Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ARTICLES AND DEVICES FOR THERMAL ENERGY STORAGE
AND METHODS THEREOF
FIELD OF THE INVENTION
[00011 The present invention relates to thermal energy storage using a
thermal
energy storage material and to the packaging of the thermal energy storage
material to
allow for both efficient heat storage and efficient heat transfer.
CLAIM OF BENEFIT OF FILING DATE
[00021 The present invention claims the benefit of the filing date of U.S.
Provisional
Patent Application 61/3731008 (filed August 12, 2010) and US Patent
Application
13/207,607 (filed on August 11, 2011), the contents of which are both
incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0003) industry in general has been actively seeking a novel approach to
capture
and store waste heat efficiently such that it can be utilized at a more
opportune time,
Further, the desire to achieve energy storage in a compact space demands the
development of novel materials that are capable of storing high energy content
per unit
weight and unit volume. Areas of potential application of breakthrough
technology
include transportation, solar energy, industrial manufacturing processes as
well as
municipal and/or commercial building heating.
[0004] Regarding the transportation industry, it is well known that internal
combustion engines operate inefficiently. Sources of this inefficiency include
heat lost via
exhaust, cooling, radiant heat and mechanical losses from the system. It is
estimated
that more than 30% of the fuel energy supplied to an internal combustion
engine
(internal combustion engine) is lost to the environment via engine exhaust.
[0005) It is well known that during a "cold start" internal combustion
engines operate
at substantially lower efficiency, generate more emissions, or both, because
combustion
is occurring at a non-optimum temperature and the internal combustion engine
needs to
perform extra work against friction due to high viscosity of cold lubricant.
This problem is
even more important for hybrid electric vehicles in which the internal
combustion engine
operates intermittently thereby prolonging the cold start conditions, and/or
causing a
plurality of occurrences of cold start conditions during a single period of
operating the
vehicle. To help solve this problem, original equipment manufacturers are
looking for a
solution capable of efficient storage and release of waste heat. The basic
idea is to
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recover and store waste heat during normal vehicle operation followed by
controlled
release of this heat at a later time thereby reducing or minimizing the
duration and
frequency of the cold start condition and ultimately improving internal
combustion engine
efficiency, reducing emissions, or both.
[0006] To be a practical solution, the energy density and the thermal power
density
requirements for a thermal energy storage system are extremely high.
Applicants have
previously filed 1) U.S. Patent Application Publication No, 2009-0211726 by
Soukhojak
at al.õ entitled "Thermal Energy Storage Materials" and published on August
27, 2009; 2)
U.S. Patent Application Publication No. 2009-0250189 by Bank at al., entitled
"Heat
Storage Devices" and published on October 8, 2009, 3) POT Application No.
PCT/US09/67823 entitled "Heat. Transfer Systems Utilizing Thermal Energy
Storage
Materials" and filed on December 14, 2009, and 4) U.S. Provisional Application
No,
61/299,565 entitled "Thermal Energy Storage" and filed on January 29, 2010.
These
previous applications are incorporated herein by reference in their entirety,
[0007] There are known heat storage devices and exhaust heat recovery devices
in
the prior art. However, in order to provide a long term (e.g., greater than
about 6 hour)
heat storage capability, they generally occupy a large volume, require pumping
of a
large volume of heat transfer fluid, require a relatively large pump to
overcome the
hydraulic resistance, and the like. Therefore, there is a need for a heat
storage system
which can offer an unprecedented combination of high energy density, high
power
density, long heat retention time, light weight, low hydraulic resistance for
heat transfer'
fluid flow, or any combination thereof.
[0008] The issue of packaging of the thermal energy storage materials for
applications requiring systems that are light weight, such as in
transportation, requires
both strong packaging and packaging that is light weight. For example, the
packaging
should be durable so that it may contain a large concentration of thermal
energy .storage
material, contain the thermal energy storage material over a wide range of
temperatures
(upon which it may undergo large changes in volume), contain the thermal
energy
storage material in a plurality of cells or capsules that are sealed from each
other, or any
combination thereof. The need for light weight thermal energy storage systems
may
require that the weight of the packaging be reduced.
[0009] For example, there is a need for thermal energy storage material that
is
encapsulated in capsules that are light weight, have a high energy density, or
have a
high power density; and are durable (e.g.,so that the capsules do not leak
upon heating
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to a temperature of about 400 (`C; the capsules do not leak upon repeated
heating
between a temperature of about 25'C and a temperature of about 240 C for
about
1,000 cycles or more; or both).
SUMMARY OF THE INVENTION
[0010] One aspect of the invention is an article comprising; a base sheet
(preferably
a metal base sheet); a cover sheet (preferably, a metal cover sheet) sealingly
joined to
the base sheet to form a capsular structure, wherein the capsular structure
includes one,
two or more sealed spaces; a thermal energy storage material, wherein the
thermal
energy storage material is contained within the sealed spaces, and wherein the
thermal
energy storage material has a liquidus temperature of about 150 C or more;
wherein the
sealed spaces are substantially free of water or includes liquid water at a
concentration
of about 1 percent by volume or less at a temperature of about 25 *C, based on
the total
volume of the sealed spaces; and wherein the article includes one or more of
the
following features: a) the pressure in a sealed space is a vacuum of about 700
Torr or
less, when the temperature of the thermal energy storage material is about 25
*C; b) the
cover sheet includes one or more one or more stiffening features, wherein the
stiffening
features include indents into the sealed space, protrusions out of the sealed
space, or
both, that are sufficient in size and number to reduce the maximum von Mises
stress in
the cover sheet during thermal cycling; c) the base sheet and/or the cover
sheet includes
one or more volume expansion features; or d) the cover sheet has a thickness,
tc, and
the base sheet has a thickness, tb, wherein t is greater than tb; so that the
article does
not leak after thermal cycling between about 25 C and about 240 C, for about
1,000
cycles. The stiffening feature may be any feature (such as an indention or a
protrusion)
that redistributes the stresses in the base sheet and the cover sheet so that
when the.
pressure in the sealed space increases (e.g., due to thermal expansion, or
melting of the
thermal energy storage material) the maximum von Mises stress is reduced
compared to.
a base sheet and/or a cover sheet without the stiffening feature and subjected
to the
same pressure. Without limitation, examples of stiffening features that may be
employed
in the metal cover sheet include dimples, chevrons, ribs, or any combination
thereof.
[0011] In a particularly preferred aspect of the invention, the capsular
structure has
one or more fluid passages which are sufficiently large to allow a heat
transfer fluid to
flow through the one or more fluid passages; and when the capsular structure
is in
contact with a heat transfer fluid, the thermal energy storage material is
isolated from the
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heat transfer fluid.
[0012] Another aspect of the invention is a device including a container and
a stack
of two or more articles within the container. For example, the device may
contain a
plurality of articles described herein. Preferably, each article includes a
fluid passage
and contains the thermal energy storage material. Preferably the articles
having a fluid
passage are stacked so that their fluid passages are generally aligned,
preferably axially.
[0013] Another aspect of the invention is a process for preparing an article,
such as
an article described herein, including the steps of: forming one, two or more
troughs in a
base sheet; ii) at least partially filling one, two or more of the troughs
with a thermal
energy storage material; and at least partially joining (e.g., sealingly
joining) a first metal
foil (e.g., the base sheet) with a second metal foil (e.g., the cover sheet)
to form a sealed
space; wherein the thermal energy storage material includes a metal salt, and
wherein
the metal salt is in a molten state during the joining step.
[0014] Yet another aspect of the invention is directed at a process for
storing heat
comprising a step of: transferring a sufficient amount of thermal energy to an
the article
of the invention, so that the thermal energy storage material in the article
is heated to a
temperature of about 200 "C or more,
[0015] The articles, devices, systems and processes of the present invention
advantageously are capable of containing a high concentration of thermal
energy
storage material so that a large amount of thermal energy can be stored (e.g.,
having a
high energy density), are capable of having a high surface area between the
heat
transfer fluid and the article containing the thermal energy storage material
so that heat
can be quickly transferred into and/or out of the thermal energy storage
material (e.g.,
having a high power density, preferably greater than about 8 kW/L), are
capable of
having multiple flow paths that have similar or equal hydraulic resistance so
that heat is
uniformly transferred to and/or transferred from different regions; have a
rotational
symmetry so that they may be arranged easily; have a structure that is strong
and
durable; have a high heat storage density so that they can be used in
applications
requiring compact designs, light weight components, or both; have lower
hydraulic
resistance for a heat transfer fluid flow (for example, a pressure drop of
less than about
1.5 kPa at a heat transfer fluid pumping rate of about 10 liters/min) so that
the pumping
requirements for the heat transfer fluid are reduced, are sufficiently strong
so that the
thermal energy storage material does not leak from a sealed space after
heating a
capsular structure including the thermal energy storage material to a
temperature of
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about 400 cC, are sufficiently durable so that the thermal energy storage
material does
not leak from a sealed space after repeatedly heating the capsular structure
with the
thermal energy storage material between about 25 `-'C. and about 240 C for
about 1,000
cycles or more, or an combination thereof.
.BRIEF DESCRIPTION OF THE FIGURES
[0016] The present invention is further described in the detailed description
which
follows, in reference to the noted plurality of drawings by way of non-
limiting examples of
embodiments of the present invention, in which like reference numerals
represent similar
parts throughout the several views of the drawings, and wherein:
[0017] FIG. 1 is a drawing of an illustrative article having a sealed
compartment,
(0018] FIG. 2A is a cross-sectional view of an illustrative article including
a plurality
of sealed spaces.
[0019] FIG. 26 is a drawing of an illustrative cross-section of a single
capsule having
a sealed space that may be employed in the article.
[0020] FIG, 3 is a drawing of an illustrative base sheet that may be employed
in the
article.
[0021] FIG, 4A is a drawing of an illustrative cover sheet having chevrons
that may
be employed in the article.
[0022] FIG. 46 is a drawing of an illustrative capsule including a cover sheet
having
dimples that may be employed in an article having one or more capsules.
[0023] FIG, 4C is a drawing of a section of an illustrative cover sheet
including.
dimples that may be employed in the article.
[0024] FIG. 4D is a drawing of an illustrative cover sheet having a plurality
of
stiffening features, such as plurality of protrusions and/or recesses that may
be used in
an article.
[0025] FIG, 5A is a drawing of an illustrative cross-section of a sealed
compartment
at the temperature at which the compartment is sealed.
[0026] FIG. 56 is a drawing of an illustrative cross-section of a sealed at a
temperature below the sealing temperature.
[0027] FIG, 5C is a drawing of an illustrative cross-section of a sealed
compartment.
at a temperature above the sealing temperature,.
[0028] FIGs. 6A, 66, and 6C are drawings of an illustrative sheet that has
been
formed to have ribs.
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(0029) FIC.3s, 7A and 76 are drawings illustrating a sheet having a volume
expansion
feature that allows the volume of the sealed space to increase (e.g, to
accommodated
the volume expansion of the thermal energy material as it is heated and/or
melts).
[00301 FIG, 8 is an illustrative graph showing the relationship between the
thickness
of the cover sheet and the maximum von Mises stress in the cover sheet when
the cover
sheet is employed in an article containing a thermal energy storage material
and the
thermal energy storage material is heated,
[0031] FIG. 9 is an illustrative graph showing the relationship between the
thickness
of the cover sheet and the maximum expected von Mises stress in the cover
sheet for a
cover sheet that is flat and for a cover sheet that includes ribs.
[0032] FIG. 10 is an illustrative graph showing the relationship between the
thickness of the cover sheet and the maximum expected von Mises stress in the
cover
sheet for a cover sheet that is flat, for a cover sheet that includes dimples,
for a cover
sheet that includes chevrons, and for a cover sheet that includes ribs.
100331 FIG, 11 is an illustrative drawing of a portion of tooling that may be
employed
in manufacturing a sheet that includes ribs.
[00341 AG.. 12 shows an illustrative stack. of articles.
[00351 FIG. 13 shows a surface of a base sheet of an article including one or
more
sealed compartment. FIG, 13 illustrates that a sealed compartment may have a
primary.
seal and one or more secondary seals.
(0036] FIG. 14 is a drawing of an illustrative heat storage device.
[0037] FIG. 15. Is a drawing of an illustrative tooling for embossing a base
sheet.
[0038] FIG. 16 shows a surface of a base sheet of an article including one or
more
spaces being filled with thermal energy storage material using a nozzle.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0039] In the following detailed description, the specific embodiments of the
present
invention are described in connection with its preferred embodiments. However,
to the
extent that the following description is specific to a particular embodiment
or a particular
use of the present techniques, it is intended to be illustrative only and
merely provides a
concise description of the exemplary embodiments. Accordingly, the invention
is not
limited to the specific embodiments described below, but rather; the invention
includes
all alternatives, modifications, and equivalents falling within the true scope
of the
appended claims.
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f00401 As will be seen from the teachings herein, the present invention
provides
unique articles, devices, systems, and process for storing thermal energy
and/or
transferring stored thermal energy to a fluid. For example, the articles and
devices for
storing thermal energy of the present invention are more efficient at storing
thermal
energy, allow for transferring thermal energy more uniformly, allow for
transferring
thermal energy with a smaller pressure drop of the heat transfer fluid, or any
combination thereof.
[0041) Various aspects of the invention are predicated on an article
including a
capsular structure having one or more sealed spaces (i.e., capsules) and one
or more
thermal energy storage materials that are encapsulated in the one or more
sealed
spaces of the capsular structure so that the thermal energy storage material
cannot flow
out of the capsular structure or otherwise be removed from the capsular
structure. When
the thermal energy storage material is heated during operation, the volume may
increase due to thermal expansion, due to difference in the densities of the
liquid and
solid phases of the thermal energy storage material, or both. The increase in
volume of
the thermal energy storage material may be about 5 9.10 or more, about 10% or
more,
about 15% or more, or even about 20% or more. For example, a metal salt, such
as
lithium nitrate, may increase in volume by more than 20% when heated from
about 23 CC
to about 300 C. It will be appreciated that as the thermal energy storage
material is
heated, the pressure in the sealed space may increase. The capsular structure
should
be sufficiently durable so that it does not leak or otherwise fail when the
thermal energy
storage material expands during use. The capsular structure preferably has a
geometry
that allows a heat transfer fluid to efficiently remove heat from the thermal
energy
storage material. Without limitation, examples, of preferred capsular
structures include
those described in U.S.. Patent Application Publication No. 2009/0250189 by
Soukhojak
et al., published on October 8, 2009, and U.S. Provisional Patent Application
No..
