Techno-economic survey of enhancing Power-to-Methane efficiency via waste heat recovery from electrolysis and biomethanation

Power -to -Gas technologies are high -capacity systems, which can be used to optimise the use of renewable energy to meet energy demands. Among them, Power -to -Methane (PtM) stands out due to the ease of storage and use of the produced methane. However, its total storing efficiency (Power -to -Methane -to -Power) is likely still low as there are various losses. This paper presents an overview of PtM improvement through the utilisation of lowtemperature waste heat produced upon the two steps by converting power to gas, namely electrolysis and methanation. An organic Rankine cycle, Stirling engine, and thermoelectric generator were chosen as promising technologies that could be implemented to recover the waste heat and improve the PtM system. Several experimental studies of each technology were reviewed. Moreover, some technological and economic surveys are described and discussed. At the end of the article, the study discussed the direction of further research and development for waste heat recovery in the system to increase the competitiveness of the PtM system and its efficiency.