All-weather thermochromic windows for synchronous solar and thermal radiation regulation

Chongjia Lin; Jun Hur; Christopher Y H Chao; Gongze Liu; Shuhuai Yao; Weihong Li; Baoling Huang

doi:10.1126/sciadv.abn7359

All-weather thermochromic windows for synchronous solar and thermal radiation regulation

Sci Adv. 2022 Apr 29;8(17):eabn7359. doi: 10.1126/sciadv.abn7359. Epub 2022 Apr 29.

Authors

Chongjia Lin¹, Jun Hur¹, Christopher Y H Chao², Gongze Liu¹, Shuhuai Yao¹, Weihong Li^{1

3}, Baoling Huang^{1

4}

Affiliations

¹ Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
² Department of Building Environment and Energy Engineering and Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
³ Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong, China.
⁴ HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute, Futian, Shenzhen, China.

Abstract

Adaptive control of solar and thermal radiation through windows is of pivotal importance for building energy saving. However, such synchronous passive regulations are challenging to be integrated into one thermochromic window. Here, we develop a solar and thermal regulatory (STR) window by integrating poly(N-isopropylacrylamide) (pNIPAm) and silver nanowires (AgNWs) into pNIPAm/AgNW composites. A hitherto unexplored mechanism, originating from the temperature-triggered water capture and release due to pNIPAm phase transition, is exploited to achieve simultaneous regulations of solar transmission and thermal emission. The STR window shows excellent solar modulation (58.4%) and thermal modulation (57.1%) and demonstrates effective regulation of indoor temperatures during both daytime and nighttime. Compared to other thermochromic technologies, the STR window reduces heat loss in cold environment while promotes heat dissipation in hot conditions, achieving efficient energy saving in all weathers. This dual solar and thermal regulation mechanism may provide unidentified insights into the advancement of smart window technology.