Numerical investigation of large‐scale seasonal rock‐pit energy storage system

Abstract

AbstractA twodimensional axisymmetric model, which is computationally inexpensive, has been proposed to predict the property changes that occur in a seasonal rock‐pit energy storage (RPES) system. The geometry of the rock‐pit has been simplified into a shape that can be extended for any seasonal storage system with a three‐dimensional conical geometry. The computational domain has been solved using both linear thermal equilibrium (LTE) and linear thermal non‐equilibrium (LTNE) models, and the former has been found to be computationally quick and accurate. The model has predicted a 95% energy saving at the highest flow conditions required in the mine. Further analysis has suggested that the increase in storage capacity by decreasing the porosity of rocks in the rock‐pit is insignificant compared to the corresponding increase in fan power. Furthermore, the investigation done on natural rocks has indicated an increased ability to store heat in the rock‐pit when rocks with higher thermal mass have been used. The use of RPES has shown a significant potential to reduce the carbon footprint. Finally, an economic analysis done on the system has shown a return on investment of just under 12 years.