Thermochromic hydrogel couple energy storage integrated smart window with adjustable temperature point and thermochromic temperature zone

The huge heat loss/gain through windows is the reason for a large amount of energy consumption in buildings. Although using the heat storage capacity of phase change material (PCM) to improve the thermal inertia of windows is an important way to reduce energy consumption, leakage and overheating at noon limit the development of windows containing solid–liquid PCM. Smart windows based on temperature-sensitive hydrogel have aroused great interest due to their excellent ability to dynamically control solar energy. However, current temperature-sensitive hydrogels with single transition temperature and uncontrollable transition speed affect indoor light comfort. Meanwhile, the low heat storage performance of hydrogels limited their energy-saving effect. Therefore, a novel smart window (P3H6) integrating temperature sensitivity and energy storage was constructed by the prepared hydrogel and form-stable PCM. The double-network hydrogel with adjustable temperature band and mechanical enhancement was constructed by acrylamide and N-isopropylacrylamide, which realized the dynamic adjustment of solar energy. The prepared form-stable PCM avoided the leakage problem and improved the heat storage capacity of the window. The comprehensive transmittance of P3H6 can be changed between 3.3 %-62.7 %-2.6 % in a day, which blocked the sunlight from transmitting heat at noon and protected privacy at night. The outdoor experiments showed that P3H6 delayed the inner surface temperature of the window to 32 °C by 1.05 h compared with traditional windows, which reduced the thermal radiation of windows to the room and improved the thermal comfort of indoor personnel. More importantly, the application of P3H6 can reduce the daytime cooling load of buildings by 28.84 %. To sum up, the proposed smart window shows great potential in energy-saving buildings.