U.S. patent application number 13/114792 was filed with the patent office on 2011-11-10 for composite material compositions, arrangements and methods having enhanced thermal conductivity behavior.
Invention is credited to Allen J. Amaro, Robert S. Block, KRS Murthy.
Application Number | 20110271951 13/114792 |
Document ID | / |
Family ID | 40626092 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110271951 |
Kind Code |
A1 |
Murthy; KRS ; et
al. |
November 10, 2011 |
COMPOSITE MATERIAL COMPOSITIONS, ARRANGEMENTS AND METHODS HAVING
ENHANCED THERMAL CONDUCTIVITY BEHAVIOR
Abstract
An arrangement includes a solar energy receiving device and at
least one component in thermal communication with the solar energy
receiving device, the at least one component formed from a
composite material, the composite material may comprise a matrix of
carbon-based fibers, the carbon-based fibers comprising one or more
of: mesophase carbon, carbon nanotubes, graphite, graphene and pan
carbon. According to a further optional aspect, there is provided a
solar energy receiving device comprising a first surface for
receiving solar energy incident thereon, and a second opposing
surface, the second surface being electrically conductive; at least
one heat transport device in direct contact with at least a portion
of the second surface, the at least one heat transport device may
comprise at least one internal passage and at least one duct; and a
heat transport media flowing within the at least one internal
passage and at least one duct. Related methods and additional
arrangements are also described.
Inventors: |
Murthy; KRS; (San Jose,
CA) ; Block; Robert S.; (Reno, NV) ; Amaro;
Allen J.; (Fremont, CA) |
Family ID: |
40626092 |
Appl. No.: |
13/114792 |
Filed: |
May 24, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12257235 |
Oct 23, 2008 |
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13114792 |
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60996273 |
Nov 8, 2007 |
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61071410 |
Apr 28, 2008 |
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61071411 |
Apr 28, 2008 |
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61071412 |
Apr 28, 2008 |
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Current U.S.
Class: |
126/569 |
Current CPC
Class: |
F24S 90/00 20180501;
Y02E 10/40 20130101; F24S 80/10 20180501; F28F 21/02 20130101; F28D
15/00 20130101; H01L 31/0521 20130101; Y02E 10/50 20130101 |
Class at
Publication: |
126/569 |
International
Class: |
F24J 2/46 20060101
F24J002/46 |
Claims
1. An arrangement comprising: a solar energy receiving device; and
at least one heat transport device in thermal communication with
the solar energy receiving device, the at least one heat transport
device formed from a composite material, the composite material
comprising a matrix of carbon-based fibers, the carbon-based fibers
comprising one or more of: mesophase carbon, carbon nanotubes,
graphite, graphene and pan carbon.
Description
[0001] The present application is a continuation of, and claims
priority pursuant to 35 U.S.C. .sctn.120 to, U.S. patent
application Ser. No. 12/257,235 filed on Oct. 23, 2008, which
claims priority pursuant to 35 U.S.C. .sctn.119(e), of: U.S.
Provisional Application No. 60/996,273 filed Nov. 8, 2007; U.S.
Provisional Application No. 61/071,410 filed Apr. 28, 2008; U.S.
Provisional Application No. 61/071,411 filed Apr. 28, 2008; and
U.S. Provisional Application No. 61/071,412 filed Apr. 28, 2008.
The entire contents of each of which is incorporated herein by
reference.
FIELD
[0002] The present invention is in the technical field of composite
materials. The present invention is in the technical field of heat
transport, extraction, and cooling. The present invention is also
related to heat transport, extraction, cooling, storage and
management for solar thermal, photovoltaic and other solar electric
power generation, as well as all types of cooling and heat
management, including but not limited to the electronics industry
in general.
BACKGROUND
[0003] In this specification where a document, act or item of
knowledge is referred to or discussed, this reference or discussion
is not an admission that the document, act or item of knowledge or
any combination thereof was at the priority date, publicly
available, known to the public, part of common general knowledge,
or otherwise constitutes prior art under the applicable statutory
provisions; or is known to be relevant to an attempt to solve any
problem with which this specification is concerned.
