Thermal and economic evaluation of phase change material volume fraction for thermocline tank used in concentrating solar power plants

The current paper investigates the phase change material (PCM) volume fraction (VF) effect on the thermal and economic behavior of a three-layer thermocline thermal energy storage (TES) tank system which is used in concentrating solar power (CSP) plants. The one dimensional transient dispersion-concentric (D-C) scheme is applied to calculate the phase change inside each capsule. Using MATLAB software, the numerical model equations have been figured out, and the current numerical results have been verified. Four different scenarios have been created to investigate the effect of PCM-VF on the thermal behavior and economic feasibility of the TES tank. The results described that the overall efficiency and the cost of capacity for all cases in order from the case (1) to the case (4) are 80.77%, 64.32%, 73.43%, 85.58%, and $45.37/kWh, $60.49/kWh, $46.28kWh, $38.58/kWh, respectively. Furthermore, case (4) demonstrates the storage capacity of 149 kWh/m³, which is 7.21%, 19.42%, and 15.78% higher than case (1), (2), and (3), respectively. In the comparative study, the results showed that case (4), which has higher VF for the bottom PCM layer, indicates that it is the most viable option of all the studied cases due to its best performance and relatively low cost.