초록 ▼

A fuel cell system has: a fuel cell having a first reactant inlet, a first reactant outlet, a second reactant inlet, a second reactant outlet, and optionally a coolant inlet and coolant outlet. A first reactant supply subsystem supplies a first reactant incoming stream to the first reactant inlet of

A fuel cell system has: a fuel cell having a first reactant inlet, a first reactant outlet, a second reactant inlet, a second reactant outlet, and optionally a coolant inlet and coolant outlet. A first reactant supply subsystem supplies a first reactant incoming stream to the first reactant inlet of the fuel cell. A second reactant supply subsystem supplies a second reactant incoming stream to the second reactant inlet of the fuel cell. A first reactant recirculation subsystem recirculates at least a portion of the first reactant exhaust stream from the first reactant outlet to an enthalpy shifting subsystem in which one portion of the heat and moisture in first reactant exhaust stream is transferred to one of the first reactant incoming stream in the first reactant supply subsystem and the second reactant incoming stream in the second reactant supply subsystem. Another portion of the heat and moisture is transferred to the other stream. A method of controlling reactant and water in a fuel cell system is also disclosed.

대표청구항 ▼

What is claimed is: 1. A fuel cell system comprising: (a) a fuel cell having a first reactant inlet, a first reactant outlet, a second reactant inlet, a second reactant outlet, a coolant inlet and coolant outlet; (b) a first reactant supply subsystem for supplying a first reactant incoming stream t

