Properties of concrete material for thermal energy storage

The selection of concrete composition has significance for concrete storage system. This research has been investigated the properties of concrete composition based on local materials in Thailand in order to determine a suitable concrete composition for thermal energy storage. The concrete samples were tested in the laboratory to determine thermal conductivity, specific heat, density, coefficient of thermal expansion, thermal diffusivity, compressive strength and permeability as well as to calculate the volumetric heat capacity of three different compositions of concrete which were (water : cement : sand :limestone: steel fiber) 0.35 : 1 : 1.2 : 1.8 : 0.03, 0.55 : 1 : 1.6 : 2.3 : 0.03 and 0.65 : 1 : 1.7 : 2.6 : 0.03. The results showed that the optimum mixing ratio of concrete was 0.55 : 1 : 1.6 : 2.3 : 0.03 which was obtained at the highest thermal conductivity 2.465 W/mK, highest specific heat 1928 J/kgK, highest volumetric heat capacity 5244.16 KJ/m³K and lowest thermal diffusivity 1.28×10^-3m²/s. This optimum ratio should be applied for the thermal concrete storage for the solar thermal power plant.