Long-term performance simulation and sensitivity analysis of a large-scale seasonal borehole thermal energy storage system for industrial waste heat and solar energy

Abstract

The goal of this study was to evaluate the long-term energy and exergy performance of a large-scale seasonal borehole thermal energy storage system for industrial waste heat and solar energy in Chifeng, China. A simulation model of the studied system was built and validated by calibrating the soil thermal properties and comparing the simulation results with measurements from the real system, and an accurate estimation of the system thermal performance was generated. The system operation of the studied system was simulated for 10 years to predict the evolution of the ground temperature distribution as well as the energy and exergy flow under the quasi-steady state. The long-term simulation predicted 83.1% cyclic energy efficiency and 40.7% exergy efficiency of the studied system. Annual exergy flow revealed that the exergy destruction through the heat transfer process inside the BTES is the major cause of exergy loss. Subsequently, a sensitivity analysis was conducted to evaluate the influence of different design parameters. The results showed that the total borehole length had the most significant influence, followed by circulation flow rate and borehole spacing. The relationship between energy efficiency and exergy efficiency is discussed, and suggestions for system design and optimization are given accordingly.