Pumped thermal electricity storage (PTES) technology is a large-scale physical energy storage technology that stores electrical energy in the form of thermal energy, playing a significant role in the integration of renewable energy. In this paper, a hybrid PTES (H-PTES) system with thermal utilization is proposed, in which a preheater is added into the organic Rankine cycle (ORC) to recover the waste heat released from the heat pump (HP) evaporator, enabling cascaded energy utilization. First, the thermodynamic and economic models of the basic PTES (B-PTES) system and the H-PTES system are established. Subsequently, the effects of thermodynamic parameters on the performance of both systems are investigated under different ORC working fluids. Finally, a bi-objective optimization of the two systems is carried out using the linear weighted evaluation function method. The results indicate that, the round-trip efficiency and exergy efficiency rise with reducing the HP condensation temperature, and reduce with reducing the HP evaporation temperature, thermal storage temperature and ORC evaporation temperature. The levelized cost of storage reduces with the reduction of HP condensation temperature and HP evaporation temperature, and rises with reducing the thermal storage temperature and ORC evaporation temperature. For both the B-PTES and H-PTES systems, the optimal ORC working fluid is R1233zd (E). Under the optimal operating parameters, the H-PTES system exhibits superior thermodynamic and economic performance, and the optimal round-trip efficiency, exergy efficiency and levelized cost of storage of H-PTES system with the R1233zd (E) are 68. 86%, 36. 42% and 0. 399/kWh, respectively.
Feng et al. (Mon,) studied this question.