Thermal storage using sand saturated by thermal-conductive fluid and comparison with the use of concrete

Abstract

The present study considers sand saturated with thermal conductive fluid as a new low-cost thermal storage material that can have better heat transfer than using concrete or sand alone and also avoids issues of heat transfer degradation associated with the mismatch of thermal expansion in concrete. The new thermal storage material (sand saturated with Xceltherm® 600 heat transfer oil) was tested in a lab-scale experimental setup from 27°C to 55°C to show the concept and also validate a 1D transient enthalpy-based model for simulation of thermal storage. The model was then applied to study and compare the thermal storage performance of sand saturated by Hitec® (heat transfer fluid) and concrete for a 600MWele CSP power plant at a thermal efficiency of 35% and thermal storage temperatures ranging from 400°C and 500°C. It was found that more energy can be stored and extracted if Hitec®-saturated sand is used as storage media, which may result in appreciable cost reduction than using concrete thermal storage system based on a study for a 600 MWele CSP system in operation for one year. As a result, Hitec®-saturated sand can be used to replace concrete as the thermal storage media in high temperature operating range (>400°C). It is expected that such a new approach of sensible heat storage is of significance to solar thermal energy storage technologies.