Tech Briefs Magazine - April 2021 - 13

Q&A

NEW!

4 AXIS SERVO
from

Electricity-Free Cooling
Professor Qiaoqiang
Gan of the University
at Buffalo (NY) and
his team developed a
unique two-in-one system that uses solar
energy for simultaneously cooling and heating - without electricity.
Tech Briefs: What got you started
on this project?
Professor Qiaoqiang Gan: We have
been working on sustainable technologies for quite a long time, focusing on
solar energy and water treatment. That
brought us to electricity-free cooling
technology, which is an emergent research area at this moment.
Tech Briefs: Could you describe
your system?
Gan: We built a V-shaped structure
with two solar absorption mirrors, each
at a tilt angle of 45°. The mirrors are
made of ten extremely thin layers of
mixed silver and silicon dioxide. In
between the mirrors is a vertically
aligned, two-sided thermal emitter
made from transparent polydimethylsiloxane (PDMS) film.
The special composition of the mirrors allows them to have a double function. Heat from the thermal emitter is
radiated from both of its sides to the
mirrors, which redirect it to the sky. At
the same time, they absorb incident
sunlight so that it will not heat the
emitter.
Our special double structure has
enabled the system to reach over 270
W/m2, as compared to the natural cooling limit of approximately 160 W/m2
for a typical radiative cooling system.
We are able to maximize the radiative
cooling effect because the energyabsorbing mirrors shield the thermal
emitter from sunlight.

Tech Briefs: How did you test your
system?

2.25 "

Gan: We actually performed the tests
under two different conditions: one
indoors and the other outdoors. For
the indoor test, the heat from the emitter was radiated to a heat sink to simulate nighttime conditions. For the outdoor test, the sky served as the heat
sink. To perform the outdoor test, we
placed the structure in a polystyrene
foam box, which was sealed with a polyethylene film.
Tech Briefs: What were the results?
Gan: Under the outdoor conditions,
we were able to reduce the temperature
in the test box by about 12 °C below
ambient. For the indoor test, we were
able to do about 14 °C.
Tech Briefs: How does the system
simultaneously accomplish
heating?
Gan: Previous radiative cooling systems just blocked the sunlight - they
didn't make full use of it. Solar energy
is around 1000 W/m2; however, our
cooling technology is only around 100
to 150 W/m2. Since our special mirrors absorb the incoming sunlight, we
can make use of that energy to heat
water.

- brushed or bldc motors
- 5 amps per axis
- 16 analog inputs
- 16 on/off drivers
- home and limit in
- live tech support
- made in the USA
See the

EZQUAD SERVO
in action!

Tech Briefs: How long until the
system is commercialized?
Gan: Currently, our startup company (Sunny Clean Water) is looking for
opportunities through federal or private agencies. So, if someone is interested and puts in resources, I believe
we can develop something within one
year.
Read the full transcript of this Q&A at
www.techbriefs.com.

Tech Briefs, April 2021

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Tech Briefs Magazine - April 2021

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