U.S. patent application number 12/644985 was filed with the patent office on 2010-06-24 for element for emission of thermal radiation.
This patent application is currently assigned to University of Technology. Invention is credited to Geoffrey Burton SMITH.
Application Number | 20100155043 12/644985 |
Document ID | / |
Family ID | 40263076 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100155043 |
Kind Code |
A1 |
SMITH; Geoffrey Burton |
June 24, 2010 |
ELEMENT FOR EMISSION OF THERMAL RADIATION
Abstract
The present disclosure provides an element for emission of
thermal radiation. The element comprises particles arranged for
receiving thermal energy and emitting at least a portion of the
received thermal energy in the form of the thermal radiation. The
thermal radiation predominantly has a wavelength or wavelength
range within an atmospheric window wavelength range in which the
atmosphere of the Earth has a reduced average absorption and
emission compared with an average absorption and emission in an
adjacent wavelength range whereby absorption by the element of
radiation from the atmosphere is reduced.
Inventors: |
SMITH; Geoffrey Burton;
(Epping, AU) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
University of Technology
Sydney
AU
|
Family ID: |
40263076 |
Appl. No.: |
12/644985 |
Filed: |
December 22, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/AU2008/000892 |
Jun 19, 2008 |
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12644985 |
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PCT/AU2008/000893 |
Jun 19, 2008 |
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PCT/AU2008/000892 |
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Current U.S.
Class: |
165/185 |
Current CPC
Class: |
F25D 2331/805 20130101;
C09K 5/14 20130101; G02B 5/26 20130101; F25B 23/003 20130101; E06B
2009/2411 20130101; F28F 2245/06 20130101; F25D 31/007 20130101;
F28F 13/18 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2007 |
AU |
2007202832 |
Sep 28, 2007 |
AU |
2007221733 |
Claims
1. An element for emission of thermal radiation, the element
comprising a component arranged for receiving thermal energy and
emitting at least a portion of the received thermal energy in the
form of the thermal radiation, the thermal radiation predominantly
having a wavelength or wavelength range within an atmospheric
window wavelength range in which the atmosphere of the Earth has a
reduced average absorption and emission compared with an average
absorption and emission in an adjacent wavelength range whereby
absorption by the element of radiation from the atmosphere is
reduced.
2. The element of claim 1 wherein the atmospheric window wavelength
range includes a minimum of the average absorption of the
atmosphere of the Earth.
3. The element of claim 1 wherein the atmospheric window wavelength
range is a wavelength range from 3 to 5 .mu.m and/or from 7.9 .mu.m
to 13 .mu.m.
4. The element of claim 1 wherein the element comprises particles
arranged for receiving thermal energy and emitting at least a
portion of the received thermal energy in the form of the thermal
radiation.
5. The element of claim 1 wherein the element comprises a layer
arranged for receiving thermal energy and emitting at least a
portion of the received thermal energy in the form of the thermal
radiation.
6. The element of claim 4 wherein the particles are distributed
throughout the element and the element also comprises a material
that is substantially transmissive for radiation having a
wavelength within the atmospheric window range.
7. The element of claim 1 comprising a cover that is substantially
transmissive for the thermal radiation and that is arranged for
reduction of exchange of thermal energy by convection.
8. The element of any claim 7 comprising wall portions that define
an interior space within which a medium that is to be cooled is in
use located.
9. The element of claim 8 wherein the wall portions comprise a
reflective material.
10. The element of claim 8 wherein at least some of the wall
portions are thermally insulating.
11. The element of claim 1 comprising a structure that has
projecting wall portions which are positioned so that, in use,
incoming radiation from regions of the atmosphere, which are near
the horizon, is substantially blocked off.
12. The element of claim 1 comprising a structure that has
projecting wall portions that are reflective for the thermal
radiation emitted by the component arranged for receiving thermal
energy and emitting at least a portion of the received thermal
energy in the form of the thermal radiation.
13. The element of claim 12 wherein the projecting wall portions
are positioned so that in use the emitted thermal radiation is
directed in a direction towards Space and in a direction away from
the horizon.
14. The element of claim 1 any one of comprising a concentrator for
concentrating radiation.
15. The element of claim 1 wherein the element is substantially
transparent for visible light.
16. The element of claim 1 wherein the element comprises a
substantially transparent polymeric material that comprises the
component for emission of the thermal radiation and wherein the
element is arranged so that in use at least a portion of the
incoming near infrared radiation is absorbed and the resulting
absorbed thermal energy is at least partially re-emitted in the
form of thermal radiation by the component arranged for emission of
radiation having a wavelength within the atmospheric window
wavelength range.
17. The element of claim 1 wherein the element forms a part of an
object.
18. A cooling system comprising thermally insulating wall portions
and comprising the element of claims 1 wherein the cooling system
is arranged for cooling an object that is positionable in, and
removable from, an interior formed by the thermally insulating wall
portion.
19. A cooling device for cooling a medium, the cooling device
comprising an element for emission of thermal radiation, the
element comprising particles arranged for receiving thermal energy
and emitting at least a portion of the received thermal energy in
the form of the thermal radiation, the thermal radiation
predominantly having a wavelength or wavelength range within an
atmospheric window wavelength range in which the atmosphere of the
Earth has a reduced average absorption and emission compared with
an average absorption and emission in an adjacent wavelength range
whereby absorption by the element of radiation from the atmosphere
is reduced.
20. The cooling device of claim 19 wherein the cooling device is
arranged so that the medium is in indirect thermal contact with the
element.
Description
FIELD OF THE INVENTION
[0001] The present invention broadly relates to an element for
emission of thermal radiation.
BACKGROUND OF THE INVENTION
[0002] Various methods are used to cool interior spaces of
buildings, refrigerate food, condense water or reduce the
temperature of objects. These methods have in common that they
require relatively large amounts of energy, which typically are
provided in the form of electrical energy. For example, in
countries which have a relatively warm climate the electrical
energy required for cooling often exceeds the available electrical
energy, which may result in a breakdown of a power grid. Further,
electrical energy is at this time still at least partially
generated using non-renewable energy resources, for example by
burning coal, which is of concern for the environment and
contributes to global warming. Consequently, it would be
advantageous if cooling could be achieved in a manner that uses
less energy. There is a need for technological advancement.
SUMMARY OF THE INVENTION
[0003] The present invention provides an element for emission of
thermal radiation, the element comprising particles arranged for
receiving thermal energy and emitting at least a portion of the
received thermal energy in the form of the thermal radiation, the
thermal radiation predominantly having a wavelength or wavelength
range within an atmospheric window wavelength range in which the
atmosphere of the Earth has a reduced average absorption and
emission compared with an average absorption and emission in an
adjacent wavelength range whereby absorption by the element of
radiation from the atmosphere is reduced.
[0004] Because the atmosphere of the Earth has very low absorption
within the atmospheric window wavelength range, only a very small
amount of radiation is returned from the atmosphere to the
particles within that wavelength range and emitted radiation is
largely directed through the atmosphere and into Space where the
typical temperature is of the order of 4 Kelvin. As a consequence,
thermal energy received by the element is "pumped" away by the
element.
[0005] The atmospheric window wavelength range typically includes a
minimum of the average absorption of the atmosphere of the Earth.
The atmosphere has atmospheric windows within the wavelength ranges
of 3 to 5 .mu.m and 7.9 .mu.m to 13 .mu.m. Within these wavelength
ranges the emission of the sun is also negligible and often
regarded as zero, which has the added advantage that even during
daytime the element only absorbs very little radiation from the sun
within that wavelength range.
[0006] The element according to embodiments of the present
invention and a medium that may be in thermal contact with the
element typically is cooled or cooling is facilitated without the
need for electrical energy. In particular during the night, or when
irradiation by the sun is avoided, cooling well below ambient
temperature is possible.
[0007] The particles may be distributed throughout the element,
which in this case also comprises a material that is substantially
transmissive for radiation having a wavelength within the
atmospheric window range. Alternatively, the element may comprise a
surface portion, such as a coating, in which the particles are
concentrated and which is arranged so that the thermal radiation
can be emitted. The element may also comprise a membrane which
locates the particles.
[0008] The element may also comprise a cover that may be suspended
over a body portion of the element or that may be provided in the
form of a cover layer that is in direct contact with the body
portion. The cover typically is transmissive for the thermal
radiation emitted by the particles and protects the particles from
hot breezes and other external influences that could reduce the
cooling efficiency. The cover typically comprises a thermally
insulating material. For example, the cover may comprise a
polymeric material such as polyethylene. Further, the cover may
comprise an oxide or sulphide material, which typically is arranged
to block at least a portion of incident UV radiation. In one
specific example the oxide or sulphide material is positioned on or
over the polyethylene material and also protects the polyethylene.