[0004] While there are many different structures, arrangements and
techniques for heat transportation, extraction and cooling in the
state of the art, there is a need for improved structures,
arrangements and techniques for cooling and heat transportation
which have improved efficiency. For example, there is a need for
such improvements in the areas of solar thermal, photovoltaic and
other solar electric power generation, nuclear power generation
cooling, as well as in the electronics industry, in general.
[0005] Cooling of photovoltaic cells is one of the main concerns
when designing concentrating photovoltaic systems. Cells may
experience both short-term (efficiency loss) and long-term
(irreversible damage) degradation due to excess temperatures.
Concentrating solar energy maximizes the ability to derive other
forms of output therefrom. However, very high heat densities are
often produced by sun concentrations of more than 1,000 times the
nominal concentration of the sun's energy. This concentration is
sometimes referred to as "1,000X" or "1,000 suns." Some or all
parts of an arrangement that are exposed to these levels of heat
density may be destroyed or are rendered ineffective or
inefficient. Consequently, at least some commercially available
solar cells specify that they are not intended for use above 1,000
suns.
[0006] Design considerations for cooling systems include low and
uniform cell temperatures, system reliability, sufficient capacity
for dealing with worst case scenarios, and minimal power
consumption by the system. For instance, an active cooling system
with a thermal resistance of less than 10.sup.-4 K m.sup.2/W is
typically necessary for solar cells under high concentrations
(>150 suns).
[0007] Conventional nuclear power generation cooling systems
typically require large volumes of water. Thus, it is common to
locate nuclear power plants in close proximity to large bodies of
water, such as lakes. However, severe drought conditions, which may
become more prevalent due to climate change, can diminish the
availability of enough water to provide adequate cooling. This can
result in a disruption of the generation of electrical power. Thus,
there is a need to provide a way to enable adequate cooling of
nuclear power generation operations with lower volumes of cooling
media than is currently utilized.
SUMMARY
[0008] The present invention provides materials, arrangements,
systems, and methods for improved efficiency in heat transport,
extraction, cooling, storage and management.
[0009] The invention can be utilized in a number of potential
applications, including but not limited to solar thermal,
photovoltaic and other solar electric power generation
applications. The present invention includes materials,
arrangements, systems and methods that may be used in applications
with very high heat densities produced by sun concentrations of up
to, for example, 10,000X.
[0010] Heat management for solar electric power generation involves
efficient extraction and transportation of heat generated by the
solar cell with an incident concentrated solar energy strength of
up to, for example, 10,000X. There are at least two notable aspects
of this system: cooling the solar cells and transporting the heat
away for other utility applications such as hot water and/or steam.
Heat management for solar thermal power generation involves
efficient extraction and transportation the heat absorbed by the
heat collector subsystem with an incident sunlight concentration of
up to, for example, 10,000X. There are at least two notable aspects
of this system: collection of heat and transporting the heat away
for other utility applications such as hot water and/or steam.
[0011] According to one aspect of the present invention there is
provided an arrangement comprising: a solar energy receiving
device; and at least one heat transport device in thermal
communication with the solar it energy receiving device, the least
one heat transport device formed from a composite material, the
composite material comprising a matrix of carbon fibers, the carbon
fibers comprising one or more of: mesophase carbon, carbon
nanotubes, graphite, graphene and pan carbon.
[0012] According to a further aspect, the present invention
provides a heat transport device comprising: an internal passage;
and at least a portion of the internal passage formed from a
composite material, the composite material comprising a matrix of
carbon fibers, the carbon fibers comprising one or more of:
mesophase carbon, carbon nanotubes, graphite, graphene and pan
carbon.
[0013] According to a further aspect, there is provided a solar
energy receiving device comprising a first surface for receiving
solar energy incident thereon, and a second opposing surface, the
second surface being electrically conductive; at least one heat
transport device in direct contact with at least a portion of the
second surface, the at least one heat transport device comprises at
least one internal passage and at least one duct; and a heat
transport media flowing within the at least one internal passage
and at least one duct.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic illustration of the molecular
structure of carbon fiber.
[0015] FIG. 2 is a schematic illustration of thermal gradients
present in an anisotropic fiber.
[0016] FIGS. 3A and 3B are schematic illustrations of plated fibers
before and after sintering.
[0017] FIG. 4 is schematic illustration of a portion of the fiber
matrix, including illustration of heat path and thermal gradient
behaviors.
[0018] FIG. 5 is a schematic illustration of a basic building block
construction including multiple layers of a designer composite.
