Energy savings due to building integration of innovative solid-state electrochromic devices

The next generation of adaptive facades includes dynamic electrochromic (EC) windows: they can dynamically modulate the daylight and solar energy entering buildings by application of an external voltage. Windows play a pivotal role in the definition of the energy balance as well as environmental impacts of buildings. Emerging technologies are focused on the optimization of these building components. We carried out an interdisciplinary study dealing with building integration of an innovative chromogenic technology, consisting in a recently designed single substrate solid-state electrochromic device, developed by some of the authors, with excellent figures and a compact device architecture. The practical implications on the building energy balance were analyzed by means of suitable simulations, carried out in Energy Plus. A reference office building was equipped with different glass technologies on the façade (clear glass, solar control, electrochromic glasses) and located in different cities (Rome, London and Aswan) to also include climatic effects in the analysis. The EC technology here presented outperforms all the others, with overall yearly energy savings as high as 40 kW h/m yr (referred to window surface) in the hottest climates, assuming the clear glazings as benchmark. Daylighting performances were significantly improved using innovative solid-state EC devices, both in terms of Useful Daylight Illuminance (UDI) and Discomfort Glare Index (DGI). In the best case, 82.7% of hours achieved optimal illuminance conditions on an annual basis.