Integrated power unit of 5 kW PEM and solid state hydrogen storage and purification system is created. To increase efficiency the chain of hydrogen purificator, hydrogen storage and fuel cell has to be consistent in operating temperatures and pressures. To avoid high energy losses for heating and cooling metal hydride units the LaNi5-based alloys with low operating temperatures (hydriding at 293 K and dehydriding at 353 K) are selected. These alloys are also characterized by high reaction enthalpy and long cycle life.
Fuel cell requires 4.5 6 atm hydrogen supply, thus desorption pressures of hydrogen storage materials have to be higher than 6 atm at 353 K along the whole desorption plateau. Also dehydriding enthalpy must be as high as possible to make absorption easier.
Alloy for hydrogen purification must have high hydrogen desorption pressure at 353 K to charge the hydrogen storage system and low absorption pressure to minimize hydrogen losses during purification process.
Preliminary compositions of intermetallic compounds were chosen by mathematical modeling, several alloys with suitable properties were synthesized and their properties including desorption isotherms were investigated. On the base of experimental data final compositions with optimized properties are created. La0.5Nd0.5Al0.1Fe0.4Co0.2Ni4.3-alloy is chosen for hydrogen storage system and LaFe0.1Mn0.3Ni4.8-alloy is chosen for hydrogen purification system.