[0019] FIG. 6 is a schematic illustration of a designer composite
in the form of an anisotropic XY cross weave, including the matrix
material in the Z direction.
[0020] FIG. 7 is a schematic illustration of a micro/nano cooling
or heat transport channel arrangement.
[0021] FIG. 8 is a schematic illustration of certain optional
details of the arrangement of FIG. 7.
[0022] FIG. 9 is a schematic cross-sectional illustration of an
arrangement formed according to an additional aspect of the present
invention.
[0023] FIG. 10 is a schematic illustration of an end view of the
arrangement of FIG. 9.
[0024] FIG. 11 is a schematic illustration of an arrangement
including a solar cell and a cooling or heat transport arrangement
formed according to one aspect of the present invention.
[0025] FIG. 12 is a schematic illustration of an arrangement
including a solar cell and a cooling or heat transport arrangement
formed according to a further aspect of the present invention.
DEFINITIONS
[0026] Unless otherwise defined herein or below in the remainder of
the specification, all technical and scientific terms used herein
have meanings commonly understood by those of ordinary skill in the
art to which the present invention belongs.
[0027] Before describing the present invention in detail, it is to
be understood that the terminology used in the specification is for
the purpose of describing particular embodiments, and is not
necessarily intended to be limiting. As used in this specification
and the appended claims, the singular forms "a", "an" and "the" do
not preclude plural referents, unless the content clearly dictates
otherwise.
[0028] Although many methods, structures and materials similar,
modified, or equivalent to those described herein can be used in
the practice of the present invention without undue
experimentation, the preferred methods, structures and materials
are described herein. In describing and claiming the present
invention, the following terminology will be used in accordance
with the definitions set out below.
[0029] As used herein, the term "heat receiving device" or
"electromagnetic energy receiving device" means one or more devices
arranged for receiving one or more forms of electromagnetic energy,
such as solar energy, infrared energy, far infrared energy,
microwave energy, sound energy, phonon energy, or radio waves, and
possibly converting the electromagnetic energy incident thereon to
one or more forms of energy which differ than the form which is
incident thereon. The converted energy may take the form of
electrical current, heat, mechanical energy and/or fluid pressure.
Such heat receiving devices include, but are not limited to,
photovoltaic solar cells and passive solar devices. One example of
a comprehended passive solar device is a tube or other structure
for transporting a heated fluid.
[0030] As used herein, the term "heat transfer media" means a
vapor, a single fluid, mixed fluids, or multiphase fluids. The heat
transfer media may have any suitable pressure, including pressures
equal to, less than, or higher than, atmospheric pressure. The heat
transfer media may include, but is not limited to, one or a
combination of: organic fluid, inorganic fluid, biological fluid,
water, steam, oil, and particles or structures of organic,
inorganic or biological materials. When present in the form of a
mixture, the heat transfer media may take the form of a colloidal
dispersion or emulsion.
[0031] As used herein, the term "duct" shall mean one or more
structures capable of conducting the heat transfer media
therethrough. The duct includes structures such as channels,
canals, tubes, conduits, passageways, tubules and capillaries. The
term "duct" is not limited to any particular material,
cross-sectional geometry or dimension. For purposes of
illustration, the duct can be provided with dimensions on the order
of 1 nm to a few centimeters.
[0032] As used herein, the term "designer" or "designer material"
refers to the ability to control physical and/or thermal properties
in the X, Y, Z material indices. Designer materials have
made-to-order properties in one or more of the three
dimensions.
DETAILED DESCRIPTION
[0033] According to certain aspects of the present invention, a
variety of anisotropic materials, composites, thin films and
matrices having high thermal conductivity have been developed.
These materials can be used in any number of different
applications. For example, the materials of the present invention
can be used to provide unexpectedly superior results as heat
transport devices such as solar cell package substrate material,
micro-channel heat transport devices and fluidic systems, component
mounts, connectors, thermal interface materials, heat spreaders,
heat sinks, heat pipes, vapor chambers, thermoelectric devices,
cooling components in nuclear power generation operations and other
cooling components.
