Patent ID: 8195407

Claim:
A method for estimating the hydrogen and/or nitrogen concentration in a fuel cell system during shut-down, start-up, or any transitional state, which can be used for scheduling hydrogen and air flows to meet emissions, durability and efficiency requirements, said fuel cell system including a fuel cell stack, anode plumbing, cathode plumbing and cathode stack headers, said fuel cell stack including an anode flow-field and a cathode flow-field, said method comprising: defining the fuel cell system as discrete volumes including an anode flow-field and anode plumbing volume, a cathode flow-field volume and a cathode header and plumbing volume; estimating, in a controller, the amount of hydrogen and nitrogen in the anode flow-field and anode plumbing volume, the cathode flow-field volume and the cathode header and plumbing volume when the fuel cell system is shut down; estimating the amount of hydrogen and nitrogen in the anode flow-field and anode plumbing volume, the amount of hydrogen in the cathode flow-field volume and the amount of hydrogen in the cathode header and plumbing volume at system start-up that is based on the estimation of hydrogen and nitrogen in the anode flow-field and anode plumbing volume, the cathode flow-field volume and the cathode header and plumbing volume at system shut-down during a first stage at system start-up when the pressure between the anode flow-field and the cathode flow-field are not in equilibrium; and estimating the amount of hydrogen in the anode flow-field and plumbing volume and the cathode flow-field volume based on the estimation of the hydrogen and nitrogen in the anode flow-field and plumbing volume, the cathode flow-field volume and the cathode header and plumbing volume in the first stage during a second stage at system start-up after the anode flow-field and the cathode flow-field have equilibrated partial pressures of hydrogen and nitrogen.