SUMMER AND WINTER MODE OPERATION OF FUEL CELL STACKS

A fuel cell subject to intermittent use may be operated in two distinct modes, a "summer" or a "winter" mode, depending on whether the cell is expected to be stored at below freezing temperatures or not. At steady state in summer mode, much of the cell interior may be fully saturated with water and thus may contain liquid water. While such conditions may be most desirable for performance reasons during operation, the presence of liquid water however may be detrimental when storing at below freezing temperatures. At steady state in winter mode, the cell interior is essentially sub-saturated throughout and liquid water is not present to form ice during storage. Winter mode operation allows for improved performance during startup, especially in automotive solid polymer electrolyte fuel cell stacks.