The intermittency of renewable energy makes its use in industrial processes difficult. We have designed a novel storage system that can deliver heat and electricity on demand.
Pumped thermal energy storage (PTES) is a promising technology for long-duration energy storage and industrial decarbonization, addressing renewable energy intermittency while supplying high-grade heat. PTES systems operate as heat pumps during charging, storing excess electricity as thermal energy in hot and cold reservoirs, and as heat engines during discharging to generate electricity again. We propose an enhanced PTES system using supercritical CO₂ as the working fluid, with molten salt for high-temperature storage and water for low-temperature storage. This system is capable of simultaneously delivering electricity and heat, guided by an optimized state-of-charge (SoC) management algorithm and integrated heat exchangers.
During operation, the system balances the storage reservoirs using the SoC management algorithm. When heat is extracted from the hot side, a portion is used to reheat the cold side for SoC balancing, enabling reliable delivery of heat at 563–420°C. However, this approach is relatively inefficient when interfaced with heat users below 420°C. To address this, we introduce an additional cycle that supplies lower-grade heat between 350–250°C, operating as a dedicated heat pump with a secondary intermediate temperature thermal storage media (Therminol 55). The modified SoC management algorithm ensures optimal operation of the PTES integrated with a process heat exchange network, significantly increasing the utilization factor and the roundtrip efficiency.
We demonstrate that PTES systems can be adapted for industrial use by incorporating additional thermal storage levels and tailoring operations to specific processes. They offer load-shifting capabilities and electrified heat supply, reducing electricity costs and supporting decarbonized industrial heating [3]. We carried out this work as part of the EPSRC project Grid Scale Thermal and Thermo-Chemical Electricity Storage.
