Organic Phase Change Materials (PCMs) represent an attractive solution for Thermal Energy Storage (TES) purposes. Indeed, their solid-liquid phase change allows them to store approximately 200-250 kJ/kg as latent heat of transformation. Notwithstanding their potential, combined with tunable transition temperatures up to 100°C, their intrinsic low thermal conductivity critically limits their performances. Different strategies are proposed in the literature to effectively tackle this issue: increasing the thermal exchange surface or dispersing a highly conductive phase in the PCM phase rather than percolating PCM in a macroscopic skeleton. Regarding this latter, Additive Manufacturing techniques enable the production of topologically complex structures. In this framework, Triply Periodic Minimal Surfaces (TPMS), offering surface energy minimization, represent a valuable candidate to be combined with organic PCMs for composite PCMs (C-PCMs) with unique thermal performances. 

Primitive-Schwarz (PS) TPMS metallic skeleton was chosen to be percolated with organic PCM. The thermal response of a small set of reference C-PCMs structures was evaluated with FEA in transient states, setting temperatures/heat flux input as boundary conditions. At first, the study compares the behaviour of the PS-based composite and the one offered by conventional metallic foams, modelled as inverse BCC structures. The advantages of adopting one rather than the other structure are  discussed. The impact of the variation of the lattice size and number of stacked cells, representative of the overall thickness of the C-PCM, on the thermal response of the PS composite is assessed under uniaxial heat flux conditions. Finally, the impact of different PCM materials is evaluated. Smaller cells at the same porosity granted faster responses and more homogeneous temperature distributions, demonstrating the importance of properly tuning the design parameters beyond the effective thermal conductivity of the C-PCM. The beneficial impact of the TPMS morphology proves to be more pronounced when the volume fraction of the PCM is higher.