This example combines the relative strength of typical polyethylene
material with the UV protective function of the sulphide or oxide
material, which also increases the lifespan of the polyethylene
material. The polymeric material and the oxide or sulphide material
typically are arranged so that relatively high transmittance for
radiation having a wavelength within the atmospheric window is
retained. For example, the oxide or sulphide material may be a
layer that is positioned on or over the polymeric material. The
sulphide or oxide layer typically has a thickness that is selected
so that in use at least the majority of incident UV radiation is
blocked and the cover is substantially transmissive for radiation
having a wavelength range within the atmospheric window wavelength
range. The thickness of the layer typically is within the range of
100 nm-1000 nm, 150 nm-300 nm and typically is of the order of 200
nm.
[0009] The element may further comprise wall portions that define
an interior space within which a medium that is to be cooled is in
use located. The wall portions typically comprise a reflective
material. The element may include thermally insulating materials
and may for example form an at least partially thermally insulated
container.
[0010] The element may also comprise a structure that has
projecting wall portions which are positioned so that, in use,
incoming radiation from regions of the atmosphere, which are near
the horizon, is substantially blocked off. It is known that for
such radiation the atmospheric window is less transmissive, because
the atmosphere is "thicker" for radiation traveling closer to the
horizon. Being less transmissive, the atmosphere then also radiates
more strongly at these wavelengths from directions close to the
horizon. Consequently, avoiding that such radiation can reach the
particles improves the cooling efficiency of the element. The
projecting wall portions typically are reflective for the thermal
radiation emitted by the particles. The structure may also comprise
the above-described cover.
[0011] The projecting wall portions typically are reflective for
the thermal radiation emitted by the particles and may be
positioned so that, in use, thermal radiation emitted by the
particles or reflected by the projecting wall portions is directed
in a direction towards Space and in a direction away from the
horizon. The projecting wall portions typically are formed from a
material that has low thermal emittance.
[0012] In one specific embodiment the element comprises a
concentrator such as a "CPC" concentrator or a parabolic dish or
trough concentrator. In this case the projecting wall portions
typically form a portion of the concentrator. The concentrator
typically is arranged so that radiation emitted form substantially
all regions of the conduit is directed towards the sky by the
concentrator. Further, the projecting wall portion has the added
advantage that heating of the particles, and/or of the medium that
is to be cooled by the particles, by a hot breeze that may in use
pass over the element is reduced.
[0013] In another specific embodiment the element forms a part of,
or is provided in the form of, an object and is arranged for
cooling of the object and/or a medium that is in thermal contact
with the object.
[0014] The element may be in contact with the portion of the object
and may also be adhered to, formed on or otherwise applied to the
portion of the object.
[0015] In one specific embodiment the object includes a container,
such as a can, in which for example food or a liquid may be
located.
[0016] For example, the object may be a container, such as a food
container or a container for transportation or storage of medicine,
organs, blood, or anything else that is to be cooled. Further, the
object may be an electronic device and the element may be arranged
for cooling of the electronic device or may form a part of any
means for transportation including automobiles, trucks, train
carriages and shipment containers and the like, which require
cooling of an interior portion.
[0017] The element may also be a part of a structure, such as a
building or a house. For example, the element may be provided in
the form of a window, roof tile, roof sheet or skylight. For
example if the element is provided in a form that is substantially
transparent for visible light, the element may comprise a
substantially transparent polymeric material that comprises the
particles for emission of the thermal radiation. The element may in
this embodiment also comprise a honeycomb-like structure that
provides additional strength. The element may further comprise a
material, such as a further type of particles, that is arranged for
absorbing incoming radiation in the near infrared wavelength range.
In this case the element may be arranged so that the incoming near
infrared radiation is absorbed and the resulting absorbed thermal
energy is at least partially re-emitted in the form of thermal
radiation by the particles arranged for emission of radiation
having a wavelength within the atmospheric window wavelength
range.
[0018] A person skilled in the art will appreciate that there are
many additional examples of objects which may comprise the element
or which the element may form.
[0019] In embodiments of the present invention the element is
arranged to enable cooling to temperatures that are 5.degree.,
10.degree., 20.degree. below an ambient temperature or even
lower.
[0020] The element may also be arranged to extract heat at a finite
rate at a temperature below ambient. The element may be arranged so
that cooling rates such as 40, 60, 80 W per m.sup.2 of cooling
material area are possible at temperatures that are 5.degree.,
10.degree. or more below ambient temperature.
[0021] The particles may be arranged for generation of ionic
surface plasmon resonances having a wavelength or wavelength range
within the atmospheric window wavelength range.
[0022] Throughout this specification the term "ionic surface
plasmon" is used for an excitation that involves movement of ions
(and consequently relates to surface phonons), such as that often
referred to as "Frohlich resonance".
[0023] The particles typically are arranged so that at least some,
typically the majority or all, of the ionic surface plasmons have a
wavelength within the wavelength range from 1-7 .mu.m, 2-6 .mu.m,
or 3-5 .mu.m, and/or any one of 5-16 .mu.m, 7-14 .mu.m, 8-13 .mu.m
and 7.9-13 .mu.m.
[0024] However, it is to be appreciated that at least a portion of
the particles may also be arranged so that the ionic surface
plasmons are generated at a wavelength range that is partially
outside the atmospheric window wavelength range. Further, the
atmospheric window wavelength range may be one of a plurality of
atmospheric window ranges, such as the wavelength range of 3-5
.mu.m and 7.9 to 13 .mu.m.
[0025] In one specific embodiment of the present invention the
particles comprise, or are entirely composed of, SiC or another
suitable material.
[0026] At least a portion of the particles may also be arranged for
emission of radiation by a physical mechanism other than that
associated with the generation of ionic surface plasmons. The
particles may be composed of any suitable material that is arranged
for emission of radiation having a wavelength within the
atmospheric window wavelength range. Alternatively or additionally,
the element may comprise a material that is arranged for emission
of radiation having a wavelength outside the atmospheric window
range.
[0027] The element may comprise a polymeric material, such as a
coating, that is transmissive for radiation of a predetermined
range of wavelength. For example, the particles may be embedded in
the polymeric material or may be located adjacent the polymeric
material.
[0028] The element may also be arranged to reflect at least some
incident radiation, such as radiation from the atmosphere and/or
from the sun in the daytime. The element may comprise a reflective
material that is provided in the form of a layer positioned below
the particles and may be arranged to reflect at least a portion of
incident radiation. Alternatively or additionally, the element may
comprise reflective particles that are dispersed within an at least
partially transparent material, such as the above-described
polymeric material.
[0029] In one embodiment the element comprises at least one channel
for a fluid whereby the element is arranged for cooling the
fluid.
[0030] It is to be appreciated that in variations of the
above-described embodiments the element may not necessarily
comprise particles that are arranged for emission of thermal
radiation having a wavelength within the atmospheric window
wavelength range, but the particles may be replaced by at least one
layer that is arranged for emission of thermal radiation having a
wavelength within the atmospheric window wavelength range. For
example, the at least one layer may comprise a granular structure,
a porous structure or may have a surface that is profiled so that
the at least one layer is arranged for generation of ionic surface
plasmon resonances having a wavelength or wavelength range within
the atmospheric window wavelength range. Alternatively, the at
least one layer may be a part of a multi-layered structure that is
arranged for generation of ionic surface plasmon resonances having
a wavelength or wavelength range within the atmospheric window
wavelength range.
[0031] The present invention provides in a second aspect an element
for emission of thermal radiation, the element comprising at least
one layer that is arranged for receiving thermal energy and
emitting at least a portion of the received thermal energy in the
form of the thermal radiation, the thermal radiation predominantly
having a wavelength or wavelength range within an atmospheric
window wavelength range in which the atmosphere of the Earth has a
reduced average absorption and emission compared with an average
absorption and emission in an adjacent wavelength range whereby
absorption by the element of radiation from the atmosphere is
reduced.
[0032] The atmospheric window wavelength range typically is a
wavelength range from 3 to 5 .mu.m and/or from 7.9 .mu.m to 13
.mu.m.
[0033] The at least one layer typically is arranged for generation
of ionic surface plasmon resonances having a wavelength or
wavelength range within the atmospheric window wavelength
range.
[0034] The at least one layer may have a structural property that
is selected so that the at least one layer is arranged for
generation of ionic surface plasmon resonances having a wavelength
or wavelength range within the atmospheric window wavelength range.