61/299,565 filed on January 29, 2010, incorporated herein by reference. For
example,.
the capsular structure may have a geometry that includes one or more fluid
passages
that are sufficiently large so that the capsular structure is capable of
allowing a. fluid (e.g.,
a heat transfer fluid) to flow through the fluid passage. The thermal energy
storage
materials may be sufficiently encapsulated in one or more of the sealed spaces
so that
when the heat transfer fluid contacts the capsular structure, the thermal
energy storage
material is isolated from the fluid,
[0042) A variety of approaches have been identified that advantageously
improve
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the durability of the capsular structure including having, a pressure in a
sealed space that
is a vacuum of about 700 Torr or less when the temperature of the thermal
energy
storage material is about 25 "C, using a metal base sheet that includes one or
more
stiffening features (e.g,, one or more ribs), using a metal cover sheet that
includes one
or more stiffening features (e.g., one or more ribs, one or more dimples, one
or more
chevrons, or any combination thereof), using a cover sheet having a thickness
greater
than the thickness of the base sheet, or any combination thereof.
[0043] By reducing the pressure of a sealed space at a temperature of about 25
cC,
the pressure of the sealed space when the thermal energy storage material is
heated
may also be reduced. The pressure of a sealed space at a temperature of about
25 GC
may be reduced to about 700 Torr or less using any convenient means. By way of
example, the cover sheet and the base sheet may be joined to formed the sealed
space
when the thermal energy storage material is at a joining temperature, T, that
is
sufficiently high so that when the thermal energy storage material in the
sealed space is
cooled, the thermal energy storage material contracts and the pressure in the
sealed
space drops below about 700 Torr. The joining temperature may be greater than
the
liquidus temperature, TLJESM) of the thermal energy storage material.
Preferably the
joining temperature, Tj, is about IT, ,TEsm -4- 10 "C or more, even more
preferably about
TcrEsm + 20 "C or more, even more preferably about TuEsm + 30 ve or more, even
more
preferably about TLTESM + 40 "C or more, even more preferably about ILTESm +
50 "C or
more, and most preferably about TLI-Ew + 60 'C or more. By way of example, -
1`, may be
about 200 'C or more, preferably about 230 'C or more, more preferably about
250 "C
or more, even more preferably about 270 CC or more., and most preferably about
290 'C
or more,. The temperature of the thermal energy storage when the base sheet
and the
cover sheet are joined may be about 700 "C or less, preferably about 500 Cc or
less,
and more preferably about 400 CC or less.
[00441 In another example, the cover sheet and the base sheet may be joined
while
a vacuum is applied to the region that becomes the sealed space. If employed,
the
vacuum should have a pressure sufficiently low so that upon sealingly joining
the base
sheet and the cover sheet, the sealed space is a vacuum. For example, a vacuum
may
be applied having a pressure of about 700 Torr or less, about 660 Torr or
less, about
600 Torr or less, about 550 Torr or less, about 500 Torr or less, about 400
Torr or less,
or about 300 Tarr or less. As such, the entire joining process may be done in
a vacuum
environment. The cover sheet and the base sheet may be joined while the
pressure in
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PCT/US2011/047355
the region that becomes the sealed space is about 0.1 'Tarr or more,
preferably about
1.0 Tarr or more, and more preferably about 10 Torr or more. Lower pressures
may also
be employed. Preferably the thermal energy storage material is at a
predetermined
sealing temperature that is at an elevated temperature when the base sheet and
the.
cover sheet are sealingly joined, so that upon cooling the article to about 25
C
vacuum is formed in the sealed space. The predetermined sealing temperature
may be
any temperature at which the density of the thermal energy storage material is
lower
than its density at 25" C. Preferably the predetermined sealing temperature is
greater
than the liquidus temperature of the thermal energy storage material (e.g.,
greater than
the liquidus temperature by about 10 Cc or more, by about 30 "C or more, or
about
60 "C or more). The predetermined sealing temperature may be about 50 "C or
more,
about 100 C or more, about 150 "C or more, about 200 C or more, about 250 "C
or
more, or about 300 "C or more. The predetermined sealing temperature
preferably is
sufficiently low so that the thermal energy storage material does not degrade
during the
sealing process. The predetermined sealing temperature may be about 500 C or
less,
about 400 eC. or less, or about 350 or less.
[0045] When the thermal energy storage material in the sealed space is at
a
temperature of about 25 eC, the sealed space preferably is a vacuum of about
600 Torr
or less, more preferably about 500 Torr or less, even more preferably about
400 Torr or
less, and most preferably about 300 Torr or less. The lower limit on the
pressure in the
sealed space when the thermal energy storage material is at 25 eC is based on
manufacturability and is preferably about 0.1 Torr or more, more preferably
about 1 Tarr
and most preferably about 10 Torr or more.
[0046] The durability of the capsular structure may be increased by adding
one or
more stiffening features to the base sheet, the cover sheet, or both. The
stiffening
feature may be any feature that redistributes the stresses in the base sheet
and the
cover sheet so that when the pressure in the sealed space increases (e.g., due
to
thermal expansion, or melting of the thermal energy storage material) the
maximum von
Mises stress is reduced compared to a base sheet and/or cover sheet without
the
stiffening feature and subjected to the same pressure. The stiffening features
may be an
indention or protrusion formed in a sheet. As such, the stiffening feature may
be a
change in the profile of the sheet. The stiffening feature may function by
redistributing
the stresses in a sealed space (e.g., the stresses obtained when heating the
sealed
space) so that the maximum von Mises stress is reduced. A stiffening feature
may be
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described by its depth (i.eõ the amount of change in the profile, such as
compared to the
region away from the stiffening feature), its length, its width, or any
combination thereof.
The stiffening feature preferably has a depth of about 0.1 mm or more, more
preferably
about 0,2 mm or more, even more preferably about 0.3 mm or more, even more
preferably about 0.4 mm or more, even more preferably about 0.5 mm or more,
and
most preferably about 0.6 mm or more. The stiffening feature preferably has a
sufficiently small depth so that the effect of packing or stacking multiple
capsular
structures, as described herein, is not greatly affected. As such, the
stiffening feature
preferably has a depth of about 10 mm or less, more preferably about 5 mm or
less,
even more preferably about '3 mm or less, and most preferably about 2 mm or
less.
Without limitation, examples of stiffening features that may be employed
include ribs,
dimples, chevrons, and the like. The stiffening features may include a
protrusion or
indention that has a length to width that is greater than about 1, preferably
about 2 or
more, even more preferably about 4 or more, and most preferably about 10 or
more,
such as a rib. If employed, two ribs in a base sheet or cover sheet in the
region of a
sealed space may be parallel, perpendicular, or at an acute angle. The
stiffening feature
may have a generally circular cross-section, such as a dimple. The stiffening
features
may be arranged in, a repeating pattern that includes a plurality of
stiffening features.
aligned in one direction and a plurality of stiffening features aligned in a
different
direction, such as a chevron pattern. The stiffening features are preferably
located on
the regions of the sheet that contain a sealed space. There may also be
stiffening
features located in the region of a sheet that does not containing a sealed
space.
[00471 The stiffening features (e.g,, the stiffening features in a cover
sheet) may
have a sufficient size and number so that the maximum von Mises stress of the
capsular
structure containing the thermal energy storage material and heated to 250 C
is lower
than the von Mises stress of an identical capsular structure, with the
exception that the
stiffening feature is eliminated (e.g., a sheet having a generally smooth
surface, is
generally flat, or both, such as a generally flat, smooth cover sheet). The
stiffening
features are preferably present in a sufficient size and number so that the
von Mises
stress in the capsular structure containing the thermal energy storage
material at 250 CC
is reduced by about 5% or more, more preferably about 10% or more, even more
preferably about 15% or more, even more preferably about 20% or more, even
more
preferably about 30% or more, and most preferably about 40% or more, compared
with
the von Mises stress of an identical capsular structure, with the exception
that the
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stiffening feature are removed (e.g., the sheet has a generally smooth
surface, is
generally flat, or both).
[00481 The stiffening feature (optionally along with one or more other
features
disclosed herein) may be used to reduce the maximum von Mises stress in a
sealed
space containing thermal energy storage material so that the at a temperature
of 250 ')C,
the ratio of the maximum von Mises stress in the base sheet and the cover
sheet,
Smax,250, to the yield stress of the metal at 250 C (e.g., the metal of the
cover sheet, or
the lower of the base sheet and the cover sheet), Sy,250, is preferably about
0,95 or less,
more preferably about 0.90 or less, even more preferably about 0.85 or less,
even more
preferably about 0,80 or less, and most preferably about 0,70 or less.
[00491 The durability of the capsular structure may be increased by adding one
or
more ribs to the base sheet, the cover sheet or both. Preferably the base
sheet, the
cover sheet include a rib structure (e.g., a sufficient number or ribs and/or
ribs of
sufficient size) that provides a sufficient rigidity to the capsular structure
so that the
capsular structure does not bend enough to yield and does not otherwise
distort enough
to yield.
(00501 It will be appreciated according to the teachings herein that the base
sheet
may have a structure, such as a structure including one or more troughs, that
is
generally more rigid than the cover sheet. Advantageously, the thickness of
the base
sheet may be sufficiently reduced so that the rigidity of the base sheet more
closely
matches the rigidity of the cover sheet. By reducing the thickness of the base
sheet, the
volume of the base sheet and/or the packaging material may be reduced, the
weight of
the base sheet and/or packaging material may be reduced, or both. Thus, a
higher
percentage of the weight of the capsular structure may be the weight of the
thermal
energy storage material. As such, the base sheet may have a thickness (e.g.,
an
average thickness) of trõ and the cover sheet may have a thickness (e.g., an
average
thickness) of about te, where le is greater than t. The ratio of Ob preferably
is about 1.05
or more, more preferably about 1,10 or more, even more preferably about 1,15
or more,
even more preferably about 1.20 or more, even more preferably about 1.25 or
more,
even more preferably about 1,30 or more and most preferably about 1,35 or
more. The
difference between tc and tt, preferably is about 0.01 mm or more, more
preferably about
0.02 mm or more, even more preferably about 0.03 mm or more, even more
preferably
about 0.035 mm or more, even more preferably about 0.04 mm or more, and most
preferably about 0.05 mm or more. The difference between t, and tb preferably
is about 1
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mm or less, more preferably about 0.5 mm or less, and most preferably about
025 mm
or less. By way of example, i) the ratio of t,ltõ may be about 1.05 or more,
about 1.10 or
more, about 1,20 or more, or about 1.3 0 or more; ii) the difference between
t,ltb may be
about 0.01 mm or more, about 0.02 mm or more, about 0.03 mm or more, or about
0.05
mm or more; or both .(i) and (ii),
[0051] The base sheet, the cover sheet or both may have one or more volume
expansion features so that the volume of the sealed space may reversibly
increase as
the thermal energy storage material expands during heating and/or melting.
Examples of
volume expansion features include wrinkles, pleats, convolutions, folds,
oscillations, and
the like. By way of example, the volume expansion feature may include one,
two, or
more convolutions, folds, or pleats. Preferable volume expansion feature may
have a
generally bellow, or accordion shape (albeit, typically without an orifice). A
stiffening
feature, such as one or more dimples, one or more chevrons, or one or more
ribs, may
also function as a volume expansion feature. It will be appreciated that the
size, shape of
a volume expansion feature and number of volume expansion features will affect
the
amount by which the volume of the sealed space is capable of expanding. If
employed,
the volume expansion features may be sufficient to increase the volume of the
sealed
space by about 5% or more, preferably by about 10% or more, more preferably by
about
13% or more, and most preferably by about 15% or more. The volume expansion
feature
may allow the sealed space to sufficiently expand so that the internal
pressure in the
sealed space changes increases by about 35 kPa or less (preferably by about 20
kPa or
less, and more preferably by about 10 kPa or less) when the thermal energy
storage
material is heated from about 25 CC to a temperature at which the thermal
energy
storage material is a liquid (e.g., to about 200 Cc, to about 240vC, or to
about 250 "C).
[0052] Other aspects of the invention include novel arrangements including a
plurality of the articles, novel devices including one or more of the
articles, novel
processes for manufacturing the article, and novel processes for using one or
more of
the articles. By employing the novel article, it is possible to assemble
devices capable of
storing a large quantity of thermal energy, capable of rapidly transferring
thermal energy
into or out of the thermal energy storage material, capable of being compact,
capable of
being light weight, capable of having a low pressure drop of a heat transfer
fluid, or any
combination thereof.
[0053] The capsular structure generally has a dimension in one direction
(i.e.., a
thickness) that is smaller than the dimensions in the other directions.
Without limitation,.
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examples of capsular structures include those disclosed in U.S. Patent
Application No.
12/389,598 entitled "Heat Storage Devices" and filed on February 20, 2009, and
U.S.
Provisional Application No. 61/2991565 entitled 'Thermal Energy Storage" and
filed on
January 29, 2010, both incorporated herein by reference.
[0054) The shape of the capsular structure and/or article may be defined by
the
packaging space and may be oddly shaped. The article may include a cover sheet
(i.e.,
a cover sheet) having a top surface and a generally opposing base sheet having
a
bottom surface. The cover sheet (e.g., the top surface of the cover sheet),
the base
sheet (e.g., the bottom surface of the base sheet), or both, may have a
portion that is (or
may be) generally flat (e.g., have a generally planar surface.), generally
arcuate, or any
combination thereof. Preferably the base sheet and/or the bottom surface of
the base
sheet includes a generally arcuate portion or is generally arcuate, the top
surface of the
article is generally planar (e.g.., the cover sheet is generally flat), or
both. In various
embodiments of the invention a generally planar cover sheet may include one or
more
stiffening features (such one or more ribs, dimples, chevrons, or other
protrusions or
recesses as described herein) and/or one or more volume expansion features. As
described herein, a cover sheet may also be replaced by a second base sheet.
As such,
the capsular structure may be define by two base sheets that are the same or
different.
[0055) The capsular structure may include one or more openings, such as a
fluid
passages. For example, the capsular structure may include one or more fluid
passages
so that a fluid, such as a heat .transfer fluid, can flow through the article
without
contacting the thermal energy storage material. Without limitation, the
capsular structure.
may include a fluid passage having one or more features described in
paragraphs 7-12,
28-43, and 54-67, and Figures 1, 2, 3, 4, 5, 6, and 7 of U.S. Provisional
.Application No.
61/2991565 entitled =Thermal Energy Storage" and filed on January 29, 2010,
incorporated herein by reference,
[00561 The cover sheet and the base sheet may include one or more openings.
The
cover sheet and the base sheet may be arranged so that at least one opening of
the
cover sheet overlaps at least one opening of the base sheet. As such, the
cover sheet
and the base sheet may have one or more corresponding openings. The cover
sheet
has an outer periphery in the regions furthest from the center of the cover
sheet. The
cover sheet may have one or more opening peripheries in the region of the
cover sheet
near an opening (preferably near the center) of the cover sheet. The base
sheet has an
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outer periphery in a region far from the center of the base sheet and may also
have an.
opening periphery near the opening (preferably near the center) of the base
sheet. Each
of the cover sheet and the base sheet may be sealingly attached to each other
or to one
or more other optional sub-structures (such as an outer ring) along the
respective outer
peripheries of the sheets, for forming one or more sealed spaces therebetween.
Each of
the cover sheet and the base sheet may be sealingly attached to each other or
to one or
more other optional sub-structures (such as an, inner ring) along the
respective opening
peripheries of the sheets, for forming one or more sealed spaces therebetween.
