PEM fuel cell current control by fuel starvation

The power output from a PEM fuel cell can be directly controlled by limiting the hydrogen feed to the fuel cell. The control is achieved by simple feedback control on the hydrogen and oxygen (or air) flows to a setpoint current. With pure dry feeds of hydrogen and oxygen 100% hydrogen utilization is achieved with 130% stoichiometric feed on the oxygen. When air was used for the oxygen, 100% hydrogen utilization with stoichiometric air feed was achieved. The control is attained by connecting the effluents to water reservoirs, where water flows in and out of the gas flow channels to create a variable internal resistance of the fuel cell. Control can only be achieved when the internal fuel cell resistance is approximately matched to the load impedance. This is an abstract of a paper presented at the AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).