[0034] The materials of the present invention can be characterized
as designer materials. Generally, conventional composites are made
simply by mixing materials of different physical properties, with
no special ordering within the composite and can only demonstrate
bulk properties. By contrast, the designer materials of the present
invention demonstrate different physical properties, thermal
conductivity being a very important physical property for cooling
and heat transport applications, in different directions and parts
of the composite. In addition to thermal conductivity, one or more
of the following properties may be tailored: coefficient of thermal
expansion (CTE); thermal spreading coefficient Ke; and isothermal
morphing of heat flux.
[0035] Designer materials of the present invention are anisotropic
composites and matrices that are thinner, lighter, and stronger,
and have eccentric heat spreading. Eccentricity is an important and
major property in the designer materials. Heat spreading behavior
in the X, Y and Z dimensions can be custom designed based on the
application needs. In addition, the thermal conductivity and heat
spreading could be custom designed to vary even along X, Y and Z
axes. For example, the thermal properties in X direction could
change as the value of X changes, which is along its length. In
addition, the thermal conductivity and heat spreading could be
custom designed to vary even along X, Y and Z axes. For example,
the thermal properties in X direction could change as the value of
X changes, which is along its length. If the heat spreading in an
isotropic material could be visualized as a spheroid, the designer
techniques enable making the shape an ellipsoid or even any random
shape. Another way to visualize the power of the designer paradigm
is an onion made up of layers, in which each layer could have
different thermal properties, and different even within the layer
surface.
[0036] Generally speaking, the designer materials of the present
invention may comprise an anisotropic carbon-based fiber component
and at least one of a high thermal conductivity filler and a high
thermal conductivity coating or cladding.
[0037] The anisotropic carbon-based fibers can comprise one or more
of: mesophase carbon fiber, carbon nanotube (CNT) based carbon
fiber, graphene-based carbon fiber, graphite-based carbon fiber,
and polyacrylonitrile (PAN) based carbon fiber. The carbon fiber
may be derived from pitches, as well known in the art. Optionally,
according to alternative embodiments, the fibers may be formed from
copper, or be clad with copper.
[0038] According to one embodiment of the present invention, the
fiber component of the composite comprises mesophase carbon fiber.
Many materials containing polymers can be converted at early stages
of carbonization to a structurally ordered anisotropic liquid
crystals called mesophase, which can in turn be used to produce an
anisotropic high quality carbon fiber.
[0039] The molecular structure 10 of one of the carbon materials
used in the composites of the present invention is illustrated in
the FIG. 1. The hexagonal crystalline structure 12 in the XY plane
has high covalent bonding 14 responsible for high thermal
conductivity in this plane. However, the adjacent planes in the Z
direction have weak Van der Walls bonding 16. This combination of
high thermal conductivity in the XY direction, with significantly
less conductivity in the Z direction makes the material anisotropic
as indicated by the indication of relevant heat flow 18.
[0040] As illustrated in FIG. 2, the thermal conductivity of
mesophase-based carbon fibers 20 is anisotropic with very high
conductivity in X-direction or along the length of the fiber, while
where the thermal conductivity along its Z-direction or thickness
or diameter is very poor. This behavior is indicated by the
illustrated isotherms 24 and thermal gradient 26. Thermal
conductivity of the mesophase-based carbon fiber along its length
ranges from 100 watts per meter-Kelvin (W/mK) to 5,000 watts per
meter Kelvin. The thermal conductivity in the thickness direction
is less than 50 watts per meter-Kelvin.
[0041] The anisotropic carbon-based fibers can be embedded with an
isotropic high thermal conductivity filler material. Suitable
filler materials include CNTs and other high conductivity materials
like silver, diamond, aluminum nitride and boron nitride. Boron
nitride and aluminum nitride have the special property of high
thermal conductivity with no electrical conductivity. The amount of
filler embedded varies depending on the desired application and
performance objectives. For example, filler can be present in
amounts of 5% to 50% by volume. By embedding such fillers, the
thermal conductivity of the carbon-based can be increased to around
2,000 watts per meter-Kelvin along its length. As used herein CNT
includes Single Wall CNT (SWCNT) and Multi Wall CNT (MWCNT), and
combinations thereof. SWCNT and MWCNT have different conductivity
and structural properties, whereas the choice between the two can
depend factors such as the amount of heat to be transferred:
[0042] The carbon-based fibers, whether embedded with filler or
not, may also be coated or clad with a high thermal conductivity
material 28. Suitable coating or cladding materials include
aluminum, copper, silver boron nitride, diamond and CNTs. The
thickness of the coating or cladding may vary depending on the
application and performance objectives, and desired final density
of the composite. For example, the coating or cladding may range in
thickness from 100 nm-5 .mu.m. According to on non-limiting
example, the coating thickness is approximately 0.5 .mu.m.
