Precooling strategies integrated with switchable insulated shading systems applied to US Office buildings

This paper examines the energy performance of innovative window shading systems dynamically adjust the optical and thermal properties of windows. Specifically, the energy benefits of deploying these switchable insulated shading (SIS) systems are estimated with and without precooling strategies in U.S. office buildings. Both ruleset-based and optimization-based controls are evaluated to operate SIS systems and implement precooling strategies to maximize free cooling. The analysis is carried out using EnergyPlus, a state-of-the-art whole building simulation too, for the rule-based controls, and a Genetic Algorithm (GA), part of MATLAB, is employed to identify optimal control settings as a theoretical benchmark. The rule-based and optimal controls reduce both energy use and daytime peak demand associated with air conditioning in office spaces. The energy performance of SIS, when applied to windows and combined with precooling strategies for indoor thermal mass, is assessed for various designs and operating conditions. The analysis indicates that integrating SIS with precooling can achieve significant reductions in air conditioning energy usage and peak daytime demand, particularly when optimal controls are utilized. Even with ruleset-based controls, SIS can achieve annual heating and cooling energy savings of over 26.6 % for office spaces in San Francisco, CA. Additionally, combining SIS with precooling can reduce peak daytime cooling demand by 34 % in office spaces in Golden, CO. These benefits can be further enhanced by incorporating other energy efficiency measures, such as lighting system upgrades and optimized office equipment, especially in office spaces with higher thermal mass.