet temperature is −173° C. (−280° F.). Fuel cell compression work is minimal because oxygen is compressed in the liquid state and recirculated air must only overcome flow resistance of recirculation at pressure. Supplemental power sources to the liquefier compressor are generated by solar insolation and wind, as available.

[0068] FIG. 3 is a schematic illustrating a further alternate preferred embodiment of the present invention of a fuel cell/gas expander system 300, in exemplary motor vehicle application. System 300 is the preferred version of the third embodiment, discussed above. Electrical output from a fuel cell generator 302 and a gas expander generator 308 provide electric drive of a vehicle. Load shifting from fuel cell generator 302 powers electric driven air liquefaction, which is supplemented by electric generation of recovered vehicle motion. The fuel cell generates electricity by chemical reaction while additional electric output is generated from pressurized fuel cell exhaust at high temperature via positive displacement expander generator 308, such as a piston engine.

[0069] System 300, includes fuel cell generator 302 with an anode channel 304 and a cathode channel 306; gas expander generator 308; a cryo-air supply 310; a primary fuel supply 312; an air pre-heater 314; a residual hydrogen burner 316; an auxiliary fuel supply 368; and an auxiliary fuel pump 370. Cryo-air supply 310 includes a cryo-compressor 334; a cryo-recuperator 336; a liquefier compressor 372 with a vehicle deceleration recovery generator 374; an aftercooler 340; and an air liquefier 342 with a liquid air feed pump 344, a liquid air dewar 346, and a liquid air extraction valve 348.

[0070] Composition of the fuel cell working fluid varies through system 300 from atmospheric intake air 301 to exhaust 303. Circulation of air, fuel, and products of reaction is described, as follows. Intake air 301 is compression heated in compressor 372 and then cooled to ambient in aftercooler 340, which recovers heat to pre-heat cathode intake air 305. Air 301 is further cooled to sub-ambient air 307 in cryo-recuperator 336. Sub-ambient air 307 enters air liquefier 342. Air liquefier 342 delivers liquid air 309 via liquid air feed pump 344 and an air vapor portion 357 of sub-ambient air 307 to cryo-compressor 334. Surplus air 311 discharges to atmosphere. Liquid air 309 also enters cryo-compressor 334. This combination emerges as cathode intake air 305, which gains heat in cryo-recuperator 336 and then in aftercooler 340, while providing cooling of intake air 301. Air 305 continues from aftercooler 340, further increasing in temperature due, in turn, to transfer of heat in pre-heater 314 and fuel cell reaction in fuel cell generator 302.

[0071] In the fuel cell, negative oxygen ions 313, generated by reduction reaction with a ceramic cathode, pass through a solid state electrolyte 315, such as yttria stabilized zirconia. The electrolyte 315 is disposed between anode channel 304 and cathode channel 306, enabling the fuel cell generator 302 to operate with a combustible fuel, such as supply hydrogen 317. Anode steam 319 and residual hydrogen 321 from anode channel 304 and oxygen depleted air 323 from cathode channel 306 then combine in burner 316 with auxiliary fuel 355 from auxiliary fuel supply 368 via auxiliary fuel pump 370. Auxiliary fuel 355 is preferably a carbon free fuel, such as hydrogen peroxide or ammonia. Exhaust, including combustion product steam 327, steam 319, and depleted air 323 from burner 316, expands through expander-generator 308. Heat of exhaust combination 319, 323, 327 is recovered to air 305 in pre-heater 314 as exhaust 303 discharges to atmosphere.

[0072] Innovative features of system 300 include feed of liquid air 309 into cryo-compressor 334; electric drive of liquefier compressor 372 by load shift of fuel cell generator 302 plus recovered energy of vehicle motion; and provision of auxiliary fuel 355. Liquid air 309 in cryo-compressor 334 increases effectiveness of cryo-recuperator 336 by decreased terminal temperature difference, while providing least work quasi-isothermal compression of air 309, 357 in cryo-compressor 334. Shifting of fuel cell electric load to the liquefier motor compressor 372 during reduced fuel cell electric demand maintains relatively constant fuel cell output to extend fuel cell life via reduced thermal transients and associated stresses. Supplemental electric power to compressor 372 is from output of fuel cell generator 302 and expander-generator 308, shown in arrowed lines between these components. Auxiliary fuel 355 is provided to minimize required hydrogen storage volume with a non-carbon liquid fuel.

[0073] The hydrogen fueled hybrid fuel cell/gas expander system exemplifies design point performance of a prime mover as shown in FIG. 3. Fuel consumption is reduced, as compared to a typical solid oxide fuel cell with heat recovery and ambient compression, due to the effect of low cryo-compression work with heat recovery. Based on 40% oxygen reacting with electrolyte and 10% unreacted residual hydrogen, the combined fuel cell and gas expander delivers 26.5 kWh/kg (12.0 kWh/lb) hydrogen with a fuel efficiency of about 65%. Operating conditions are: fuel cell pressure=10 atm. at discharge temperature=700° C. (1292° F.), gas expander pressure ratio=10 at inlet temperature=750° C. (1382° F.) with temperature increase due to combustion of residual hydrogen and auxiliary fuel. The auxiliary fuel is preferably carbon free, such as ammonia, hydrazine, or hydrogen peroxide to avoid discharge of carbon dioxide to atmosphere. Cryo-compressor inlet temperature is −173° C. (−280° F.). Cryo-compression reduces fuel cell compression work to about 10% of total generating capacity, as compared to 25% with ambient air at excess air ratio of 2.5. Baseline power to the liquefier compressor is from load shifting during vehicle coasting with supplemental power from energy of recovered vehicle motion, providing 100% liquid air for cryo-compression of working fluid in system 300. Highly variable liquid air production due to load shifting vehicle deceleration recovery is estimated at one-half of system electric output, providing twice the liquid air for export as fuel cell baseline. Fuel consumption in motor vehicles using the export liquid air is estimated at 5 times higher than fuel consumption to maintain steady state fuel cell electric output

[0074] A solid oxide fuel cell for hybrid arrangement with expansion engines is available from Mitsubishi Hitachi Power Systems of Yokahama, Japan. Several major motor vehicle manufacturers have advanced development programs for fuel cell expander hybrids. Several types of positive displacement expanders, and expansion cooled air liquefiers and solar heaters are commercially available in a wide range of sizes. Other components, including heat exchangers (superheaters, aftercoolers), valves, compressors, and turbines are available “off the shelf” to meet the full range of size requirements.

[0075] Now referring to FIG. 4, steps of method 400 for operating a fuel cell system with co-generation means of the present invention are provided. Method 400 includes the steps of maintaining constant electricity generation in a fuel cell for an application requiring electricity 402; determining a time of reduced demand for the electricity generated in the generating step 404; providing excess generated electricity during the time of reduced demand to a fluid liquefier 406; and producing liquid fluid 408. The providing step may be providing excess generated electricity during the time of reduced demand to an air liquefier 410 or providing excess generated electricity during the time of reduced demand to an air/oxygen liquefier 412. Providing step 410 results in producing liquid air 414. Providing step 412 results in producing liquid air/oxygen 416.

[0076] Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the description should not be limited to the description of the preferred versions contained herein.