From waste to value: Utilising waste foundry sand in thermal energy storage as a matrix material in composites

Abstract

Waste foundry sand (WFS) is a by-product of the casting industry, which poses increasing economic and environmental issues due to the costs associated with landfill maintenance and stricter environmental regulations. This study proposes a novel solution for WFS as a material for thermal energy storage. The approach involves blending WFS with NaNO3 and a proprietary additive, X, to fabricate a composite phase change material (CPCM). The CPCM is found to be structurally stable up to 400 °C, and an optimal composition with a mass ratio of NaNO3:WFS:X = 0.6:0.3:0.1 is achieved. This composition yields an energy storage density of 628 ± 27 kJ/kg, and an average thermal conductivity of 1.38 W/mK over the temperature range of 25–400 °C. The CPCM also exhibits good mechanical strength and a low coefficient of thermal expansion compared to NaNO3. Currently, only a small portion of WFS is recycled, most commonly in building applications. The CPCM presented in this study has the potential for medium-to-high temperature heat storage in waste heat recovery applications, offering a sustainable solution for upcycling WFS.