Paraffin PCMs (Phase Change Materials) are widely used for thermal energy storage due to their homogeneity and stability. However, one of their main drawbacks lies in their poor thermal conductivity, usually around 0.2 W·m⁻¹·K⁻¹. In the context of the Horizon Europe project “ECHO” (Efficient Compact Modular Thermal Energy Storage System), the integration of metal foams within paraffin PCM was investigated in order to increase the overall thermal conductivity, thus speeding up the melting and solidification phases. Tests were carried out in a thermostatic bath using at first pure aluminum foam. Then, considering the consistent price these materials usually have, other commercial and much cheaper foams were also tested, namely a stainless-steel foam and a brass one. As expected, pure aluminum had the best performance among the three foams. However, the behavior of the brass foam was quite close to that of pure aluminum, which means that interesting improvements can be achieved even with low-cost materials. As regards the stainless-steel foam, barely any improvement is observed.

The construction sector is among the major players responsible for global energy consumption and therefore related emissions, both because of the constantly increasing indoor air quality standard which requires increasingly higher energy demands as well as the great share of historical buildings which are now obsolete and are not up to date with current regulations. Phase change materials (PCMs) applied on the building envelope represent a feasible possibility to improve the performance of existing buildings, also the historical ones, increasing their thermal inertia without violating any legal restriction or causing further alterations to the structure. More specifically, focus of this research was on the addition of a granular paraffin PCM into a lime-based plaster. Experimental tests at lab scale and numerical simulations with COMSOL Multiphysics were carried out to characterize the plasters realized, namely one reference lime-based plaster and one with incorporated 10% by mass of granular PCM (named REFp and PCMp, respectively). The behavior of these plasters applied on the exterior side of a wall was then simulated and compared in terms of temperatures and heat fluxes. However, considering that the estimated thermal conductivity of the reference lime-based plaster was lower than the values found in literature, the simulations were carried out considering an additional plaster, namely a lime-based plaster (renamed LITp), whose properties were found in literature and considered quite representative of a consistent share of existing historical buildings. Great improvements were observed from the application of PCM into the plaster, with reductions of the incoming energy between 9% and 18%.