Review on thermal applications for metal hydrides in fuel cell vehicles: Operation modes, recent developments and crucial design aspects

Hydrogen compression for state-of-the-art hydrogen storage systems to pressures of 350 or 700 bar is obviously energy consuming and the resulting loss in efficiency is taken for granted. However, there exists the possibility to transform at least part of this energy into another form of energy leading to an improved overall efficiency. This can be realized by metal hydride devices acting as continuous or discontinuous converter of potential energy into thermal energy. One example is the increase of efficiency for a fuel cell driven vehicle, when part of the energy stored in the compressed hydrogen can contribute to the heating and air conditioning system. With a worldwide steadily growing hydrogen infrastructure, further applications for this type of innovative pressure converter can arise. Thus, the present manuscript summarizes recent developments in this field and gives detailed recommendations for further development of the technology with a focus on mobile applications as discontinuous preheating systems or continuous cooling devices