Preferably the cover sheet and the base sheet are sealingly attached to each
other
along their respective outer peripheries, along at least one of their
respective
corresponding opening peripheries, or both. Most preferably the cover sheet
and the
base sheet are sealingly attached to each other both along their respective
outer
peripheries and along at least one of their respective corresponding opening
peripheries.
It will be appreciated that the cover sheet and the base sheet may also be
sealingly
attached to each other or to one or more other optional sub-structures along
one or more
additional regions (other than their peripheries) so that a plurality of
sealed spaces are
formed.
[0057] The capsular structure may optionally include one or more sub-
structures that
when sealingly attached to a base sheet and a cover sheet forms one or more
sealed
spaces. Without limitation, the sub-substructure, if employed, may include one
or any
combination of the features described in U.S. Provisional Application No.
61/2991565
entitled "Thermal Energy Storage" and filed on January 29, 2010, incorporated
herein by
reference. For example, the base sheet, the .over sheet, or both may be
attached to one
or more rings, such as one or more inner rings, one or more outer rings, or
both, The
substructure, if employed, may include a honeycomb or. other open cell
structure, such
as described in paragraph 83 of U.S. Patent Application Publication No. 2009-
0250189
by Bank et al., published on October 8, 2009, incorporated herein by
reference.
[0058] The thickness of the capsular structure is defined by the average
separation
between the top surface of the article (e.g., the top surface of the cover
sheet) and the,
bottom surface of the article (e.gõõ the bottom surface of the base sheet).
The article may
have a geometry sufficiently thin so that heat can be rapidly provided from a
fluid to
thermal energy storage material and/or rapidly removed from the thermal energy
storage
material to a fluid, The article may have a thickness that is less than the
length or
diameter of the article,.
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PCT/US2011/047355
[0059] For example, ratio of the length or diameter of the article to the
thickness of
the article may be about 2 or more, about 5 or more, about 10 or more, or
about 20 or
more. 'Without limitation, the ratio of the length or diameter of the article
to the thickness
of the article may be about 1,000 or less, preferably about 300 or less, and
more
preferably about 150 or less. Preferably, the thickness of the article is 80
mm or less,
more preferably about 20 mm or less, even more preferably about 10 mm or less,
and
most preferably about 8 mm or less. The thickness of the article preferably is
greater
than about 0.5 mm, more preferably greater than about 1 mm.
[0060] The longest dimension of the article (e.gõ the length or diameter of
the
article) is typically much greater than the thickness of the article so that
the article can
both have a large volume (e.g., for containing a large volume of thermal
energy storage
material), and a large surface area (e.g., for rapid transfer of thermal
energy). The
longest dimension of the article preferably is greater than about 30, more
preferably
greater than about 50 mm and most preferably greater than about 100 mm. The
longest
dimension is defined by the use, and can be any length that meets the need for
heat
storage, heat transfer, or both, in a particular use. The longest dimension of
the article
typically is less than about 2 m (i.e., 2000, mm), however articles having a
longest
dimension greater than about 2 m may also be employed,
[0061] The article may have one or more side surfaces. For example the
article may
have one or more side surfaces that are nonplanar. The article may have a
single side
surface that is generally arcuate, generally nonplanar, generally continuous,
or any
combination thereof. Preferably the one or more side surfaces are generally
equidistant
from a center of the article so that the article can be placed in a container
having a
generally cylindrical cavity with a cavity diameter that is only slightly
larger than the
average diameter of the article. When the ratio of the cavity diameter to the
average
diameter of the article is low, a 'large amount of the cavity is occupied by
the article_ For
example, the ratio of the maximum diameter of the article to the average
diameter of the
article may be less than about 1.8. preferably less than about 1.2, more
preferably less
than about 1,1, and most preferably less than about 1.05. It will be
appreciated that the
ratio of the maximum diameter to the average diameter of the article is about
1.0 or more
(e.g., about 1.001 or more).
[0062] A large portion of the volume of the capsular structure is the
encapsulated
volume ( the volume of the one or more sealed spaces) so that the article
can
contain a relatively large amount of the thermal energy storage material. The
total
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volume of the one or more sealed spaces of the article is preferably at least
about 50
volume percent, more preferably at least about 80 volume percent, even more
preferably
at least about 85 volume percent and most preferably about 90 volume percent
based
on the total volume of the article. The total volume of the one or more sealed
spaces of
the article is typically less than about 99.9 volume percent based on the
total volume of
the article. The remaining volume, not occupied by the thermal energy storage
material,
may include or consist substantially entirely of the capsular structure, void
spaces (e.g.,
containing one or more gases), one or more structures for improving the heat
transfer
between the thermal energy storage material and the capsular structure, or any
combination thereof. Structures for improving heat transfer between the
thermal energy
storage material and the capsular structure include any structure formed of a
material
having a relatively high thermal conductivity (e.g., relative to the thermal
energy storage
material) that is capable of increases the rate of heat flow from the thermal
energy
storage material to a heat transfer fluid. Preferable structures for improving
the rate of
heat flow include fins, wire mesh, protrusions into the sealed space, and the
like.
[0083] The article preferably is easy to stack with other identical shaped
articles, or
other articles having a generally mating surface. For example, two articles to
be stacked
may have opposing surfaces that are generally mating surfaces so that when
stacked,
the two articles nest together. It will be appreciated that one approach for
stacking
articles so that they easily nest together is to select a shape (e.g., a shape
of an arcuate
surface, a shape of the sealed spaces, or both) having a rotational symmetry
of a high
order. The rotational symmetry may be about an axis in the stacking direction
(e.g., an
axis through the fluid passage of the capsular structure). The order of the
rotational
symmetry typically describes the number of distinct rotations between the two
surfaces
being stacked together in which they will nest together. The order of the
rotational
symmetry of the article, the base sheet (e.g., the arcuate surface of the base
sheet), or
both, preferably is at least 2, more preferably at least 3, even more
preferably at least 5,
and most preferably at least 7.
[0064) The article preferably has a capsular structure that is difficult to
bend. For
example, the capsular structure may be free of a cross-section in which a
cover sheet
and a base sheet are in contact throughout most or even all of a length of the
cross-
section (such as a diameter of the capsular structure). There are various
approaches
that may be employed for assuring that the capsular structure will be
difficult to bend,
including selecting an arrangement of the capsules so that the order of
rotational
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symmetry is not an even number, selecting an arrangement of the capsules se
that there
is no rotational symmetry, selecting, an arrangement of capsules including two
or more
rings of capsules (such as concentric rings) that are rotated relative to each
other so that
every radial section includes at least one sealed space, or any combination
thereof. It
will be appreciated that other geometries and other means may be employed to
make
the capsular article resistant to bending. For example, the materials for the
capsular
structure may be chosen to be generally stiff, the structure may include one
or more ribs.
(e.g., in a tangential direction), and the like.
[00651 All of the thermal energy storage material of the article may be in a
single
sealed space. The thermal energy storage material of the article may
optionally be
divided between a plurality of sealed spaces so that if a sealed space is
punctured or
otherwise leaks, despite the improvements described herein, only a portion of
the
thermal energy storage material can be removed. As such, the number of sealed
spaces
in the article (e.g., sealed spaces that contain thermal energy storage
material) may be 1
or more, 2 or more, 3 or more, 4 or more, or 5 or more. The upper limit on the
number of
sealed spaces is practicality and for a particular application is defined by
the need of the
application. Nevertheless, the number of sealed spaces in the article
typically is less
than 1,000. However, it will be appreciated that very large articles may have
1,000 or
more sealed spaces. For the same reasons, the volume fraction of the thermal
energy
storage material that is found in any single sealed compartment may be about
100%,
less than about 55%, less than about 38%, than about 29%, or less than about
21%,
based on the total volume of the thermal energy storage material in the
article. Typically
a sealed space includes at least 0.1 volume % of the thermal energy storage
material in
the article. However, it will be appreciated that the article may include one
or more
sealed spaces that are substantially or even entirely free of the thermal
energy storage
material.
[00661 The sealed spaces may optionally be arranged in a pattern which
facilitates
efficient stacking of the articles of the invention and efficient energy
transfer to and/or
from the capsules, such as a plurality of concentric rings, including an
innermost ring
(e.g., a ring closest to an opening periphery) and an outermost ring (e.g., a
ring closest
to the outer periphery), each containing one or more sealed spaces. The sealed
spaces.
in one ring may have a generally repeating pattern. For example, each sealed
space or
each groups of 2, 3, 4 or more sealed spaces in a ring may have generally the
same
shape and size. The number of sealed spaces in each ring may be the same or
different.
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Preferably the outermost ring has more sealed spaces than the innermost ring,
the
average length of the sealed spaces of the outermost ring is less than the
average
length of the sealed spaces of the innermost ring (where the average length is
measured
in the radial direction from the opening to the outer periphery), or both, so
that the
volume variation between the sealed spaces of the outermost ring and the
innermost
ring is reduced.
[00671 As discussed hereinafter, the article may be placed in a container,
such as a
container having a generally cylindrical shaped cavity. Preferably, the cavity
may be only
slightly greater in dimension than the longest dimension of the article. For
example, the
diameter of the cavity of the container may be only slightly larger than the
diameter of
the capsular structure of the article. The diameter of the cavity should be
sufficiently
large so that the article can be inserted into the cavity. When the article
(or a stack of the
articles) is placed in the container, it may be desirable for a fluid to be
capable of flowing
between the outer periphery of the article and an interior wall of the
container. This can
be achieved by designing the relationship of the interior of the container and
the shape
of the article to create and maintain fluid flow paths. Any means of creating
such fluid
flow paths may be used. As such, the article may optionally have one or more
indents
along its periphery (e.g., the cover sheet and the base sheet may have one or
more
corresponding indents along their respective outer peripheries) so that a
space is formed
for flowing a heat transfer fluid. Alternatively, or in addition, the cavity
of the container
may have a surface with one or more grooves for flowing a fluid between the
outer
periphery of the article and the surface of the container. As another example,
the
diameter of the article may be sufficiently small in relation to the diameter
of the interior
of the cavity so that a fluid can flow along the entire outer periphery of the
article. For
example, the article may have one or more indents or the container may have
one or
more grooves, for each sealed space in the outermost ring of sealed spaces. An
indent
or a groove may have any shape, such as a polygonal shape, an arcuate shape, a
wedge shape, and the like, provided it has a sufficient size to allow for the
heat transfer
fluid to flow. If employed, the smallest dimension of the indents and/or
grooves is
typically at least about 0.1 mm). It will be appreciated that a combination of
two or more
means of creating a fluid flow path may be used. For example, the article may
have one
or more indents along its outer periphery and the article may have a
sufficiently small
diameter so that fluid can flow along its entire outer periphery when placed
in a cavity.
[0068] The article for containing thermal energy storage material includes a
base
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sheet that is. formed so that it includes one or more troughs suitable for
holding a liquid.
The base sheet may used in a process in which one or more troughs are filled
with a
thermal energy storage material, covered with a 'generally flat cover sheet
and then
joined to the cover sheet (preferably while the thermal energy storage
material is at least
partially in a molten state). The base sheet may optionally have one or more
protrusions,
so that when the article is stacked with another article having a surface that
generally
mates with the base sheet, the two articles only partially nest. As such the
one or more
protrusions may function as a spacer to separate the generally mating surfaces
so that a
fluid (e.g.õ a heat transfer fluid) can flow between the mating surfaces. If
employed, the
protrusions preferably cover only a small portion of the surface are of the
base sheet so
that the one or more protrusions do not substantially interfere with the flow
of the fluid.
The height of the protrusions may be selected to define the height (e.g., the
average
height) of the flow path between the two generally mating surfaces.
[0069) The base sheet may additionally include one or more volume expansion
features and/or one or more stiffening features, such as one or more ribs, one
or more
dimples, one or more chevrons, or any combination thereof, that function to
stiffen the
base sheet. it has been surprisingly observed that the troughs, the stiffening
features,
the volume expansion features, or any combination thereof of the base sheet
may
reduce the maximum stress on the base sheet when an article containing a
thermal
energy storage material is heated. For example the maximum stress, such as
the.
maximum von 'Mises stress, on a base sheet may be less than the maximum von
Mises
stress of a flat cover sheet made of the same material (e.gõ the same metal)
and having
the same thickness as the base sheet when the thermal energy storage material
in a
sealed space is heated. The relatively low stress in the base sheet may
provide an
opportunity to reduce the weight of the article and/or increase the amount of
thermal
energy storage material in the article by using a base sheet having a lower
thickness.
a thickness that is less than the thickness of the cover sheet).
[00701 It has also been surprisingly observed that the thickness of the base
sheet, ,
the cover sheet, or both may be further reduced by adding the optional
stiffening
features such as ribs, dimples, or chevrons to the base sheet. If employed,
the stiffening
features preferably have a sufficient size, shape and number so that the
maximum von
Mises stress of the sheet (e.g., the base sheet or the cover sheet) is
reduced, preferably
by about 2% or more, more preferably by about 5% or more, and most preferably
by
about 10% or more. The stiffening features may include features that are
protrusions
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(.e., that go away from the sealed space), features that are recesses (i.e.,
that go into
the sealed space), or both. Preferred stiffening features protrude or recess
by a
depth/height of about 0.2 mm or more, more preferably about 0.4 mm or more,
and most
preferably about U.S mm or more. Preferred stiffening features protrude or
recess by a
depth/height of about 5 mm or less, more preferably about 3 mm or less, and
most
preferably about 1 mm or less.
[0071] When stacking articles, they may be arranged so that cover sheets from
two
adjacent articles are at least partially in contact with each other. It may be
desirable for
the two cover sheets to have a large contact area so that they are in good
thermal
communication and/or for there to be little gaps or spaces between the two
cover sheets
so that space is not wasted. As such, the cover sheets may only include
recesses. Good
contact between two cover sheets may also be achieved by having cover sheets
that are
generally mating surfaces. For example, a first cover sheet may have one or
more
recesses that mate with one or more protrusions of a second cover sheet and/or
vice
versa.
[0072] The base sheet and the cover sheet are attached so that a sealed space
is
formed that includes a thermal energy storage material. The attachment of the
base
sheet and the cover sheet may include a primary seal around one or more (e.g,,
all) of
the sealed paces so that a sealed space is isolated from any other sealed
space and/or
from regions outside of the article. The attachment of the base sheet and the
cover
sheet may include one or more secondary seals, such as a seal that isolates a
sealed
space from a region outside of the article and/or from other sealed spaces in
the event
that a primary seal fails.
[0073] Without limitation,. preferable thermal energy storage materials for
the heat
storage device include materials that are capable of exhibiting a relatively
high density of
thermal energy as sensible heat, latent heat, or preferably both. The thermal
energy
storage material is preferably compatible with the operating temperature range
of the.
heat storage device.. For example the thermal energy storage material is
preferably a
solid at the lower operating temperature of the heat storage device, is at
least partially a
liquid (e.g., entirely a liquid) at the maximum operating temperature of the
heat storage
device, does not significantly degrade or decompose at the maximum operating
temperature of the device, or any combination thereof. The thermal energy
storage
material preferably does not significantly degrade or decompose when heated to
the
maximum operating temperature of the device for about 1,000 hours or more, or
even for
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about 10,000 hours or more..
