Comprehensive analytical model of energy and exergy performance of the thermal energy storage

Determining the performance of heat storage units is essential to reliably determine the capability of entire energy storage systems, as several energy loss and dissipation phenomena can significantly degrade its final efficiency. Previous scientific works has not focused on the detailed treatment of the heat storage tank and its impact on the functioning of other system components. The work emphasizes the presentation of a in-house numerical model of Thermal Energy Storage filled with rock material. The comprehensive numerical model has been presented that also takes into account the variable operating parameters of the compressor and air expander. The multivariate nature of the model used makes it possible to estimate the influence of individual factors on the final efficiency of the system. The calculations made it possible to determine the potential of a system with a capacity of 175 MWh using post-mining shafts. The long-term energy efficiency of the system was 57.47%, with a heat storage energy efficiency of 91.96% and an exergy efficiency of 82.93%. Implementation of the model has the potential to provide more accurate estimations of the potential of proposed energy systems using heat storage.