Evaluation of electricity generation subsystem of power-to-gas-to-power unit using gas expander and heat recovery steam generator

Power-to-hydrogen technology allows the effective use of electricity produced during the energy demand valleys, mainly in stochastic renewable energy sources. The dynamics of implementing such systems in the economy is correlated with the development of technologies enabling safe use of hydrogen. Currently, planning investments in power-to-hydrogen requires considering the risks associated with the possibility of reduced hydrogen demand. A way of protection against permanent or periodic reduction in the demand for hydrogen may be investments in electricity generation systems, which, thanks to the use of by-product of the electrolysis process - oxygen, can allow using of not only hydrogen but also natural gas. This paper discusses the thermodynamic and economic study of a hydrogen-to-power system using methanation and oxy-combustion combined cycle. The thermodynamic calculations focus on analysis of heat recovery steam generator (HRSG) structures and determining the energy efficiency of the system. The obtained energy storage efficiency are in the range of 16.29-24.95%. Within economic considerations, an electricity generation unit consisting of methanation and single-pressure HRSG systems cooperating with 100 MW hydrogen generators unit is considered. Sensitivity analyzes are performed and the value of investment outlays in hydrogen production unit and the price of electricity are decision variables. (C) 2020 Elsevier Ltd. All rights reserved.