Performance optimization and comparison of pumped thermal and pumped cryogenic electricity storage systems

Two generic models, one of a PTES (pumped thermal electricity storage) system and another of a PCES (pumped cryogenic electricity storage) system, are established in which the finite-rate heat transfer and external heat leakage losses are considered and several important parameters connecting the charging and discharging phases are introduced. Analytic expressions for the round trip efficiency and power output of PTES and PCES systems are derived. The influences of some important parameters on the performance characteristics of the PTES and PCES systems are presented, and the optimally operating region of each system is determined. The performances of PTES and PCES systems are compared. The advantages of the PTES system are highlighted. The effects of external heat leakage losses are discussed in detail. Notably, the results reveal that external heat leakage losses must be considered in the performance investigation of the PTES system. (C) 2016 Elsevier Ltd. All rights reserved.