Heat pump integration for waste heat recovery from a 20 MW_e green hydrogen plant to increase global efficiency

This paper is focused on the technical and economic analysis of waste heat availability in a 20 MW_e green hydrogen (H₂) production plant, considering not only waste heat from the polymer electrolyte membrane (PEM) electrolyser cooling circuit, but also from hydrogen and oxygen compression stages. The main objective is to study the behavior of this waste heat along 10 years, until electrolyser End of Life (EoL), representing a maximum of 37.4 % of the total energy consumed by the plant, at an average temperature of 56.5 °C. On the other hand, waste heat upgrade is assessed as a key factor to increase global plant efficiency and so, a strong source to reduce current hydrogen price. In this case, hot water generation through heat pump technology for a 90 °C district heating network is analyzed to define equivalent CO₂ emission removal and economic savings, which make the investment technical and economically feasible. At electrolyser EoL, global plant efficiency increases from a present value of 56.5 % up to 90.1 % if heat pump upgrading is considered.