Energy, exergy, economic performance investigation and multi-objective optimization of reversible heat pump-organic Rankine cycle integrating with thermal energy storage

Abstract

Reversible heat pump-organic Rankine cycle (HP-ORC) system is a kind of prospective energy storage technology, which can store the surplus electricity and waste heat recovery simultaneously and realize a high round-trip efficiency even beyond 100%. However, the comprehensive evaluation of energy, exergy and economic performance of HP-ORC are still not enough as a novel system, hindering the deep understanding and further development and application. This study will first select proper candidate working fluids based on theoretical analysis of the thermophysical properties and operating characteristics of HP-ORC system. Then effects of different combinations of crucial parameters in HP-ORC system are evaluated on the energy, exergy and economic performance. Finally, multi-objective optimization will be conducted to analyze the optimal performance of HP-ORC system under designed parameters. The optimization results indicate that R245ca is the optimal working fluid among all the investigated working fluids. Under the optimal parameters, the exergy destruction during the discharging cycle accounts for 68.23% during the reversible operating process, which is significantly greater than that of the charging cycle. In the discharging cycle, the top three exergy destruction are successively taken by the evaporation process, expansion process and condensation process cycle, and the corresponding proportions are 26.81, 21.67% and 19.54% respectively.

Keywords

• Thermal energy storage
• Heat pump
• Organic Rankine cycle
• Thermo-economic analysis
• Multi-objective optimization