NZ620848B2 - Thermal energy storage apparatus - Google Patents
Thermal energy storage apparatus Download PDFInfo
- Publication number
- NZ620848B2 NZ620848B2 NZ620848A NZ62084812A NZ620848B2 NZ 620848 B2 NZ620848 B2 NZ 620848B2 NZ 620848 A NZ620848 A NZ 620848A NZ 62084812 A NZ62084812 A NZ 62084812A NZ 620848 B2 NZ620848 B2 NZ 620848B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- heat
- thermal energy
- block
- energy storage
- heat storage
- Prior art date
Links
- 238000004146 energy storage Methods 0.000 title claims abstract description 26
- 238000005338 heat storage Methods 0.000 claims abstract description 46
- 239000000463 material Substances 0.000 claims abstract description 43
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 38
- 239000010703 silicon Substances 0.000 claims abstract description 38
- 229910052752 metalloid Inorganic materials 0.000 claims abstract description 33
- -1 silicon metalloid Chemical class 0.000 claims abstract description 24
- 239000011358 absorbing material Substances 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 17
- 239000010439 graphite Substances 0.000 claims description 17
- 229910002804 graphite Inorganic materials 0.000 claims description 17
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 11
- 230000005496 eutectics Effects 0.000 claims description 8
- 238000003860 storage Methods 0.000 claims description 3
- 229940035295 Ting Drugs 0.000 claims description 2
- 238000010276 construction Methods 0.000 abstract 1
- 239000011230 binding agent Substances 0.000 description 15
- 229910010271 silicon carbide Inorganic materials 0.000 description 15
- HBMJWWWQQXIZIP-UHFFFAOYSA-N Silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 14
- 150000002738 metalloids Chemical class 0.000 description 9
- 239000002245 particle Substances 0.000 description 9
- 239000000919 ceramic Substances 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 238000010304 firing Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000005485 electric heating Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910021364 Al-Si alloy Inorganic materials 0.000 description 1
- 241000229754 Iva xanthiifolia Species 0.000 description 1
- 241000220317 Rosa Species 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N Silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 230000001808 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 229910003465 moissanite Inorganic materials 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000002694 phosphate binding agent Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 230000001131 transforming Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
- B23P15/26—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass heat exchangers or the like
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2254/00—Heat inputs
- F02G2254/40—Heat inputs using heat accumulators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S60/00—Arrangements for storing heat collected by solar heat collectors
- F24S60/10—Arrangements for storing heat collected by solar heat collectors using latent heat
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
- F28D20/0056—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using solid heat storage material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
- F28D20/02—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
- F28D20/02—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat
- F28D20/025—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat the latent heat storage material being in direct contact with a heat-exchange medium or with another heat storage material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F7/00—Elements not covered by group F28F1/00, F28F3/00 or F28F5/00
- F28F7/02—Blocks traversed by passages for heat-exchange media
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/40—Solar thermal energy, e.g. solar towers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/14—Thermal energy storage
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/4935—Heat exchanger or boiler making
Abstract
Thermal energy storage apparatus (10), containment vessel for phase change material, and method of construction of vessel. The apparatus includes a block (12) of a heat-absorbing material. The block (12) is a contiguous block of heat-absorbing material having a plurality of holes (14). Heat storage elements are seated within each of the holes (14) and is in thermal contact with the block (12). Each heat storage element includes a phase change material, in this case silicon metalloid, stored in a containment vessel. The containment vessel has a substantially cylindrical sidewall with an inner surface that tapers inwardly from a first end to a second end. This when the phase change material undergoes a phase change the material will preferentially expand in the direction of the first end due to the relatively greater thickness of the sidewall. elements are seated within each of the holes (14) and is in thermal contact with the block (12). Each heat storage element includes a phase change material, in this case silicon metalloid, stored in a containment vessel. The containment vessel has a substantially cylindrical sidewall with an inner surface that tapers inwardly from a first end to a second end. This when the phase change material undergoes a phase change the material will preferentially expand in the direction of the first end due to the relatively greater thickness of the sidewall.
Description
THERMAL ENERGY STORAGE APPARATUS
Field of the Invention
The present invention relates to a l energy storage apparatus.
Background of the Invention
There has been a push in recent years to move away from fossil fuels as an energy source.
