Slag as an Inventory Material for Heat Storage in a Concentrated Solar Tower Power Plant: Experimental studies on design and performance of the thermal energy storage

Abstract

1. Introduction Thermal energy storage (TES) systems are essential for concentrated solar power (CSP) plants to guarantee continuous energy output. Currently used molten salt technologies are very expensive and demand continues technical attention. An option for cost reduction and efficiency increase is to use regenerator-type energy storages. By using waste metallurgical slag from electric arc furnace as an inventory material for the TES, further cost reduction can be achieved. However, as this type of slag has not been considered as an inventory material for this purpose yet, it is important to clarify fundamental questions about this low-cost material and storage design. The European project REslag deals with those questions. 2. Experimental studies on design and thermal performance On the basis of a preliminary identified lead TES design thermomechanical experiments were conducted. Uniaxial compression tests (UCT), see Fig.1 (left), were performed to determine possible inventory and insulation damages occurring during cyclic operation of the TES. Those demonstrated the mechanically suitability of slag for the use in TES. Also insulating bricks in combination with protection layers were tested and design concepts without damages have been identified. The thermal behavior of the slag-based TES is currently being investigated at the HOTREG pilot plant at DLR in Stuttgart. The aim of the study is the experimental confirmation of the performance presented by simulation. 4. Conclusion Slag-based TES for CSP plants could help to improve the economic outlook for this technology, further. The investigations carried out so far in the project REslag clearly show the suitability of the slag used as heat storage material. The pilot tests finished in the next month should complete the picture. In the oral presentation, all results will be presented and summarized to a total conclusion.