On-demand electro-/thermo-chromic smart windows with self-adaptive sensible heat storage for multimode synergistic building energy conservation

Conferring smart windows with sensible heat storage capacity could enable powerful energy and optical modulation capacity in buildings toward the desired net-zero carbon goal. However, fabricating transparent chromic devices using thermal energy storage materials to achieve heat storage and on-demand optical modulation remains a challenge. Herein, an energy-efficient smart window that enables heat storage capacity and multimode optical modulation is demonstrated by integrating a thermochromic (TC) hydrogel with thermal energy storage ability and an electrochromic (EC) material. Specifically, the developed chromic device exhibits an outstanding specific heat capacity of ∼4.45 J·g−1·K−1 for self-adaptively (SA) storing/releasing the heat and can achieve high optical modulation (∆TSol = 69.90 % with a wavelength range of 250–2500 nm) through optional heat/electricity combinations. These intriguing properties endow the smart window with multiple management modes toward heat and transmittance including the SA mode, EC mode, and TC mode, which can realize an indoor temperature drop of 21.8 °C, 24.1 °C, and 28.0 °C under a sun irradiation of 1 kW·m−2. Energy simulation results further demonstrate the substantial building energy conservation (43.32 MJ·m−2) of this smart window while providing remarkable indoor comfort. This work offers a viable yet simple strategy to realize more energy-efficient buildings with a minimum carbon footprint for global carbon neutrality.