Fast and stable solar/thermal energy storage via gradient SiC foam-based phase change composite

Phase change materials with high latent heat can bridge the gap between constant energy demand and intermittent supply. However, the intrinsically low thermal conductivity and leakage problems severely limit the charging/discharging rate and cyclic stability in practical applications. Here, a leakage-proof phase change composite strategy based on gradient SiC foam is proposed to achieve fast and stable latent heat storage. The thermal conductivity of composites achieves 1.9 W·m⁻¹·K⁻¹, which is 760% as high as that of paraffin wax, while the latent heat (120 J·g⁻¹) still maintains 85.7% of paraffin wax. Excellent leakage-proof property is demonstrated with nearly unchanged latent heat over 1000 cycles, due to the enhanced capillary interaction provided by the gradient pore structures. The influence of volume fraction, input power, and thermal conductivity on the melting behavior are systematically investigated, demonstrating fast thermal charging performance of gradient SiC foams. Efficient and rapid solar-thermal charging performance are also achieved benefitting from high volumetric solar absorptance and high thermal conductivity. This work guides the design of ceramic based phase change composites for rapid, stable, and efficient solar/thermal energy storage.