Optimization of multi-carrier energy system based on new operation mechanism modelling of power-to-gas integrated with CO2-based electrothermal energy storage

Abstract

The rapid development of power-to-gas (P2G) technology promotes the integration of renewable energy and converts excess renewable generation to synthetic natural gas at the appropriate time. However, with only a 45% conversion rate, P2G recycles wind energy inefficiently because a significant percentage of energy is lost in the form of heat via electrolysis. With the increasing demands of the multi-carrier energy system (MES), the greater recycling of surplus wind electricity via P2G can meet the growing energy demand and reduce the cost of the system. To increase the conversion efficiency of P2G, this paper establishes an MES optimization model based on the coordinated operation modelling of P2G and CO2-based electrothermal energy storage (ETES). This model considers heat recovery in the power-to-hydrogen process. CO2-based ETES is introduced as a storage element for heat recovery in the electrolysis process, which also participates in the methanation reaction as a CO2 supplier. Formulations to explain the coordinated operation of the CO2-based ETES and P2G are derived as well. The optimization model is further linearized to a tractable version and solved by popular optimization solvers. Case studies show that the model established in this study achieves more than a 70.5% recovery efficiency of the excess wind power.