For example, the at least one layer may comprise grains, or may at
least in part be of a porous structure and the structural property
may be associated with a grain size or a thickness of residual
solid between pores, respectively. Further, the at least one layer
may have a surface roughness and the structural property may be
associated with thickness or width of surface features of the at
least one layer. The grain size, the thickness of residual solid
between pores and the thickness or width of surface features of the
at least one layer typically are within the range of 50 nm-150
nm.
[0035] Alternatively, the at least one layer may be a part of a
multi-layered structure having layer thicknesses that are selected
so that the multi-layered structure is arranged for generation of
ionic surface plasmon resonances having a wavelength or wavelength
range within the atmospheric window wavelength range.
[0036] The present invention provides in a third aspect a cooling
system comprising the above-described element in accordance with
the first or second aspect of the present invention, the element
forming a part of an object and the cooling system comprising a
thermally insulating wall portion for reducing exchange of thermal
energy between a portion of the object an environment of the
cooling system.
[0037] The element may be in contact with the portion of the object
and may also be adhered to, formed on or otherwise applied to the
portion of the object.
[0038] The object may include a container, such as a can, in which
for example food or a liquid may be located.
[0039] The thermally insulating wall portion typically is arranged
so that the element of the object is in use enabled to emit thermal
radiation in a direction away from the cooling system. The cooling
system typically is also arranged so that the object is
positionable in, and removable from, an interior formed by the
thermally insulating wall portion.
[0040] The cooling system may further comprise a removable
lid-portion and a base portion that together with the thermally
insulating wall portion form an enclosure in which in use the
object is positioned, the lid-portion being formed from a material
that is transmissive for thermal radiation emitted by the particles
of the element.
[0041] The present invention provides in a fourth aspect a cooling
device for cooling a medium, the cooling device comprising an
element for emission of thermal radiation, the element comprising
particles arranged for receiving thermal energy and emitting at
least a portion of the received thermal energy in the form of the
thermal radiation, the thermal radiation predominantly having a
wavelength or wavelength range within an atmospheric window
wavelength range in which the atmosphere of the Earth has a reduced
average absorption and emission compared with an average absorption
and emission in an adjacent wavelength range whereby absorption by
the element of radiation from the atmosphere is reduced.
[0042] For example, the cooling device may comprise the element for
emission of thermal radiation in accordance with the first aspect
of the present invention.
[0043] The atmospheric window wavelength range typically includes a
minimum of the average absorption of the atmosphere of the Earth.
The atmosphere has atmospheric windows within the wavelength ranges
of 3 to 5 .mu.m and 7.9 .mu.m to 13 .mu.m. Within these wavelength
ranges the emission of the sun is also negligible and often
regarded as zero, which has the added advantage that even during
daytime the element of the cooling device only absorbs very little
radiation from the sun within that wavelength range.
[0044] The cooling device may be arranged so that the medium is in
direct or indirect thermal contact with the element.
[0045] The medium typically is in use cooled or cooling is
facilitated without the need for electrical energy. In particular
during the night, or when irradiation by the sun is avoided,
cooling well below ambient temperature is possible.
[0046] For example, the cooling device may be an air-conditioning
device or a refrigerator or the like. The element of the cooling
device may be in thermal contact, ether directly or indirectly,
with a fluid, such as a liquid or gaseous medium, and may be
arranged for cooling of the fluid or facilitating cooling of the
fluid.
[0047] The cooling device may also be arranged to facilitate
operation of another device. For example, the cooling device may be
arranged to correspond with the other cooling device and may be
mountable on, or in the proximity of the other device so that a
"hybrid" device is formed. In one specific embodiment the cooling
device is arranged to facilitate operation of an air-conditioning
device or refrigerator. For example, the cooling device may be
arranged to cool a fluid, especially during the night, which is
then used to facilitate heat exchange of the other cooling device,
such as the refrigerator or the air-conditioning device. In one
variation the cooling device is arranged to store the cooled fluid
for a period of time, for example during the night.
[0048] In one specific embodiment the cooling device is arranged so
that in use the element receives thermal energy from a fluid. In
this embodiment the cooling device comprises a conduit that is
arranged for directing the fluid to and from the proximity of the
element of the cooling device so that in use the cooling device
results in cooling of the fluid. The cooling device is arranged so
that the element receives thermal energy directly or indirectly
from the fluid. In this embodiment the conduit may provided in the
form of a tubular portion and at least a portion of the conduit may
be arranged for mounting at an exterior surface of a building or
structure. Further, the cooling device may be arranged so that in
use at least a portion of an interior of the building or structure
is cooled by the cooling device and the cooling device may be
arranged so that the fluid is directed in a closed cycle along the
proximity of the element and along a portion from which the fluid
in use absorbs thermal energy from the interior of the building or
structure. In one example the conduit comprises a region at which
in use the element is enabled to emit the thermal radiation in a
direction away from the cooling device. The conduit may further
comprise a thermally insulated region that is arranged to reduce
exchange of thermal energy between the fluid and an environment of
the conduit. The cooling device may further be arranged so that the
region at which in use the element is enabled to emit the thermal
radiation is oriented so that the thermal radiation is emitted in a
direction directly towards Space.
[0049] In another example the cooling device is provided in the
form of an evaporative cooling device and the cooling device may be
arranged for cooling of a liquid prior to evaporation of the liquid
or may otherwise facilitate cooling of the evaporative cooling
device. The cooling device may also be provided in the form of a
radiator or heat exchanger and the element may enable or facilitate
the cooling.
[0050] The particles may be distributed throughout the element of
the cooling device, which may also comprise a material that is
substantially transmissive for radiation having a wavelength within
the atmospheric window range. Alternatively, the element of the
cooling device may comprise a surface portion, such as a coating,
in which the particles are concentrated and which is arranged so
that the thermal radiation can be emitted. The element of the
cooling device may also comprise a membrane which locates the
particles.
[0051] The cooling device may also comprise a cover that may be
suspended over a body portion of the element or that may be
provided in the form of a cover layer that is in direct contact
with the body portion. The cover typically is transmissive for the
thermal radiation and protects the particles from hot breezes and
other external influences that could reduce the cooling efficiency.
The cover typically is arranged for reduction of exchange of
thermal energy by convection. For example, the cover may comprise a
polymeric material such as polyethylene. Further, the cover may
comprise an oxide or sulphide material, which typically is arranged
to block at least a portion of incident UV radiation.
[0052] In one specific example the oxide or sulphide material is
positioned on or over the polyethylene material and also protects
the polyethylene. This example combines the relative strength of
typical polyethylene material with the UV protective function of
the sulphide or oxide material, which also increases the lifespan
of the polyethylene material. The polymeric material and the oxide
or sulphide material typically are arranged so that relatively high
transmittance for radiation having a wavelength within the
atmospheric window is retained. For example, the oxide or sulphide
material may be a layer that is positioned on or over the polymeric
material. The sulphide or oxide layer typically has a thickness
that is selected so that in use at least the majority of incident
UV radiation is blocked and the cover is substantially transmissive
for radiation having a wavelength range within the atmospheric
window wavelength range. The thickness of the layer typically is
within the range of 1000 nm-100 nm, 300 nm-150 nm and typically is
of the order of 200 nm.
[0053] The cooling device may further comprise wall portions that
define an interior space within which a medium that is to be cooled
is in use located. The cooling device may include thermally
insulating materials and may for example form an at least partially
thermally insulated container.
[0054] Further, the cooling device may comprise a closure that is
removable so that the medium is locatable within the interior space
and the interior space is closable. The cooling device may also be
arranged to cool the medium that after removal from the cooling
device, is used to cool another medium. For example, the medium may
comprise a phase change material.
[0055] The cooling device may also comprise a conduit for guidance
of emitted radiation from the particles to a remote location. For
example, the conduit may be provided in the form of a hollow tube
with reflective interior wall portions that are arranged to reflect
the emitted thermal radiation and thereby guide the thermal
radiation to an end-portion of the conduit that may be open or
covered with a suitable material that is substantially transmissive
for the thermal radiation.
[0056] The cooling device may also form a part of, or may be
provided in the form of, a water condenser. The water condenser may
be arranged so that water is generated by condensation of water
vapour in air, for example in an environment that has insufficient
supply of fresh water, including, but not limited to, remote areas
and areas on or near an ocean. The water condenser may form a part
of a water desalination device in which the cooling by the element
facilitates condensation of water.
