The Role of Waste Heat Recovery in Enhancing Power-to-hydrogen and Power-to-methane Systems
Abstract
Power-to-Gas technologies offer significant potential to decouple energy demand from supply, enhancing flexibility of future renewable energy systems. This review focuses on Power-to-Hydrogen and Power-toMethane pathways and examines the impact of waste heat recovery on their exergetic efficiency. In Proton Exchange Membrane (PEM) and Alkaline Water Electrolysers (AWE), approximately 25–40% of the input energy is lost as low-temperature heat (50–90 °C). Solid Oxide Electrolysis Cells (SOEC), operating with water vapor at around 800 °C, requires not only electricity input but also heat input offering potential for thermal integration by utilizing high-temperature waste heat. In Catalytic methanation (CatM) and Biological methanation (BioM), approximately 10–29% of the input energy is lost as high-temperature heat (200-550 °C) respectively 22-24% as low-temperature heat (< 80 °C). Integrating waste heat recovery improves the mean exergetic efficiency by 6.4% for PEM/AWE, 4% for PEM/AWE + BioM, and 6.8% for PEM/AWE + CatM. The highest overall exergetic efficiency for Power-to-Methane, 76.3%, is achieved in integrated SOEC + CatM systems.
Keywords
Green Hydrogen, Solar fuels, Power-To-X, Thermal integration, Waste heat utilisation, Electrolysis, Methanation