Abstract
Subcooled compressed air energy storage system is a trigeneration technology that has been recently introduced to the literature. In the charging mode, the system stores the surplus power of a renewable energy system in the form of compressed air in a cavern and generates much heat as well. In the discharging mode, when the renewable power plant demands extra electricity, the system reclaims the compressed air to be expanded through a specific type of turbine and thereby generates electricity as well as a large amount of cold. At nominal load, when all the components are working at their optimal states, a high coefficient of performance of about 1.5 has been achieved for the system over a complete charging-discharging round. This paper, however, investigates thermodynamically and environmentally the performance of this technology while working at off-design conditions. For this, realistic performance curves for various components of the system are employed and the system operation is simulated for various operational conditions. The results show that the storage unit is best to work on its highest possible charging-discharging loads; otherwise, the overall efficiency would fall remarkably. The trigeneration/storage system overall performance coefficient will decrease to 1.27% and 1.05% if the operational load drops to 50% and 10%, respectively. (C) 2019 Elsevier Ltd. All rights reserved.