Energy performance of control strategies for smart glazed windows applied to office buildings

Abstract

This paper presents a systematic analysis for the energy performance of control strategies specific to smart glazed windows when applied to office spaces. In particular, the energy efficiency benefits of rule-based and optimized controls to operate smart glazing are evaluated for office spaces. Several rule-based control strategies are considered to operate smart glazed windows including those that switch to specific tint levels using measurable environmental parameters such as outdoor ambient air temperatures as well as direct and total solar radiations. In addition, the analysis evaluates optimal controls that minimize the total energy consumption for the office space with and without daylighting capabilities using hourly, daily, or monthly switching frequencies. The results of various sensitivity analyses indicate that optimized controls perform generally better than rule-based controls even when their threshold settings are adequately selected. However, the performance of rule-based controls can be substantially enhanced when optimal threshold settings are used to switch between various smart glazing tint states. These optimal switching settings depend on various factors including the type of smart glazing used as well as orientation and size of the windows and the location of the office space. Moreover, the analysis indicates that optimized hourly settings provide higher energy savings than any other control strategy with reduction of annual energy consumption of the office spaces reaching up to 20% relative to static glazing.