[0043] The anisotropic carbon-based fibers can be spun and aligned
to form linear matrix, and then heated to sinter the clad or coated
materials to fuse the fibers 28 together. The fibers adhere to each
other and pull close together into a compacted or dense matrix. The
process boosts the density of the matrix by 5 to 25 times. Other
factors being equal, higher density results in better thermal
conductivity. Several other factors may also affect the density of
the resulting matrix, such as the fiber diameter, density, type and
quality of the embedded high conductivity filler material, and the
CNT type (single wall or multi-wall). When present, the manner in
which the CNTs are grown can also be an important factor that
impacts the resulting shape and density of the matrix.
[0044] The coating or cladding 28 deposited on the anisotropic
carbon-based fibers 20 can be provided with any suitable thickness
t. For example, in order to fill the voids between longitudinal
fibers to obtain a theoretical packing density of the matrix of
89.7%. As shown in FIGS. 3A-3B, the thickness t of the cladding 28
required to fill the void between compressed fibers 20 is when
t=0.0502r. With r being the mean radius of the fiber and R=r+t. For
a packing density of more than 80% t=0.055r. The range of fiber
diameters used can optionally be r=2.0 nm-100 .mu.m, more
specifically 10 nm to 50 .mu.m, and even more specifically 2.5
.mu.m-10 .mu.m. The void fill area A=0.1616r.sup.2.
[0045] According to an alternative embodiment, the composite of the
present invention may comprise the abovementioned anisotropic
carbon-based fiber, high thermal conductivity filler and a foam
material. Foam composites are made by air blowing and foaming
similar to the way all metal foam composites are manufactured. The
foam composites of the present invention made from anisotropic
carbon-based fiber will be lighter than metal foams made solely
from aluminum.
[0046] According to a further embodiment, the embedded and/or clad
anisotropic carbon-based fibers 20 can be woven in various
patterns, thereby forming a woven matrix composite designer
material 31. One such woven composite structure is shown in FIG. 4.
This is a cross-section illustrating the transverse heat path 32
and thermal gradient 34 through this particular woven matrix
composite 31. For applications requiring heat spreading instead of
linear thermal conductivity, the matrix can be designed to have
very high thermal conductivity in the X and Y direction compared to
its Z direction. By choosing weaves with a given direction like
only X or only Y, the spreading can be controlled or improved only
in that chosen direction. When the matrix is designed to have the
thermal conductivity in X, Y and Z directions to be different from
each other, the heat spreading will all be different from each
other, thus making the heat spreading eccentric. The thermal
conductivity in metals like copper and aluminum, which are often
used in such applications, is the same in all the three directions.
By contrast the designer materials of the present invention allows
the thermal spreading properties to be controlled in chosen
directions.
[0047] The composite matrix of the present invention can be
provided with any suitable size or dimension. For example, the
composite matrix can have a thickness from 10 nm-1,000 .mu.m, more
specifically 10 nm-800 nm, or 1 .mu.m-1,000 .mu.m. According to an
alternative embodiment, a plurality of layers of composite matrix
material can be fused together to build a thicker composite matrix.
FIG. 5 shows multiple layers 42, 44, 46, 48, 50 of composite matrix
material which can form the basic building blocks for cooling or
heat transfer components. Each layer of composite matrix material
can be provided with distinct dimensions, weave pattern or
orientation, and/or composition to impart the desired properties to
the resulting cooling or heat transfer component formed therefrom.
For example, an eccentric thermal conductivity profile can be
achieved by varying the number and type of the composite matrix
material layers in building a cooling or heat transport component
therefrom. According to an illustrative non-limiting example, each
of the layers has a thickness T of 20 .mu.m to 100 .mu.m.
[0048] The composite matrix material and cooling or heat transport
components formed therefrom can be made by any number of suitable
techniques or methods. The following is an illustrative,
non-limiting discussion of such techniques and methods.