[0057] In one specific embodiment the cooling device forms a part
of a water purifier. In this case the cooling device may comprise a
first layer that includes the particles for emission of thermal
radiation and a second layer that is spaced apart from the first
layer. The second layer comprises in this embodiment a material
that is arranged for absorbing a portion of incoming solar
radiation and thereby increasing the temperature of the second
layer. The cooling device typically is arranged so that the first
layer is in use positioned over the second layer. A fluid, such as
water containing impurities, may be directed through the space
formed between the first and the second layer. The water will be
heated in the proximity of the second layer and, as the first layer
is cooled by the particles for emission of the thermal radiation,
developed water vapour will condense at the first layer. The water
formed by condensation of water vapour at the first layer typically
is substantially free of the impurities, such as salt in the case
of sea water.
[0058] The cooling device may also comprise a structure that has
projecting wall portions which are positioned so that, in use,
incoming radiation from regions of the atmosphere, which are near
the horizon, is substantially blocked off. It is known that for
such radiation the atmospheric window is less transmissive, because
the atmosphere is "thicker" for radiation traveling closer to the
horizon. Being less transmissive, the atmosphere then also radiates
more strongly at these wavelengths from directions close to the
horizon. Consequently, avoiding that such radiation can reach the
particles improves the cooling efficiency of the cooling device.
The structure may also comprise the above-described cover.
[0059] The projecting wall portions typically are reflective for
the thermal radiation emitted by the particles and may be
positioned so that, in use, thermal radiation emitted by the
particles or reflected off the projecting wall portions is directed
in a direction towards Space and in a direction away from the
horizon. The projecting wall portions typically are formed from a
material that has low thermal emittance.
[0060] In one specific embodiment the cooling device comprises a
concentrator such as a "CPC" concentrator or a parabolic dish or
trough concentrator. In this case the projecting wall portions
typically form a portion of the concentrator. For example, the
cooling device may comprise a conduit for fluid that is positioned
at or near a focal region of the concentrator. The conduit may
comprise the particles that emit in use the thermal radiation. A
fluid may be directed through the conduit so that in use the fluid
is cooled. The concentrator typically is arranged so that radiation
emitted form substantially all regions of the conduit is directed
towards the sky by the concentrator. Further, the projecting wall
portion has the added advantage that heating of the particles,
and/or of the medium that is to be cooled by the particles, by a
hot breeze that may in use pass over the is reduced.
[0061] The cooling device may be arranged so that cooling is
facilitated by the element. Alternatively, the cooling device may
be arranged so that cooling is effected solely by the element.
[0062] In another specific embodiment the cooling device forms a
part of an object and is arranged for cooling of the object and/or
a medium that is in thermal contact with the object.
[0063] For example, the object may be a container, such as a food
container or a container for transportation or storage of medicine,
organs, blood, or anything else that is to be cooled. Further, the
object may be an electronic device and the cooling device may be
arranged for cooling of the electronic device or may form a part of
any means for transportation including automobiles, trucks, train
carriages and shipment containers and the like, which require
cooling of an interior portion.
[0064] The following will describe a selection of further possible
features and the function of the cooling device in more detail.
[0065] In embodiments of the present invention the cooling device
is arranged to enable cooling to temperatures that are 5.degree.,
10.degree., 20.degree. below an ambient temperature or even
lower.
[0066] The cooling device may also be arranged to extract heat at a
finite rate at a temperature below ambient. The cooling device may
be arranged so that cooling rates such as 40, 60, 80 W/m.sup.2 of
cooling material area are possible at temperatures that are
5.degree., 10.degree. or more below ambient temperature.
[0067] The particles may be arranged for generation of ionic
surface plasmon resonances having a wavelength or wavelength range
within the atmospheric window wavelength range.
[0068] The particles typically are arranged so that at least some,
typically the majority or all, of the ionic surface plasmons have a
wavelength within the wavelength range from 1-7 .mu.m, 2-6 .mu.m,
or 3-5 .mu.m, and/or any one of 5-16 .mu.m, 7-14 .mu.m, 8-13 .mu.m
and 7.9-13 .mu.m.
[0069] It is to be appreciated, however, that at least a portion of
the particles may also be arranged so that the ionic surface
plasmons are generated at a wavelength range that is partially
outside the atmospheric window wavelength range. Further, the
atmospheric window wavelength range may be one of a plurality of
atmospheric window ranges, such as the wavelength range of 3-5
.mu.m and 7.9 to 13 .mu.m.
[0070] In one specific embodiment of the present invention the
particles comprise, or may be entirely composed of, SiC or another
suitable material.
[0071] At least a portion of the particles may also be arranged for
emission of radiation by a physical mechanism other than that
associated with the generation of ionic surface plasmons. The
particles may be composed of any suitable material that is arranged
for emission of radiation having a wavelength within the
atmospheric window wavelength range. Alternatively or additionally,
the cooling device may comprise a material that is arranged for
emission of radiation having a wavelength outside the atmospheric
window range.
[0072] The element of the cooling device may comprise a polymeric
material, such as a coating, that is transmissive for radiation of
a predetermined range of wavelength. For example, the particles may
be embedded in the polymeric material or may be located adjacent
the polymeric material.
[0073] The cooling device may also be arranged to reflect at least
some incident radiation, such as radiation from the atmosphere
and/or from the sun in the daytime. The cooling device may comprise
a reflective material that is provided in the form of a layer
positioned below the particles and may be arranged to reflect at
least a portion of incident radiation. Alternatively or
additionally, the element may comprise reflective particles that
are dispersed within an at least partially transparent material,
such as the above-described polymeric material.
[0074] In one embodiment the cooling device comprises at least one
channel for a fluid whereby the cooling device is arranged for
cooling the fluid.
[0075] It is to be appreciated that in variations of the
above-described embodiments the element may not necessarily
comprise particles that are arranged for emission of thermal
radiation having a wavelength within the atmospheric window
wavelength range, but the particles may be replaced by at least one
layer that is arranged for emission of thermal radiation having a
wavelength within the atmospheric window wavelength range. For
example, the at least one layer may comprise a granular structure,
a porous structure or have a surface that is profiled so that the
at least one layer is arranged for generation of ionic surface
plasmon resonances having a wavelength or wavelength range within
the atmospheric window wavelength range. Alternatively, the at
least one layer may be a part of a multi-layered structure that is
arranged for generation of ionic surface plasmon resonances having
a wavelength or wavelength range within the atmospheric window
wavelength range.
[0076] The present invention provides in a fifth aspect a cooling
device for cooling a medium, the cooling device comprising an
element for emission of thermal radiation, the element comprising
at least one layer arranged for receiving thermal energy and
emitting at least a portion of the received thermal energy in the
form of the thermal radiation, the thermal radiation predominantly
having a wavelength or wavelength range within an atmospheric
window wavelength range in which the atmosphere of the Earth has a
reduced average absorption and emission compared with an average
absorption and emission in an adjacent wavelength range whereby
absorption by the element of radiation from the atmosphere is
reduced.
[0077] The atmospheric window wavelength range typically is a
wavelength range from 3 to 5 .mu.m and/or from 7.9 .mu.m to 13
.mu.m.
[0078] The at least one layer typically is arranged for generation
of ionic surface plasmon resonances having a wavelength or
wavelength range within the atmospheric window wavelength
range.
[0079] In one example the at least one layer has a structural
property that is selected so that the at least one layer is
arranged for generation of ionic surface plasmon resonances having
a wavelength or wavelength range within the atmospheric window
wavelength range. For example, the at least one layer may comprise
grains, or may at least in part be of a porous structure and the
structural property may be associated with a grain size or a
thickness of residual solid between pores, respectively. Further,
the at least one layer may have a surface roughness and the
structural property may be associated with thickness or width of
surface features of the at least one layer. The grain size, the
thickness of residual solid between pores and the thickness or
width of surface features of the at least one layer typically
within the range of 50 nm-150 nm.
[0080] Alternatively, the at least one layer may be a part of a
multi-layered structure having layer thicknesses that are selected
so that the multi-layered structure is arranged for generation of
ionic surface plasmon resonances having a wavelength or wavelength
range within the atmospheric window wavelength range.
[0081] The present invention provides in a sixth aspect a cooling
system comprising the above-described cooling device, the cooling
device comprising wall portions that define an interior space
within which a medium that is to be cooled is in use located, the
cooling system further comprising a cooling container that is
arranged to receive the medium cooled by the cooling device so that
the cooled medium is enabled to cool an interior portion of the
cooling container.
[0082] The cooling device typically includes thermally insulating
materials.
[0083] Further, the cooling container may comprise a closure that
is removable so that the cooled medium is locatable within the
interior of the cooling container and the cooling container is
closable.
