Parametric optimisation and thermo-economic analysis of Joule–Brayton cycle-based pumped thermal electricity storage system under various charging–discharging periods

Abstract

The Joule–Brayton cycle-based pumped thermal electricity storage (PTES) system has a simple structure, high energy density, and geographical independence, which has broad application prospects. This study carried out multi-dimensional optimisation, detailed loss and thermo-economic performance analyses for PTES systems with charging–discharging duration ratios in the range of 1:3–3:1. The reservoirs' length-to-diameter and discharge compression ratios were optimised. An uncertainty analysis of the capital cost and levelised cost of storage (LCOS) was performed. The results indicate that with an increase in the charging/discharging duration, the optimal length-to-diameter ratio of cold reservoir increases, which of hot reservoir initially increases, then shifts to decreasing. For systems with the same storage capacity, longer charging/discharging duration will achieve better economic performance. The highest round-trip efficiency of 70.97% and lowest LCOS of 0.190 ± 0.043 $/kWh can be achieved for a 60-MWh PTES system. LCOS decreases significantly with the increase of installed capacity. The peak and valley hours should be fully utilised to obtain the best techno-economic performance. The abovementioned optimisation and analysis based on the exergy method provides a theoretical basis for the design and application of the Brayton-cycle-based PTES system.