Abstract: A fuel cell arrangement consisting of several fuel cells, arranged at least essentially in parallel, with cooling gaps formed between neighboring cells extending between an inlet and an outlet and through which a coolant flows, characterized by the fact that the specific surface, i.e. the area of the cooling surfaces emitting heat to the coolant, increases in the direction from the inlet to the outlet and/or that the local heat transfer coefficient of the cooling areas emitting heat to the coolant increases in the direction of flow from the inlet to the outlet and/or that the support materials of the fuel cells, i.e. the membrane-electrode assemblies, exhibit a coefficient of thermal conductivity above 200 W/(m·K). In this way, a uniform temperature in the fuel cells can be assured to that the power density can be increased while avoiding hot spots and/or the service life can be increased.

Abstract: A fuel cell system is described with a so-called direct methanol fuel cell (DMFC). To minimize the methanol crossover the concentration of the methanol/water mixture supplied to the anode of the fuel cell is made dependent on the magnitude of the electrical power takeoff. In order to be able to adapt the concentration of the methanol quickly in the case of a load change, it is proposed that a separating column be introduced into the anode cycle which reduces the concentration of the methanol. To achieve adapted increases in the concentration of methanol, both a concentrated methanol/water mixture from a secondary cycle and possibly additionally pure methanol from a tank are supplied. In the case of a reduction in the power demand only the secondary cycle needs to be blocked with the result that a lean mixture is available immediately.

Abstract: A fuel cell system is described with a so-called direct methanol fuel cell (DMFC). To minimize the methanol crossover the concentration of the methanol/water mixture supplied to the anode of the fuel cell is made dependent on the magnitude of the electrical power takeoff. In order to be able to adapt the concentration of the methanol quickly in the case of a load change, it is proposed that a separating column be introduced into the anode cycle which reduces the concentration of the methanol. To achieve adapted increases in the concentration of methanol, both a concentrated methanol/water mixture from a secondary cycle and possibly additionally pure methanol from a tank are supplied. In the case of a reduction in the power demand only the secondary cycle needs to be blocked with the result that a lean mixture is available immediately.

Abstract: A fuel cell system having two fuel cell stacks with different operating temperatures, i.e. a low temperature stack (LT stack) and a high temperature stack (HT stack). The high temperature stack is connected in front of the low temperature stack with respect to the process flow of fuel through the fuel cell system.

Abstract: A fuel cell arrangement consisting of several fuel cells, arranged at least essentially in parallel, with cooling gaps formed between neighboring cells extending between an inlet and an outlet and through which a coolant flows, characterized by the fact that the specific surface, i.e. the area of the cooling surfaces emitting heat to the coolant, increases in the direction from the inlet to the outlet and/or that the local heat transfer coefficient of the cooling areas emitting heat to the coolant increases in the direction of flow from the inlet to the outlet and/or that the support materials of the fuel cells, i.e. the membrane-electrode assemblies, exhibit a coefficient of thermal conductivity above 200 W/(m·K). In this way, a uniform temperature in the fuel cells can be assured to that the power density can be increased while avoiding hot spots and/or the service life can be increased.