Abstract: A fuel cell is provided, which includes a first plenum around an anode for receiving fuel, and a second plenum around a cathode for receiving oxygen. A fluid controller controls the supply of fuel to the first plenum or oxygen to the second plenum. A sensor detects the load on the fuel cell, and a controller controls the fluid controller in response to the load detected by the sensor. A method for controlling the output of a fuel cell is also provided, which includes the step of providing a fuel cell having a reaction area with an effective area where reactions may occur. The demand on the fuel cell is detected and the effective area of the reaction area is varied in response to the demand. Alternatively, the fuel cell may have an internal resistance, and the method may include varying the internal resistance in response to the demand.