Investigating experimentally the performances of a natural gas reciprocating compressor adapted to pure hydrogen up to 30 MPa

Hydrogen as an energy carrier can be integrated into various value chains, enabling the decarbonization of hard-to-abate processes. Hydrogen storage is necessary to handle the intermittency of renewables. Moreover, it allows hydrogen to be deployed in sectors such as mobility and backup power. Currently, high-pressure vessels are typically used for hydrogen storage. The compression process is required since hydrogen production occurs at lower pressure than storage. This study examines a three-stage reciprocating compressor for natural gas, which is operated with pure hydrogen. The compressor, driven by a 3-kW electric motor, can deliver 30 MPa starting from pressures between 0.3 and 0.8 MPa. The aim is to assess the energy impact of compression on hydrogen production and analyze potential issues such as leakages or contamination that can arise after changing the fluid. The study involves measuring hydrogen flow rates, inlet and outlet pressures, and electric power consumption during the filling of a vessel. The experiment shows a specific power input of 1.2 kW/(Nm3/h), more than 1/3 of the lower heating value, maximum isothermal efficiency of 21% and maximum isentropic efficiency of 34%. The optimal compression ratio is found to be between 25 and 30. Based on the few data available in literature, the performances do not reach state-of-art levels of 55-80% isentropic efficiency. However, the device was optimized for the compression of natural gas, and the scope of this study was to use it with fewer possible modifications.