The move towards what are generally characterised as cleaner fuel s has seen
significant development in the use of solar or wind energy as a means of ing usable
forms of energy.
By its very nature, solar energy’s biggest pitfall is the fact that at certain times of the day,
the sun is unable to provide the necessary flux of photons to various devices that utilise
solar energy. rly, wind turbines and the like are only effective when there is
sufficient wind strength to drive them.
Interrupted or inconsistent supply of energy from a source makes it, in many instances,
unreliable and also uneconomical.
In addition, at certain times, the sun’s rays can be so excessive that the resultant heat and
energy are dissipated as over-supply, rather than being usable by a solar—powered .
A us attempt to address the above difficulties used a silicon metalloid material as a
means of storing thermal energy inside the al for use at a later time, for example,
when solar input was no longer available, such as during the evenings or times of
inclement weather. During peak solar activity the silicon metalloid material would absorb
thermal energy as it underwent a phase change from a solid to a liquid.
Silicon metalloid material is characterised in part by the property that on undergoing a
phase change from liquid to solid, there is an expansion of the material rather than
contraction as would be expected for most other materials.
The thermal energy stored within the silicon metalloid material could be ted into
electrical and/or ical action through electrical devices such as a Stirling engine and
so forth, thus providing a source of power at times when solar activity was not available.
A antage of silicon metalloid al is that it requires significant care and
understanding of its al transformation during its expansion and contraction as it
absorbs and es thermal energy during phase changes. The expansion and contraction
of the silicon metalloid material creates significant build-up of pressure on an enclosure in
which it is placed. For e, if silicon metalloid material in the form of ingots is placed
directly in contact with a refractory heat—absorbing al such as graphite, the metalloid
would be absorbed by the te on undergoing a phase change to its liquid form. If the
silicon metalloid is stored in a separate enclosure before being inserted into the refractory
material, the continual pressure build-up and collapse of the silicon metalloid ingots as
they undergo phase changes can result in fissuring of the enclosure.
If the ingots are stored within separate enclosures there would also be a need for the
enclosure of the silicon metalloid ingots to efficiently transport heat, released during phase
change of the silicon metalloid material, to the surrounding graphite.
PCT Application (published as ), the ts of
which are hereby incorporated in their entirety by reference, sought to address these
ms by ing an enclosure in the form of an elongate canister formed of
ceramics, the elongate canister including a pressure dispersion punt and a series of grooves
in one of its ends, the series of grooves acting as a heat sink. In the thermal energy storage
apparatus described in , a series of such canisters are used to store
silicon oid, and are packed in interleaved arrangement with a series of sintered
graphite rods. It has been found, though, that in such an arrangement the canisters are
prone to cracking, particularly in the region of the grooves.
H:\nui\lmtrwoven\N DCC\MZI\l()098592_l.DOCv5/05/2016
It would be desirable to me or alleviate the above mentioned difficulties, or at least
provide a useful alternative.
Summary of the Invention
In accordance with one aspect of the present invention, there is provided a thermal energy
storage apparatus, including:
a block of a heat—absorbing material, the block being a contiguous block of
compressed material in the form of sintered graphite and machinable; and
a plurality of heat storage elements, the heat storage elements including a phase
change material stored in a containment vessel;
wherein each heat e element is in thermal contact with the block of heat-
absorbing material, each storage element being received in a respective hole machined in
the block.
In one embodiment, the block of heat-absorbing material includes a heat storage region
having a first plurality of holes formed therein, the heat storage ts being seated in
respective ones of said holes.
In one example of the invention, the holes are formed with predetermined als
etween. The predetermined intervals may be chosen to optimise heat transport in the
heat storage region.
' The thermal energy storage apparatus may further include one or more heating elements in
thermal contact with the heat storage region. The one or more heating elements may be
seated in a second plurality of holes in the heat storage region.
ably, the heating elements are ic heating elements. The g elements may
3O be individually controllable to supply different amounts of heat to different areas of the
heat storage region. The apparatus may fu1ther comprise one or more temperature sensors
H:\|xizi\lma'wovm\N RPonbl\DCC\MZI\l ()(198592al .DOC-S/OS/ZOI 6
associated with each of the different areas of the heat e region.
