Conceptual design and modelling of an industrial scale power to gas-oxy-combustion power plant

The intermittent nature of renewable energy sources is a key challenge to their integration into the electricity grid. The aim of this paper is to introduce an advanced concept of Power-to-Gas (PtG) plant, which is designed to bring a closed-loop solution able to absorb electricity surplus and to restore it later, via the transient storage of energy carriers. After a brief conceptual overview of the studied unit and its individual components, the paper introduces the key results of the steady state model used to assess process flowsheets as well as operating conditions of the industrial scale unit. These results indicate that during the storage phase, a 200 MW power supply to the electrolysis process leads to a corresponding 155 MW of Synthetic Natural Gas (SNG) produced in a thermally integrated methanation process with an efficiency of 83.1%. By producing and storing enough amount of SNG and oxygen, an Oxy-combustion power plant can be subsequently used to recover up to 480 MW electric power as well as to produce CO2 rich gas with an overall efficiency of 51.8%. Lastly, a thorough sensitivity analysis was conducted to show that the Electrolysis-Methanation-Oxy-combustion (EMO) unit performance can be further improved by adjusting key design parameters accordingly.