Patent ID: 9614236
Date: 2017-04-04
CPC Classifications: H01M,Y02E,Y02T

Claim:
1. A fuel cell system comprising: a fuel cell stack including an anode side and a cathode side; a compressor for providing an air flow to the cathode side of the fuel cell stack; a hydrogen source for providing hydrogen gas to the anode side of the fuel cell stack; a first switch for connecting power from the stack to a primary load; a second switch for connecting power from the stack to an auxiliary load; a third switch for connecting power from the stack to a shorting resistor that dissipates stack output power; a cross-over valve for providing the air flow from the compressor to the anode side of the stack; a re-circulation line for re-circulating cathode exhaust gas to the cathode side of the stack; a bleed valve for selectively bleeding hydrogen gas into the re-circulating line; and a controller programmed to control the system at start-up and shut-down, wherein the controller opens the first switch and closes the second switch to disconnect the first primary load and couple an output of the stack to the auxiliary load when the stack output voltage is reduced to a first predetermined range, re-circulates the cathode exhaust gas through the re-circulation line, bleeds a predetermined concentration of hydrogen gas into the re-circulation line, and uses the cross-over valve to purge the anode side of the stack with air at shut-down, and wherein the controller re-circulates the cathode exhaust gas through the re-circulation line, bleeds hydrogen gas into the re-circulation line until the stack voltage decreases to a second predetermined range and closes the third switch to short-circuit the stack at start-up.