Integration of energy storage technology and supercritical CO2 gas turbines: a comparison of supercritical CO2 heat pump and electrolyzer systems
Renewable energy sources (solar and wind) are intermittent, which makes them unreliable for a consistent and predictable energy supply. To address this intermittency challenge, efficient energy storage and conversion systems are essential. Although there is a variety of energy storage technologies (thermo-electrical, thermomechanical, electrochemical), there is still a need for the development of integrated energy systems that are able to store energy for long duration and efficiently convert it back to electricity when needed. Supercritical CO2 gas turbines have received significant interest due to their high thermal efficiency, compactness, and responsiveness to varying demands, making them suitable for the discharging mode of an energy storage system. Different technologies may be integrated with a supercritical CO2 gas turbine to be used as a charging mode. This study investigates and compares a supercritical CO2 heat pump and an electrolyzer concerning their integration with a supercritical CO2 gas turbine. The study compares the systems’ characteristics, including round-trip efficiency, specific energy, compactness, and possibilities for longduration energy storage. Firstly, for a system integrated with an electrolyzer, the supercritical CO2 gas turbine cycle reaches a higher gas turbine inlet temperature, due to direct hydrogen combustion. As a result, high thermal efficiency (up to 60%) can be achieved, reaching a round-trip efficiency of up to 40%. Whereas, for a system integrated with a supercritical CO2 heat pump, which achieves a high COP (up to 2), a round-trip efficiency of up to 64% can be achieved. Secondly, a supercritical CO2 heat pump / gas turbine system has the benefit of using the same components for both operation modes. Thirdly, renewable hydrogen has the benefit of storing energy for a long duration. The key findings show the benefits and areas of application of supercritical CO2 heat pumps and electrolysers when integrated with a supercritical CO2 gas turbine.