[0074j The thermal energy storage material may be a phase change material
having
a solid to liquid transition temperature. The solid to liquid transition
temperature of the
thermal energy storage material may be a iiquidus temperature, a melting
temperature,
or a eutectic .temperature. The solid to liquid transition temperature should
be sufficiently
high so that when the thermal energy storage material is at least partially or
even
substantially entirely in a liquid state enough energy is stored to heat the
one or more
objects to be heated to a desired temperature. The solid to liquid transition
temperature
should be sufficiently low so that the heat transfer fluid, the one or more
objects to be
heated, or both, are not heated to a temperature at which it may degrade. As
such the
desired temperature of the solid to liquid transition temperature may depend
on the
object to be heated and the method of transferring the heat. For example, in
an
application that transfers the stored heat to an engine (e.g., an internal
combustion
engine) using a glycol/water heat transfer fluid, the maximum solid to liquid
transition
temperature may be the temperature at which the heat transfer fluid degrades.
As
another example, the stored heat may be transferred to an electrochemical cell
of a
battery using a heat transfer fluid where the heat transfer fluid has a high
degradation
temperature, and the maximum solid to liquid temperature may be determined by
the
temperature at which the electrochemicai cell degrades or othetwise fail. The
solid to
liquid transition temperature may be greater than about 30 "C, preferably
greater than
about 35 CC, more preferably greater than about 40 CC, even more preferably
greater
than about 45 C, and most preferably greater than about 50 C. The thermal
energy
storage material may have a solid to liquid transition temperature less than
about 400 CC,
preferably less than about 350 C, more preferably less than about 290 "C,
even more
preferably less than about 250 C, and most preferably less than about 200 C.
It will be
appreciated that depending on the application, the solid to liquid transition
temperature
may be from about 30 "C to about 100 C, from about 50 CC to about 150 "C.
from about
100 C to about 200 C., from about 150 CC to about 250 C, from about 175 "C
to about
400 cC, from about 200 CC to about 375 cC, from about 225 C to about 400 C,
or from
about 200 C to about 300 C.
100751 For some applications, such as transportation related applications, it
may
desirable for the thermal energy material to efficiently store energy in a
small space. As.
such, the thermal energy storage material may have a high heat of fusion
density
(expressed in units of megajoules per liter), defined by the product of the
heat of fusion
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(expressed in megajoules per kilogram) and the density (measured at about 25
CC and
expressed in units of kilograms per liter). The thermal energy storage
material may have
a heat of fusion density greater than about 0.1 MJ/liter, preferably greater
than about 02
MJ/liter, more preferably greater than about 0.4 MJ/liter, and most preferably
greater
than about 0.6 MJ/liter. Typically, the thermal energy storage material has a
heat of
fusion density less than about 5 Ma/liter, However, thermal energy storage
materials
having a higher heat of fusion density may also be employed..
[0076] For some applications, such as transportation related applications, it
may be
desirable for the thermal energy storage material to be light weight. For
example, the
thermal energy storage material may have a density (measured at about 25 '''C)
less
than about 5 gicm3, preferably less than about 4 gicm3, more preferably less
than about
3.5 g/cm3, and most preferably less than about 3 gicm3. The lower limit on
density is
practicality. The thermal energy storage material may have a density (measured
at about
25 (C) greater than aboutØ6 g/ce, preferably greater than about 1.2 glee,
and more
preferably greater than about 1.7 gice,
[0077] The sealed spaces may contain any art known thermal energy storage
material. Examples of thermal energy storage materials that may be employed in
the
thermal energy storage material compartments include the materials described
in Atul
Sharma, V.V. Tyagi, C.R. Chen, D. Buddhl, "Review on thermal energy storage
with
phase change materials and applications", Renewable and Sustainable Energy
Reviews
13 (2009) 318-345, and in Belen Zalba, Jose Ma Mari, Luisa F. Cabeza, Harald
Mehlingõ "Review on thermal energy storage with phase change: materials, heat
transfer
analysis and applications", Applied Thermal Engineering 23 (2003) 251-283,
both
incorporated herein by reference in their entirety. Other examples of
preferred thermal
energy storage materials that may be employed in the heat transfer device
include the
thermal energy storage materials described in U.S. Patent Application
Publication Nos.
2009/0211726 (entitled "Thermal Energy Storage Materials" and published on
August 27,
2009) and 2009/0250189 (entitled "Heat Storage Devices' and published on
October 8,
2009), and paragraphs 54-63 of U.S. Provisional Patent Application No.
61/299,565
(entitled "Thermal Energy Storage' and .filed on January 29, 2010).
[0078] The thermal energy storage material may include an organic material,
an
inorganic material or a mixture of an organic and an inorganic material that
exhibits the
solid to liquid transition temperature, the heat of fusion density, or both,
described
here.inbefore. Organic compounds that may be employed include paraffins and
non
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paraffinic organic materials, such as a fatty acid. Inorganic materials that
may be
employed include salt hydrates and metallics. The thermal energy storage
material may
be a compound or a mixture (e.g., a eutectic mixture) having a solid to liquid
transition at
generally a single temperature. The thermal energy storage material may be a
compound or a mixture having a solid to liquid transition over a range of
temperatures
(e.g.., a range of greater than about 3 '2Cõ or greater than about 5 DC).
[0079] Without limitation, the thermal energy storage material may include
one or
more inorganic salts selected from the group consisting of nitrates, nitrites,
bromides,
chlorides, other halides, sulfates, sulfides, phosphates, phosphites,
hydroxides,
carboxides, bromates, mixtures thereof, and combinations thereof.
[0080] The thermal energy storage material may include (or may even consist
essentially of or consist of) at least one first metal containing material,
and more
preferably a combination of the at least one first metal containing material
and at least
one second metal containing material. The first metal containing materiai, the
second
metal containing material, or both, may be a substantially pure metal, an
alloy such as
one including a substantially pure metal and one or more additional alloying
ingredients
(e.g., one or more other metals), an intermetallio, a metal compound (e.g., a
salt, an
oxide or otherwise), or any combination thereof. One preferred approach is to
employ
one or more metal containing materials as part of a metal compound; a more
preferred
approach is to employ a mixture of at least two metal compounds. By way of
example, a
preferred metal compound may be selected from oxides, hydroxides, compounds
including nitrogen and oxygen (e.g., nitrates, nitrites or both), halides, or
any
combination thereof. It is possible that ternary, quaternary or other multiple
component
material systems may be employed also. The thermal energy storage materials
herein
may be mixtures of two or more materials that exhibit a eutectic.
[0081] The volume of the thermal energy storage material in the one or more
sealed
spaces of the article is sufficiently high so that the article can store a
large amount of
thermal energy. The ratio of the volume of the thermal energy storage material
contained
in the article to the total volume of the one or more sealed spaces, the ratio
of the
volume of the thermal energy storage material to the total volume of the
article, or both
(the volumes measured at a temperature of about 25 '"C, or at a temperature at
which
the thermal energy storage material is a liquid) preferably is greater than
about 0.5, more
preferably greater than about 0.7, and most preferably greater than about 0.9.
The ratio
of the volume of the thermal energy storage material contained in the article
to the total
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volume of the one or more sealed spaces, the ratio of the volume of the
thermal energy
storage material to the total =volume of the article, or both (the volumes
measured at a
temperature of about 25 C, or at a temperature at which the thermal energy
storage
material is a liquid) is typically less than about 1.0, and more typically
less than about
0.995,
[0082] The sealed space may include a volume that contains a gas, such as
air, N2,
or an inert gas such as He, Ar, and the like, so that the thermal energy
storage material
can expand when heated For example, the sealed space may have a region that is
free
of thermal energy storage material at a temperature of about 25 C, so that
upon heating
the thermal energy storage material above its liquidus temperature, the
thermal energy
storage material can expand without forming a hole in the cover sheet or base
sheet or
causing one or more sheets to delarninate.). The volume of a sealed space that
is free of
thermal energy storage material (e.g., the volume of the sealed space that
contains a
gas) at 25 "Cõ may be at least about 0.5%, preferably at least about 1%, and
most.
preferably at least about 1,5%, based on the total interior volume of the
sealed space, =
[0083] The thermal energy storage material, the sealed space, or both may
be
substantially free of, or entirely free of materials that undergo vaporization
or sublimation
when the article is used to store heat so that the pressure in the sealed
space is not
greatly increased. For example, the thermal energy storage material, the
sealed space,.
or both may be substantially free of materials that undergo vaporization or
sublimation at
a temperature from about 25 "C to about 100 *C, preferably from about 25 "C to
about
150 "C, more preferably about 25 "C to about 200 C, and most preferably from
about
25 "C to about 300 C. As such, the thermal energy storage material, the
sealed space,
or both may be substantially free of water. in applications that employ
temperatures of
about 100 C or more for storing thermal energy, it may be desirable for the
sealed
space to be substantially free of, or even entirely free of water. If present
the
concentration of water in the sealed space may be about 6 wt.% or less, more
preferably
about 1 wt.% or less, even more preferably about 0.2 wt.% or less, and most
preferably
about 0.1 wt.% or less.
[0084] FIG, 1 is a drawing that illustrates a portion of an article 2
having a capsular
structure, .A portion of the outer surface (bottom surface) of the base sheet
12 of the
article is shown in FIG, 1. The article includes a plurality of capsules 10.
As shown in
Fla 1, the capsules 10 may be positioned in a periodic arrangement 11 The base
sheet
may have one or more trough 8, such as a trough that may be employed to hold
the
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thermal energy storage material before and/or during the attachment of a base
sheet to
a cover sheet, The base sheet also includes a lip region 6. The lip region may
be
employed to attach the base sheet to a cover sheet. As such, the lip region
may be a
region that does is not covered with thermal energy storage material when the
base
sheet and the cover sheet are attached.
[0085] FIG. 2A is a cross-sectional view of an illustrative capsular
structure 2 that
includes one or more sealed spaces 18. FIG, 2B is a cross-sectional view of a
single
capsule , such as a capsular structure having one capsule 10 or a portion of a
capsular
structure 2 having a plurality of capsules 10. As illustrated in FIGs. 2A and
28, the
capsule 10 may be a sealed space 18 that contains a thermal energy storage
material
16, and optionally a gap 20 or other space that is generally free of thermal
energy
storage material. The article may include one or more primary seals 22, such
as a seal
that isolates the sealed space 18 from a region outside of the article 24,
from other
sealed spaces, or both. The article may include one or more secondary seals 22
that
may isolate the sealed space in the event a primary seal 22 fails. As
illustrated in FIGs.
2A and 28, the sealed space 18 may be formed by attaching a base sheet 12
about a lip
region 6 to a cover sheet 14 (e.g.., a cover sheet that is generally flat).
The base sheet
may also includes a trough region B. The thickness 13 of the base sheet may
be.
reduced (e.g., relative to the thickness 15 of the cover sheet) due to the
stiffening of the
base sheet by the troughs 8'. The seals (e.gõ the primary seal 11, the
secondary seal
221, or both) may be formed by welding the base sheet and cover sheet, such as
by
laser welding,
[00861 The one or more sealed spaces may be prepared by joining a metal cover
sheet and a metal base sheet with one, two, or more welds, wherein the welds
completely encloses the one or more sealed spaces. An individual sealed space
may be
prepared using a single continuous weld, or a plurality of welds. The
plurality of welds
may form a continuous perimeter. The plurality of welds may be discontinuous.
For
example, an individual sealed space may have one weld along an outer perimeter
and a
second weld along an inner perimeter.
(00871 FIG. 3 is a schematic drawing of a portion of a formed sheet 40 (e.g.,
a base
sheet 12) that may be employed in an article 2 having a plurality of sealed
spaces. The
formed sheet may have an opening 46 (e.g., a generally circular opening) near
the
center of the sheet. FIG. 3 shows only about 1/4 of the formed sheet 40 and
thus only
1/4 of the opening 46 is shown. FIG. 3 shows the bottom surface 41 of the
formed sheet
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40. The formed sheet has a plurality of trough regions 8 and a plurality of
lip regions 6.
The trough regions preferably provides troughs 55 that are capable of
containing thermal
energy storage material. The trough regions 8 may be arranged in a plurality
of rings of
troughs 50, 50', 50". As illustrated, the formed sheet may have an innermost
ring of
troughs 50 and an outermost ring of troughs 50'. The formed sheet may also
have one
or more additional rings of troughs 50", between the innermost and the
outermost rings
of troughs 50, 50, As illustrated in FIG. 3, some or all of the troughs in a
ring, or even
some or allot the troughs in different rings may have about the same shape,
about the
same volume, be substantially congruent, or any combination thereof. It will
be
appreciated that the number of troughs in the innermost ring of troughs may be
more
than, less than or the same as the number of troughs in the outermost ring of
troughs.
Preferablyõ the number of troughs in the innermost ring of the formed sheet 40
is less
than the number of troughs in the outermost ring, as illustrated in FIG. 6,
Some, or
preferably all of the troughs regions 8 have a lip region 6 around the trough
region. As
such, a trough region 8 may be separated by the other trough regions by a lip
region 6.
The formed sheet 40 may have an outer periphery 45, an inner periphery 47, or
both. As
illustrated in FIG, 3, the formed sheet may have one or more indents 51 near
the outer
periphery 45. The one or more indents may be used for flow channels or flow
paths
along the outer periphery 45. Preferably the outer perimeter of the bottom
surface of the
formed sheet 40 has a generally circular shape (excluding the optional one or
more
indents 51). As illustrated in FIG. 3, the outer periphery 45, the inner
periphery 47, and
preferably both, may be lip regions S.
[0088] FIG. 4A illustrates a portion of a cover sheet 14 having chevrons 30.
The
dimensions (e.g., x, y, z, or any combination thereof) in FIG. 4A may be in
units of mm.
The chevrons 30 may have a periodicity (in one or more directions) of about 3
mm or
more, a periodicity of about 50 mm, or less, or both. The periodicity of the
chevrons may
be sufficiently small so that the portion of a cover sheet over an individual
sealed space
has a plurality of chevrons 30. For exampleõ the number of chevrons 30 over
the region
of a cover sheet 14 over a single sealed space may be about 2 or more, about 5
or more,
about 10 or more about 20 or more, or about 30 or more. The chevrons 30 may
have a
periodicity of about 5 mm, The chevrons 30 may have a depth of about 0,2 mm or
more,..
a depth of about 4 mm or less, or both. For example, the chevrons 30 may have
a depth
of about 1 mm. It will be appreciated that chevrons having a higher or lower
periodicity
and/or a higher or lower depth may also be employed. The dimensions (e.g., x,
y, z, or
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any combination thereof) in FIG. 4A may be in any arbitrary units that are the
same or
different, or may be in units of mm. The chevrons may be in a section of the
cover sheet
that covers a sealed space, in a region of a cover sheet that is away from
sealed spaces,
or both. it will be appreciated that chevrons may be employed in a base sheet,
a cover
sheet or both.