The apparatus may further se means for extracting heat from the heat e
elements, including for e a closed—cycle heat engine associated with the block of
heat-absorbing material. The closed—cycle heat engine may be any closed-cycle heat engine
which operates according to ion and compression of a working gas. Examples of
such heat engines include Stirling engines and Brayton engines.
In one example, the closed-cycle heat engine is a Stirling engine which is coupled to the
heat storage region via a wick.
A preferred phase change material for use with embodiments of the invention includes
silicon metalloid or a eutectic, hypereutectic or hypoeutectic silicon composition.
There is also sed herein a containment vessel for a phase change material, including:
a ntially cylindrical sidewall, a first end, and a second end;
wherein the sidewall has a thickness which increases along its length from the first end
to the second end,
such that, on undergoing a phase change, the phase change material preferentially
expands in the direction of the first end.
The sidewall preferably includes n carbide. Preferably, the sidewall is formed from
particles having a particle size distribution spanning the range from about 8 US Mesh to
—200 US Mesh. In preferred embodiments, the sidewall includes not less than 90% silicon
carbide.
Embodiments of the contaimnent vessel may advantageously be used with embodiments of
the thermal energy storage apparatus as described herein.
3O There is also disclosed herein a method of fabricating a containment vessel for a phase
change al, the containment vessel having a body including n carbide, the
i\lnu:rwovu)\NRPonbl\DCC\MZI\l0()98592_1DOC—51050016
method including:
ing particles of silicon carbide with a binder; and
heating the particles in a kiln according to a kiln schedule including steps of
predetermined duration and temperature;
wherein the ermined duration is sufficient to form bonds between the
particles throughout the body of the containment vessel.
There is also disclosed herein a method of storing thermal energy, including:
providing a block of a bsorbing material; and
placing a plurality of heat storage elements in thermal contact with the block;
wherein the heat e elements include a phase change material stored in a
nment vessel.
The phase change material may include silicon metalloid or a eutectic, hypereutectic or
hypoeutectic silicon composition. The containment vessel may comprise silicon carbide.
Preferably, the method includes embedding the heat storage elements in the block. For
example, the method may include providing a heat storage region by forming a plurality of
holes in the bsorbing material to receive one or more of the heat storage elements. A
plurality of heating elements may be provided in the heat e region.
In one embodiment, the heating elements are dually controllable to supply different
amounts of heat to different areas of the heat storage region.
In one example, the method further includes maintaining a melt fraction of the phase
change material between 1% and 99%.
H:\l'nll“IIIWOVUIWRPOHbl\DCC\MZI\5002889_1AlOC'S/OS/ZO16
Brief Description of the Drawings
Preferred embodiments of the invention will now be described, by way of non-limiting
example only, with reference to the accompanying drawings in which:
Figure 1 shows one embodiment of a thermal energy e apparatus;
Figure 2 is a cross—section through a containment vessel for use with the thermal energy
storage tus of Figure 1;
Figure 3 is a cross—section through the line A—A of Figure 2;
Figure 4 shows a thermal wick for use with the thermal e apparatus of Figure 1;
Figure 5 is a front plan view of the wick of Figure 4;
Figure 6 is a cross-section h the line C-C of Figure 5;
Figure 7 shows an alternative thermal energy storage apparatus;
Figure 8 is a top plan view of the tus of Figure 7;
Figure 9 is a cross-section through the line B—B of Figure 8; and
Figure 10 shows temperature vs. time curves recorded during testing of a containment
vessel.
Detailed Description of Preferred Embodiments
Referring initially to Figure 1, there is shown a l energy storage apparatus 10
including a block 12 of a heat—absorbing material. The block 12 is a contiguous block of
heat-absorbing material having a plurality of holes 14 formed therein.
As used herein, the term "contiguous" refers to a single mass of material, whether solid or
, in which any two points within the mass may be joined by a continuous path.
One or more heat storage elements is seated within each of the holes 14, and each heat
storage element is in thermal contact with the block 12 of heat—absorbing material. The
umuwovmwRPonbl\DCC\MZI\6002889_1.doc-S/t)5/2016
region of the block 12 containing the heat storage elements will be ed to herein as a
heat storage region.
