Thermoelectric Energy Storage Based on Transcritical CO2 Cycle

by Jaroslav Hemrle, Mehmet Mercangoez, Lilian Kaufmann, & Christian Ohler
ABB Switzerland

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A novel concept for large-scale site-independent thermoelectric energy storage (TEES) is presented. The search for new electric energy storage concepts is stimulated by current trends in development of modern electric power networks, such as increasing penetration of renewable energy sources and growing demands on transmission infrastructure. Despite the urgent need, commercial site-independent alternatives with performance and cost comparable to pumped hydro plants are not available.

The presented TEES concept uses a transcritical CO2 cycle operated in heat pump mode for charging and, in reverse, in heat engine mode for discharging of the storage. Water is used as the hot thermal storage material, and ice production/melting forms the cold end for the site-independent system. CO2 as the working fluid and water as the storage material are both low-cost, safe, environmentally-benign fluids with excellent thermal properties allowing for scalability and high efficiency of the storage. The concept also offers potential for cost and efficiency improvements at favorable locations, for example by utilization of very low grade waste heat for charging.