Analysis of a silica glass based high temperature thermal energy storage unit for concentrated solar power applications

The design of a directly-charged high temperature thermal energy storage (TES) unit based on molten silicaglass is presented. The 126 kWh_th thermal storage unit developed is aimed to operate within a solar-driven domestic scale power generation system. The paper discusses the proposed design for the unit as well as the restrictions set by the power generation system's requirements. The transient mathematical model used to analyze the behavior and performance of the thermal energy storage unit during the different stages of the intended work cycle is thoroughly explained. An important feature of the mathematical model is that the performance of the unit is not only evaluated from an energy viewpoint, but an in-depth exergy analysis has been additionally carried out. The results obtained through the model are exhaustively analyzed; special focus has been given to the assessment of the performance of the storage unit to guarantee that the operational requirements of the power generation system are met. The overall performance of the TES unit is satisfactory; the unit is capable of supplying the required 4 kWth output throughout the 16-hour discharge while it reaches its fully charged state during the subsequent 8-hour recharge. The proposed designed for the TES unit exhibits a round trip exergyefficiency of 59%.