A comprehensive material and experimental investigation of a packed bed latent heat storage system based on waste foundry sand

The EU's industrial sector discards about 18.9% of its energy as waste heat, much of which has the potential for recovery. This study addresses the challenge by focusing on the advancement of latent heat thermal energy storage (LHTES) using phase change materials (PCMs) encapsulated within industrial waste foundry sand (WFS). WFS, a problematic by-product, is repurposed as a supportive matrix for NaNO₃ and solar salt PCMs, tailored for effective integration into high-temperature industrial processes. The paper provides a thorough mechanical and thermal examination of the WFS-salt PCMs, highlighting their improved thermal stability, performance, and compatibility with direct thermal energy systems. The composite PCMs demonstrated melting points well-suited for industrial waste heat applications and achieved an energy density of 542.0 ± 8.3 kJ/kg for NaNO₃ and 516.0 ± 4.5 kJ/kg for solar salt, An experimental cascade PBLHS, based on these CPCMs, with a capacity of 262 MJ, designed to mimic an industrial heat source at 450 °C, was systematically tested to assess its energy density and efficiency over repeated charging/discharging and free cooling cycles. Its overall system efficiency is found to be 68.5%. These findings position WFS-salt PCMs as a promising and environmentally beneficial approach to enhance industrial energy efficiency and utilisation.