Thermally Driven Metal Hydride Hydrogen Compressor for Medium-Scale Applications

A promising method of hydrogen compression driven by low-grade heat and not requiring the usage of moving parts, is the application of metal hydrides (MH). However, being upscaled to higher productivities necessary for industrial processes (≥1 m3 H2/h STP), the method will inevitably meet a number of problems related to complication of system layout, high costs and significant labour resources for the manufacturing, and low thermal efficiency.This work presents a development of a prototype MH compressor operating in a temperature range 20 to 150°C and providing compression of hydrogen from 10 to 200 bar with average productivity up to 1 m3/h. The compressorrealises two stage layout where the first stage uses AB5-and the second AB2-type hydride-forming intermetallic alloys. A special engineering solution allows for the usage of quite big MH containers (up to 15 kg of the MH material, or ∼2 m3 STP H2 capacity), so that the required productivity is provided by just four containers assembled in two compression elements each of which comprises one first- and one second-stage MH containers. The compressor's layout also provides heat regeneration thus reducing the consumption of hot and cold heat transfer fluids and increasing the overall efficiency.