Advanced exergy analysis of a Joule-Brayton pumped thermal electricity storage system with liquid-phase storage

Pumped thermal energy storage systems integrated with a concentrating solar power section: Conceptual design and performance evaluation

“…However, as highlighted by McTigue et al [10], the achieved performance in terms of roundtrip efficiency is highly sensitive to the losses occurring in compression and expansion processes. This was confirmed by the exergy analysis conducted by Zhao et al [11], indicating the maximum exergy destruction rate in the expander during the discharging phase. Advanced exergy analysis further revealed that, among the system components studied, the cold heat exchanger during discharge is associated with the largest share (95%) of the avoidable exergy destruction rate.…”

“…In addition to the hot and cold reservoirs, the system is equipped with two compressors (C1 and C2), two turbines (T1 and T2), an electric motor/generator (M/G) and two water coolers (WCO1 and WCO2). The system operates as a Brayton heat pump during the charging phase: the working fluid is compressed by C1 (10)(11), reaching the maximum cycle pressure and temperature, and subsequently sent to the hot reservoir for charging this TES system (11)(12). A further cooling (12)(13) is performed in WCO1 to allow the working fluid to close the thermodynamic cycle, overcoming the turbomachinery irreversibilities.…”

Pumped Thermal Energy Storage Technology (PTES): Review

“…Exergy analysis conducted by Zhao et al [66] indicated that the expander discharge caused the greatest amount of exergy loss. In addition, advanced exergy analysis indicated that cold heat exchangers during discharge account for a significant portion of avoidable exergy destruction (95%) among the system components studied.…”

Techno-economic analysis of recuperated Joule-Brayton pumped thermal energy storage

“…[23] and a solution using nitrate molten salts is currently being developed commercially by Malta Inc. who are aiming for deployment by 2023 [24]. Recent research has investigated sources of exergy losses within this system [25], and the present work aims to improve the design by also considering the lifetime cost. The use of liquid stores has the advantage that, although not necessary, the working fluid may be pressurized, thereby increasing power density and reducing per-kW capital cost.…”

“…However, higher temperature systems require more expensive materials and components, and this trade-off is explored in this article by considering several different hot storage fluids. Potential hot-storage fluids include mineral and synthetic oils (with top temperatures of around 300°C and 400°C respectively) and nitrate molten salts [25], which typically operate in the range 250 − 565°C, the lower limit being required to prevent freezing. Substantial experience has been gained in the use of molten salt storage via the CSP industry.…”