Study of the Efficiency of a HT Power-to-Gas Process

Abstract

Power-to-Gas processes are investigated since they offer solutions for renewable energy storing and transportation. In the present study, an original Power-to-Substitute Natural Gas (SNG) process combining high-temperature steam electrolysis and CO2 methanation is designed and simulated. A specific modelling approach of the electrolysis based on experimental measurements is used, and a methanation modelling involving a kinetic law is also introduced. Both of these modelling are then integrated into the whole process simulation as well as a unit for residual CO2, H2 and H2O gas cleaning. Having set all the process units, simulation is performed for a reference case where the electrolyser and the methanation reactors are designed. This case allows to produce 2.7 Nm 3 SNG/h/m 2 SOEC with an electrical-to-HHV fuel efficiency equalling 74.5 %, whereas current low-electrolysis processes show an HHV efficiency near 60 %. The produced SNG meets the specifications required for network injection. A sensitivity analysis has been made around the working point conditions of the electrolyser and the methanation units. From this study, we observed that no parameter set allows to have higher values of both process efficiency and SNG production than in the reference case.