Scalable Fabrication of Thermochromic Smart Windows for Broadening Temperature Ranges and Their Coupled Thermoelectric Power Generation

Abstract

Thermochromic materials exhibit variable optical properties in response to ambient temperature changes and are promising for the development of smart windows aimed at reducing energy consumption in buildings. However, scaling up the thermochromic materials-based smart window with a broad color-changing range remains a significant challenge for practical engineering applications. In this study, we present a series of PNIPAm-based thermochromic hydrogels with controllable discoloration temperatures ranging from 24 to 43 °C, achieved by regulating the swelling–dissolution transition. These materials demonstrate a high solar modulation capacity (>81%), excellent transmittance (>83%), and low haze value (<9.87%). Two strategies for the integration of smart windows are provided, and their effectiveness in reducing energy consumption is verified. Practical application tests conducted in Shanghai during the summer show that using smart windows can reduce indoor temperatures by up to 13 °C. Simulation results further indicate that these smart windows offer significant energy-saving benefits in various cities, particularly those with high daily energy consumption and poor thermal insulation. Additionally, the thermochromic hydrogel is coupled with a thermoelectric hydrogel, utilizing the residual heat from the glass surface to generate electricity, thus powering small electrical appliances.