This study discusses and thermodynamically analyzes several energy storage systems, namely; pumped-hydro, compressed air, hot water storage, molten salt thermal storage, hydrogen, ammonia, lithium-ion battery, Zn-air battery, redox flow battery, reversible fuel cells, supercapacitors, and superconducting magnetic storage through the first and second law of thermodynamics. By fixing an electrical output of 100 kW for all systems, the energy efficiencies obtained for the considered energy storage methods vary between 10.9% and 74.6% whereas, the exergy efficiencies range between 23.1% and 71.9%. The exergy destruction rates are also calculated for each system ranging from 1.640 kW to 356 kW. The highest destruction rate is obtained for the solar-driven molten salt thermal energy storage system since it includes thermal energy conversion via the heliostat field. Furthermore, the roundtrip efficiencies for the electrochemical and electromagnetic storage systems are compared with the analyzed systems, ranging from 58% to 94%. Renewable sources (solar, wind, ocean current, biomass, and geothermal) energy conversion efficiencies are also considered for the final round-trip performances. The molten salt and hot water systems are applicable to solar, geothermal, and biomass. The highest source-to-electricity efficiency is obtained for the super magnetic storage with 37.6% when using wind, ocean current, and biomass sources.

Energy Vol 19

Manal AlShafi, Yusuf Bicer

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