Thermal coupling of PEM fuel cell and metal hydride hydrogen storage using heat pipes

This paper presents a mathematical model to study opportunities for simultaneous passive thermal management of an integrated PEM fuel cell and metal hydrogen (MH) storage system by thermal bridging of these two components, using heat pipes. The thermal coupling arrangement is expected to be promising, because, as more power is drawn from the PEMFC, more heat is generated that can be used to enhance the rate of release of hydrogen from the MH storage. Heat pipes can provide an effective passive thermal bridge for this purpose on account of their high thermal conductivity, and thus avoid parasitic energy penalties associated with active methods of cooling. The main components modelled analytically in MATLAB in this study are the PEMFC, heat pipes, and MH hydrogen storage. This simulation has been used to size the heat pipe system needed for thermal coupling of a 500 W PEMFC and MH storage canisters. The performance improvement of the MH system after receiving the fuel cell heat, and the cooling capacity of the MH system to be used as heat sink for thermal management of the fuel cell stack, has been studied. The MH canisters used to supply hydrogen to this stack each had the maximum supply capability of 2.5 slpm at 25 °C, while the fuel cell demand was 7.2 slpm at its rated power (500 W). The results show that just under 20% of the total cooling load of the stack (i.e. ∼880 W) at its maximum power point is demanded by the MH canisters (∼170 W) to achieve the required hydrogen discharge rate of 7.2 slpm at 35 °C provided the MH canisters are thermally well insulated.