Numerical Optimization for the Design of Geopolymer Concrete Walls with Phase Change Materials in the Mediterranean Climate

The adoption of phase change materials (PCMs) is a promising solution for the improvement of building energy performances and indoor comfort, and the integration of geopolymer concrete (GPC) allows recycling materials and reducing the demand for raw materials in concrete production. Both materials contribute to reducing the carbon dioxide emission in the building lifecycle. In this frame, this paper proposes a complete numerical approach for selecting the optimal wall package made of GPC and PCMs in a Mediterranean climate. The first step of the method consists of a parametric analysis for evaluating the incidence on energy performance and thermal comfort of the main designing variables: insulation thickness, air cavity type and its thickness, and PCMs type. Then, assuming the discomfort hours as a limiting constraint, a multi-objective optimization is applied to a subset of solutions for determining the Pareto front solutions. The advantage of the proposed methodology is the combined evaluations of multiple variables with a simplicity in execution; for this reason, it is useful for other researchers aimed at studying innovative solutions. According to obtained results, the better exposure for the proposed wall package is the north or northeast one. The minimization of the cooling energy demand requires the adoption of two PCMs, on internal and external sides, with melting temperature of 26 °C. The optimization of yearly performance requires the adoption of the maximum insulation level on both sides and a not-ventilated air gap between the modules. The cooling and heating energy need can be reduced, respectively, by around −29% and −57%, compared to a reference configuration with vacuum insulation panels and thermal transmittance of 0.4 W/m2 K.