Simultaneous design and control optimization of smart glazed windows

Abstract

The paper examines the benefits of simultaneous optimization of various design and control parameters for smart glazing windows of office buildings. The design variables include the window U-value, solar heat gain coefficient (SHGC), visible transmittance (Tvis), and window-to-wall ratio (WWR). The tint-switching control strategies reviewed include outdoor air temperature (OAT), indoor air temperature (IAT), incident total solar radiation (ITSR), and incident beam solar radiation (IBSR). These variables are optimized independently and simultaneously to determine the best specifications to minimize operating costs while maintained desired thermal and visual comfort levels. Specifically, electrochromic (EC) smart glazed windows are optimally designed and controlled when installed for a prototypical medium office building in Denver, Colorado. The optimization analysis results are considered to determine the breakeven installation costs required for smart glazing systems to be cost competitive compared to their static glazing counterparts. The analysis found that the annual energy cost savings from optimally designed and controlled smart glazed windows ranged from 11% − 18%. Of the design parameters, the U-value proved to be the most impactful on energy and cost reductions, followed by SHGC and WWR. Indoor and outdoor air temperature-based controls are determined the most effective operation strategies. Simultaneously optimizing for the design and control parameters provided the highest annual savings.