Performance criteria for dynamic window systems using nano-structured behaviors for energy harvesting and environmental comfort

Contemporary commercial building types continue to incorporate predominantly glazed envelope systems, despite the associated challenges with thermal regulation, visual comfort, and increased energy consumption. The advantage of window systems that could adaptively respond to changes in the environment while meeting variable demands for building energy use and occupant comfort has led to considerable investment towards the advancement of dynamic window technologies. Although these technologies demonstrate cost warranting improvements in building energy performance, they face challenges with visible clarity, color variability and response time. Furthermore, they remain challenged with respect to their ability to adequately control important qualitative criteria for daylighting such as glare and balanced light redistribution within occupied spaces. The material dependent limitations of advanced glazing technologies have initiated a search for new thin film solutions, with new device possibilities emerging across many fields. Idealized window performance has traditionally been defined as the dynamic control of solar transmittance, glare, solar gain and daylighting at any time to manage energy, comfort and view. However, in the context of wider goals towards building energy self-sufficiency through the achievement of on-site net zero energy, emerging material systems point towards other physical phenomena for achieving transparency modulation and energy harvesting, demanding a broader range of criteria for advanced glazing controls that allow the glazed building envelope to exist as a transfer function that can address and potentially accommodate the following five principal criteria: 1. Thermal management; 2. Daylighting harvesting and modulation; 3. Maintenance of views; 4. Active power capture, transfer, storage and redistribution; 5. Information Display. Building upon the existing set of performance requirements for high-performance glazing, this paper prescribes additional system functions using nano-structured behaviors operating within insulated glazing units (IGU) for energy harvesting opportunities and increased environmental comfort. Specifically, the proposed goal is to incorporate multiple functions that span energy performance with culturally valuable attributes such as variable patterning and information display.