Power-to-Gas: storing surplus electrical energy. A design study

In this work a conceptual design of a Power-to-Gas (PtG) process for storing electrical energy in form of synthetic natural gas (SNG) of gas grid quality H is presented. The combination with a conventional lignite fired power plant (LPP) was investigated for possible improvement of its economic performance in times of fluctuating renewable energy supply. In this study for a PtG facility using 80 MWel (10% of LPP nominal capacity) a capital expenditure (CAPEX) of M$ 126 and operational (OPEX) of 31-33 M$/a were estimated. PtG provides a good alternative for storing surplus electrical energy and guaranteeing a viable LPP operation if the remuneration for the flexible operation is above 45 k$/operating hour respectively 56 $/operating hour/MWel which is at least 50% additional operational&maintenance (O&M) costs for a LPP. With decreasing alkaline electrolysis costs and an increasing share of renewable energy supply this concept would represent an energy strategic as well as economic advantage for energy suppliers in future