Power-to-gas (P2G) process: Basics

Abstract

The explicit tendency to increase the power generation from stochastic renewable resources forces us to look for technological solutions of energy management and storage. In the recent years, the concept of power-to-gas where the excess energy is converted into hydrogen and/or further methanized into renewable methane is gaining high popularity. The concept presented in this article suggests the conversion of CO2-containing gases into methane in a pressurized reactor using hydrogen produced via electrolysis. The reaction heat released by the exothermic methanation reaction leads to a temperature rise of the gas in reactors. Several different reactor concepts can be used for the methanation reaction. The conversion of carbon dioxide is limited in accordance to the chemical equilibrium which depends strongly on temperature and pressure. For maximum carbon dioxide conversion, it is convenient to split the methanation process into several stages adding cooling sections in between. Critical aspects of the P2G process are the availability of CO2 sources and especially economics as well as the efficiency. In opposite, advantages of the system are strategic benefits such as integrated management of electricity and gas networks. The concept brings the possibility of connecting the power grid to different sectors, where CH4 is needed such as mobility and industry.