Each heat storage element includes a phase change material, in this case silicon metalloid,
stored in a containment vessel. The containment vessels preferably form an interference fit
within the holes 14.
n metalloid has a latent heat storage capacity of imately 497 W/kg at a
temperature of 1410°C. In some circumstances it may be advantageous to employ, instead
of silicon metalloid, a eutectic (or hypoeutectic or hypereutectic) silicon composition,
which has a lower heat capacity but also a lower phase transition temperature. For
example, a eutectic Al—Si alloy having an Al:Si ratio of 1:12 has a much lower transition
temperature of 580°C, whilst still having a vely large storage capacity of
approximately 200 W/kg.
The heat—absorbing material is a machinable material, in particular sintered graphite, which
may include a binder or other material impregnated therein. The holes 14 are formed in the
block 12 by precision boring using techniques known in the art. The relative placement of
the holes 14 is chosen in order to se heat transport within the block 12. The spacings
between holes 14 may be optimised, having regard to the coefficients of thermal expansion
of the ed graphite and the heat storage elements, by s known in the art. For
example, the thermal transport properties of the block 12 in the heat storage region may be
calculated using finite element methods, such as those incorporated in the multiphysics
simulation modules provided in the ANSYS modelling software (ANSYS, Inc.,
burg, Pennsylvania).
While sintered graphite is used in the presently described embodiments, it will be
appreciated by the skilled person that other heat-absorbing materials will also be suitable,
provided they have suitably high thermal conductivity and can be machined to
odate the nment vessels.
H:\mzi\lmurwovmWRPortthCC\MZI\60()2889_1.doc-5/05/2016
It would of course be possible to allow the block 12 of heat-absorbing material to be
heated directly by solar energy, for example by providing one or more solar trators
to focus sunlight onto the block 12 at one or more locations. However, providing electric
heating elements 20 at predetermined ons adjacent to the heat storage elements
affords greater control over heating of the block 12.
Electric heating ts 20 are received in a second plurality of holes in the block 12,
preferably forming an interference fit within respective ones of the second plurality of
holes. The heating elements 20 are placed in gaps between adjacent holes 14. The second
plurality of holes is also formed by precision boring.
It has been found that installing the heat storage elements in a single block of heat
absorbing material, for example Via precision-bored holes as described above, avoids the
fracturing problems associated with previous ches. In particular, a block structure is
not subject to the shifting, during the heating and g phases, which is experienced by
the graphite rods and associated containment vessels in the arrangement described in
. It is thought that this shifting es stresses on the containment
vessels, ing in fracturing. The shifting also results in poorer heat transport properties
than are obtainable with the presently described embodiment since it allows air gaps to
develop between the heat e elements and the surrounding graphite.
In operation of the thermal energy storage tus 10, electric current is supplied to the
electric heating elements 20 by an al energy source. For example, the current may be
a DC current from a oltaic array or an AC current from a wind turbine. As current
passes through the heating elements 20, ive heating of the nding graphite
results. Heat is then transported to the phase change material of the heat storage elements
Via the walls of the containment vessels, which are in thermal contact with the graphite
block. The silicon metalloid (or eutectic silicon composition, for example) absorbs le
heat until its temperature reaches melting temperature, at which point further heat input to
3O the silicon metalloid is stored as latent heat of fusion. When the external energy source
(solar or wind) is no longer available, or drops below the level required to maintain the
core temperature of the g elements above the melting temperature, the silicon
metalloid solidifies. The stored heat is then released to the surrounding graphite.
The g elements 20 are preferably formed of silicon carbide, and may be d to a
current source in tional fashion, for example by copper cabling.
In order to extract heat to perform mechanical and/or electrical work, the apparatus 10 may
be coupled to a heat engine, such as a Stirling engine or a Brayton engine, via a wick 200
which is in thermal contact with the block 12. When the heat e region is at a higher
temperature than the head of the heat engine, heat is transported from the heat storage
region by thermal conduction through the wick 200.
The wick 200, as shown more particularly in s 4 to 6, includes a plurality of
through-holes 210 and a blind bore 212. These are provided to allow positive location of
corresponding protrusions on the head of the Stirling engine to mechanically couple the
head and the wick, and to ensure proper thermal contact between the Stirling engine and
the wick 200 (and consequently the block 12).