[0084] The present invention provides in a seventh aspect a method
of cooling a medium comprising the steps of: [0085] receiving
thermal energy by a medium; [0086] directing the thermal energy to
a remote location; [0087] receiving the thermal energy by an
element positioned at the remote location; and [0088] emitting at
least a portion of the thermal energy received by the element in
the form of the thermal radiation predominantly having a wavelength
or wavelength range within an atmospheric window wavelength range
in which the atmosphere of the Earth has a reduced average
absorption and emission compared with an average absorption and
emission in an adjacent wavelength range.
[0089] The method typically comprises moving the medium so that the
thermal energy received by the medium transported to the
element.
[0090] The invention will be more fully understood from the
following description of specific embodiments of the invention. The
description is provided with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0091] FIG. 1 shows an a device incorporating an element for
emission of thermal radiation according to an embodiment of the
present invention;
[0092] FIGS. 2, 3 (a), 3(b) and 4 show objects incorporating an
element for emission of thermal radiation according to an
embodiment of the present invention;
[0093] FIG. 5 shows a transmission spectrum of the atmosphere of
the Earth as a function of wavelength;
[0094] FIGS. 6-8 show elements for emission of thermal radiation
according to embodiments of the present invention;
[0095] FIG. 9 shows a cooling system according to a specific
embodiment of the present invention;
[0096] FIG. 10 shows an a cooling device according to an embodiment
of the present invention;
[0097] FIGS. 11 and 12 show cooling devices according to
embodiments of the present invention;
[0098] FIGS. 13-18 show further examples of cooling devices
according to embodiments of the present invention;
[0099] FIG. 19 shows a cooling system according to a embodiment of
the present invention; and
[0100] FIG. 20 shows a cooling device according to a further
embodiment of the present invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0101] Generally, the element comprises particles that are arranged
for emission of radiation having a wavelength within a range
referred to as the "atmospheric window wavelength range". The
atmospheric window wavelength range is a wavelength range within
which the absorption and emission of radiation by the atmosphere of
the Earth is strongly reduced or zero. Radiation emitted from the
element within that wavelength range is largely transmitted through
the atmosphere to Space where the average temperature is 4 Kelvin.
Further, as within that wavelength range typically very little or
no radiation is received by the element, the element functions as a
pump of thermal energy.
[0102] The element comprises a cooling material that is disclosed
in Australian provisional patent application No 2007903673 and U.S.
patent application Ser. No. 11/765,217. These patent applications
are hereby incorporated by cross-reference. Further details of the
function of the element will be discussed with reference to FIGS.
4-7.
[0103] Referring initially to FIGS. 1-3, examples of elements and
objects incorporating the element according to specific embodiments
of the present invention are now described.
[0104] FIG. 1 shows a cooling element 10 in accordance with an
embodiment of the present invention. For example, the element 10
may be arranged for cooling a medium that is in thermal contact
with a portion of the element 10. The element 10 is arranged so
that thermal radiation can be emitted from surface portion 12 to
the atmosphere either directly or indirectly. The element 10 is
arranged so that a portion of the thermal energy received from the
medium is emitted by the element 10 in the form of thermal
radiation so that cooling of the medium is facilitated by the
element 10.
[0105] The cooling element 10 may form a part of an evaporative
cooling device. In this case the element 10 typically is arranged
to cool a liquid, typically water, prior to evaporation.
Alternatively, the element 10 may form a part of any other type of
air-conditioning device and the element 10 may be arranged for
facilitating cooling of a fluid that in use circulates though
portions of the air-conditioning unit.
[0106] Further, the element 10 may form a part of be a radiator,
heat exchanger, or refrigerator or any other type of cooling
device. A person skilled in the art will appreciate that there are
numerous examples of cooling devices in which the element 10 may be
incorporated.
[0107] FIG. 2 shows an example of a structure 14 in which an
element for emission of the thermal radiation according to
embodiments of the present invention is incorporated. The structure
14 is in this embodiment a house or building or the like and
includes roof-covering and/or other external coverings that are
provided in the form of objects 16. For example, each object 16 may
be a roof tile or a roof-sheet which comprises a metallic, ceramic
or polymeric material. The object 16 comprises a surface portion
that incorporates the particles for emission of the thermal
radiation and is positioned over the metallic, ceramic or polymeric
material. For example, the particles may be embedded in a coating
material that is applied by painting or otherwise to the metallic,
ceramic or polymeric material of the object 16. The coating
material is substantially transmissive for radiation having a
wavelength within the atmospheric window wavelength range.
Alternatively, the particles may be positioned on a surface portion
of the object 16 without being embedded in a coating material.
[0108] The object 16 is arranged so that thermal radiation is
emitted which results in cooling of a roof space of the house or
building 14. This particular application has significant advantages
in particular for warmer regions of the Earth. During hot summer
days roof spaces gain a substantial amount of thermal energy and
often maintain a substantial portion of that thermal energy during
the night. The element 16 facilitates cooling of the roof space and
thereby improves comfort of living in the house or building 14. In
one specific embodiment of the present invention large portions of
the external surface, such as the roof area of a house or building
14, are covered by the object 16.
[0109] Referring again to FIG. 2, the structure 14 may also include
further objects that incorporate an element for emission of the
thermal radiation and that are provided in the form of windows,
such as window 18. The window 18 is arranged so that a portion of
near-infrared radiation is blocked.
[0110] Referring now to FIG. 3 (a), a further example of an object
that incorporates the element 10 for emission of thermal radiation
is now described. The object 20 is in this example a container for
containing food, medical articles, blood or organs and the like or
any other objects or matter that requires cooling. An external
surface portion of the object 20 comprises the particles arranged
for emission of thermal radiation. Emission of the thermal
radiation results in cooling of the container 20 and an interior
portion thereof.
[0111] FIG. 3 (b) shows an example of a further variation of a
container that includes the element 12. In this case the container
22 has wall portions 24 that are composed of a thermally insulating
material. The container 22 also comprises a top portion 26 that is
composed of a material that is substantially transmissive for the
thermal radiation having a wavelength range within the atmospheric
window wavelength range. The top portion may also have thermally
insulating properties and may for example comprise iron oxide or
ZnS. A medium that is to be cooled is positioned adjacent the
element 12. This embodiment has the added advantage that the
thermally insulating wall portions further increase the cooling
efficiency. Further, the element 10 and the medium that is to be
cooled are protected from any hot breezes that may also reduce the
cooling efficiency.
[0112] A person skilled in the art will appreciate that there are
numerous examples of objects in which the element for emission of
thermal radiation maybe incorporated. For example, the element may
form a portion of an electronic device, such as an integrated
electronic device, and may be arranged for cooling of the
electronic device.
[0113] FIG. 4 shows a structure 28 that is largely transmissive for
visible radiation and may be used as a roof-sheet, window or sky
light and the like. The structure 28 comprises a first layer 30 and
a second layer 32. The first layer 30 and the second layer 32 are
connected by members 34 so that a honey-comb like structure is
formed that is relatively stabile. The structure 28 comprises a
polymeric material and has particles incorporated within that
material so that the structure 28 has advantages analogous to those
of the above-discussed element.
[0114] A person skilled in the art will also appreciate that the
cooling element has numerous applications for cooling objects, or
fluids. If an object or fluid is to be cooled, the cooling element
may be arranged to cool the object or fluid directly.
Alternatively, the cooling element may be arranged for cooling the
object or fluid indirectly by cooling another fluid of material,
which then cools the fluid or object that is to be cooled.
[0115] Referring now to FIGS. 5 and 6, the function of the element
for emission of thermal radiation according to a specific
embodiment of the present invention are now described in further
detail. FIG. 5 shows a transmission spectrum 34 of the atmosphere
of the Earth for substantially cloud free conditions. The average
transmission is increased to nearly 1 within the range of
approximately 7.9 to 13 .mu.m compared to adjacent wavelength
ranges. Further, the average transmission of the atmosphere is
increased within a wavelength range of 3-5 .mu.m. Within these
wavelength ranges the atmosphere of the Earth has "windows". Plot
36 is an estimation of the emission spectrum of a black body having
a temperature of 100.degree. C., which was calculated using Wein's
law and gives an example of the emission spectrum for a medium that
may be cooled using the cooling material according to embodiments
of the present invention.
[0116] FIG. 6 shows a secondary electron microscopy micrograph of a
surface portion of the element according to a specific embodiment
of the present invention.
[0117] The element 40 comprises a reflective metallic layer 42,
which in this embodiment is provided in the form of an aluminum
layer positioned on a substrate. Further, the element 40 comprises
SiC particles 44, which are positioned on the metallic layer 42.
The SiC particles 44 have an average diameter of approximately 50
nm and are deposited using suitable spin coating procedures.