[0049] There are many considerations to keep in mind for the
manufacture of the anisotropic carbon-based fiber embedded with
high thermal conductivity fillers of the type mentioned above, like
CNT and other nano/micro materials. It may be advantageous to
collocate different related and associated manufacturing, testing
and quality control processes to minimize the total cost of
production by making the whole manufacturing process continuous. It
may also minimize the post manufacturing and shipping processes
generally associated with distributed manufacturing processes.
[0050] The manufacturing process can be continuous starting from
the mesophase or the liquid crystal phase of the carbon fiber
precursor material, until and including the finished product line
of a cooling or heat transport component. The different steps of
the continuous processes may include one or more of the following,
in any particular order.
[0051] One or more high thermal conductivity nano and micro filler
materials, such as CNTs and diamond, are embedded into carbon fiber
at the mesophase and during the drawing of the fiber through
fiber-drawing dies and the fiber spinnerets. The amount filler
materials used depend on the desired increase in thermal
conductivity. The drawing orifice chosen depends on the amount and
type of filler materials as well as the filament diameter that make
up the spun carbon fiber. If the orifice is smaller than a micron,
the filler material and the carbon fiber filament become few
hundred to hundreds of nanometers as the fiber filament drops down
due to gravity and joins the other filaments from the other
orifices of the drawing tool, thus resulting in thinner spun fiber.
If diamond is used as the filler, the conductivity in the Z
direction is also higher, because diamond has much higher
conductivity than carbon fiber in all the three directions. The
spun fiber has much higher thermal conductivity than unfilled
carbon fiber due to CNT and other embedded nano and micro
materials.
[0052] The next steps may include heating, re-crystallization and
cooling through a continuous microwave heating and cooling process.
Depending on the desired thermal conductivity, heating up to the
mesophase formation temperature is required. This temperature can
be on the order of 2000.degree. C. to 3000.degree. C.
[0053] The heat treated fiber can be sent through a pretreatment
process for coating or cladding. A variety of metals with high
thermal conductivity, such as copper, is coated on the fiber. The
coating thickness can be approximately 10 nm-5 .mu.m, and is
controlled by the speed at which the fibers pass through the
plating cycle.
[0054] The coated or clad fibers may be sintered together, as
described above, which allows the fibers to come together or
densify.
[0055] The fiber can be spooled into an array of spools.
[0056] The fibers may be sent through a fiber line up and weave
processes. FIG. 6 shows a cross-woven matrix 52. This is a reel to
reel process. The process may include two steps: in-line weaving
and cross weaving. The woven fibers can go through a continuous
microwave sintering process, where the coated fibers get fused
while at the same time forming a woven composite designer matrix
material.
[0057] The composite matrix material may be layered and fused
together by a continuous roll-to-roll heating process. The type and
thickness of the layers are chosen to define the thermal
conductivity of the final designer matrix.
[0058] The designer composite matrix layers or films can be spooled
into a shippable array of spools for use in the subsequent
manufacture of a variety of cooling or heat transport devices or
components.
[0059] Some heat transport components may even be manufactured in
collocated next steps. A full range of cooling or heat transport
components and materials can be made at least in part from a
composite material of the present invention. Components and
materials to include thermal interface materials (TIM), heat sinks,
heat pipes, microchannel heat transport components, heat spreaders,
stiffeners, packaging materials, PC board laminates, substrate
material, microprocessor lid and other specialty packaging
materials.
[0060] The composite materials of the present invention can be
utilized in the construction of the devices, systems, arrangements
and methods disclosed in: U.S. Provisional Application No.
60/996,273 filed Nov. 8, 2007; U.S. Provisional Application No.
61/071,410 filed Apr. 28, 2008; U.S. Provisional Application No.
61/071,411 filed Apr. 28, 2008; and non-provisional U.S. patent
application Ser. No. ______ entitled "Solar Concentration and
Cooling Devices, Arrangements and Methods," by inventors KRS
Murthy, Robert S. Block and Allen J. Amaro filed on an even date
herewith. Each of the abovementioned patent applications being
incorporated herein by reference in their entirety.
