Method of operating a fuel cell/battery passive hybrid power supply

Abstract

The method of operating a passive hybrid power supply in, or near, zero connected load conditions comprises the steps of: supplying a stream of substantially pure hydrogen to the anode of the fuel cell; supplying an stream of substantially pure oxygen to the cathode of the fuel cell; monitoring an electric current supplied by the storage battery; monitoring an output voltage shared by the fuel cell and the battery; evaluating a state of charge (SOC) of the battery based on the electric current and the output voltage; monitoring a hydrogen pressure in the fuel cell; monitoring an oxygen pressure in the fuel cell; limiting the stream of hydrogen and the stream of oxygen and actuating the hydrogen and oxygen recirculating pumps in such a way as to bring and maintain the hydrogen and oxygen pressures below 0.7 barabsolute while maintaining the hydrogen pressure between 70 and 130% of the oxygen pressure, in such a way as to ensure that the output voltage is maintained at a level corresponding to less than 0.90 volts / cell and does not exceed the maximum voltage limit of the battery.

Description

technical field [0001] The present invention relates to a method for limiting the output voltage of a fuel cell / battery passive hybrid power supply without having to stop the fuel cell or disconnect it from the battery The power supply operates at or near zero load conditions in such a way that neither exceeds the upper voltage limit of the battery. The invention relates more particularly to a method in which the fuel cell of the power source is of the type designed to use hydrogen as fuel and pure oxygen as oxidant. Background technique [0002] Electrochemical fuel cells of the type mentioned above convert reactants (ie, hydrogen and oxygen streams) into electricity and water. A proton exchange membrane fuel cell (PEMFC) typically includes a solid polymer electrolyte membrane disposed between two porous conductive electrode layers to form a membrane electrode assembly (MEA). To induce the desired electrochemical reaction, the anode electrode and the cathode electrode eac...

AI Technical Summary

Problems solved by technology

The first of these conditions is known as "high cell voltage"; subjecting a fuel cell to low or zero current conditions is known to result in a high degradation rate compared to operation at an average constant current

The second non-ideal condition is "low cell voltage"; peak current draw from fuel cells is also known to lead to increased degradation rates

However, start-stop cycling also results in degradation of fuel cell system performance, and disconnecting the fuel cell system without shutting it down requires the use of resistive loads to dissipate the energy produced by the battery pack

This results in a considerable waste of energy

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