Solar and thermal dual-band electrochromic windows for energy-efficient buildings
Jian Chen1,2, Jianwei Hu1,2, Banghai Wang2
1National Laboratory of Solid State Microstructures, School of Sustainable Energy and Resources, Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Suzhou, PR China.
Abstract:
Windows mediate over 60% of solar gain (0.38‒2.5 μm) in summer and more than 40% of radiative loss (2.5‒20 μm) in winter. Traditional electrochromic (EC) smart windows can manipulate heat only in visible and near-infrared wavelength regions by adjustable transmission, while neglecting the thermal radiation of long-wave infrared emissivity (ɛLWIR). Here, we report a solar and thermal dual-band EC (STDEC) window that independently modulates solar transmission (∆Tsol = 52.2%) and ɛLWIR (∆ɛLWIR = 0.87) by integrating a dynamic copper-bismuth (Cu-Bi)-based reversible metal electrodeposition system with a spatial rotation architecture. Consequently, the STDEC window lowers summer daytime temperatures by up to 22.2 °C and raises winter nighttime temperatures by up to 1.5 °C versus normal glass in outdoor thermal tests. Furthermore, building energy simulations suggest that our window demonstrates higher year-round energy savings and thus global carbon dioxide (CO2) emission reduction. This STDEC window provides a sustainable pathway towards energy-efficient buildings.
