Experimental investigation of a cementitious heat storage medium incorporating a solar salt/diatomite composite phase change material.

• Experimental investigation of high temperature thermal storage concrete materials. • Phase change materials (solar salt) added to concrete to increase energy density. • Thermal and mechanical characterization of concrete and 2 wt% phase change material. • Thermal and mechanical properties increase with no phase change materials leakage. • Better behaviour of phase change material/diatomite even after 250 °C. Thermal energy storage is one of the most appropriate technologies to correct the gap between the energy generation and supply and to address energy challenges. Concrete is generally the preferred "solid" heat storage material because its low cost and good thermal conductivity. The major disadvantage is its low heat stored density involving the use of large amounts of concrete. Latent heat storage materials (or phase change materials), have received more attention due to much higher heat storage density and extremely smaller temperature variation during the thermal energy charge/discharge process. These materials can be incorporated in the concrete by using different methods. When the phase change material is encapsulated or added in a shape-stabilized new material, as diatomite, the phase change material leakage is avoided. Thermal and mechanical characteristics of a new heat storage material, composed by concrete with the addition of 2% Solar Salts by weight (as phase change material) in powder or capsules form, were analyzed. The results showed an increase of the main thermal (volumetric heat capacity and conductivity) and mechanical properties while phase change material leakage was not observed. In particular, the phase change material/diatomite capsules provide a better behavior even after 250 °C. [ABSTRACT FROM AUTHOR]