The wick 200 is preferably formed of the same material as the block 12, or at least of a
material which has the same or a very similar l conductivity to the material of the
block 12. In the presently described embodiment, the wick 200 is fabricated from a
machinable sintered graphite which may be of the same grade as the sintered graphite of
the block 12.
Although the wick 200 is shown as a separate element in Figures 1 and 4 to 6, it will be
appreciated that the location apertures 210 and 212 may be machined directly into a
surface of the block 12 in situ. A te wick 200 may in some circumstances be
advantageous in providing a system with an increased degree of modularity.
3O The heating elements 20 may be individually controllable to supply different amounts of
heat to different areas of the uous region of material 12. The different areas may
H:\m‘/.i\lnlu'wovm\N RPonbl\DCC\MZI\60()1889J .dm-S/05/20 1 6
each have one or more temperature sensors associated therewith. ature readings
from each sensor may be communicated to a control system (not shown), and the readings
used by the control system to adjust the electric t flowing to the respective heating
elements 20, and thus the degree of heating. For example, if the temperature readings
indicate that some areas of the contiguous region 12 are at temperatures well above the
phase transition temperature of the n metalloid (or other phase change material) while
others are well below, the current flowing to the respective areas can be adjusted
ingly so that each area has a temperature just above the phase transition temperature.
This provides more efficient energy storage by heat storage elements associated with the
respective areas.
Referring now to Figures 2 and 3, there is shown a nment vessel 100 having a
substantially cylindrical ll, with a cylindrical outer surface 102 and a tapered inner
surface 104. The containment vessel 100 may be sealed by a lid 106, for example using a
refractory . The inner e 104 tapers inwardly from a first end 107 to a second
end 108 of the containment vessel 100, such that the sidewall increases in thickness along
its length from the first end 107 to the second end 108.
When a phase change material is stored in the containment vessel 100 and expands on
undergoing a phase change from liquid to solid (or vice , the material will
preferentially expand in the direction of the first end 107 due to the relatively greater
thickness of the sidewall at the second end 108.
Containment vessels 100 fabricated from silicon carbide may be used to store silicon
metalloid or eutectic silicon compositions, thereby to act as a heat storage element suitable
for use with the thermal energy storage apparatus described above. Suitable silicon carbide
compositions, and methods for fabricating the vessels 100, will be described below.
We have found that a taper angle substantially in the range from about 1.2 degrees to 3.2
degrees, more preferably from 1.33 degrees to 2.92 s, is suitable for containment
vessels fabricated from silicon carbide and used to hold silicon metalloid or eutectic (or
hypereutectic or hypoeutectic) silicon compositions.
Referring now to Figures 7 to 9, there is shown an alternative thermal energy storage
apparatus 400 which includes a contiguous block 402 of sintered graphite. The block 402
is sandwiched between upper 441 and lower 442 layers of an ting material. The
layers 441, 442 may employ different insulating materials depending on the operating
temperatures experienced by the top and bottom of the apparatus 400.
The block 402 includes a ity of heat storage regions 412 each having a plurality of
holes 414 formed therein. As best shown in Figure 9, each hole 414 receives a pair of
silicon e containment vessels 100 of the type shown in Figures 2 and 3, placed one
on top of the other. The containment vessels 100 each contain n metalloid and
thereby act as heat storage elements as described above.
Each heat e region 412 is configured similarly to the heat storage region 12 shown in
Figure 1, and includes a ity of heating elements 20 with which may be associated
temperature sensors as bed above. Further, each heat storage region 412 is in thermal
contact with a wick 430 for coupling to the head of a Stirling engine 450 for extracting
stored heat from the system.
Fabrication ofcontainment vessels
Containment vessels were fabricated starting with refractory grade silicon carbide particles
having a SiC content of not less than 98% and a Fe content (in all forms, ing Fe203)
of not greater than 0.2%. The grain size of the les was graduated from 8 US Mesh
down to about —200 US Mesh. The grain sizes will generally follow a normal or an
approximately normal distribution, although other non—uniform grain size distributions
known in the art may also be employed.
A ceramic oxide binder was then added to the silicon carbide particles and the binder and
silicon carbide mixed according to s known in the art. The particular binder used
was A1203, which was added to the mixture at 4% by . Other ceramic oxide binders,
or even non—oxide binders such as silicon nitride, may of course be used, and it will be
understood that the proportion of binder may be ed accordingly. Further, the silicon
carbide particles may self—bind, so that a binder may be omitted altogether under n
circumstances.
