Multi-objective optimization of electrochromic windows in office buildings for different climatic conditions

Abstract

Electrochromic windows stand out as a subset of smart windows that effectively manage sunlight, thereby contributing significantly to energy efficiency and occupant comfort. In this paper, a methodology is presented for determining the optimal properties of electrochromic windows in six distinct cities characterized by varying climates. The cities under examination include Tehran, Sari, Yazd, Shiraz, Esfahan, and Tabriz. The optimization method uses a multi-objective approach to optimize various design variables for electrochromic windows, such as thickness of glass panes, gas layer properties, and window-to-wall ratio. Additionally, it identifies optimal illuminance, heating, and cooling setpoints to enhance electrochromic window performance. The objectives under consideration include the total annual electricity consumption (E) and the Predicted Percentage of Dissatisfied (PPD) coefficient. To facilitate this optimization, Non-Dominated Sorting Genetic Algorithm II (NSGA-II) is employed, generating a Pareto front. The Discomfort Glare Index (DGI) parameter is subsequently computed at the Pareto points to determine the final optimal solution. The results demonstrate that in Esfahan, the implementation of optimum electrochromic windows yields the most substantial reductions in electricity consumption (27.6 %) and PPD coefficient (29.7 %). Furthermore, Krypton gas is identified as the most suitable gas for deployment in optimal electrochromic windows. © 2025 Elsevier Ltd