The integration of phase change materials (PCMs) and metal foam has been widely concerned recently. To decrease non-uniformity of uniform metal foam-PCMs, adaptive metal foam arrangement strategy with increasing porosity from inside to outside has attracted widespread attention. This work conducted a symmetric simulation model of vertical thermal energy storage (TES) tube validated by experiments, for optimization of adaptive metal foam arrangement in basic design (0.94–0.94–0.94). It was followed by assessing the performance of gradient metal foam structures that included 27 cases with radial foam gradients of larger porosity on the outside and smaller porosity on the inside. Results demonstrated that a smaller difference between the inside and outside subregions resulted in better thermal performance when the same porosity of the intermediate subregion was used. More intense natural convection with stronger liquid paraffin vortex could be obtained by an adaptive arrangement. With the same average porosity, the faster phase change evolution, which was influenced by the maximum promotion of stronger natural convection, was achieved by using a larger intermediate porosity and a larger porosity difference between the inside and outside regions. The optimal strategy (0.87–0.94–0.97) could significantly shorten the melting duration as maximal as 17.15% compared with the original uniform (0.94–0.94–0.94), which contributed to efficient vertical metal foam TES systems, also as light and cost-effective as possible while also avoiding sacrificing thermal capacity.

Solar energy, as a kind of renewable energy, offers a large reserve to be harvested at a reasonably low cost for engineering applications. To decouple the temporal and spatial relevance of the continuous energy supply of solar energy, latent heat thermal energy storage can deal with this problem at different temperatures. Aiming to improve energy efficiency, a novel hybrid metal foam-pin fin structure is designed and assessed. Upon conducting measurements on a well-designed experimental bench, the phase change processes of paraffin that is filled in fins, metal foam, and a combination of both (hybrid structure) are evaluated. During the experiments, the transient melting interface is snapshotted and temperature development is documented under five different heat source temperatures of 61 °C, 63 °C, 65 °C, 68 °C, and 70 °C. In the foreground of the novel hybrid structure, each segment of the hybrid is also justified and discussed. Results indicate that the hybrid structure augments marked heat transfer. Compared to pure PCM, complete melting time decreases by 63.4% and simultaneously the temperature response rate increases by 143.9% as implementing the hybrid. Attempts to design hybrid structure find a solution to assess and operate thermal storage applications for solar engineering.