Dynamic response of the direct methanol fuel cell under variable load conditions

The transient response of the direct methanol fuel cell (DMFC) is of paramount importance when it is used for transportation applications. With the aid of a computer-controlled load unit we have applied a variety of loading cycles on a small-scale single DMFC in order to evaluate the effect of the loading pattern and operating conditions on the cellʹs response time and performance. The cell responds rapidly, and reversibly, to changes in magnitude and rate of change of load. Under dynamic operation the cell voltage response can be significantly better than that achieved under steady state operation. Open circuit potentials are also increased, by up to 100 mV, by imposing a dynamic loading strategy. This improvement, accredited, in part, to a reduction in the effect of methanol crossover, is potentially attractive in vehicle applications where higher power density and fuel efficiency can be realised.