Properties of bulk materials for high-temperature air-sand heat exchangers

Kurzfassung

Dispatchability of CSP and a further reduction of levelized electricity costs are strong incentives for the development of cost-efficient technical solutions for thermal storage systems. A heat storage system using fine-grained particles as its storage material is a technology option that offers novel low-cost solutions. The implementation of this concept however depends on a viable concept for an air-to-particle heat exchanger, a component that is needed to heat up the particle flow and that is not available on the market today. Solar- Institut Jülich (SIJ) and the German Aerospace Centre (DLR) are developing and testing a new air-to-particle heat exchanger (Warerkar et al., 2009). Relevant problems include high temperature gradients in sand and frame structure, the pressure drop through the heat exchanger, the thermodynamic behavior and the fluid dynamic interaction within the bulk material. In this paper open questions on material properties of the sand-like inventory are addressed. High requirements are placed on the particulate materials used in sand-air heat-exchanger to ensure a smooth and efficient operation for many years. Hence, a detailed analysis of candidate bulk materials and their properties are of ample importance for the development of the technology. The focus of this work is put on properties like effective thermal bulk conductivity, thermal shock resistance, and attrition aspects.