Exergy and cost analyses of hydrogen-based energy storage pathways for residual load management

摘要

Hydrogen is considered to become a main energy vector in the renewable energy systems to store large amounts of intermittent wind and solar power. In this work exergy efficiency and cost analyses are conducted to compare pathways of hydrogen generation (PEM, alkaline or solid oxide electrolysis), storage (compression, liquefaction or methanation), transportation (trailer or pipeline) and utilization (PEMFC, SOFC or combined cycle gas turbine). All processes were simulated with respect to their full and part-load efficiencies and resulting costs. Furthermore, load profiles were estimated to simulate a whole year of operation at varying loads. The results show power-to-power exergy efficiencies varying between about 17 and 38 %. The main losses occur at utilization and generation. Methanation features both lower efficiency and higher costs than compressed hydrogen pathways. While gas turbines show very high efficiency at full load when considering a load following operation they drop significantly while fuel cells can maintain their efficiency. Lower costs are commonly reached at higher overall efficiencies. Installation costs are identified as predominant because of the low amount of full-load hours. An increase of these e.g. by accounting for an electrolysis base-load to provide hydrogen for vehicles shows significant decreases in costs per stored energy.