Performance Analysis and Optimization of Pumped Thermal Energy Storage System Coupled with Low Temperature Waste Heat Recovery

Abstract

In order to improve the cascade utilization efficiency of low-temperature flue gas waste heat in steel industry, an improved pumped thermal energy storage (PTES) system coupled with low temperature waste heat recovery is proposed in the current study, and the thermodynamic and economic models of PTES system are constructed. The effects of HP condensation temperature (Tcon,HP), thermal storage temperature (Tts), ORC evaporation temperature (Teva,ORC) and ORC superheat degree (ΔTsup) on the thermal economic performance of PTES system under different ORC working fluids are studied, and the system thermodynamic parameters are optimized. The results show that reducing the Tcon,HP, rising the Tts and Teva,ORC can improve the power-to-power efficiency (ηP2P) and exergy efficiency (ηex) of PTES system. Among the selected working fluids, the ηex of R1234ze(Z) initially rises and then reduces with rising the ΔTsup, and the ηP2P and ηex of other working fluids generally exhibit a peak at lower ΔTsup. The levelized cost of storage (LCOS) of PTES system reduces first and then rises with the rise of Tts. The higher the Tcon,HP and ΔTsup are, and the lower the Teva,ORC is, the larger the LCOS is. In addition, R1233zd(E) is used as the ORC working fluid with the highest ηP2P of 60.22% and the lowest LCOS of 0.4038$/kWh, which should be preferred as the ORC working fluid of PTES system driven by the low-temperature flue gas waste heat.

Keywords: Waste heat recovery, Pumped thermal energy storage, Organic Rankine cycle, Thermal-economic performance, Parameter optimization