[0118] The SiC particles 44 are in this embodiment nano-particles
and the majority of the surface of the particles 44 is exposed to
air. The particles 44 show resonantly enhanced absorption and
emission of radiation at a wavelength range of 10 to 13 .mu.m.
Within that wavelength range ionic surface plasmons are generated.
The wavelength range of resonant ionic surface plasmon emission is
within the above-described atmospheric window wavelength range. For
that wavelength range the average absorption of the atmosphere of
the Earth is very low and consequently very little radiation in
this wavelength range is transferred from the atmosphere to the
element 40.
[0119] The energy associated with the emitted radiation is largely
drawn from the thermal energy of the particles 44 and/or from a
medium that is in thermal contact with the particles 44. Due to the
atmospheric window, the emitted radiation is largely transmitted
through the atmosphere and directed to Space where the temperature
typically is 4 Kelvin. Consequently, the element 40 functions as a
pump of thermal energy even if the cooling material, or a medium
that is in thermal contact with the cooling material, has a
temperature below ambient temperature.
[0120] The reflective material 42 has the added advantage that a
large portion of incident radiation is reflected away from the
element 40 and consequently thermal absorption of radiation having
a wavelength within or outside the atmospheric window is reduced,
which increases cooling efficiency.
[0121] In variations of the above-described embodiment the
particles 44 may be composed of other suitable materials that show
ionic surface plasmon resonances, such as BN and BeO. Further, the
particles 44 may also be composed of materials that are not
arranged for ionic plasmon generation at a wavelength within the
atmospheric window wavelength range, but may be arranged for
emission of radiation within that wavelength range by any other
possible mechanism. For example, SiO, silicon oxynitride particles
exhibit relatively strong emissions within that wavelength
range.
[0122] The reflective material 42 improves the cooling efficiency.
However, it is to be appreciated that the element may not
necessarily comprise a reflective material. Further, the particles
44 may be embedded in a transparent material, such as a suitable
polymeric material that is positioned upon the reflective material
42. For example, the polymeric material may comprise polyethylene
or a fluorinated material.
[0123] Referring now to FIG. 7, an element according to a second
specific embodiment of the present invention is now described.
[0124] In this embodiment the element 50 also comprises the
above-described particles 44. In this example, however, the
particles 44 are positioned within a matrix of a polymeric material
54 that is largely transparent to thermal radiation within a black
body wavelength range, such as radiation having a wavelength within
the range of 3-28 .mu.m, or a wavelength range outside one or both
of 3-5 and 7.9-13 .mu.m, or most of solar spectral range in
addition to the black body radiation range. For example, the
polymeric material 54 may comprise polyethylene or a fluorinated
polymeric material.
[0125] In contrast to the element 40, incident radiation is not
reflected, but largely transmitted through the cooling material 50,
which also reduces thermal absorption of radiation directed to the
element 50 and thereby improves the cooling efficiency.
[0126] In addition, the element 50 comprises particles 56. In
general, the particles 56 have a spectrally selective property that
complements a spectrally selective property of the particles 44. In
this example, the particles 56 are arranged for generation of
electronic surface plasmons in the near infrared (NIR) wavelength
range. Within that wavelength range the particles 56 absorb
radiation, such as radiation originating from the sun. This
inhibits transmission of a portion of incident radiation, which
facilitates the cooling. In this embodiment the cooling material 50
is arranged so that the thermal energy, that is present as a
consequence of the absorbed solar radiation, is emitted by the
particles 44.
[0127] For example, the element 50 may be provided in the form of a
skylight or a window, such as window element 18. In this case the
cooling material 50 typically is arranged so that a large portion
of the visible light originating from the sun can penetrate through
the element 50. The particles 44 emit radiation within the
atmospheric window wavelength range, which results in cooling, and
the particles 56 partially "block" thermal radiation originating
from the sun which facilitates the cooling.
[0128] For example, the particles 56 may comprise indium tin oxide,
tin oxide, LaB6, SbSn oxide, or aluminium doped ZnO.
[0129] It is to be appreciated, however, that in variations of the
above-described embodiment the particles 56 may also be arranged
for generation of electronic surface plasmons at any other suitable
wavelength range.
[0130] In addition, the element 50 may comprise a layered structure
of dielectric and/or metallic materials having layer thicknesses
that are selected to effect reflection of thermal radiation, such
as thermal radiation originating from the atmosphere, which further
facilitates cooling.
[0131] Further, the element 30 may also comprise a layer structured
material that is arranged so that a portion of light within the
visible wavelength range is reflected and light that is transmitted
though the element 50 is of a particular colour, which has
advantageous applications for aesthetic purposes.
[0132] With reference to FIG. 8 an element 60 according to another
specific embodiment of the present invention is now described. The
element 60 corresponds to the element 50 shown in FIG. 7 and
described above, but is in this embodiment positioned on a
reflective layer 62. The element 60 is particularly suited for
cooling a medium that may be in thermal contact with the cooling
material 60. In this embodiment the reflective layer 62 is a
metallic layer that is arranged to reflect radiation having a wide
wavelength range and originating, for example, from the sun.
[0133] For example, the reflective layer 62 may be arranged to
reflect the majority of thermal radiation and visible radiation
originating from the sun and from the atmosphere, which facilitates
cooling of the cooling material 60. The reflective material may
comprise for example Al, Cu, Ag, Au, Ni, Cr, Mo, W or steel
including stainless steel.
[0134] In a variation of the embodiment shown in FIG. 8, the
reflective material may not be provided in form of a layer, but may
be provided in form of reflective particles that are incorporated
in the material 54.
[0135] The elements 50 and 60 may be incorporated into the cooling
device 10 or objects 16 and 20. The element 60 has particularly
advantageous applications as window or skylight, such as window
18
[0136] Referring now to FIG. 9, a cooling system in accordance with
an embodiment of the present invention is now described. FIG. 9
shows the cooling system 90 which comprises an object 92. For
example, the object may be a container, such as a food container,
or a can, such as a beverage can. The object 92 includes a top
portion 94 to which the above described element for emission of
thermal radiation is applied. For example, the element may be
provided in the form of a coating functioning in the same manner as
the elements 40, 50 and 60 described with reference to FIGS. 6 to
8.
[0137] In this embodiment, the cooling system 90 comprises a
thermally insulating housing 96 in which the object 92 is
positioned. Further, the cooling system 90 comprises a lid-portion
98 which is composed of material that is transmissive for thermal
radiation emitted by the particles of the element 94. Further, the
cooling system 90 comprises a base portion on which the housing
portion 96 and the object 92 are positioned. In this embodiment,
the housing portion 96 is taller than the object 92 so that in use
the likelihood of incidence of direct sunlight on the object 92 is
reduced. Further, the housing portion 96 is sufficiently tall so
that in use incoming radiation from the atmosphere, which is
incident at angles which are closer to the horizon than to the
zenith, is substantially blocked off. The housing portion 96 is
reflective for the thermal radiation emitted by the particles and
is in use positioned so that thermal radiation emitted by the
particles is directed in a direction towards Space and in a
direction away from the horizon. Interior wall portions of the
housing portion 96 comprise a material that has low thermal
emittance.
[0138] The lid-portion 98 creates a barrier for transfer of heat by
convection and, at the same time, is transmissive for thermal
energy emitted by the particles of the element 94.
[0139] In use, the particles of element 94 absorb thermal energy
from an adjacent portion of the object 92 and emit the absorbed
thermal energy in the form of thermal radiation having a wavelength
range within the atmospheric wavelength range. The housing portion
96 and the base portion 100 provide thermal insulation and
consequently facilitate cooling of the object 92. The cooling
system 90 is arranged so that the object is removable from an
interior of the housing portion 96.
[0140] It is to be appreciated, however, that the cooling system 90
may be provided in various different forms. For example, the object
92 may not necessarily be a container for food or liquid, but may
alternatively be any other type of object. Further, the element 94
may be applied to any side portion of the object and may also be in
indirect thermal contact to the object. In addition, the housing
portion 96 may have any suitable shape.
[0141] Further, it will be appreciated by those skilled in the art
that the particles of the element, such as element 50 or 60 shown
in FIGS. 7 and 8, may also be positioned in a membrane that has
openings which a suitably sized to locate one or more of the
particles. In addition, the element may also comprise projecting
wall portions, which may or may not be reflective and which are
arranged so that in use it is avoided that radiation that
penetrated to atmospheres at regions near the horizon.