[00891 FIG. 4B is schematic view of an illustrative capsule 10 having a cover
sheet
14 that includes dimples 32. FIG. 4C is a top view of the portion of a cover
sheet 14 over
a single capsule, such as the capsule illustrated in FIG. 4B. As illustrated
in FIGs. 4Ba
and 4C, the cover sheet 14 may include one or more dimples 32, and
particularly one or
more recessed dimples 33. The dimples 32 may be in any arrangement. For
example,
the dimples may have a brick wall pattern, so that adjacent rows of dimples
are shifted.
The dimples preferably have a periodicity of about 1 mm or more, more
preferably about
2 mm or more, and most preferably about 3 mm or more. The periodicity of the
dimples
preferably is about 30 mm or less, more preferably about 16 mm or less, and
most
preferably about 10 mm or less. The periodicity of the dimples may be
sufficiently small
so that the portion of a cover sheet over an individual sealed space has a
plurality of
dimples 32. For example, the number of dimples 32 over the region of a cover
sheet 14
over a single sealed space may be about 2 or more, about 5 or more, about 10
or more
about 20 or more, or about 30 or more. The dimples preferably have a depth of
about
0.1 mm or more, more preferably about 0.2 mm or more, even more preferably
about 0.3
mm or more, even more preferably about 0.6 mm or more, and most preferably
about
0.5 mm or more. The dimples preferably have a depth of about 3 mm or less,
more
preferably about 2 mm or less, and most preferably about 1 mm or less. It will
be
appreciated that dimples having a higher or lower periodicity and/or a higher
or lower
depth may also be employed. The dimples 32 may be in a section of the cover
sheet that
covers a sealed space, in a region of a cover sheet that is away from sealed
spaces, or
both. it will be appreciated that dimples may be employed in a base sheet, a
cover sheet
or both..
10090] FIG. 40 shows an illustrative to view of a portion of a sheet (e.g., a
cover
sheet 14) that includes stiffening features. The stiffening .features 34 may
be arranged in
a generally random pattern. As illustrated in FIG. 40, the stiffening features
34 may have
different shapes, different sizes, or both. The periodicity of the stiffening
features may be
sufficiently small so that the portion of a cover sheet 14 over an individual
sealed space
has a plurality of stiffening features 34. For example, the number of
stiffening features 34
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over the region of a cover sheet 14 over a single sealed space may be about 2
or more.,
about 5 or more, about 10 or more about 20 or more, or about 30 or more,
[00911 FIG. 5A, 58, and 5C illustrate the pressure 36, 36, 36" in a sealed
space 18'.
18"' at different temperatures and sealed at different sealing temperatures.
As illustrated
in FIG. 5A, at the sealing temperature, the pressure inside 36 and the
pressure outside
38 of the sealed space 18', 18" may be about the same. As illustrated in FIG
58, the.
pressure inside 36' the sealed space 18' may be higher than the external
pressure 38
when the sealed space 18' is sealed at a low temperature and the wide 2 is
heated to a.
higher temperature. As illustrated in FIG, 58, there may be a net outward
force 35 on the
cover sheet 14 due to the pressure difference when the temperature is greater
than the
sealing temperature. FIG. 50 illustrates that the pressure inside 36" the
sealed space
18" may be less than the external pressure 38 when sealing at a high
temperature and
then reducing the temperature. As illustrated in FIG. 5B, there may be a net
inward
force 35 on the cover sheet 14 due to the pressure difference when the
temperature is
below the sealing temperature.
[0092] FIGs. 6A, 68, and 60 shows an illustrative example of a sheet (e.g., a
cover
sheet) that includes a rib structure 39 that includes protrusions and
recesses. FIG. 6A is
a topographical drawing of the region of the sheet for a single capsule. FIG.
68 is a
photograph of a portion of a sheet including a plurality of the features of
FIG 6A, FIG 6C.
illustrates the effect of the structural features on the forces on the sheet
when a sealed
space including the sheet is heated. As illustrated in FIG. 6, the ribs may be
confined to
the region of the top sheet that is around the sealed space. For example, the
cover
sheet may have a lip region that is free of the ribs or other stiffening
features in the
region where the cover sheet is attached to a base sheet.
[0093j FIGs. 7A and 78 illustrate a sheet 60 (e.g., a base sheet 12) that
includes
volume expansion features 62 so that the sealed space is capable of increasing
in
volume as the thermal energy storage material in the sealed space expands, and
decreasing in volume as the thermal energy storage material contracts. FIG 8A
is a
schematic of a section of a base sheet. 12 having a volume expansion feature
62. As
illustrated in FIG. 7A, the volume expansion feature 62 may include one or
more
wrinkles, such as one more convolutions 64. The volume expansion feature may
include
a bellow. FIG. 7A illustrates a volume expansion feature 62 in a base sheet
12. However,
it will be appreciated that the base sheet 12, the cover sheet 14 or both may
include one
or more volume expansion features fa The volume expansion feature may function
by
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allowing a sheet to reversibly contract into the sealed space. FIG. 7E3 is an
illustrative
cross-section of a portion of a capsule 10 iiicluding the sheet 60 having the
volume
expansion feature 62, a cover sheet 14, and the themtal energy storage
material 16.
The thermal energy storage material 16 may be in a sealed space 18, which is
sealed by
a primary seal 22, and preferably a secondary seal 22.
[0094] FIG. 8 shows an illustrative relationship between the expected peak
Von
Mises stress in a cover sheet when the capsule 10 is heated to about 250 CC as
a.
function of the thickness of the cover sheet 15. FIG. 8 also shows the yield
stress of the
metal employed in forming the cover sheet. At low thickness, the peak von
Mises stress
is higher than the yield stress of the metal and the cover sheet may yield or
crack. At
higher thicknesses, the peak von Mises stress is lower than the yield stress
of the metal
and the cover sheet does not yield or fail. FIG, 9 shows an illustrative
relationship
between the expected peak Von Mises stress in a cover sheet when the capsule
is
heated to about 250 CC as a function of the thickness of the cover sheet 15
for cover
sheets that are generally flat and for cover sheets that have the rib
structure shown in
FIG, S. The thickness of the cover sheet required to prevent yielding of the
cover sheet
may be reduced when a ribs structure is employed. As such, the rib structure
of FIG. 6,
may allow for articles and heat storage devices that are light weight, contain
a greater
amount of thermal energy storage material, or both.
[0095] FIG. 10 shows an illustrative relationship between the expected peak
Von
Mises stress in a cover sheet when the capsule is heated to about 250 CC as a
function
of the thickness of the cover sheet for cover sheets that are generally flat
and for cover
sheets that have the rib structure shown in FIG. 6, the chevron structure of
FIG, 4A, and
the dimple pattern of FIG, 48. The thickness of the cover sheet required to
prevent
yielding of the cover sheet may be reduced when the different stiffening
structure are
employed. As such, the structure of FIGs. 4A, 48, and 6 may allow for articles
and heat
storage devices that are light weight, contain a greater amount of thermal
energy
storage material, or both,.
[0096] FIG. 11 illustrates a portion of tooling 61 that may be employed in
preparing a
sheet (e.g., a cover sheet 14) having one or more stiffening features, such as
one or
more ribs. Such tooling may be employed in an embossing process. It will be
appreciated that an embossing process may be a continuous process or a batch
process,
[0097] The articles containing the thermal energy storage material preferably
are
capable of being stacked either with other identical articles or with a second
article
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WO 2012/021673 CA 02806469 2013-01-23 PCT/US2011/047355
having a generally mating surface (such as a generally mating base sheet). The
articles
may be stacked in axial layers with a space between adjacent axial layers so
that a heat
transfer .fluid can flow between the axial layers. An axial layer will
generally contain one,
two or more article. An axial layer (e.g., each axial layer) preferably
contains one or two
articles. For example, an axial layer may have two articles that are in
contact on a
surface, such as a base surface or a cover surface, so that a fluid cannot
generally flow
between the two articles). As such, some of the articles (e.g., each article
except the
articles at an end of a stack) may have a first surface (e.g., a base surface)
that is
generally in complete contact with a surface of a first adjacent article so
that a fluid
cannot flow along the first surface, and a second surface that is separated
from a
second adjacent article (e.g., having an opposing surface that is generally a
mating
surface with the second surface) so that a fluid can flow along some, most, or
even all of
the second surface. The separation between two adjacent axial layers may be
due to
any art known spacing means. By way of example, preferable spacing means
include
one or more protrusions on a surface of at least one of the articles, a spacer
material
between, the two layers, a capillary structure between two layers, or any
combination
thereof, Preferably the second surface of the article has a generally arcuate
shape and
the article partially nests with the second adjacent article. The spacing
between two
articles that partially nest preferably is generally constant (except for the
protrusions or
other spacers that cause the adjacent articles to be separated). It will be
appreciated
that the stacking of the articles may include a step of rotating an axial
layer (e.g., rotating
an article), or otherwise arranging it so that the axial layer at least
partially nests with an
adjacent axial layer. The flow of a fluid between two opposing surfaces of two
adjacent
axial layers will generally be in a radial direction and may be described as a
generally
radial flowõ Each pair of axial layers that are spaced apart will have a
radial flow path.
The stack of articles will typically have a plurality of radial flow paths
(e.gõ, 2, 3, or more).
Two or more (e.g., each radial flow path may have the same flow length, the
same
thickness, the same cross-sectional shape, or any combination thereof. For
example,
two or more (e.g.., all) of the radial flow paths may be congruent. It will be
appreciated
that if the opening fluid passage) is at the center of the article, the radial
flow path
may be generally symmetric, irrespective of the flow direction.
[0098) When stacked (e.g., in a stack containing 3, 4 or more articles), the
articles
preferably each have at least one opening that corresponds with an opening
from each
of the other articles (except possibly an article at one end of the stack), so
that a portion
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WO 2012/021673 CA 02806469 2013-01-23PCT/US2011/047355
of a fluid can flow from a first article in the stack to a last article in the
stack by flowing
through each of the corresponding openings of the articles interposed between
the first
and last article without flowing between adjacent articles (Le., without a
generally radial
flow). The flow through the openings will generally be in an axial direction
and may be
described as a generally axial flow,
[0099] As described above, the stack of articles may define a central axial
flow path
(e.g., through the central axis formed by the openings of the articles) and
one or more
radial flow paths that are generally perpendicular to the central axial flow
path.
[00100] The stack of articles will generally be tightly packed (e.g.,. except
for the radial
flow paths) so that the stack of articles is compact and contains a large
amount of
thermal energy storage material. As such, the radial flow path has a height
(in the
direction between the adjacent articles), e.g., an average height, that is
generally small.
The height of the radial flow path preferably is less than about 15 mm, more
preferably
less than about 5 mm, even more preferably less than about 2 mm, even more
preferably less than about 1 mm, and most preferably less than about 0.5 mm.
The
height of the radial flow path typically is large enough so that the fluid can
flow through
the path. Typically the height (e.g., the average height) of the radial flow
path is greater
than about 0.001 mm (e.g., greater than about 0.01 mm).
[00101] FIG. 12 illustrates an aspect of the invention that includes a
plurality of
articles 2õ each having one or more sealed spaces 18 for containing a thermal
energy
storage material 16 arranged to form a stack of articles 70. The articles 2
may include a
formed sheet, such as a base sheet 12 having a generally arcuate surface 41.
The
surface 41 of one article may generally mate with the surface of a second
article. The
articles may be arranged so that adjacent articles partially nest together.
The articles
illustrated in FIGõ 12 have an inner ring of 9 generally identical capsules
and an outer
ring of 17 generally identical capsules. The articles illustrated in FIG. 12
have a
rotational symmetry of order 1 and thus have only 1 position in which two
facing articles
will partially nest. To facilitate in the stacking of articles, each article
may have one or
more locating features. It will be appreciated that articles with a higher
order of symmetry
may be employedõ For example, the article may have a single ring of capsules
(or even
a single capsule), or the article may have a first ring of capsules having an
integer
multiple of capsules (e.g., 1, 2, 3, or more) for each capsule of a second
ring of capsules.
As illustrated in FIG. 12, the articles 2 may have a generally circular cross-
section (e.g.,
in a direction perpendicular to the stacking direction). The outer periphery
of each article
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may have a plurality of indents 51 that are large enough to allow for a fluid
flow. The
articles 2 may have sealed spaces 74 arranged in one or more concentric rings
of
sealed spaces. Each article 2 may have a fluid passage 46. The fluid passage
46 may
be ge=nerally near the center of the articles 2 so that when the articles are
stacked (e.g.,
stacked in an axial direction), an axial flow path 84 is formed. The axial
flow path 84.
preferably includes a fluid passage 46 of each article 2,
[00102) FIG. 13 illustrates an article 2 that includes an odd number of
capsules 10.
The article may have an odd rotational symmetry, so that it cannot be easily
deformed
about a diameter. The article 2 may have a generally circular cross-section
with one or
more openings 46 in the center of the article. The opening 46 may be generally
circular.
As illustrated in FIG. 13, one or more, or even each of the capsules or sealed
spaces
may have a primary seal 22 that isolates the sealed space from the outside of
the article.
The article may also have one or more secondary seals 221, The secondary seal
may
include a seal near an inner periphery 47 (Le., an opening periphery) of the
article, a
seal near an outer periphery 45 of the article, or both. The secondary seal
22' may be
sufficient to prevent leaking of a thermal energy storage 16 material from a
sealed space
18 if a primary seal fails 22.
[001031 The articles (e.g., a stack of articles) described herein may be
employed in a
heat storage device. The heat storage device may include a container or other
housing =
having one or more orifices for flowing a heat transfer fluid into the
container and one or
more orifices for flowing a heat transfer fluid out of the container. The heat
storage
device has one or more heat transfer fluid compartments. Preferably, the heat
storage
device includes a single heat transfer fluid compartment. A heat transfer
fluid
compartment may include or consist substantially of a contiguous space in the
container
between the inlet and the outlet, where the heat transfer fluid can flow. The
container
preferably is at least partially insulated so that heat losses from the
container to the
ambient may be reduced or minimized.
[00104] The heat storage device may be designed so that it contains a large
concentration of thermal energy storage material, so that it can transfer
thermal energy
between a heat transfer fluid and the thermal energy storage material rapidly
and/or
uniformly, so that it is generally compact, so that it can store heat for a
long time, or any
combination thereof.
