Nanostructured metal hydride – Polymer composite as fixed bed for sorption technologies. Advantages of an innovative combined approach by high-energy ball milling and extrusion techniques

Abstract

Different metal alloys can react highly exothermically and reversibly with hydrogen to form metal hydrides. Based on these reactions several application have been developed, e.g. in fuel cell, in storage for hydrogen gas and in sorption heat pumps. By exploiting the thermodynamical properties of some metal hydriding alloys, cooling energy can be generated by using renewable, sustainable and/or disposable energy sources. However, hydriding alloys show some limitations in their behaviour mainly regarding their intrinsic low thermal conductivity and mechanical stability during the hydriding process. A proper management of these issues is required in practical applications in particular when the metal hydrides have to be stably packed as fixed beds with good mechanical stability, high thermal conductivity, fast kinetics, reproducibility, durability.In this work a composite material containing a high metal fraction is obtained by an innovative bulk and low cost processing approach by combining high-energy ball milling and extrusion techniques. The methodology is presented and the characterization of a representative LaNi5-type based composite is given. The developed composites were used as fixed beds in the implementation of a Metal Hydride Cooling System. Finally, the system was integrated into a refrigerated transportation vehicle, currently under testing. Some results are reported coming from a preliminary test campaign.