Optimization of Low-Carbon Operation in a Combined Electrical, Thermal, and Cooling Integrated Energy System with Liquid Carbon Dioxide Energy Storage and Green Certificate and Carbon Trading Mechanisms

The liquid carbon dioxide energy storage system (LCES), as a highly flexible, long-lasting, and environmentally friendly energy storage technology, shows great potential for application in integrated energy systems. However, research on the combined cooling, heating, and power supply using LCES in integrated energy systems is still limited. In this paper, an optimized scheduling scheme for a low-carbon economic integrated energy system is proposed, coupling LCES with power-to-gas (P2G) technology and the green certificate/carbon trading mechanism. Mathematical models and constraints for each system component are developed, and an optimization scheduling model is constructed, focusing on the economic and low-carbon operation of the integrated energy microgrid system. The objective function aims to minimize total system costs. A case study based on a northern China park is conducted, with seven scenarios set for comparative optimization analysis. The results demonstrate that the use of the combined cooling, heating, and power LCES system reduces total costs by USD 2,706.85 and carbon emissions by 34.57% compared to the single-energy flow operation. These findings validate the effectiveness of the proposed model in optimizing system costs and reducing carbon emissions.