Work

All-optical seasonal energy saving windows

Year: 2025

Type: article

Abstract: Adaptive thermal regulation is crucial for year-round energy savings in buildings, especially in mid-latitude regions. Here, leveraging the seasonally varying angles of direct sunlight, we report a microprism-array sheet that enables seasonal energy saving windows. Guided by geometric optics, the asymmetric microprism-array sheet, featuring a silver coating on the sky-facing facets, exhibited an average transmittance of 10% in summer and 53% in winter at predominant sunlight angles, compared to 30% and 38% of a standard tint film, respectively. During outdoor testing in South Korea (37°N), a south-facing window integrated with the microprism-array sheet reduced floor temperatures by up to 5°C during direct sunlight hours, relative to a tinted window. Notably, in east-facing windows, the microprism-array sheet transitioned from heating to cooling around 9:00 a.m., highlighting its potential for modulating seasonal thermal management.

Source: iScience

DOI: 10.1016/j.isci.2025.112514

Authors: Beom-Su Kim, Jae-Hyun Kim, Gumin Kang, Hyungduk Ko, Qiaoqiang Gan, Sun-Kyung Kim

Institutions: Kyung Hee University, Korea Institute of Science and Technology, King Abdullah University of Science and Technology

Language: English

Topic: Thermal Radiation and Cooling Technologies

Subfield: Civil and Structural Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action

Open Access status: gold

Estimated APC paid: $3,240