Process improvements and multi-objective optimization of compressed air energy storage (CAES) system

Intermittency and high cost were the main barriers to the large-scale commercialization of renewable energy decades ago. The cost of renewable energy has decreased dramatically in the last decade. The intermittency of renewable energy, however, remains a serious challenge to be overcome. Compressed Air Energy Storage (CAES) is widely considered to be a promising energy storage technology at utility-scale and receives increasing attention from both academic and industrial communities. In this study, two novel CAES systems are proposed and a thorough investigation and comparison of the thermodynamic performance of both conventional and novel CAES systems have been performed. The turbine inlet temperature and the maximum cavern storage pressure are identified as the bottlenecks of CAES plants. The round-trip efficiency and energy density are chosen as the conflicting objectives. Pareto fronts are obtained based on the simulation-based multi-objective optimization framework developed in this study. The energy density of a diabatic CAES plant is within the range between 4.24 and 11.58 kWh/m³, while that value becomes 1.28–7.96 kWh/m³ for a conventional adiabatic CAES system. The novel two-pressure level adiabatic CAES system can improve the round-trip efficiency by at least 3.5% compared with the conventional adiabatic CAES system. The novel indirect heating diabatic CAES system can improve the round-trip efficiency by at least 2%. The Pareto fronts can be a useful tool for the grassroot design or retrofit of a CAES plant. Solutions to improve the CAES system performance have been proposed based on the optimization results of this study.