[0142] Further, it is to be appreciated that in variations of the
above-described embodiments the element may not necessarily
comprise particles that are arranged for emission of thermal
radiation having a wavelength within the atmospheric window
wavelength range, but the particles may be replaced by at least one
layer, such as a multi-layered structure, that is arranged for
emission of thermal radiation having a wavelength within the
atmospheric window wavelength range. The layers of the
multi-layered structure typically have thicknesses that are
selected so that in use ionic surface plasmon resonances are
generated and the ionic surface plasmon resonances have a
wavelength or wavelength range within the atmospheric window
wavelength range. For example, the multi-layered structure may
comprise SiO and SiC layers having a thickness of the order of
50-150 nm.
[0143] Alternatively, the particles may be replaced by grains of a
layer having a granular structure, such as a suitable SiC layer. In
this case the average diameter of the grains is selected so that
the layer is arranged for emission of thermal radiation having a
wavelength within the atmospheric window wavelength range. The
particles may also be replaced by a porous layer or a layer having
a rough surface, such as a suitable SiC layer. In this case an
average pore spacing or surface profile, respectively, is selected
so that the layer is arranged for emission of thermal radiation
having a wavelength within the atmospheric window wavelength
range.
[0144] In addition, it is to be appreciated that the element may
comprise the above-described particles in addition to the
above-described at least one layer. The at least one layer and the
particles may both be arranged for emission of thermal radiation
having a wavelength range within the atmospheric window wavelength
range.
[0145] Referring now to FIGS. 10-12, examples of cooling devices
according to specific embodiments of the present invention are now
described. Generally, the cooling device may comprise the
above-described element for emission of thermal radiation.
[0146] FIG. 10 shows a cooling device 110 that incorporates the
element 112. For example, the cooling device may be an
air-conditioning device, a radiator, or any other type of cooling
device. The cooling device 110 may be arranged for cooling a medium
that is in thermal contact with a portion of the cooling device
110. The element 112 is arranged so that thermal radiation can be
emitted from surface portion 114 to the atmosphere either directly
or indirectly. The cooling device 110 is arranged so that a portion
of the thermal energy received from the medium is emitted by the
element 112 in the form of thermal radiation so that cooling of the
medium is facilitated by the element 112.
[0147] The cooling device 110 may for example be provided in the
form of an evaporative cooling device. In this case the element 112
typically is arranged to cool a liquid, typically water, prior to
evaporation. Alternatively, the cooling device 110 may be any other
type of air-conditioning device and the element 112 may be arranged
for facilitating cooling of a fluid that in use circulates though
portions of the air-conditioning unit.
[0148] Further, the cooling device 110 may be a radiator, heat
exchanger, or refrigerator or any other type of cooling device. A
person skilled in the art will appreciate that there are numerous
examples of cooling devices in which the element 112 may be
incorporated.
[0149] For example, the cooling device 112 may be provided in the
form of a container for containing food, medical articles, blood or
organs and the like or any other objects or matter that requires
cooling. A person skilled in the art will appreciate that there are
numerous further examples of cooling devices in which the cooling
device may be incorporated. For example, the cooling device may
form a portion of an electronic device, such as an integrated
electronic device, and may be arranged for cooling of the
electronic device.
[0150] Referring now to FIG. 11, another specific example of a
cooling device is now described. In this embodiment the cooling
device 127 comprises a body portion 128 which includes particles
for emission of the thermal radiation. Further, the cooling device
127 comprises a conduit 129. The conduit 129 is a hollow tubular
portion with reflective internal wall portions that are arranged to
reflect the radiation and thereby guide the radiation to a distal
end-portion of the conduit. The conduit 129 is used to channel
thermal radiation emitted by the particles of the body portion 128
to the distal end-portion of the conduit 129 that is exposed to the
atmosphere.
[0151] For example, the body portion 128 may comprise a thermally
absorptive material that is also arranged to reflect the thermal
radiation having a wavelength within the atmospheric window
wavelength range. This would ensure that radiation generated by the
particles of the cooling device 127 is largely directed into the
conduit 129.
[0152] It is to be appreciated that the conduit may be provided in
any suitable form and may also comprise bent portions.
[0153] FIG. 12 shows another example of the cooling device. Cooling
device 130 comprises in this case body portion 31, which is
arranged to cool a fluid that is channeled through the body portion
131. The body portion 131 comprises the particles for emission of
thermal radiation. The cooled fluid is directed by thermally
insulated tubes 132 to and from body portion 133, where heat is
absorbed. Consequently, the cooling device 130 functions as heat
pump and moves thermal energy from an area within which the body
portion 133 is positioned, such as an interior of a building, to
the body portion 131, which may be positioned outside the
building.
[0154] A person skilled in the art will appreciate that the cooling
device 130 has numerous applications. For example, the body portion
131 may be positioned at the exterior of a shipping container and
the body portion 133 may be positioned so that an interior portion
of the shipping container is cooled. In this case the cooling
device 130 may also be arranged for cooling a relatively small area
of the interior of the container, such as the interior of a
refrigeration box, within which relatively low temperatures can be
achieved.
[0155] FIG. 13 shows a variation of the cooling device that forms a
water purifier. FIG. 13 shows a structure 200 that comprises a
first layer 202 and a second layer 102. The first layer 204 and the
second layer 204 are coupled by members 206. The layer 202 is in
this example corrugated and comprises the particles 44. The
particles 56 are separated from the particles 44 and are
distributed in the second layer 204. A fluid is in use directed
along the second layer 204 and in channels that are formed by the
members 206. The particles 56 increase the temperature of the
second layer 204 by absorbing near-infrared radiation and the
particles 44 of the first layer 202 cool the second layer 202,
which results in formation of water vapour and condensation of the
water vapour at the first layer 202. The condensed water is
substantially free of impurities, such as salt, that the water may
contain. Because of the corrugation of the first layer 202, the
condensed water is collected in channels 208 and available for
use.
[0156] It is to be appreciated that the first and second layer of
the element 200 may alternatively be mechanically coupled by any
other suitable arrangement.
[0157] Referring now to FIG. 14, a cooling device according to a
further embodiment of the present invention is now described.
Cooling device 210 comprises reflectors 212, which in this
embodiment are shaped so that a "CPC" concentrator is formed. The
cooling device 210 comprises a tube 214 through which in use a
fluid is conducted. The tube 214 is coated with a material
comprising the particles 44 for emission of thermal radiation
having a wavelength within the atmospheric window wavelength range
and which in use cool the fluid. The emitted thermal radiation is
directed by the reflector portions 212 through cover 216, which is
transmissive for the radiation and may be comprise iron oxide or
ZnS.
[0158] The concentrator has a number of practical advantages. The
concentrator is in use oriented so that it is substantially avoided
that incoming radiation, that is emitted by regions of the
atmosphere near the horizon, can reach the tube 214. It is known
that the atmospheric window is becoming less transmissive for
radiation which travels through the atmosphere at a longer
distance, such as radiation that is directed through the atmosphere
near the horizon. Consequently, avoiding that that radiation can
reach the particles improves the cooling efficiency. Further, the
shape of the reflector portions 212 allows that the thermal
radiation emitted from a lower portion of the tube 214 is directed
to the atmosphere.
[0159] In addition, the reflector portion 212 comprise projecting
wall portions that, together with the top cover 216, avoid heating
of the particles and the fluid by a hot breeze that may in use pass
over the element 210. In a variation of this embodiment the element
210 does not comprise the cover 216 and consequently the projecting
wall portions of the reflector portions 212 will then alone have
that function.
[0160] The cooling device according to any one of the described
embodiments may also comprise a cover that may be suspended over a
body portion or that is provided in the form of a cover layer that
is in direct contact with the body portion. The cover is
transmissive for the thermal radiation and protects the particles
from hot breezes and other external influences that would reduce
the cooling efficiency. The cover may also comprise a thermally
insulating material. In one specific example, the cover comprises
polyethylene and oxide or sulphide material, such as ZnS or iron
oxide, which is positioned over the polyethylene material and also
protects the polyethylene.
[0161] It will be appreciated that the alternatively the reflector
portions 212 may have any other suitable shape, such as a parabolic
dish and trough shape.
[0162] Referring now to FIG. 15, a further example of a cooling
device in accordance with a specific embodiment of the present
invention is now described. FIG. 15 (a) shows a cross-sectional
view of a portion of a cooling device 220 and FIG. 15 (b) shows a
perspective view of a portion of the cooling device 220. FIG. 15
(c) shows a front view of the portion of the cooling device
220.
[0163] In this embodiment, the portion of the cooling device 220 is
arranged for mounting on a surface, such as an exterior surface of
a building or structure. The cooling device 220 comprises tubular
portions 222 which are arranged for directing a fluid. Further, the
cooling device 220 comprises a thermally insulating material 224
which is arranged to reduce exchange of thermal energy between the
fluid and an exterior of the portion of the cooling device 220. The
cooling device 120 also includes elements 226 for emission of
thermal radiation. In this embodiment, the elements are provided in
the form of coatings and are of the type as described above.
