Phase Change Materials Shape Stabilized in Biochar for Energy Efficiency and Structural Strength Enhancement in Buildings

In this work, a commercial phase change material (PCM) was stabilized in biochar, by vacuum impregnation technique and later incorporated into cement pastes to be used in real building applications. The selected paraffin is characterized by a phase transition temperature of 27 ℃, i.e., within the most common thermal comfort conditions in building applications. The obtained compounds were analyzed at various scales of investigation using advanced thermo-chemical techniques, to properly assess the composites’ thermophysical performance and long-term stability. The obtained results highlight the promising thermal buffer capability of the shape-stabilized samples during the early-stage hydration process. In general, all the compounds tend to lose PCM during cycling, but significant leakage was only found after 1000 thermal cycles, suggesting a relatively stable behavior. Adding the shape stabilized PCM lowers the peak temperature by about 4 and 5 ℃ compared to the normal and the biochar-doped composite with positive consequences regarding compressive strength.