Motivation HEAT TRANSFER IRREVERSIBILITY IN RECIPROCATING COMPRESSORS AND EXPANDERS FOR ENERGY STORAGE APPLICATIONS For a sustainable energy supply and successful integration of renewable energies large storage capacities will be required. Pumped thermal energy storage (PTES) Advantages: high energy density not dependant on geological aspects efficiencies of up to 70% are predicted [1]. fast responds time capital cost per MWh is low storage on a large scale is possible. High temperature ratio heat pump converts electrical energy into thermal energy Energy stored as temperature difference between two thermal reservoirs. For discharge the heat pump is run backwards and thermal energy is converted back to electricity.
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