[001051 The inside of the container of the heat storage device may have any
shape
capable of holding a stack of articles. Preferably, the shape of the inside of
the container
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WO 2012/021673 CA 02806469 2013-01-23
PCT/US2011/047355
is such that the stack of articles occupies a large portion of the interior
volume of the
container. The ratio of the total volume of thermal energy storage material
(e.g..,
measured at about 25 ')C) contained in the sealed spaces of the articles in
the container
to the total interior volume of the container (e.g., at a temperature of about
25 C) may
be greater than about 0,3, preferably greater than about 0,5, more preferably
greater
than about 0.6, even more preferably greater than about 0,7, and most
preferably
greater than about 0.8. The upper limit on the volume of thermal energy
storage material
in the container is the need for space for a heat transfer fluid that contacts
the articles for
transferring thermal energy. The ratio of the total volume of thermal energy
storage
material (e.g., measured at about 25 'DC) contained in the sealed spaces of
the articles in
the container to the total interior volume of the container (e.g.,. at a
temperature of about
25 cC) may be less than about 0.99, preferably less than about 0,95,.
[00106] The heat storage device has a heat transfer fluid compartment for
flowing a
capable of containing a heat transfer fluid as it circulates through the
device. The heat
transfer fluid compartment preferably is connected to one or more orifices
(e.g. one or
more inlets) for flowing a heat transfer into the heat transfer fluid
compartment. The heat
transfer fluid compartment preferably is connected to one or more orifices one
or
more outlets) for flowing a heat transfer out of the heat transfer fluid
compartment. The
heat transfer fluid compartment may be a space at least partially defined by
one or more
heat transfer fluid compartment wails, a space at least partially defined by
one or more
articles, a space at least partially defined by a housing or container of the
heat storage
device, or any combination thereof.
[00107] The heat transfer fluid compartment defines the flow path of a heat
transfer
fluid through the heat storage device The heat transfer fluid compartment
includes a
generally axial flow path through the openings of the stack of articles. The
heat transfer
fluid compartment includes a generally radial flow path between two adjacent
articles, it
will be appreciated that the radial flow may be an inward flow from an outer
periphery to
the opening of an article, or an outward flow from an opening to the outer
periphery of an
article. The heat transfer fluid compartment includes a flow path having a
generally axial
component (and optionally a tangential component) between an outer periphery
of the
article and a wall of the container. Preferably the combined radial flow paths
have a
relatively high hydraulic resistance. For example, the combined radial flow
paths has a
hydraulic resistance that is greater than (more preferably at least two times
greater than)
the hydraulic resistance of the central axial flow path, the outer axial flow
path, or both,.
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[00108.1 The heat transfer fluid compartment preferably has sufficient thermal
communication with the sealed spaces containing the thermal energy storage
material
so that it can remove heat or provide heat to the thermal energy storage
material. The
heat transfer fluid compartment preferably is in direct thermal communication
with one or
more (or more preferably all) of the sealed spaces. A direct thermal
communication can
be any path of shortest distance between a sealed space and a portion of the
heat
transfer fluid compartment that is free of a material having low thermal
conductivity. Low
thermal conductivity materials include materials having a thermal conductivity
less than
about 100 Wl(m.k), preferably less than about 10 Wi(m.k), and more preferably
less
than about 3 W/(m.K). For example, the heat transfer fluid or the heat
transfer fluid
compartment may contact a wall of one or more (or preferably all) of the
sealed. or be
separated from the sealed spaces substantially or entirely by materials having
high
thermal conductivity (e.g., greater than about 5 Wi(m,K), greater than about
12 Wl(m,K),
or greater than about 110 Wt(m.K),
[00109] The heat transfer fluid compartment preferably is in direct thermal
communication with one or more (or more preferably all) of the sealed spaces
in the heat
storage device. A direct thermal communication can be any path of shortest
distance
between a thermal energy storage compartment and a portion of the heat
transfer fluid
compartment that is free of a material having low thermal conductivity. For
example, the
heat transfer fluid or the heat transfer fluid compartment may contact a wall
of one or
more (or preferably air) of the sealed paces (such as a base sheet or a cover
sheet), or
be separated from the sealed spaces substantially or entirely by materials
having high
thermal conductivity (e.g., greater than about 5 Wi(m. lc), greater than about
12 Wi(rm K),
or greater than about 110 W/(m=K). It will be appreciated that a very thin
layer (e.g., less
than about 0.1 mm, preferably less than about 0.01 mm, and more preferably
less than
about 0.001 mm) of a material having a low thermal conductivity may be between
the
heat transfer fluid compartment and a thermal energy storage material
compartment
without appreciably affecting the heat transfer.
[00110] The size and shape of the sealed spaces and/or articles may be chosen
to
maximize the transfer of heat to and from the phase change material contained
in the
capsules. The average thickness of the article may be relatively short so that
the heat
can quickly escape from the center of the sealed spaceõ The average thickness
of the
article, sealed space, or both may be less than about 100 mm, preferably less
than
about 30 mm, more preferably less than about 10 mm, even more preferably less
than
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about 5 mm, and most preferably less than about 3 mm. The average thickness of
the
article, the sealed space, or both, may be greater than about 0.1 mm,
preferably greater
than about 0.5 mm, more preferably greater than about 0.8 mm, and most
preferably
greater than 1.0 mm.
[00111] The articles preferably have a relatively high surface area to volume
ratio so
that the area of contact with the heat transfer fluid is relatively high. For
example, the
article may have a surface that maximizes the contact with a heat transfer
fluid
compartment, the article may have a geometry that maximizes the transfer of
heat
between the capsule and the heat transfer fluid compartment, or both. The
ratio of the
total surface area of the interface between the heat transfer fluid
compartment and the
articles in the heat storage device to the total volume of the thermal energy
storage
material in the heat storage device may be greater than about 0.02 mill'',
preferably
greater than about 005 mm.1, more preferably greater than about 0.1 mm4, even
more
preferably greater than about 0.2 mm-', and most preferably greater than about
0,3 mm-1.
[00112] The heat storage device has a container for containing the stack of
articles.
The stack of articles may be contained in one or more cavities of the
container. Without
limitation, examples of containers that may be employed include those
described in U.S.
Patent Application Publication No, 2009-0211726 (published on August 27,
2009), POT
Application No. PCT/U809/67823 (filed on December 14, 2009), and U.S.
Provisional
Application No, 611299,565 (filed on January 29, 2010). Preferable containers
may have
one or more orifices (e.g., one or more inlets) for flowing a heat transfer
fluid into the.
cavity of the container and one or more orifices (e.g.,. one or more outlets)
for flowing a
heat transfer fluid out of the cavity of the container. The inlet and the
outlet may be on
the same side or on different sides (e.g., opposing sides) of the heat storage
device.
Other than the orifices, the container preferably is sealed or constructed so
that a fluid
flowing through the container does not leak out of the container, so that a
fluid flowing
through the container may have a pressure greater than ambient pressure, or
both,.
[00113] The heat storage device may be used in applications that require
storing heat
for long periods of time, storing heat in a generally cold environment (e,43õ
an
environment having a temperature less than about 0 C, or even less than about
-30 'IC),
or both. Preferably the heat stored in the heat storage device is slowly lost
to the
environment. Therefore some form of insulation is preferably used in the
present
invention. The better the insulation of the system is, the longer is the
storage time.
[00114] Any known form of insulation which reduces the rate of heat loss by
the heat
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WO 2012/021673 CA 02806469 2013-01-23 PCT/US2011/047355
storage device may be utilized. For example, any insulation as disclosed in
U.S, Patent
No. 6,889,751, incorporated herein of its entirety by reference, may be
employed. The
heat storage device preferably is (thermally) insulated container, such that
it is insulated
on one or more surfaces. Preferably, some or all surfaces that are exposed to
ambient
or exterior will have an adjoining insulator. The insulating material may
function by
reducing the convection heat loss, reducing the radiant heat loss, reducing
the
conductive heat loss, or any combination. Preferably, the insulation may be
through the
use of an insulator material or structure that preferably has relatively low
thermal
conduction. The insulation may be obtained through the use of a gap between
opposing
spaced walls. The gap may be occupied by a gaseous medium, such as an air
space, or
possibly may even be an evacuated space (e.g., by use of a Dewar vessel), a
material
or structure having low thermal conductivity, a material or structure having
low heat
emissivity, a material or structure having low convection, or any combination
thereof.
Without limitation, the insulation may contain ceramic insulation (such as
quartz or glass
insulation), polymeric insulation, or any combination thereof. The insulation
may be in a
fibrous form, a foam form, a densified layer, a coating or any combination
thereof. The
insulation may be in the form of a woven material, a knit material, a nonwoven
material,
or a combination thereof. The heat transfer device may be insulated using a
Dewar
vessel, and more specifically a vessel that includes generally opposing walls
configured
for defining an internal storage cavity, and a wall cavity between the
opposing walls,
which wall cavity is evacuated below atmospheric pressure. The walls may
further utilize,
a reflective surface coating (e.g., a mirror surface) to minimize radiant heat
losses.
[001 151 Preferably, a vacuum insulation around the heat storage device and or
the
heat storage system is provided. More preferablyõ a vacuum insulation as
disclosed in
U.S. Patent No. 8,975l, incorporated by reference herein in its entirety, is
provided.
t00116] The heat storage device may optionally include one or more compaction
means to a stack of articles so that the spacing between layers is generally
maintained.
The compaction means may be any means capable of applying a compressive force
to
the stack of articles. The compressive force should be sufficiently high so
that two.
articles do not rotate relative to each other, do not move axially relative to
each other, or
both. The compressive force may be sufficiently low so that an article is not
permanently.
deformed, cracked, or both. Preferred means of compaction will allow for some
changes
in the thickness of the articles as the temperature of the thermal energy
storage material
changes, as the thermal energy storage material changes between a solid and a
liquid
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phase, or both. By way of example, the one or more means of compaction may
include
one or more springs above the stack of articles, one or more springs below the
stack of
articles, or both. Without limitation, a Means of compaction such as a spring,
may be
employed to reduce or minimize the change in the thickness of a radial flow
path
between two adjacent articles when the thermal energy storage material is
heated,
undergoes a phase transition (such as a solid to liquid transition) or both.
[00117] The heat storage device may have a plurality of flow paths for the
flow of a
heat transfer fluid through the device. Each flow path may include at least
one radial flow
between two adjacent articles. Preferably two or more (e.g.., each) of the
flow paths
through the heat storage device has a similar total length, a similar total
hydraulic
resistance, or both, Without limitation, the heat storage device may include
one or more
seals, one or more plates, one or more connectors, or one or more flow paths
for a heat
transfer fluid as described in U.S. Patent Application Publication No. 2009-
0211726
(published on August 27, 2009), PCT Application No. PCT/US09/67823 (filed on
December 14, 2009), and U.S. Provisional Application No. 61/299,565 (filed on
January
29, 2010).
[00118] The capsular structure and the articles containing the thermal energy
storage
material may be formed using any method that provides for the encapsulation of
the
thermal energy storage material. Without limitation, the process may employ
one or any
combination of the following: cutting or punching an opening (e.g., a hole)
through a
cover sheet, cutting or punching an opening (e.g., a hole) through a base
sheet (e.g., a
thin sheet such as a foil), forming (e.g., thermoforming, stamping, embossing
or
otherwise deforming) a base sheet to define a pattern in the sheet including
at least one
depression or trough region, forming a base sheet to define a pattern in the
sheet
including one or more lip regions and one or more trough regions, cutting or
punching an
outer periphery (e.g., a generally circular outer periphery) on a base sheet,
cutting or
punching an outer periphery (e.g., a generally circular outer periphery) on a
cover sheet,
filling a trough (e.g., a trough formed from the base sheet) with a thermal
energy storage
material, covering a trough (e.g., a filled trough) with a cover sheet,
sealingly attaching a
cover sheet (e.g., to a base sheet) so that one or more sealed spaces
containing thermal
energy storage material are formed, sealingly attaching a base sheet along an
outer
periphery, sealingly attaching a base sheet along an opening periphery,
sealingly
attaching a cover sheet (e.g., to a base sheet) along an opening periphery, or
sealingly
attaching a cover sheet (e.g., to a base sheet) along an outer periphery. The
process of
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forming the article preferably includes a step of stamping, embossing, or
thermoforming
a base sheet. The process of forming the article may employ one or more of the
process
steps for producing a capsule described in U.S. Patent Application No.
12/389,598
entitled "Heat Storage Devices" and filed on February 20, 2009. The method for
forming
the article may .optionally include one or any combination of the following:
sealingly
attaching a base sheet to one or more substructures such as an inner ring, an
outer ring,
or both; sealingly attaching a cover sheet to one or more substructures such
as an inner
ring, an outer ring, or both; or cutting, stamping or punching one or more
indents along
the outer periphery of a base sheet and/or a cover sheet. FIG. 15 is a
photograph of an
illustrative tooling that may be employed for embossing a sheet (e.g.., a base
sheet). FIGõ
15 illustrates a sheet 5 placed in the tooling 61 prior to forming the sheet 5
into a base
sheet 12.
[00119] The process for preparing a cover sheet, a base sheet; or both may
include
one or more steps of embossing or otherwise forming the sheet so that it
includes one or
more stiffening features such as one or more dimples, one or more ribs, one or
more
chevrons, or any combination thereof.
[00120] The process for preparing an article may include a step of filling a
base sheet.
with a thermal energy storage material. The base sheet may be filled when the
thermal
energy storage material is in a solid state or in a molten state. Preferably
the base sheet
is filled when the thermal energy storage material is in a molten state. As
such, the
process may include a step of heating and/or melting a thermal energy storage
material.
[00121] The process for preparing an article may include a step of joining
atop sheet
and a base sheet so that one or more sealed spaces is formed. The step of
joining may
include a step of forming a primary seal. Preferably the step of joining
includes both a
step of forming a primary seal and a step of forming a secondary seal. The
step of
joining preferably occurs while the thermal energy storage material is in a
molten state.
For example, the step of joining may occur when the thermal energy storage
material is
at a temperature of about 100 *C or more, about 150 "C or more, about 200 "C
or more,
about 250 "C or more, or about 300 *C. or more.
[00122] The process for preparing an article may include a step of partially
joining a
base sheet and a cover sheet to form a partially sealed space that can contain
a liquid
when the base sheet and the cover sheet are not in a generally horizontal
orientation. A
space between the base sheet and the cover sheet may be at least partially
filled by
inserting an end of a nozzle into the space to be filled and pumping thermal
energy
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storage material (preferably in a molten state) through the nozzle and into
the partially
sealed space. Thus, the space between a base sheet and a cover sheet may be at
least
partially 'filie.d while the sheets are in a troughs in the base sheet may be
filled while the
base sheet is generally vertical. It will be appreciated that such an approach
for filling a
space with thermal energy storage material may result in a higher volume of
thermal
energy storage material.. For example, the percent of the volume of a sealed
space that
is occupied by air or other gas may be about 8% or less, about 6% or less,
about 5% or
less, about 4% or less, about 3% or less, about 2% or less, or about 1% or
less. This
approach for tilling a space may also be used for filing a space between two
base sheets.