What is claimed is: 1. A fuel cell system comprising: (a) a fuel cell having a first reactant inlet, a first reactant outlet, a second reactant inlet, a second reactant outlet, a coolant inlet and coolant outlet; (b) a first reactant supply subsystem for supplying a first reactant incoming stream to the first reactant inlet of the fuel cell; (c) a second reactant supply subsystem for supplying a second reactant incoming stream to the second reactant inlet of the fuel cell; (d) an enthalpy shifting subsystem comprising a first enthalpy shifting device that comprises an integral unit for both extracting at least a portion of the heat and moisture from the first reactant exhaust stream and transferring heat and moisture to the first reactant incoming stream in the first reactant supply subsystem, and a second enthalpy shifting device that comprises an integral unit for both extracting at least a portion of the heat and moisture from the first reactant exhaust stream and transferring heat and moisture to the second reactant incoming stream in the second reactant supply subsystem; (e) a first reactant circulation subsystem for circulating at least a portion of a first reactant exhaust stream from the first reactant outlet through the enthalpy shifting subsystem for transfer of heat and moisture from the first reactant exhaust stream to the first reactant incoming stream in the first reactant supply subsystem and the second reactant incoming stream in the second reactant supply subsystem; wherein the first and second enthalpy shifting devices are connected in the series in the enthalpy shifting subsystem, such that the heat and moisture from the first reactant exhaust stream is first transferred to the second reactant incoming stream through the second enthalpy shifting device and then to the first reactant incoming stream through the first enthalpy shifting device, and wherein the enthalpy shifting system further comprises a bypass line that bypasses the second enthalpy shifting device so that a portion of the first reactant exhaust stream in the first reactant circulation subsystem flows to the first enthalpy shifting device without passing through the second enthalpy shifting device. 2. A fuel cell system as claimed in claim 1, further comprising a second reactant recirculation system for recirculating at least a portion of a second reactant exhaust stream from the second reactant outlet to the second reactant supply subsystem, whereby the at least a portion of the second reactant exhaust stream mixes with the second reactant incoming stream. 3. A fuel cell system as claimed in claim 2, wherein the second reactant supply subsystem comprises a flow regulating means for regulating the flow rate of the second reactant incoming stream supplied to the second reactant inlet of the fuel cell. 4. A fuel cell system as claimed in claim 3, wherein the flow regulating means is at least one forward pressure regulator. 5. A fuel cell system as clamed in claim 4, wherein the flow regulating means comprises a plurality of forward pressure regulators, each having a different set point. 6. A fuel cell system as claimed in claim 3, wherein a draining means is provided in the first reactant circulation subsystem adjacent the first reactant outlet to drain at least a portion of the water of the first reactant circulation subsystem. 7. A fuel cell system as claimed in claim 6, wherein the draining means comprises a suitably sized drain line so that water is automatically and regularly drained along the drain line. 8. A fuel cell system as claimed in claim 3, wherein the second reactant supply subsystem comprises a second reactant water separator to separate at least a portion of the water in the second reactant incoming stream after the second reactant incoming stream passes through the second enthalpy shifting device. 9. A fuel cell system as claimed in claim 8, wherein the second reactant water separator is positioned in the second reactant supply subsystem so that it separates water out of the mixture of the at least a portion of the second reactant exhaust stream from the second reactant recirculation subsystem and the second reactant incoming stream. 10. A fuel cell system as claimed in claim 9, wherein the first reactant supply subsystem comprises a first reactant water separator to separate at least a portion of the water in the first reactant incoming stream after the first reactant incoming stream passes through the first enthalpy shifting device. 11. A fuel cell system as claimed in claim 10, further comprising a second reactant purge subsystem that purges at least a portion of the second reactant exhaust stream from the second reactant outlet. 12. A fuel cell system as claimed in claim 11, wherein the second reactant purge subsystem comprises a purge control means for controlling the purge of the at least a portion of the second reactant exhaust stream. 13. A fuel cell system as claimed in claim 12, wherein the purge control means is selected from the group consisting of: a solenoid valve, a proportional solenoid valve and a venturi. 14. A fuel cell system as claimed in claim 13, wherein the enthalpy shifting subsystem has an outlet for discharging the first reactant exhaust stream after the first reactant exhaust stream passes therethrough, and the fuel cell system further comprises a discharge subsystem for mixing the first reactant exhaust from the outlet of the enthalpy shifting subsystem with the second reactant exhaust stream from the second reactant purge subsystem and discharging the mixture. 15. A fuel cell system as claimed in claim 14, wherein the discharge subsystem comprises an exhaust water separator that separates water out of the mixture. 16. A fuel cell system as claimed in claim 15, further comprises a first cooling loop having a coolant tank, coolant is directed from the coolant tank to flow through the fuel cell and return to the coolant tank. 17. A fuel cell system as claimed in claim 16, further comprises a second cooling loop and a first heat exchanger is disposed between the first and second cooling loops to effect heat exchange in non-mixing manner between the coolants in the first and second cooling loops. 18. A fuel cell system as claimed in claim 17, wherein the second cooling loop is an open loop in which coolant is drawn from and returned to a coolant reservoir. 19. A fuel cell system as claimed in claim 16 or 17, wherein water separated from the first reactant water separator, the second reactant water separator and the exhaust water separator is directed to the coolant tank. 20. A fuel cell system as claimed in claim 16, wherein the first reactant supplying subsystem further comprises, upstream of the enthalpy shifting means, a compressing means for compressing and supplying the first reactant to the first reactant inlet of the fuel cell and a second heat exchanger, and wherein the fuel cell system further comprises a third cooling loop that runs through the compressing means and the second heat exchanger to cool the compressing means and the pressurized first reactant stream. 21. A fuel cell system as claimed in claim 2, 3, 8, 11, 14 or 16, wherein the second reactant recirculation system comprises a variable speed pump for recirculating at least a portion of the second reactant exhaust stream in variable flow rate from the second reactant outlet to the second reactant supply subsystem. 22. A method of controlling the reactants and water in a fuel cell system, the fuel cell having a first reactant inlet, a first reactant outlet, a second reactant inlet, a second reactant outlet, said method comprises: (a) providing a first reactant incoming stream to the first reactant inlet; (b) providing a second reactant incoming stream to the second reactant inlet; (c) circulating at least a portion of a first reactant exhaust stream from the first reactant outlet through first and second enthalpy shifting devices, each of the first and second enthalpy shifting devices comprising an integral unit; (d) in the first enthalpy shifting device, extracting at least a portion of the heat and moisture in the first reactant exhaust stream and transferring heat and moisture to the first reactant incoming stream and, in the second enthalpy shifting device, extracting another portion of the heat and moisture in the first reactant exhaust stream and transferring heat and moisture to the second reactant incoming stream; wherein step (d) comprises transferring said one portion of the heat and moisture of the first reactant exhaust stream first to the second reactant incoming stream and subsequently transferring said other portion of the heat and moisture of the first reactant exhaust stream to the first reactant incoming stream; and wherein at least a portion of the first reactant exhaust flows through a bypass line around the second enthalpy shifting device and to the first enthalpy shifting device. 23. A method as claimed in claim 22, further comprises: (e) collecting at least a portion of a second reactant exhaust stream from the second reactant outlet; (f) mixing the at least a portion of the second reactant exhaust stream with the second reactant incoming stream. 24. A method as claimed in claim 23, wherein step (b) includes regulating the flow of the second reactant incoming stream to provide dynamic supply of the second reactant incoming stream in response to the demand from the fuel cell. 25. A method as claimed in claim 24, wherein step (f) further comprises: separating water from the mixture of the at least a portion of the second reactant exhaust stream and the second reactant incoming stream. 26. A method as claimed in claim 25, wherein step (d) further comprises separating water from the first reactant incoming stream. 27. A method as claimed in claim 26, wherein step (e) further comprises purging at least a portion of the second reactant exhaust stream from the second reactant outlet. 28. A method as claimed in claim 27, further comprises; (g) mixing the first reactant exhaust stream after said one portion and said other portion thereof have transferred heat and moisture to both the first reactant incoming stream and the second reactant incoming stream, with the purged second reactant exhaust stream; (h) discharging the mixture. 29. A method as claimed in claim 28, wherein step (g) further comprises: separating water from the mixture. 30. A method as claimed in claim 29, further comprises: cooling the fuel cell stack with a coolant running through a coolant loop. 31. A method as claimed in claim 30, wherein step (a) includes compressing the first reactant incoming stream. 32. A method as claimed in claim 31, wherein step (a) further comprises: cooling the pressurized first reactant incoming stream. 33. A method as claimed in claim 23, 24, 27, 28 or 30, wherein step (e) comprises recirculating at least a portion of the second reactant exhaust stream in variable flow rate from the second reactant outlet.