[0061] According to a further embodiment of the present invention,
a heat transport device is provided. A heat transport device of the
present invention can be formed, at least in part, from the
composite matrix designer material described above. An exemplary
heat transport device 60 is illustrated in FIG. 7. It bears
emphasizing that the present invention is not limited to the
particular device illustrated in FIG. 7. In the illustrated
embodiment, the device 60 comprises an internal passage 62
optionally having one or more ducts 64. The ducts 64 can have any
suitable dimensions, such as a width of 10 nm-5 mm. The ducts 64
can be designed to have a high aspect ratio, such as at least 10:1
or 50:1, of height H to width W. At least a portion of the internal
passage 62 and/or at least a portion of the one or more ducts 64 is
formed from the designer composite matrix material. As illustrated
in FIG. 8, the ducts 64 can be imprinted with nano grooves 66
and/or spikes 68 to create turbulence and hence efficient heat
transfer from the channel surface. Instead, or in addition, CNTs 70
can be coated on the one or more of the inside walls of the ducts
64.
[0062] A heat transfer media 72 may be provided within the internal
passage 62 and in communication with the at least one duct 64. The
heat transfer media 72 can contain CNTs and/or other nano or micro
size particles 74 to help create the turbulence and break up
laminar flow to enhance the convective heat transport efficiency.
The CNTs and/or nano or micro particles 74 impinge on the walls of
the ducts 64 and collect heat therefrom then bounce back into the
heat transfer media 72 and quickly disperse and transfer the heat
into the heat transfer media 72, thus acting as heat transfer
agents between the ducts 64 and the heat transfer media 72. The
particles 74 also break up laminar boundary layer flow and create
or add to the turbulent flow of the heat transfer media 72. Only
appropriate volumes of these high conductivity particles 74 should
be added to the heat transfer media 72 to minimize any
coagulation/lumping in the fluidics channel system, valves,
filters, membranes and pumps which may be present in such systems.
Alternatively, the heat transport device 60 may comprise a closed
system containing a set volume of heat transfer media 72, that may
circulate, if at all, only in a closed loop. Appropriate curvature
is designed into the ducts 64 to enhance the fluid flow turbulence.
The inside walls of the ducts 64 may be provided with CNTs and/or
nano/micro fibers 70 are grown vertically from the surface
protruding into the heat transfer media. These protrusions transfer
the conducted heat into the heat transfer media, swaying back and
forth in the flow thereof.
[0063] The heat transport device 60 can be manufactured by any
suitable technique. For example, nano-imprint lithography (NIL) can
be used as a low cost method for forming nanometer-scale features
such as ducts, nano-grooves and/or spikes. This method also
conforms to the International Technology Roadmap for
Semiconductors. NIL may be the lithography solution at the 32 and
22 nm fabrication nodes.
[0064] According to an additional embodiment of the present
invention, a heat transport device, of the type described above, is
incorporated into an arrangement including one or more solar cells,
and is used for cooling the solar cell and/or transporting heat for
other uses. An exemplary arrangement 80 is illustrated in FIG. 9.
As illustrated therein, the arrangement 80 includes a solar cell
82. The solar cell 82 comprises a first surface 84 and a second
surface 86. The heat transport device 60 is placed in thermal
communication with the solar cell 82, optionally in thermal
communication with at least a portion of the second surface 86.
According to one embodiment, a heat transport device 61 is in
communication with the entire second surface 86 of the solar cell
82. The heat transport device 61 may be formed at least in part
from the designer composite material as described herein. The heat
transport device 61 may otherwise have any suitable configuration.
Thus, for example, the heat transport device 61 can be an actively
cooled device having a heat transfer media circulated therethrough
(e.g. FIG. 10). Alternatively, the heat transport device 61 can
comprise a passive device having a sealed internal chamber 63. A
heat transfer media may be provided within the chamber 63.
According to a further alternative embodiment, the heat transport
device 61 is provided with one or more of the features described
herein in connection with the heat transport device 60. The
arrangement 80 may include a thermal interface 88, material (TIM)
between the solar cell 82 and the heat transport device 60. The
thermal interface material 88 is thermally conductive, electrically
conductive, or both. One suitable thermal interface material is a
silver-based material. The solar cell 82 can be mounted directly on
the heat transport device 60 without the use of the package that
comes with the solar cell 82. Because the solar cells 82 are
typically mounted on a substrate and packaged with materials which
have a comparatively low thermal conductivity, mounting the solar
cells directly on the cooling assembly enables maximum heat
transfer from the solar cell to the heat transport device.
