Power plants – Motive fluid energized by externally applied heat – Process of power production or system operation
Reexamination Certificate
2000-01-06
2001-03-06
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Process of power production or system operation
C060S651000, C060S671000
Reexamination Certificate
active
06195999
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electrochemical engine particularly useful for a vehicle.
BACKGROUND OF THE INVENTION
As fuel cell power plants are being integrated into useable vehicles, developing efficient ways of supplying the fuel needed to operate the fuel cell stack becomes more critical. Hydrogen gas is the common fuel input to the stack and may be stored on-board in suitable tanks. While pure hydrogen gas is an efficient fuel, storing it on-board a vehicle has drawbacks related to packaging and mass.
As an alternative to storing pure hydrogen gas on-board a vehicle, other fuels such as gasoline or methanol may be stored on-board and processed through a reformer to convert the fuel to reformate comprising hydrogen, carbon dioxide, carbon monoxide, and water vapor. The reformate may be passed through a shift converter and gas purifiers to remove carbon monoxide before delivering the hydrogen to the fuel cell stack. This complete reformation process is not only complex to engineer, but consumes valuable packaging space and mass.
A further consideration in designing a vehicle powered by an electrochemical engine is how to manage the heat produced by the electrochemical reaction in the fuel cell stack. The stack may produce waste heat ranging in temperatures from 80° C. to 100° C. If a traditional thermal management system including a radiator is employed, the radiator will require significant surface area to meet the demands of the electrochemical engine and will be impractical for a commercial vehicle.
SUMMARY OF THE INVENTION
The present invention provides a commercially practical electrochemical engine (ECE) for use in a vehicle.
The electrochemical engine comprises a storage tank containing hydrogen-retention material which reversibly takes-up and stores hydrogen at a hydrogen-storage temperature and releases it as a gas upon heating to a release temperature. A fuel cell stack uses the released hydrogen gas to produce electricity and heat by-product. Heat by-product is transferred from the fuel cell stack to the storage tank via a primary coolant flow circuit that heats the hydrogen-retention material to release hydrogen for fueling the fuel cell stack. A bypass coolant flow line is also provided from the fuel cell stack to the radiator, bypassing the storage tank.
The electrochemical engine may also include a heat generator within a superheater coolant flow loop having a bypass valve intermediate the storage tank and the radiator and operable to isolate coolant within the superheater coolant flow loop and a pump to circulate coolant therethrough. Coolant in the superheater coolant flow loop is heated by the heat generator and circulated through the storage tank to further release hydrogen gas from the hydrogen-retention material.
In order to regenerate the hydrogen-retention material with hydrogen, the storage tank may need to be cooled. Therefore, the ECE provides the capability to circulate pre-refueling coolant from an external source, through the storage tank, thereby cooling the hydrogen-retention material to a temperature where it may take-up and store hydrogen.
Accordingly, the ECE of the present invention provides a more simple solution to managing the input fuel to the fuel cell stack in a less massive and space-intensive package than on-board reforming or storage of pure hydrogen. Further, once the fuel cell stack rises to its normal operating temperature, the process becomes self-sustaining as fuel cell by-product heat is used to release the hydrogen from its stored state. Since a portion of by-product heat is recycled in the engine operation, the thermal management system does not have to manage as much thermal energy.
REFERENCES:
patent: 4503682 (1985-03-01), Rosenblatt
patent: 4537031 (1985-08-01), Terry et al.
patent: 4739180 (1988-04-01), Yanoma et al.
patent: 4788824 (1988-12-01), Spurr et al.
patent: WO 93/22044 (1993-11-01), None
patent: WO 97/10969 (1997-03-01), None
Arnold Gerd
Bereisa Jonas
McIlwaine Steve
McManis James V.
O'Connell Daniel B.
General Motors Corporation
Hargitt Laura C.
Nguyen Hoang
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