Development of Double-Stage Metal Hydride-Based Hydrogen Compressor for Heat Transformer Application

For the development of a double-stage metal hydride-based heat transformer (DS-MHHT), three metal hydrides, namely, A, B, and C, with different thermo-physical properties are required. Hydrides A and B together act as a hydrogen compressor, and hydride C upgrades the heat input quality. In the present paper, the performance tests of a double-stage metal hydride-based hydrogen compressor (DS-MHHC) employed in the development of metal hydride-based heat transformer are presented. The metal hydrides chosen for the present study are LaNi5 and La0.35Ce0.45Ca0.2Ni4.95Al0.05. The effects of supply pressure and heat source (desorption) temperature on the delivery pressure, amount of hydrogen compressed, and isentropic efficiency of the hydrogen compressor were investigated. It is observed that an increase in supply pressure up to 10 bar significantly increases the delivery pressure, which reduces the compressor efficiency significantly. A maximum compression ratio of 22 was obtained when the DS-MHHC operated at 2 bar supply pressure and 140 degrees C heat source temperature. At supply conditions of 10 bar supply pressure and 140 degrees C heat source temperature, the maximum delivery pressure achieved was 74 bar. (C) 2014 American Society of Civil Engineers.