US 2004/0001980 A1Published application

System and method for shutting down a fuel cell power plant

AssigneeUTC Fuel Cells, LLC

InventorsRyan J. Balliet, Carl A. Reiser

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Abstract

The invention is a system and method for shutting down a fuel cell power plant having at least one fuel cell, a primary load, and an auxiliary load that receive electrical current from electrodes of the fuel cell through an external circuit. Shutting down the plant includes disconnecting the primary load; terminating flow of the oxidant through a cathode flow field; connecting the auxiliary load to consume oxygen within the fuel cell; disconnecting the auxiliary load; connecting a power supply to the fuel cell electrodes to increase a concentration of hydrogen within the cathode flow field; and, then, decreasing or eliminating flow of hydrogen into an anode flow field after an equilibrium gas concentration of at least 0.0001% hydrogen, balance fuel cell inert gases, is achieved in both the anode and cathode flow fields.

Claims14

Dependent claims

A system for shutting down a fuel cell power plant, the system comprising:

a. at least one fuel cell for generating electrical current from hydrogen containing reducing fluid and process oxidant reactant streams, the fuel cell including an anode electrode and a cathode electrode on opposed sides of an electrolyte, an anode flow field adjacent the anode electrode for directing the reducing fluid stream to flow adjacent to the anode electrode, and a cathode flow field adjacent the cathode electrode for directing the process oxidant stream to flow adjacent the cathode electrode;
b. an external circuit connected to the anode and cathode electrodes for conducting the electrical current generated by the fuel cell;
c. a primary load connected through a primary load switch to the external circuit;
d. an auxiliary load connected through an auxiliary load switch to the external circuit so that whenever the primary load switch disconnects the primary load from receiving current, the auxiliary load switch connects the auxiliary load to receive any electrical current from the fuel cell to thereby consume oxygen remaining within the fuel cell;
and,
e. a power supply connected through a power supply switch to the external circuit, so that whenever the primary load switch disconnects the primary load from receiving the electrical current, and the auxiliary load switch disconnects the auxiliary load from receiving electrical current from the fuel cell, the power supply switch connects the power supply to the external circuit to increase a concentration of hydrogen within the cathode flow field.

3 more elements

A method of shutting down a fuel cell power plant, the fuel cell power plant including at least one fuel cell for generating electrical current from hydrogen containing reducing fluid and process oxidant reactant streams, the fuel cell including an anode electrode and a cathode electrode on opposed sides of an electrolyte, wherein during operation of the fuel cell, the reducing fluid stream flows through an anode flow field adjacent the anode electrode, the process oxidant stream flows through a cathode flow field adjacent the cathode electrode, an external circuit connected to the anode and cathode electrodes conducts the electrical current generated by the fuel cell, and a primary load is connected through a primary load switch to the external circuit to receive the electrical current, the method of shutting down the fuel cell power plant comprising the steps of:

a. disconnecting the primary load switch so that the primary load ceases receiving the electrical current from the fuel cell;
b. terminating flow of the process oxidant through the cathode flow field;
c. connecting an auxiliary load to the external circuit to receive any electrical current from the fuel cell to thereby consume oxygen remaining within the fuel cell;
d. disconnecting the auxiliary load after oxygen remaining within the fuel cell has been consumed;
e. then, connecting a power supply through a power supply switch to the external circuit so that electrical current from the power supply flows through the external circuit to the anode and cathode electrodes to increase a concentration of hydrogen within the cathode flow field;
and,
f. then, disconnecting the power supply and decreasing or eliminating flow of the hydrogen containing reducing fluid into the anode flow field after an equilibrium gas concentration of at least 0.0001% hydrogen, balance fuel cell inert gases, is achieved in both the anode and cathode flow fields while the fuel cell power plant is shut down.

4 more elements

Dependencies are inferred from the claim text.