[0164] The cooling device 220 comprises further tubular portions
(not shown) that direct the fluid to an interior portion of the
building or structure where the fluid is enabled to absorb thermal
energy. A pump (not shown) then directs the fluid from the interior
portion of the building or structure to the exterior portion or
structure where the elements 226 receive the thermal energy from
the fluid and emit the received thermal energy in the form of
thermal radiation. Consequently, the fluid is cooled by the
elements 226. The cooled fluid is then directed back into the
interior of the building or structure and consequently results in
cooling of the interior of the building or structure.
[0165] It is to be appreciated that the cooling device 220 may be
used to cool the interior of shipping containers, office buildings,
domestic buildings or any other type of structure building of
structure. The portion of the cooling device 220 typically is
mounted to the exterior portion of the building or structure so
that the elements 226 are enabled to emit thermal radiation towards
the sky.
[0166] FIGS. 16 and 17 show examples of portions of cooling devices
230 and 240, respectively. The cooling devices 230 and 240 are
arranged to operate in the same manner as the cooling device 220.
However, the cooling devices 230 and 240 comprise tubular portions
232 and 242, respectively, which have a substantially square
cross-sectional shape. The tubular portions 232 comprise elements
for emission of thermal energy at top surfaces of the tubular
portions 232, which are slightly angled so that the elements are
enabled to emit thermal radiation towards the sky.
[0167] The tubular portions 242 of the cooling device 242 also
comprise elements for emission of thermal radiation at top surfaces
of the tubular portions, but in this case, the tubular portions are
not angled and are located at differing distances relative to a
wall 244 in a manner such that overshadowing by upper tubular
portions is reduced.
[0168] The portions of the cooling devices 220, 230 and 240
typically are mounted at exterior portions of the buildings or
structures which direct sunlight is reduced or avoided, as such
location further increases the cooling efficiency.
[0169] FIG. 18 (a) shows components of a cooling device 250
according to an embodiment of the present invention and FIG. 18 (b)
shows assembled components and a further component of the cooling
device 250. The cooling device 250 comprises a metallic body
portion 252 and a lid-portion 254. The lid-portion 254 comprises an
element for emission of thermal radiation as described above. The
body portion 252 is shaped so that a cavity is formed in which an
article may be positioned and which is closed by the lid-portion
254 and a closure 256. The body portion 252 is positioned in a
thermally insulating shell 158.
[0170] The cooling device further comprises a concentrator portion
255 which is in use positioned over the lid-portion 254. In this
example the concentrator portion 255 has a plurality of projecting
wall portions that are arranged so that a plurality of smaller and
substantially square concentrator areas are formed. The projecting
wall portions are formed from a material that has a low thermal
emittance and is reflective for the thermal radiation emitted by
the particles. The projecting wall portions are arranged so that in
use the thermal radiation is predominantly directed towards the Sky
in a direction away from the horizon. Further, the projecting wall
portions are positioned so that, in use, incoming radiation from
regions of the atmosphere, which are near the horizon, is
substantially blocked off.
[0171] For example, the cooling device 250 may be used for cooling
food, liquids or any other matter that requires cooling. The
articles are positioned in the cavity of the body portion 252,
which is then closed by the lid-portion 256. The cooling device
then cools the article by absorbing thermal energy from the
article, which is then emitted by the element of the lid-portion
254.
[0172] FIG. 19 shows components of a cooling system in accordance
with an embodiment of the present invention. The cooling system 260
comprises of the cooling device 250. Further, the cooling system
260 comprises a cooling container 262 having a lid-portion 264. In
this embodiment the cooling device 250 is arranged to cool
liquid-filled elements 266. For example, the liquid-filled elements
266 may be provided in the form of water-filled containers or bags.
The cooling device 250 is then used to cool the liquid-filled
elements 266 so that ice is formed within the elements 266. The
elements 266 are then removed from the cooling device 250 and
positioned in cavities of the food container 262. Articles that
require cooling, such as food items, may then be positioned in the
cooling container 262 which is then closed by the lid-portion
264.
[0173] Referring now to FIG. 20, a cooling device in accordance
with another embodiment of the present invention is now described.
FIG. 20 shows a cooling device 270 which comprises housing portions
272 and 274. The housing portions 272 and 274 comprise thermally
insulated wall portions 276 and 278, respectively. In this
embodiment, the housing portions 272 and 274 comprise threaded
portion 280 and 282, which are arranged for mechanically coupling
the housing portions 272 and 274 with each other. The housing
portion 272 further comprises an element 284 having particles for
emission of thermal radiation within the atmospheric window
wavelength range. The element 284 is of the type as described
above. Further, the housing portion 272 comprises a projecting wall
portion 286 that is in this embodiment composed of a metallic
material, such as aluminium, which has a relatively high thermal
conductivity.
[0174] The wall portion 286 is arranged to receive a container,
such as a beverage can. The can is in use positioned within the
projecting wall portion 286, which in turn is located within the
housing portion 274 when the housing portions 272 and 274 are
coupled to each other. The can typically is in thermal contact with
the element 284 and the wall portion 286. The element 284 is
arranged to cool the wall portion 286 and the can. Once the can has
been cooled, the housing portion 272 is separated from the housing
portion 274 in a manner such that the can remains in the housing
portion 274, which continues to provide thermal insulation.
[0175] In this embodiment, the housing portion 272 is taller than
the can and the element 284 is positioned below an upper portion of
the housing portion 272 so that in use the likelihood of incidence
of direct sunlight onto the element 284 is reduced. Further, the
housing portion 272 is sufficiently tall so that in use incoming
radiation from regions of the atmosphere, which are near the
horizon, is substantially blocked off. The housing portion 272 also
comprises an interior wall portion 288 that is reflective for the
thermal radiation emitted by the particles and is in use positioned
so that thermal radiation emitted by the particles is directed in a
direction towards Space and in a direction away from the horizon.
Interior wall portions of the housing portion 274 comprise a
material that has low thermal emittance.
[0176] In use, the particles of the element 284 absorb thermal
energy from the can positioned at the element 284 and within the
projecting wall portion 286. The absorbed thermal energy is emitted
in the form of thermal radiation having a wavelength range within
the atmospheric wavelength range. The housing portions 272 and 274
provide thermal insulation and consequently facilitate cooling of
the can.
[0177] It is to be appreciated, however, that the cooling device
270 may be provided in various different forms. For example, the
cooling device 270 may not necessarily be arranged to receive a
can, but may alternatively be any other type of object. In
addition, the housing portions 272 and 274 may have any suitable
shape.
[0178] Although the invention has been described with reference to
particular examples, it will be appreciated by those skilled in the
art that the cooling device may also be arranged to facilitate
operation of another device so that a "hybrid" device is formed.
The cooling device may be arranged to cool a fluid, especially
during the night, which is then used to facilitate heat exchange of
a refrigerator or an air-conditioning device. In one variation the
cooling device is arranged to store the cooled for a period of
time, for example during the night.
[0179] Further, it is to be appreciated that in variations of the
above-described embodiments the element of the cooling device may
not necessarily comprise particles that are arranged for emission
of thermal radiation having a wavelength within the atmospheric
window wavelength range, but the particles may be replaced by at
least one layer, such as a multi-layered structure, that is
arranged for emission of thermal radiation having a wavelength
within the atmospheric window wavelength range. The layers of the
multi-layered structure typically have thicknesses that are
selected so that in use ionic surface plasmon resonances are
generated and the ionic surface plasmon resonances have a
wavelength or wavelength range within the atmospheric window
wavelength range. For example, the multi-layered structure may
comprise SiO and SiC layers having a thickness of the order of
50-150 nm. Alternatively, the particles may be replaced by grains
of a layer having a granular structure, such as a suitable SiC
layer. In this case an average diameter of the grains is selected
so that the layer is arranged for emission of thermal radiation
having a wavelength within the atmospheric window wavelength range.
The particles may also be replaced by a porous layer or a layer
having a rough surface such as a suitable SiC layer. In this case
an average pore spacing or a surface profile, respectively, is
selected so that the layer is arranged for emission of thermal
radiation having a wavelength within the atmospheric window
wavelength range.
[0180] In addition, it is to be appreciated that the element of the
cooling device may comprise the above-described particles in
addition to the above-described at least one layer. The at least
one layer and the particles may both be arranged for emission of
thermal radiation having a wavelength range within the atmospheric
window wavelength range.
* * * * *