Surface processes optimisation in a novel CO2-based electrothermal energy and geological storage trigeneration system

A. Carro, C. Ortiz, S. Unger, A. Stoikos, A.-S. Kyriakides, I.N. Tsimpanogiannis, J.A. Becerra, S. Voutetakis, U. Hampel and R. Chacartegui

Applied Energy, 2025, vol. 395, issue C, No S0306261925008955

Abstract: Electrothermal energy storage is a promising technology for high penetration of renewable energy. In recent years, the integration of this energy storage system with geological CO2 storage has been introduced. The system consists of a reversible heat pump formed by transcritical CO2 cycles with thermal storage at two temperature levels, enabling the simultaneous operation of geological CO2 storage and the storage/production of renewable electrical energy. This work focuses on studying high and low-temperature thermal energy storage. Step heating on the high-temperature side allows for better integration of the supercritical and subcritical temperature profiles of the CO2 and the thermal storage fluid. Thermal storage at different temperature levels provides a higher turbine inlet temperature, improving the efficiency of the power production cycle and increasing heating applications such as district heating or domestic hot water. Considering four high-temperature tanks, round-trip efficiency increases from 52.8 to 55.4 %. It presents a thermal demand coverage range of about 20–150 °C, with temperature increases of approximately 30 °C. The phase change temperature shift on the low-temperature side directly impacts electric power production and enables new cooling applications. The system's efficiency increases as the low-temperature phase change temperature decreases, reaching 58.7 % at −30 °C. Using alternative configurations in the transcritical CO2 cycle, such as the recuperative cycle and multi-stage compression and expansion, high-efficiency values can be maintained with lower system requirements.

Keywords: Renewable energy storage; Electrothermal energy storage; Transcritical CO2; Geological storage; CO2; Trigeneration (search for similar items in EconPapers)
Date: 2025
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DOI: 10.1016/j.apenergy.2025.126165

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