Experimental and numerical investigations of solar charging performances of 3D porous skeleton based latent heat storage devices

Volumetric-absorption-based solar charging via phase change processes is an emerging technology to harvest solar energy, however, how pore-scale radiation transport interacts with latent heat thermal energy storage processes is still vague. In this paper, volumetric-absorption-based solar charging processes at pore scale are investigated by experiments and numerical simulations based on Monte Carlo ray tracing coupled with the Finite Volume Method. The solar radiation transport, temperature distribution, liquid fraction, and solar thermal energy storage efficiency are systematically evaluated under different radiation intensities and skeleton thermal conductivities. Compared to the traditional surface-absorption-based mode, solar thermal energy storage efficiency of the volumetric-absorption mode is enhanced by 94% due to presence of multi-region heat sources. The solar thermal energy storage efficiency reaches a peak value of 54.09% at a radiation intensity of 10 kW·m⁻². That is because low radiation intensities increase the melting time while too high intensities lead to large temperature nonuniformity, leading to high heat losses for both scenarios. Increasing the skeleton thermal conductivity can continuously improve the efficiency by reducing temperature nonuniformity, but further enhancement becomes marginal for thermal conductivity over 90 W·m⁻¹·K⁻¹. This work paves the way for the design and deployment of efficient integrated solar thermal conversion and latent heat storage systems.