Material screening and compatibility for thermocline storage systems using thermal oil

Among existing heat storage technologies, dual-media thermocline systems are considered an economical option, experimentally demonstrated at several scales. To obtain cost reduction for these storage systems, a part of the heat transfer fluid is replaced by a low-cost solid. The contact between these two media raises the question of their compatibility and behavior in time, as the storage performance directly depends on it. Ageing and compatibility tests have been performed at the laboratory scale with Jarytherm® DBT oil and various solid media. These tests, carried out at 340°C for 500 h, have shown the strong influence of the solid composition on its compatibility with oil. A strong incompatibility has been highlighted between Jarytherm® DBT oil and the selected natural rocks at 330°C, through chromatographic analysis and oil properties evaluation before and after ageing. To the contrary, glass, steel and alumina fared well, and are thus considered as promising storage media.