Radiative cooler that cools down even under sunlight

Date:
October 20, 2020
Source:
Pohang University of Science & Technology (POSTECH)
Summary:
Now that autumn is upon us, there is a large temperature gap between
day and night. This is due to the temperature inversion caused by
radiative cooling on the Earth's surface. Heat from the sun during
the day causes its temperature to rise and when the sun sets during
the night, its temperature cools down. Recently, a research team
has demonstrated a daytime radiative cooling effect which exhibits
lower temperatures than its surroundings even during the day.



FULL STORY ==========================================================================
Now that autumn is upon us, there is a large temperature gap between day
and night. This is due to the temperature inversion caused by radiative
cooling on the Earth's surface. Heat from the sun during the day causes
its temperature to rise and when the sun sets during the night, its
temperature cools down.

Recently, a joint research team from POSTECH and Korea University has demonstrated a daytime radiative cooling effect which exhibits lower temperatures than its surroundings even during the day.


========================================================================== Professor Junsuk Rho and Ph.D. candidate Dasol Lee of departments of
mechanical engineering and chemical engineering and Professor Jin Kon
Kim and Ph.D.

candidate Myeongcheol Go in the Department of Chemical Engineering at
POSTECH have conducted a joint study with Professor Heon Lee of Materials Science Engineering at Korea University to successfully realized an
energy-free radiative cooling technology using silica-coated porous
anodic aluminum oxide.

The study was published in the latest online edition of Nano Energy,
an international journal in the energy sector.

With growing interest in energy consumption, such as environmental
pollution and limitations in using fossil fuels, attempts to lower
the temperature without consuming energy continue. Radiative cooling
is an example of structures installed on windows or walls to reduce the building temperature by reflecting sunlight or by absorbing and radiating far-infrared light. Radiative cooling is a technology that allows objects
to receive less energy from the sun and lower temperatures by emitting radiative heat.

Unlike conventional cooling systems, radiative cooling is difficult to
apply to large areas, although it has the advantage of significantly
reducing energy consumption like electricity. Research to overcome this
issue is being actively carried out around the world but it is still challenging to commercialize the technology.

To this, the joint research team found a very simple solution. Just by
coating the porous anodic aluminum with a thin film of silica, it has
been confirmed that there is a cooling effect that exhibits a lower
temperature than the surroundings even under direct sunlight.

Experiments have confirmed that an optimized structure can have a
reflectivity of 86% in the solar spectral region and a high emissivity
of 96% in the atmospheric window (8-13 ?m). In addition, the radiative
cooling material - - produced in centimeters -- showed a cooling
efficiency of up to 6.1DEGC during the day when the sunlight was strong.

"This newly developed radiative cooling material can be easily produced," explained POSTECH Professor Junsuk Rho. He added optimistically,
"It will help solve environmental problems if applied to heating and
cooling systems since it can be readily applied to large areas."

========================================================================== Story Source: Materials provided by Pohang_University_of_Science_&_Technology_(POSTECH).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Dasol Lee, Myeongcheol Go, Soomin Son, Minkyung Kim, Trevon
Badloe, Heon
Lee, Jin Kon Kim, Junsuk Rho. Sub-ambient daytime radiative cooling
by silica-coated porous anodic aluminum oxide. Nano Energy, 2021;
79: 105426 DOI: 10.1016/j.nanoen.2020.105426 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201020105545.htm

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