rexresearch
Zhan CHEN, et al.
ZnSe
Radiative Cooler
https://techfinder.stanford.edu/technology/ultrahigh-performance-radiative-cooler
Ultrahigh
Performance Radiative Cooler
[ PDF ]
Stanford researchers at the Fan Group have designed and tested a
highly efficient radiative cooler prototype with the following
record-breaking performance results:
Temperature drop of 42 degrees Celsius (and theoretical drop of
60 degrees C). which approaches the fundamental limit on cooling
Daytime performance surpassed previous record by almost an order
of magnitude
Nighttime performance, carried out in a populous area at sea
level, significantly exceed previous record carried out at a
mountain-top desert.
This work demonstrates significant potential for radiative
cooling, which can have practical impacts ranging from passive
building cooling, renewable energy harvesting, and passive
refrigeration in arid regions.
Figure description - Experimental concept. a) Schematic of the
experimental setup. The key feature is to minimize parasitic
heat losses of convection and air conduction using a vacuum
system. Radiation shields and long hollow ceramic pegs are
exploited to further reduce the radiation and conduction losses
through the backside of the selective emitter. The shinny sun
shade and mirror cone are used to minimize solar irradiation.
ZnSe is selected for its transparency in the mid-infrared
wavelength range. b) In-situ experimental setup. c) Details of
the vacuum chamber, including the selective emitter and the ZnSe
window.
A radiative cooler is
provided having a thermally insulated vacuum chamber housing
that is configured to support a vacuum level of at least 10-5
Torr, an infared-transparent window that is sealably disposed on
top of the thermally insulated vacuum chamber and is transparet
in the range of 8-13 μm, a selective emitter disposed inside the
chamber, a mirror cone on the infared-transparent window, a
selective emitter inside the chamber and is configured to
passively dissipate heat from the earth into outer space through
the infared-transparent window and is thermally decoupled from
ambient air and solar irradiation but coupled to outer space, a
heat exchanger with inlet and outlet pipes disposed below the
selective emitter to cool water flowing through the pipe, a sun
shade disposed vertically outside the chamber to minimize direct
solar irradiation, and a mirror cone to minimize downward
atmospheric radiation.
https://www.nature.com/articles/ncomms13729
Nature Communications volume 7, Article number:
13729 (2016)
Radiative
cooling to deep sub-freezing temperatures through a 24-h
day–night cycle
Zhen Chen, Linxiao
Zhu, Aaswath Raman & Shanhui Fan
[ PDF ]
Radiative cooling
technology utilizes the atmospheric transparency window
(8–13 μm) to passively dissipate heat from Earth into outer
space (3 K). This technology has attracted broad interests from
both fundamental sciences and real world applications, ranging
from passive building cooling, renewable energy harvesting and
passive refrigeration in arid regions. However, the temperature
reduction experimentally demonstrated, thus far, has been
relatively modest. Here we theoretically show that ultra-large
temperature reduction for as much as 60 °C from ambient is
achievable by using a selective thermal emitter and by
eliminating parasitic thermal load, and experimentally
demonstrate a temperature reduction that far exceeds previous
works. In a populous area at sea level, we have achieved an
average temperature reduction of 37 °C from the ambient air
temperature through a 24-h day–night cycle, with a maximal
reduction of 42 °C that occurs when the experimental set-up
enclosing the emitter is exposed to peak solar irradiance.