A self-sustaining renewable energy driven hydrogen refuelling system utilising a metal hydride-based compressor

Abstract

The transition towards carbon-free transportation is only possible by the adoption of renewable energy alternatives. Hydrogen-based transportation is an attractive option considering the availability of the required refuelling infrastructure. A well-established network of hydrogen refuelling infrastructure is important for the widespread commercialization of fuel-cell electric vehicles. The most expensive H2 refuelling components originate from hydrogen compression. Due to their ability to run on solar thermal energy, a metal hydride hydrogen compressor is used in this study. In this communication, the aim is to present a study on solar thermal based hydrogen compressors for a hydrogen refuelling station. An analytical study is presented on the energy assessment of a metal hydride compressor by considering three candidate pairs of metal hydrides (Pair 1: Ti0.95Zr0.05Cr0.8Mn0.8V0.2Ni0.2/Ti0.8Zr0.2Cr0.95Fe0.95V0.1; Pair 2: TiCr1.55Mn0.2Fe0.2/Ti0.9Zr0.1Mn1.4Cr0.35V0.2Fe0.05, Pair 3: La0.35Ce0.45Ca0.2Ni4.95Al0.05/Ti0.8Zr0.2Cr0.95Fe0.95V0.1) to achieve refuelling pressure of 700 bar. The variation in thermal efficiency of the compressor and thermal energy requirements with changes in heat source temperature, supply pressure and heat losses are presented. Furthermore, the economics of three pairs of alloys for high-pressure compression is compared. It was found that Ti0.95Zr0.05Cr0.8Mn0.8V0.2Ni0.2/Ti0.8Zr0.2Cr0.95Fe0.95V0.1 pair has the maximum compressor efficiency of 7.2% at supply pressure and heat source temperature of 25 bar and 150 °C, respectively. In addition, the study revealed that heat losses from the reactor could reduce efficiency by around 12.5%. The economic study revealed that the Ti0.95Zr0.05Cr0.8Mn0.8V0.2Ni0.2/Ti0.8Zr0.2Cr0.95Fe0.95V0.1 pair has the least cost for hydrogen compression among the other chosen pairs.