Performance analysis of a molten salt packed-bed thermal energy storage system using three different waste materials

Concentrated Solar Power (CSP) is a critical technology for the renewable energy transition, offering high power output at elevated temperatures. However, further integration of CSP plants requires a reduction in investment costs. This study investigates the use of cost-effective, sustainable, waste-based TES materials—such as Electric Arc Furnace Black Slag (BS) and Tundish (TN) from the steel industry, as well as Demolition Waste (DW) from urban regeneration projects—as packing materials in TES systems to reduce the capital expenditure of CSP plants. A One-Dimensional Continuous Solid Phase (1D-2P) model was employed to evaluate and compare the performance of DW, TN, and BS. The results revealed that all materials demonstrated comparable properties, with TN exhibiting the highest energy storage capacity (44.7 kWh) and energy storage density (296 kWh/m³). With high utilization rates of 73–75 %, waste-based TES systems show strong potential for application in CSP plants. The TES systems were scaled for a 110 MW CSP plant, which currently operates with a 2-tank molten salt TES system providing 4648.4 MWh of storage capacity. TN required the smallest storage volume of 22,273 m³ for the 110 MW CSP plant. The reduction of molten salt usage by up to 31,000 tons in the waste-based packed-bed TES system could significantly enhance the economic feasibility of CSP plants.