Stability testing of thermal oil in direct contact with rocks used as filler material for thermal energy storage in CSP power plants

A Thermocline Thermal Energy Storage (TES) system potentially offers a cheap and simple way of achieving dispatchability of energy after sunset or during intermittent cloudy weather conditions. The system performance depends on the properties of the suitable media selected. As very promising solid TES material, natural rocks can be chosen as filler material for energy storage system owing their availability and many advantages such as high volumetric heat capacity and stable physical and chemical performance. In previous tests, quartzite rock was identified as a potential filler material for TES. In the present paper, the compatibility of the heat transfer fluid (HTF) with rocks and silica sand was tested in laboratory under defined conditions. Physicochemical and thermal characterizations of the studied materials were performed in order to evaluate their sustainability after extended time over a range of temperature. It has been concluded that no significant deterioration of tested oil aged in contact with quartzite and silica sand can affect the performance of the thermocline thermal energy storage system. (C) 2015 The Authors. Published by Elsevier Ltd.