Fig. 4: Real-world performance and energy-saving assessment of PDH smart windows.

a Experimental house model. In the control group, the interior was lined with thermal insulation, and the roof was fitted with a conventional glass window and temperature sensors; the experimental group was arranged identically except that the roof window was replaced with a hydrogel smart window. This figure was created with Microsoft PowerPoint. b Schematic illustration of the PDH hydrogel film (PHF) and the PDH hydrogel packaged film (PHPF). c Transmittance spectra of PHF smart window (SW) and PHPF smart window in the solar wavelength range. d Comparison of the temperature regulation performance of PHF and PHPF smart windows, along with real-time ambient temperature (yellow curve) and solar irradiance (bar chart). e Differences in service life and mass retention among PNIPAm hydrogel film, PHF, and PHPF. Red circles indicate the time point at which the smart window (SW) lost its thermochromic capability. f Photographs of windows made from PHPF, low emissivity (Low-E) film, and conventional glass in real building applications, shown here with the PHPF smart window in its opaque state. g Comparison of the temperature regulation performance of windows made from PHPF, Low-E film, and conventional glass, together with real-time ambient temperature (yellow curve) and solar irradiance (bar chart). h Variation of heat flux density of the PHPF smart window (experimental group) over time and its estimated daily energy savings.