Thermo-economic analysis and multi-objective optimization of a reversible heat pump-organic Rankine cycle power system for energy storage

The rapid growth in renewable energy has reinforced the efforts to develop new scalable energy storage to balance the mismatch between energy production and demand. The reversible heat pump-organic Rankine cycle (HP-ORC) Carnot battery system is a possible candidate for this. Further investment cost reduction and the utilization of low-temperature energy were extremely beneficial to its development and application. A low-temperature and simple reversible HP-ORC storage system based on a compression and expansion dual-function unit was developed in this paper. A screening of 3 candidate working fluids was performed and R1233zd (E) was selected as the final candidate for the demonstrator. A mathematical model of the presented system was built to analyze the energy, exergy, and economic performance. Additionally, a multi-objective optimization of the system was carried out to find the optimal storage temperature taking economic and energy criteria into account. Finally, exergy analysis was performed under the optimal condition. The results show that the higher isentropic efficiency and temperature of the heat source are, the better the performance of the system is. When the optimal upper and lower storage temperatures are 126 ℃ and 99 ℃, the power-to-power efficiency (P2P), electrical storage capacity (ESC), levelized cost of storage (LCOS), and exergy efficiency are 28.16 %, 1.77 kW∙h/t, 0.36 $/kW∙h, and 61.82 %, respectively. The condenser and evaporator need to be improved in terms of their large exergy loss rate and low exergy efficiency.