As such, the cover sheet may be a second base sheet. After filling a space
with thermal
energy storage material, the remainder of the primary seal may be formed so
that the
filled space is a sealed space. With respect to a secondary seal, if any, at
least a portion
of the secondary seal (e.g., in the region where a nozzle is inserted) is not
formed until
after the thermal energy storage material is inserted into the space. An
article having a
plurality of sealed spaces may be filled by a process including one or more of
the
following steps: partially sealing one or more spaces (e.g., by joining a base
sheet and a
cover sheet, or by joining two base sheets) by forming a portion of a primary
seal,.
inserting thermal energy storage material into the one or more spaces,
'forming the
remainder of the primary seal (e.g,õ so that the space is sealed), rotating
the article being
filled, inserting thermal energy storage material into one or more additional
spaces that
have a portion of a primary seal, and forming the remainder of the primary
seal of the
one or more additional spaces.
[00123] FIG. 16 illustrates an example of an article 2 having one or more
(e.g., four)
capsules 10 that have been filled with thermal energy storage material and one
or more
(e.gõ a fifth space) that is being filled. The space being filled may have a
partial primary
seal 74. The space being filled may optionally include a partial secondary
seal 75,The
space being filled preferably has a fill region 76 that does not have a
complete primary'
- seal 22 and does not have a complete secondary seal 22'. The sealed space
may be
filled using a nozzle 77 that is inserted or otherwise placed in the fill
region 76. It will be
appreciated that the nozzle may be placed in the fill region before, during,
or after
forming the partial primary seal 74. As illustrated in FIG. 16, a nozzle 77
may be may be
inserted into the top of the space being filled, so that the thermal energy
storage material
16 does not leak out of fill region 76. After inserting the thermal energy
material 16 into
the space being filled, the process may include one or more of the following
steps:
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WO 2012/021673 CA 02806469 2013-01-23PCT/US2011/047355
removing the nozzle (preferably before rotating the article), forming the
remainder of the
primary seal (preferably before rotating the article), or forming a secondary
seal or the
remainder of a secondary seal. As such, the article may be prepared using a
machine
that is capable of 1) forming a partial primary seal between two sheets (e.g.,
by laser
welding the two sheets), 2) injecting thermal energy storage material (e.g,õ
in a molten
state) into a space between the two sheets, 3) completing the primary seal. If
a plurality
of sealed spaces are desired, the process may include one or more steps of
rotating the.
sheets so that another space between the sheets can be filled.
[001241 Suitable sheets for encapsulating the thermal energy storage material
include
any thin metal sheets (e.g., metal foil) that are durable, corrosion
resistant, or both, so
that the sheet is capable of containing the thermal energy storage material,
preferably
without leakage. The metal sheets may be capable of functioning in a vehicle
environment with repeated thermal cycling for more than 1 year and preferably
more
than 5 years. The metal sheet may otherwise have a substantially inert outer
surface
that contacts the thermal energy storage material in operation. The outer
surface of the
metal sheet that contacts the thermal energy storage material should include
or consist
essentially of one or more materials that do not significantly react with,
corrode, or both,
when contacted with the thermal energy storage material. Without limitation,
exemplary
metal sheets that may be employed include metal sheets haying at least one
layer of
brass, copper, aluminum, nickel-iron alloy, bronze, titanium, stainless steel
or the like.
The sheet may be a generally noble metal or it may be one that includes a
metal which
has an oxide layer (e.g. a native oxide layer or an oxide layer which may be
formed on a
surface). One exemplary metal sheet is an aluminum foil which comprises a
layer of
aluminum or an aluminum containing alloy (e.g. an aluminum alloy containing
greater
than 50 weight percent aluminum, preferably greater than 90 weight percent
aluminum).
Another exemplary metal sheet is stainless steel. Preferable stainless steels
include
austenitic stainless steel, ferritic stainless steel or martensitic stainless
steel. Without
limitation, the stainless steel may include chromium at a concentration
greater than
about 10 weight percent, preferably greater than about 13 weight percent, more
preferably greater than about 15 weight percent, and most preferably greater
than about
17 weight percent. The stainless steel may include carbon at a concentration
less than
about 0.30 weight percent, preferably lesa than about 0.15 weight percent,
more
preferably less than about 0.12 weight percent, and most preferably less than
about 0.10
weight percent. For example, stainless steel 304 (SAE designation) containing
19 weight
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WO 2012/021673 CA 02806469 2013-01-23PCT/US2011/047355
percent chromium and about 0,08 weight percent carbon. Preferable stainless
steels
also include molybdenum containing stainless steels such as 316 (SAE
designation).
The metal sheet may have any art known coating that may reduce or eliminate
the
corrosion of the metal sheet,
[00125] The metal sheet has a thickness sufficiently high so that holes or
cracks are
not formed when forming the sheet, when filling the capsules with thermal
energy
storage material, during use of the capsules, or any combination thereof. For
applications such as transportation, the metal sheet preferably is relatively
thin so that
the weight of the heat storage device is not greatly increased by the metal
sheet. The
thickness of the metal sheet may be greater than about 10 km, preferably
greater than
about 20 km, and more preferably greater than about 50 km, The metal sheet may
have
a thickness less than about 3 mm, preferably less than 1 mm, and more
preferably less
than 0.5 mm (e.g., less than about 0,25 mm).
[00126] FIG. 14 illustrates a cross-sec.tion of an exemplary heat storage
device 80
having a plurality of articles 2" and 2¨ each having thermal energy storage
material 16
encapsulated in a plurality of sealed spaces 18. The articles are arranged in
an insulated
container 82 which may have a generally cylindrical shape. The device includes
an
article 2" having a first adjacent article 29"(a) and a second adjacent
article 2"(b). The
article 2" and its first adjacent article 2"(a) may be arranged with the top
surfaces (i.e.,
exterior surfaces) of their respective fiat cover sheets generally in contact.
The article 2"
and the second adjacent article 2"'(b) may have generally mating surfaces
(e.g., the
exterior surfaces of their respective base sheets may be generally mating
surfaces) and
may be arranged so that they partially nest together. A spacer (not shown) may
be used
to maintain a distance between the article 2" and its second adjacent article
2'1(b) so
that a heat transfer fluid can flow through a radial flow path 83 in a
generally radial
direction between the two articles, 2" and 21b). The space between the article
2" and
the second adjacent article 2"(b) may be formed from one of the sheets of the
article 2.
As illustrated in FIG. 14, each article may have a surface (e.g., a surface of
the base
sheet) that is capable of contacting a heat transfer fluid so that the heat
transfer fluid can
be in direct contact with each article and preferably each sealed space. As
illustrated in
FIG. 14, each radial flow path 83 may have the same length, the same cross-
section, or
even may be congruent. Each article 2 may have an opening 46 near its center.
The
openings may be part of a compartment that allows a heat transfer fluid to
flow throught
the device. The articles 2" and 2" may be arranged so that their openings form
a central
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axial flow path 84. The space between the outer periphery of the articles 2"
and 2"' and
the interior surface of the container 85 is also part of the heat transfer
fluid compartment
and forms an outer axial flow path 86. The heat storage device may have a
first orifice
87 that is in fluid connection with a central axial flow path 84. The heat
storage device 80
may have a first seal or plate 88 that separates a first orifice 87 from the
outer axial flow
path 86. The container 82 may have a second orifice 89 which may be on the
same side
of the container as the first orifice 87, or on a different side of the
container, as illustrated
in FIG. 14. The heat storage device may have a second seal 90 .that separates
the
second orifice 89 from the central axial flow path. The first seal, the second
seal, or both
may prevent a fluid from flowing between the two axial flow paths 84 and 86,
Without
flowing through a radial flow path 83. The container 82 preferably is
insulated. For
example, the container may have an inner wall 91 and an outer wall 92. The
space
between the two walls 93 may be evacuated or filled with an insulating
material having
low thermal conductivity. The device may also have one or more springs, such
as one or
more compression springs 94, that exert a compressive force on the stack of
articles.
[001271 FIG. 14 illustrates a heat storage device 80 having two orifices 87
and 89 on
one side of the container. Such a device may employ a tube 95 that is
connected to the
first orifice 87 for flowing the fluid between the first orifice and a region
96 of the central
axial flow path 84 furthest from the first orifice. With reference to FIG, 14,
the first seal 88
and the second seal 90 may be employed to prevent a fluid from flowing from
the first
orifice 87 to the second orifice 89 without first flowing through a radial
flow path 83. By
selecting the sizes for the two axial flow paths 84 and 86, the heat storage
device 80
may be characterized as a Tichelmann system.
[00128] The pressure in one or more, or even all of the sealed spaces may be
less.
than atmospheric pressure, e.g. under a vacuum, when the temperature is about
25 C.
For example, the pressure in a sealed space at 25 "C may be preferably about
600 Torr
or less, about 500 Torr or less, about 400 Torr or less, about 300 Torr or
less, or about
100 Torr or less. A vacuum in a sealed space may be a result of applying a
vacuum
when sealingly joining the cover sheet and the base sheet, a result of
sealingly joining
the cover sheet and the base sheet when the thermal energy storage material is
at an
elevated temperature, or both. For example, the process of sealingly joining
the base
sheet and the cover sheet may include a step of applying a vacuum of about 600
Torr or
less, about 500 Torr or less, about 400 Torr or less, about 300 Torr or less,
about 200
Torr or less, about 100 Torr or less, or about 50 Torr or less to a trough
region of a base
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WO 2012/021673 CA 02806469 2013-01-23PCT/US2011/047355
sheet,
1001291 The heat storage device may be used in a heat storage system that
employs
one or more heat transfer fluids for transferring heat into the heat storage
device, for
transferring heat out of the heat storage device, or both,
[00130] The heat transfer fluid used to transfer heat into and/or out of the
thermal
energy storage material may be any liquid or gas so that the fluid flows
(e.g.., without
solidifying) through the heat storage device and the other components (e.g., a
heat
providing component, one or more connecting tubes or lines, a heat removing
component, or any combination thereof) through which it circulates when it is
cold. The
heat transfer fluid may be any art known heat transfer fluid or coolant that
is capable of
transferring heat at the temperatures employed in the heat storage device. The
heat
transfer fluid may be a liquid or a gas. Preferably, the heat transfer fluid
is capable of
flowing at the lowest operating temperature that it may be exposed to during
use (e.g.,
the lowest expected ambient temperature). For example, the heat transfer fluid
may be a
liquid or gas at a pressure of about 1 atmosphere pressure and a temperature
of about
25 "C, preferably about 0 C, more preferably -20 "C, and most preferably at
about -
$0 C. Without limitation, a preferred heat transfer fluid for heating and/or
cooling the
one or more electrochemical cells is a liquid at about 40 C.
[001311 The heat transfer fluid should be capable of transporting a large
quantity of
thermal energy, typically as sensible heat. The heat transfer fluid may have a
specific
heat (measured for example at about 25 "C) of at least about 1 J/g,K,
preferably at least
about 2 J/g,K., even more preferably at least about as J/g=K, and most,
preferably at
least about 3 Preferably the heat transfer fluid is a liquid.
[00132) Heat transfer fluids and working fluids that may be employed include
those
described in U.S. Patent Application Publication 2009-0250189 (published on
October 8,
2009) and POT Application No, PCl/US09/67823 (filed on December 14, 2009. For
example, any art known engine coolant may be employed as the heat transfer
fluid. The
system preferably employ a single heat transfer fluid for transferring heat
into the.
thermal energy storage material in the heat storage device and for removing
heat from
the thermal energy storage material in the heat storage device. Alternatively,
the system
may employ a first heat transfer fluid for transferring heat to the thermal
energy storage
material and a second heat transfer fluid .for removing heat from the thermal
energy
storage material,
[001331 Without limitation, heat transfer fluids which may be used alone or as
a
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mixture include heat transfer fluids known to those skilled in the art and
preferably
includes fluids containing water, one or more alkylene glycols, one or more
polyalkylene
glycols, one or more oils, one or more refrigerants, one or more alcohols, one
or more
betaines, or any combination thereof.
[00134] The heat storage system may optionally include one or more heaters.
The
heater may be any heater that is capable of increasing the temperature of the
thermal'
energy storage material in the heat storage device to a temperature above its
transition
temperature. The heater may be any heater that converts energy (e.gõ
electrical energy,
mechanical energy, chemical energy, or any combination thereof) into heat
(i.e., thermal
energy). The one or more heaters may be one or more electric heaters. The one
or more
heaters may be employed to heat some or all of the thermal energy storage in
the heat
storage device. Preferably the system includes one or more heaters that are in
thermal
communication with a heat storage device. For example, the system may include
one or
more heaters within the insulation of a heat storage device. An electric
heater may
employ electricity from one or more electrochemical cells, from an external
source, or
both. For example, when a vehicle is plugged into an outlet connected to a
stationary
object, the heat storage device may be maintained at a temperature above the
liquidus
temperature of the thermal energy storage material in the heat storage device
using the
electricity form an external source. When the vehicle is not plugged into an
outlet
connected to a stationary object, the heat storage device may be maintained at
a
temperature above the liquidus temperature of the thermal energy storage
material in
the heat storage device using electricity generated from an electrochemical
cell,
[00135] The heat storage device may be used in a process for heating one or
more
components. The process may include flowing a heat transfer fluid through the
heat
transfer device. The step of flowing a heat transfer fluid through the heat
storage device
may include flowing a heat transfer fluid having an initial temperature
through an inlet of
the device; flowing the heat transfer fluid through an axial flow path so the
heat transfer
fluid can be divided into a plurality of radial flow paths; flowing the heat
transfer fluid
through, a radial flow path so that it can remove heat from the thermal energy
storage
material, wherein the thermal energy storage material has a temperature
greater than
the initial temperature of the heat transfer fluid; flowing the heat transfer
fluid through a
different axial flow path so that a plurality of radial flow paths can
recombine; flowing the
heat transfer fluid having an exit temperature through an outlet of the
device; or any
combination thereof. Preferably the heat transfer fluid exit temperature is
greater than
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the initial temperature of the heat transfer fluid. The process for heating
one or more
components may employ a flow path through the heat storage device including
one of a
selection of radial flow path and two axial flow paths, the flow path having a
total flow
length, wherein the total flow length is generally constant for the different
radial flow
paths,
[00136] The heat storage device and/or the heat storage system may
characterized
as having a relatively high power (e.g., as measured during the initial 30 or
60 seconds
of heating) so that it can rapidly heat a component, such as an internal
combustion
engine. The heat storage device and/or the heat storage system may be
characterized
by an average power greater than about 6 watts, preferably greater than about
10 watts,
more preferably greater than about 15 watts, and most preferably greater than
about 20
watts.
[00137] The heat storage device and/or the heat storage system may be
characterized as having a relatively high power density, so that it can hold a
large
quantity of thermal energy in a relatively small compartment. For example, the
heat
storage device and/or the heat storage system may be characterized as having a
power
density greater than about 4 kWIL, preferably greater than about 8 kW/L, more
preferably greater than about 10 kW/L., and most preferably greater than about
12 kW/L.
[00138] The heat storage device and/or the heat storage system. may be
characterized as having a relatively low pressure drop of the heat transfer
fluid
(measured at a heat transfer fluid flow rate of about 10 Llmin). For example,
the heat
storage device and/or the heat storage system may be characterized as having a
heat
transfer fluid pressure drop less than about 2.0 kPa, preferably less than
about 1.5 kPa,.
more preferably less than about 1.2 kPa, and most preferably less than about
1.0 kPa.
