Evaluation of the potential impact of electrochromic windows on the energy performance of commercial buildings

Electrochromic windows appear to be the most promising emerging technology to improve building performance as they provide greater control of solar gains; they have a potentially significant impact on the indoor visual environment and energy requirements of commercial buildings. The research work presented in this thesis, which is accomplished using computer simulation, proposes to undertake an engineering evaluation of the performance of electrochromic glazings and to advance knowledge in the field by developing a new model to simulate their control. First, the performance of an experimental electrochromic coating is compared relative to conventional glazing types. The APPLIED FILM LAMINATOR and WINDOW 4.1 computer programs are used to evaluate the global parameters characterizing window performance (solar and visible transmittance, U-value, and solar heat gain coefficient). A critical evaluation of existing control strategies is performed using DOE-2.1E to study the effect of several driving variables for switching on the cooling load of an existing large commercial building. The present capabilities of the DOE program are expanded using the Functional Values approach in order to study the effect of the electrochromic glazing switching time for the building's perimeter zones. Since electrochromic windows affect both building energy consumption and visual quality, the optimization of the switching time is formulated as a multi-objective model with two conflicting objectives (energy and visual quality). Pareto optimum solutions are shown for different weighting coefficients applied to both objectives. This approach constitutes the basis of an automated optimized electrochromic glazing switching strategy that is developed and incorporated in the DOE-2.1E program