Multi-criteria evaluation and optimization of a thermal energy storage systems

This research focuses on a sub-cooled CAES unit that produces electricity and cooling during peak demand. The study evaluates energy efficiency and payback period under various operating conditions. A computer program was created in MATLAB to solve the necessary equations with an appropriate time interval. The results show that increasing compression and expansion stages enhances energy efficiency. Having more compression stages reduces the payback period of the system, while more expansion stages lengthen it. The system works best when the tank temperature matches the surrounding temperature. In a practical scenario where 900 kW of power is generated over 4 h, the payback period was 15 cents per kWh, without considering an eight-year inflation rate. By using the current net value method, the system becomes profitable after 11 years.