Application of Proton Exchange Membrane Fuel Cell for Lift Trucks

In this study a general PEMFC (Proton Exchange Membrane Fuel Cell) model has been developed to take into account the effect of pressure losses, water crossovers, humidity aspects and voltage over potentials in the cells. The model is zero dimensional and it is assumed to be steady state. The effect of concentration loss is neglected while the effect of activation and ohmic losses is investigated in the system.

Some semi-empirical equations are required to predict the amount of exchange current density for calculation of ohmic loss and water diffusion coefficient through membrane. These equations are applied in order to account for water back diffusion. Further Membrane water content is assumed to be a linear function of thickness.

PEM fuel cell is working at rather low operating conditions which makes it suitable for the automotive systems. In this paper motive power part of a lift truck has been investigated thermodynamically. The system includes a compressor, an air humidifier, set of heat exchangers and a stack which together build up the anode circuit, the cathode circuit and the cooling loop.

Since fuel humidification is carried out via water cross over from cathode to anode, there is no humidifier in the anode side. The electricity needed for auxiliary components is produced by the stack. The system is set at different electrical powers. In this paper several issues are discussed; voltage losses, system efficiency as well as electrical power at different operating conditions.