Progress in passive daytime radiative cooling from spectral design to real application

Frequent heatwaves and rising global temperatures underscore the urgent need for energy-efficient cooling solutions. Traditional cooling systems consume 10% of global electricity and exacerbate greenhouse gas emissions. In contrast, passive daytime radiative cooling (PDRC) operates without energy input by reflecting solar radiation and emitting heat directly to outer space through the atmospheric transparency window (ATW, 8–13 μm), achieving sub-ambient temperatures even under sunlight.

A team of chemical scientists led by Rufan Zhang from Tsinghua University in Beijing, China, has recently reviewed the advancements in PDRC over the past decade, covering aspects from spectral design to practical applications. PDRC represents an ideal solution for addressing global warming due to its ability to cool passively without external energy input. Current research focuses on optimizing solar band and long-wave infrared radiation band spectrum to maximize practical cooling power, particularly during daylight hours. Additionally, PDRC materials have been enhanced with additional practical characteristics to meet user demands.

The team published their review in Carbon Future on January 7, 2025.

“Our review not only summarizes breakthroughs in PDRC design but also addresses the gap between lab research and practical implementation,” said Prof. Zhang, a tenured associate professor and doctoral supervisor in Tsinghua’s Department of Chemical Engineering. “By tailoring spectral properties and enhancing durability, we aim to make PDRC a mainstream solution for global cooling demands.”

PDRC leverages the outer space environment (~3 K) as a natural cold sink by dissipating thermal radiation through ATW, while simultaneously reflecting solar heat input (~5800 K) by designed photonic structures. This mechanism enables continuous and spontaneous thermal dissipation.

The team highlighted applications in diverse fields:

1. Building Design: PDRC coatings reduce indoor temperatures without electricity.
2. Human Thermal Management: Radiative textiles cool the body by emitting heat outward.
3. Photovoltaics: Cooling solar panels to improve efficiency.
4. Water Harvesting: Condensing atmospheric moisture in arid regions.

However, substantial challenges remain for PDRC technology, particularly regarding its limited application scenarios and functionality. Different contexts necessitate tailored spectral designs and enhanced performance from PDRC materials. In previous research efforts by Zhang’s team, they developed an all-weather radiative textile designed specifically for human body cooling. This innovative textile not only facilitates heat dissipation from the human body but also emits radiation outward to optimize subambient cooling efficiency. “We are pleased to observe that PDRC technology is attracting increasing interest from researchers aiming to enhance its cooling performance and bridge the gap between academic research and practical applications.” remarked Rufan Zhang.

The review also emphasizes interdisciplinary collaboration to advance PDRC’s role in mitigating climate change. The team envisions PDRC as a cornerstone of sustainable cooling strategies.

Other contributors include Zhuojing Zhao, Siming Zhao, Jiaqi Xu, Xueke Wu, Zhenyu Guo, and Ya Huang from Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology in Department of Chemical Engineering at Tsinghua University in Beijing, China.

This work was supported by the National Key Research and Development Program of China (2020YFA0210702, 2020YFC2201103) and the Tongcheng R&D Foundation.

About Carbon Future

Carbon Future is an open access, peer-reviewed, and international interdisciplinary journal Sponsored by Tsinghua University, published by Tsinghua University Press, and exclusively available via SciOpen. It serves as a platform for researchers, scientists, and industry professionals to share their findings and insights on carbon-related materials and processes, including catalysis, energy storage and conversion, as well as low carbon emission process and engineering. It features cutting-edge research articles, insightful reviews, perspectives, highlights, and news and views in the field of carbon (the article publishing charge is covered by the Tsinghua University Press).

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