Energy–Comfort–Cost Nexus: Optimizing PCM-Enhanced Thermal Mass in Continental Climates

This article presents the results of a computational parametric study, a global sensitivity analysis, multi-objective optimization, and a technical and economic evaluation of the parameters of phase-change materials (PCMs) incorporated into the building envelope of an office building in a sharply continental climate (using Astana, Kazakhstan, as an example). The study was conducted using simulation modeling, incorporating dynamic thermal calculations in the EnergyPlus software package and the NSGA-II genetic algorithm. The CondFD algorithm was used, for which results of independent verification and experimental validation conducted by other researchers have previously been published. This study used this validated implementation without conducting additional experimental verification of the structure under consideration. Based on the results of a parametric analysis (1232 calculations) and an optimization run (≈25,000 calculations), the range of quasi-optimal phase transition temperatures for the PCM was determined to be 23–25 °C. For further analysis and a technical–economic evaluation, a value of 24 °C was selected as the recommended compromise solution, with a PCM layer thickness of 16 mm and a distance of 15 mm from the inner surface of the wall. This compromise solution reduces annual specific energy consumption for heating and cooling by 22% and hours of thermal discomfort by 42% compared to a reference concrete wall without PCM. A technical and economic assessment, based on post-processing of the simulation results using current electricity rates and market data on the cost of PCM, shows a simple payback period ranging from 3.8 to 38 years, depending on the assumed cost of the encapsulated PCM layer. The results are limited to the specific case considered (south-facing orientation, standalone office module, and continuous ventilation) and are intended for subsequent experimental verification. The information in this article can be used by architects and engineers in the early stages of designing energy-efficient office buildings in regions with a sharply continental climate.