[00139] By way of example, the thermal energy storage system may be employed
in
a transportation vehicle (e.g., an automotive vehicle) for storing energy from
an engine
exhaust gas. When the engine produces exhaust gas, a bypass valve may either
direct
the flow of the gas through the heat storage device so that the heat storage
device is
charged, or through a bypass line to prevent the heat storage device from
overheating.
When the engine is shut down, e,g, during a period when the vehicle is parked,
a
substantial portion of the heat stored in the heat storage device may be
retained for a
long time (e.g,, due to vacuum insulation surrounding the heat storage
device).
Preferably at least 50% of the thermal energy storage material in the heat
storage device
remains in a liquid state after the vehicle has been parked for 16 hours at an
ambient
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temperature of about -40 'C. If the vehicle is parked for a long enough time
(e.gõ at least
two or three hours) for the engine to cool down substantially (e.g., so that
the difference
in temperature between the engine and the ambient is less than about 20 CC),
the heat
stored in the heat storage device may be discharged into the cold engine or
other heat
recipient indirectly by flowing a heat transfer fluid (such as the engine
coolant) through
the heat exchanger that includes the condenser for the working fluid. The
working fluid is
circulated in a capillary pumped loop using the capillary structure inside the
heat storage
device where the working fluid is vaporized. The heat from the working fluid
is
transferred to the engine coolant in the heat exchanger. By employing the heat
storage
device, heat that otherwise would be wasted may be captured during a previous
trip to
mitigate cold start andior provide instant cockpit heating.
[00140) The transfer of heat using the working fluid may begin by opening the
working
fluid valve (i.e., the discharge valve). The sealed working fluid reservoir
connected to the
loop via an additional liquid line serves to accommodate changes in the
working fluid
liquid volume inside the loop without substantial pressure changes. Once
sufficient or all
useful heat is transferred from the heat storage device, the discharge valve
may close.
The remaining working fluid in the heat storage device may evaporate (e,g.,
from heat
remaining in the heat storage device or when the heat storage device begins to
charge)
and then condenses in the condenser. As the heat storage device becomes
evacuated
of the working fluid, the liquid level of the working fluid level may change
(e.g., rise).
[00141] The heat storage device may optionally be a cross-flow heat exchanger
(i.e.,
having a flow direction for the working fluid and a perpendicular flow
direction for the flow
of the exhaust gas). For example, during operation, the heat storage device
may include
three chambers occupied by 1) exhaust gas; 2) stagnant phase change material
(e.g.,
inside capsules, such as a blisters pack); and 3) working fluid. All three
chambers are
kept separate by thin walls made of an appropriate material, preferably
stainless steel.
Exhaust gas may flow between the surfaces (e.g., the curved surfaces) of the
capsules
of phase change material inside blisters, and the working fluid may flow
between
different surfaces (e.g., flat surfaces) of the capsules of phase change
material inside
blisters in a direction, that is generally perpendicular to the exhaust gas
flow direction.
The liquid working fluid entering its chamber preferably wets a capillary
structure (e.g., a
metal wick) and gets transported up against the combined forces of gravity and
vapor
pressure by the capillary forces acting upon the working fluid liquid menisci
formed
inside the capillaries. This flow is sustained by continuous evaporation of
the liquid using
WO 2012/021673 CA 02806469 2013-01-23PCT/US2011/047355
the heat drawn from the phase change material inside blisters. The vapor of
working
fluid leaves the capillary structure and escapes to the top of the device via
vapor
channels which may be interdigitated between columns of the capillary
structure
squeezed between the surfaces (e.g., the flat surfaces) of the 'capsules of
phase change
material inside blisters. The vapor of working fluid flows into the condenser
where it
transfers its heat of vaporization and sensible heat to the cold coolant and
becomes
liquid again to return to the heat storage device and continue its circulation
in the loop,
being pumped only by the capillary forces existing inside the capillary
structure (e.g.,
metal wick) that is partially impregnated by liquid working fluid. All columns
of the
capillary structure may be connected to a common porous base. Such a porous
base
may be employed to distribute the liquid working fluid entering from the
bottom of the
device to the different columns,
[00142) Furthermore, the present invention may be used in combination with
additional elements/components/steps. For example, absorption or adsorption
cycle
refrigeration system for air conditioning may be used as the heat recipient
instead of or
in addition to the cold coolant (e.g., the condenser may serve also as an
evaporator for
the refrigerant circulating inside an air conditioner's fluid loop), in
another application, a
steady-state waste heat recovery system using a heat engine, e.g. a Rankine
cycle, can
be constructed so that it uses the same or different capillary pumped loop
working fluid
and adds a mechanical power generating turbine to the vapor line between the
heat
storage device and the condenser, (e.g., to overcome high vapor pressure
upstream
from the turbine), and/or adds a liquid pump to the liquid line between the
condenser and
heat storage device. The above turbine can convert a part of the captured from
the
exhaust gas waste heat into useful mechanical or electrical work and thus
improve the
overall fuel efficiency of the vehicle.
EXAMPLES
[00143] Example 1 is an article including 7 sealed spaces containing thermal
energy
storage material and suitable for heat storage. The packs are formed by
filling a base
sheet having 7 troughs with a thermal energy storage material. Each trough is
capable of
containing about 7 cm 3 of a liquid. The base sheet is covered with a flat
cover sheet. The
base sheet and the cover sheet are made of stainless steel 304 and have a
thickness of
about 0.102 mm. The thermal energy storage material is a metal salt and has a
liquidus
temperature of about 195 "C. The thermal energy storage material is anhydrous
or has a
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moisture concentration of about 0õ01 wt.% or less. The two sheets are joined
while the
thermal energy storage material is in a solid state (about 23 cC).. A primary
seal is.
provided by laser welding together the base sheet and the cover sheet about
the
periphery of each sealed space. When heated to a temperature of about 250 C,
the
sealed space has an internal pressure of about 69 kPa (about 10 psi),
Thermal Cyclic Testing
[00144] About 10 articles of Example 1 are stacked and placed in a container
having
an inlet and an outlet. The inlet is connected to a hot reservoir of a heat
transfer fluid at a
temperature of about 250 C and a cold reservoir of a heat transfer fluid at a
temperature
of about 15 "C, The heat transfer fluid is allowed to flow through the
container until the
temperature of the thermal energy storage material is about 240 CC, then the
cold heat
transfer fluid is allowed to flow through the container until the temperature
of the thermal
energy storage material is about 25 "C. The temperature of the thermal energy
storage
material is cycled about every 5 minutes for about 1,.000 cycles..
[00145] One or more sealed spaces of Example 1 rupture and/or develop a leak
in
the primary seal during the thermal cyclic testing prior to reaching 1,000
cycles. Thermal
energy storage material leaks out of one or more sealed spaces and Example 1
fails the
thermal cycling test.
Heat Test
[00146] An article of Example 1 is placed in an oven at a temperature of about
400 CC
for about 30 minutes, The article is then evaluated to determine if there are
any leaks or
ruptures that would allow thermal energy storage material to leak out of the
article. One
or more leaks and/or ruptures are observed and Example 1 fails the heat test.
[00147] Example 2 is an article including 7 sealed spaces prepared using the
method
of Example 1, except that a secondary seal is prepared by laser welding the
base sheet
and the cover sheet near their outer peripheries and near their opening
peripheries. The
articles are tested using the same method as described for Example 1. The
maximum
von Mises stress is above the yield stress of the foil. During the thermal
cycling, the
primary seal fails around one or more sealed spaces. The secondary seal does
not fail
after 1,000 thermal cycles and the thermal energy storage material does not
leak out of
the article.
[00148] Another article of Example 2 is tested by heating to 400 "C. At 400
(t, one or
more primary seals fail. However, the secondary seal does not fail and thermal
energy
storage material does not leak.
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[00149] Example 3 is an article including 7 sealed spaces prepared using the
method
of Example 1, except the base sheet and the cover sheet both use foils having
a.
thickness of about 0.204 mm. The articles are tested using the same method as.
described for Example 1, The maximum von Mises stress is below the yield
stress of foil.
The primary seal does not fail after 1,000 thermal cycles and the thermal
energy storage
material does not leak out of the article.
[00150] Another article of Example 3 is tested by heating to 400 C for 20
minutes. At
400 "C, none of the seals fail and the thermal energy storage material does
not leak,
[00151] Example 4 is an article including 7 sealed spaces prepared using the
method
of Example 1, except the cover sheet uses a foils having a thickness of about
0,204 mm.
The articles are tested using the same method as described for Example 1. The
maximum von Mises stress is reduced to about 180 MPa, below the yield stress
of foil.
The primary seal does not fail after 1,000 thermal cycles and the thermal
energy storage
material does not leak out of the article,.
(001521 Another article of Example 4 is tested by heating to 400 "C for 20
minutes. At
400 "=C, none of the seals fail and the thermal energy storage material does
not leak.
[00153] Example 5 is an article including 7 sealed spaces prepared using the
method
of Example 1, except the cover sheet is embossed so that the cover sheet over
each
sealed space containing thermal energy storage material has about 15 ribs
including
both indentions and protrusions each having a depth of 0,1 to 0.5 mm. The
articles are
tested using the same method as described for Example I. The maximum von Mises
stress is about 233 MPa, below the yield stress of foil. The primary seal does
not fail
after 11000 thermal cycles and the thermal energy storage material does not,
leak out of
the article. It will be appreciated that one, two, or more ribs may be
employed and that
ribs may be indentions, protrusions, or both,
[00154] Another article of Example 5 is tested by heating to 400 "C for 20
minutes. At
400 "C, none of the seals fail and the thermal energy storage material does
not leak.
[00155] Example 6 is an article including 7 sealed spaces prepared using the
method
of Example 1, except the cover sheet is embossed so that a sealed space
including.
thermal energy storage material has about 34 dimples that recess about 0.6 mm
into the
sealed space. The dimples in the cover sheet are in a brickwail pattern as
shown
schematically in FIG. 48, The articles are tested using the same method as
described
for Example 1, The maximum von Mises stress is about 590 MPa and is above the
yield
stress of foil. The primary seal fails during the thermal cycling and the
thermal energy
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storage material leaks out of the article. It will be appreciated that fewer
or more dimples
may be employed and that the dimples may be deeper or shallower,
[00156] Another article of Example 6 is tested by heating to 400 C for 20
minutes. At
400 "C, the seals fail and the thermal energy storage material leaks.
[00157] Example 7 is an article including 7 sealed spaces prepared using the
method
of Example 6, except the cover sheet is made of a foil having a thickness of
about 0.153
mm, The articles are tested using the same method as described for Example 1.
The,
maximum von Mises stress is about 282 MPa and is below the yield stress of
foil. The.
primary seal does not fail during the thermal cycling and the thermal energy
storage.
material does net leak out of the article after 1,000 thermal cycles.
[00158] Another article of Example 7 is tested by heating to 400 C for 20
minutes. At
400 C, the seals do not fail and the thermal energy storage material does not
leak.
[00159] Example 8 is an article including 7 sealed spaces prepared using the
method
of Example 1, except the cover sheet is embossed with a plurality of chevrons
that.
include recesses and protrusions of about 0.5 mm. The chevrons in the cover
sheet are
in a repeating pattern as shown schematically in Fla 4A. The articles are
tested using
the same method as described for Example 1. The maximum von Mises stress is
about
600 MPa and is above the yield stress of foil,
(001601 Example 9 is an article including 7 sealed spaces prepared using the
method
of Example 1, except a vacuum of about 200 Torr is applied when the cover
sheet and
the base sheet are welded together. When the thermal energy storage material
is at a
temperature of about 25 'C, the pressure in the sealed space is less than
about 400 Torr.
The articles are tested using the same method as described for Example 1. The
maximum von Mises stress is less than the yield stress of foil. The primary
seal does not
fail during the thermal cycling and the thermal energy storage material does
not leak out
of the article after 1,000 thermal cycles.
[00161] Another article of Example 9 is tested by heating to 400 "C for 20
minutes. At
400 "C, the seals fail and the thermal energy storage material leaks.
[00162] Example 10 is an article including 7 sealed spaces prepared using the
method of Example 1, except the cover sheet and base sheet are welded together
when
the thermal energy storage material is at a temperature of about 250 CC. When
the
thermal energy storage material is at a temperature of about 25 C, the
pressure in the
sealed space is less than about 400 Torr. The articles are tested using the
same method
as described for Example 1. The maximum von Mises stress is less than the
yield stress
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of the foiL The primary seal does not fail during the thermal cycling and the
thermal
energy storage material does not leak out of the article after 1,000 thermal
cycles,
[001631 Another article of Example 10 is tested by heating to 400 CC for 20
minutes,
At 400 QC, the seals fail and the thermal energy storage material leaks.
[00164] The preferred embodiment of the present invention has been disclosed.
A
person of ordinary skill in the art would realize however, that certain
modifications would
come within the teachings of this invention. Therefore, the following claims
should be
studied to determine the true scope and content of the invention,
[00165] Any numerical values recited in the above application include all
values from
the lower value to the upper value in increments of one unit provided that
there is a
separation of at least 2 units between any lower value and any higher value.
As an
example, if it is stated that the amount of a component or a value of a
process variable
such as, for example, temperature, pressure, time and the like is, for
example, from 1 to
90, preferably from 20 to 80, more preferably from 30 to 70, it is intended
that values
such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly .enumerated
in this
specification. For values which are less than one, one unit is considered to
be 0.0001.,
0.001, 0,01 or 0.1 as appropriate. These are only examples of what is
specifically
intended and all possible combinations of numerical values between the lowest
value
and the highest value enumerated are to be considered to be expressly stated
in this
application in a similar manner. Unless otherwise stated, all ranges include
both
endpoints and all numbers between the endpoints. The use of 'about" or
"approximately".
in connection with a range applies to both ends of the range. Thus, .'about 20
to 30" is
intended to cover "about 20 to about 30", inclusive of at least the specified
endpoints.
Parts by weight as used herein refers to compositions containing 100 parts by
weight. The disclosures of all articles and references, including patent
applications and
publications, are incorporated by reference for all purposes. The term
"consisting
essentially or to describe a combination shall include the elements,
ingredients,
components or steps identified, and such other elements ingredients,
components or
steps that do not materially affect the basic and novel characteristics of the
combination,
The use of the terms 'Comprising" or "including" to describe combinations of
elements,
ingredients, components or steps herein also contemplates embodiments that
consist
essentially of the elements, ingredients, components or steps. Plural
elements,.
ingredients, components or steps can be provided by a single integrated
element,.
ingredient, component or step. Alternatively, a single integrated element,
ingredient,
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component or step might be divided into separate plural elements, ingredients,
components or steps. The disclosure of "a" or one to describe an element,
ingredient,
component or step is not intended to foreclose additional elements,
ingredients,
components or steps..
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