Power-to-Gas through thermal integration of high-temperature steam electrolysis and carbon dioxide methanation - Experimental results

This article presents the experimental results of a novel Power-to-Gas (PtG) concept combining a pressurized high-temperature steam electrolysis (SOEC) and a CO2-methanation module in stand-alone and thermally integrated operation. For the electrolyser, steam conversion and energy demands at pressures up to 15 bar were examined. In terms of the methanation module, cooling performance, steam production and product gas quality were of main interest. Additionally, temperature profiles inside the fixed beds were gathered by a multipoint thermocouple at pressures up to 30 bar and load modulations from 20 to 100%. With less than 2 vol% H-2 and over 97 vol% CH4 in the finally produced synthetic natural gas (SNG), it can be directly injected into the existing German natural gas grid without further gas cleaning and without capacity limitations. The achieved overall PtG efficiency of 76% is significantly higher than state of the art plants and has the potential to reach 80% in industrial scale.