Construction and Measurement of Thermochemical Pre-Heater based on Metal Hydrides for Fuel Cells in Vehicles

A proton exchange membrane fuel cell for automotive application is a most interesting technology for electric cars. It can generate electricity during driving but it has limitation of operating in winter time. It cannot run if at temperatures lower than freezing temperature of water. It causes a failure start up, which is a key factor for commercialisation. A heater is necessary to increase the temperature of the fuel cell to above 0 °C. A pre-heater using thermochemical conversion of the metal hydride LaNi4.85Al0.15 is developed. LaNi4.85Al0.15 is investigated under winter time conditions. The pre-heater is aimed to utilise the potential energy from hydrogen storage tank on board the vehicle to supply hydrogen to the pre-heater. The investigations were carried out at -20°C with variation pressure from 0.12 bar up to 4.2 bar. The results are LaNi4.85Al0.15 can produce thermal power up to 132 kW/kg of LaNi4.85Al0.15 at -20°C and 4.2 bar hydrogen supply pressure. The pre-heater is designed according to the fuel cell conditions and material characteristics to optimise heat transfer and integration to the fuel cell. The heat transfer optimisation preheater have advantage in good heat transfer surfaces and compact construction, while the integration pre-heater has advantage in versatile design and leakage protection