Aqueous mid-infrared electrically switchable opaque building envelopes for all-season radiative thermoregulation

Radiative thermoregulation has been considered a promising approach for reducing the heating, ventilation, and air-conditioning (HVAC) energy consumption of buildings and solving the global climate change issues. Electrochromism is a powerful way to dynamically control the heat balance of buildings in response to fluctuating weather conditions, but it has been largely limited to visible and near-infrared wavelength regimes. Here, we develop an aqueous flexible electrochromic system based on graphene ultra-wideband transparent conductive electrode and reversible electrodeposition, which can non-volatilely tune the thermal emissivity between 0.07 (heating) and 0.92 (cooling) with substantial long-term stability and durability. Building energy simulation demonstrates that applying our electrochromic device to building envelopes can save the year-round operational HVAC energy consumption across the U.S., especially in cold climate zone (up to 43.1 MBtu on average among climate zones 5-8). Furthermore, such a dynamic building envelope shows more profound benefits on less insulated buildings, with up to 19.44% of the year-round operational HVAC energy saving for building with only 25% insulation layer, which can serve as a technological solution to retrofit historical buildings or to complement newly constructed buildings with less insulation for lower embodied carbon.