[0065] Alternatively, the present invention can be combined
directly with conventional packaged solar cell arrangements that
include a standard solar cell soldered onto a 15 mil thick ceramic
substrate having electrical connectors provided thereon, and still
provide advantages and benefits due to the exceptional cooling and
heat transport properties.
[0066] According to a further embodiment, the arrangement 80
additionally may comprise optics or other suitable means 90 for
producing concentrated solar energy 92 incident upon the solar cell
82. An arrangement formed consistent with the principles of the
present invention is capable of amplifying the concentration of
sunlight up to, for example, 10,000 times the nominal solar
intensity level (10,000X). Additional optional features of the
arrangement include electrical connections 94 and a printed circuit
board 96. In addition, as illustrated in FIG. 10, the heat
transport device 60 may additionally include an inlet 98 and outlet
100 for circulation of a heat transfer media therein. Finally, it
should be understood that the arrangement may include an array of
solar cells. A single heat transport device can be associated with
the entire array. Alternatively, each individual cell may be
provided with a corresponding heat transport device, or any
variation is also envisioned wherein there are fewer individual
heat transport devices than the number of individual solar cells
(i.e., each heat transport device is associated with a plurality of
individual solar cells that are smaller in number that the number
in the array).
[0067] According to a further embodiment of the present invention,
a heat transport device, of the type described above, is
incorporated into the cooling system of a nuclear power generation
operation. The heat transfer media described above may optionally
be utilized with or without the heat transport device. The improved
efficiencies of the heat transport device constructed according to
the present invention and/or the use of the heat transfer media
described herein should provide greater cooling while requiring
lower volumes of coolant than conventional arrangements.
[0068] An arrangement formed according to the principles of the
present invention may include a combination of heat transport
devices and other heat transport and/or cooling system components.
FIG. 11 shows an arrangement 110 wherein heat transfer media flows
across the solar cell strip 112 through manifolds 114. One example
of the heat transfer media is water. Heat transfer media enters the
manifolds 114, passes through the solar cells 112, picks up the
heat and carries the extracted heat away. The main heat transfer
media inlet 116 is designed to be maintained at a level higher than
the manifold 114 and the heat transfer media outlet 118 out of the
manifold 114 is designed to be maintained at a level lower than the
manifold 114, so that heated media does not enter back into the
solar cells 112. Flow rate through the manifold 114 is controlled
based on the amount of incident sun light on the concentrator and
the solar cell strip 112.
[0069] FIG. 12 shows an alternative arrangement 120. In this
embodiment, the same general features are present as in the
embodiment depicted in FIG. 11. However, in the embodiment of FIG.
12, heat transfer media inlet 122 and the heat transfer media
outlet 124 are constructed such that the direction of the flow of
fluid is not significantly changed by the arrangement.
[0070] As illustrated, for example, in FIGS. 9, 11 and 12, the heat
transport arrangements of the present invention, as described
herein, may be directly connected to solar cell arrays or strips.
In other words, cooling or heat transport arrangements of the
present invention can be combined with conventional solar cell
constructions, but where the substrate and/or mounting components
of such conventional solar cell arrangements has been removed so as
to allow direct connection between the solar cell arrays or strips
with the cooling or heat transport arrangements of the present
invention, thereby improving the cooling/heat transport performance
of the overall arrangement. Alternatively, the present invention
can be combined directly with conventional solar cell arrangements
that include their standard substrate and/or mounting and still
provide advantages and benefits due to the exceptional cooling and
heat transport properties as described herein.
[0071] All numbers expressing quantities of ingredients,
constituents, reaction conditions, and so forth used in the
specification are to be understood as being modified in all
instances by the term "about." Notwithstanding that the numerical
ranges and parameters set forth, the broad scope of the subject
matter presented herein are approximations, the numerical values
set forth are indicated as precisely as possible. Any numerical
value, however, may inherently contain certain errors resulting,
for example, from their respective measurement techniques, as
evidenced by standard deviations associated therewith.
[0072] Although the present invention has been described in
connection with preferred embodiments thereof, it will be
appreciated by those skilled in the art that additions, deletions,
modifications, and substitutions not specifically described may be
made without departing from the spirit and scope of the invention.
Terminology used herein should not be construed in accordance with
35 U.S.C. .sctn.112, 6 unless the term "means" is expressly used in
association therewith.
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