The mixture of silicon carbide and binder was then press—moulded to form a cylinder with
a tapered internal surface, as shown in Figure 2.
The press-moulded cylinder was then placed in a kiln and ed according to the kiln
firing schedule having the sequence of steps (segments) of predetermined duration and
temperature (target set point) shown in Table 1.
Table 1: kiln firing schedule
Segment# 227,1,4 i5 6 l 8
Target Set
Point 100 C 300 C 500 C 800 C ‘ 950 C 1100 C ‘ 1425 C ‘ 1425 C
Segment
time 30mins '
. 1Hr 1.5Hrs 15Hrs \ 1Hr 2Hrs ‘
Target Set
Point 900 C 650 C
time 45mins 45mins
The particular le shown in Table 1 has been found suitable for forming the ceramic
bond throughout the body of the sintered silicon carbide cylinder. It will be appreciated
that the schedule may be varied to take into account various factors such as the particular
binder used, the proportion of binder present, the distribution of silicon carbide particles,
and so on. In particular, care should be taken when adjusting the target set points and
durations so that the water content of the binder is kept at a level which facilitates
formation of the ceramic bond. If the kiln temperature is raised too y, water in the
binder can be boiled out too quickly, thus compromising the strength of the finished
cylinder.
H:\m7.i\lmu'wovcuWRPonleCCWIZM002889} .doc-S/US/ZOI 6
_13_
Testing ainment vessels
Two silicon e containment vessels were fabricated according to the procedure
described above. 18 kg of silicon metalloid ingots were placed in each vessel and the
vessels then compacted in sintered graphite inside a n carbide muffle in a gas-fired
industrial kiln. The vessels were sealed using a refractory mortar having similar
composition to the material of the vessel, with the assistance of a phosphate binder. We
have also found from further testing that the ate binder may be omitted whilst still
achieving satisfactory results.
A type R thermocouple was placed inside the sintered te to monitor core
temperature.
Once inside the kiln, the vessels were purged with argon gas, and lids fitted to each vessel.
A kiln firing sequence was then ted to raise the kiln temperature to above 1410
degrees C, the melting temperature of the silicon metalloid. The maximum kiln
temperature used in the firing sequence was 1480 degrees C.
The kiln temperature and core temperature as a function of time are shown in Figure 10.
The kiln ature curve 502 is ed as a dotted line, and core temperature curve
602 as a solid line.
The kiln was initially fired such that its temperature increased 503 rapidly towards a peak
value of 1480 degrees C. The core temperature also increased 603 at a similar rate as the
silicon metalloid ed energy as sensible heat, until the core temperature reached 1410
degrees C, the melting point of the silicon metalloid. The kiln temperature was then
maintained 504 at 1480 degrees C. The core temperature remained 604 at 1410 degrees C,
indicating that energy was being absorbed as latent heat. This continued until the core
temperature began 605 to rise again, indicating that a melt fraction of 100% for the silicon
metalloid had been achieved.
The kiln was then cooled 505 and then refired 506 towards a target temperature of 1480
degrees C. As a result of the cooling, the core temperature fell 606 and then rose again
towards 1410 degrees C as a result of increasing kiln temperature, indicating a return to
sensible heat absorption by the n metalloid. The core temperature ed 607 at
1410 degrees C while the kiln temperature was maintained 507 at 1480 s C. The
core ature eventually rose 608 again, once again indicating that a 100% melt
fraction had been achieved.
Multiple cycles of heating and cooling were carried out in similar fashion to the above.
The containment s were then removed from the muffle and inspected. It was found
that the vessels had not suffered any damage as a result of the repeated cycles of heating
and cooling.
Many modifications of the above embodiments will be apparent to those skilled in the art
without departing from the scope of the present invention.
hout this specification, unless the context requires otherwise, the word "comprise",
and variations such as "comprises" and "comprising", will be understood to imply the
inclusion of a stated integer or step or group of integers or steps but not the exclusion of
any other integer or step or group of integers or steps.
THE
Claims (12)
- l. A l energy storage apparatus, including: a block of a heat-absorbing material, the block being a contiguous block of 5 compressed material in the form of sintered graphite and machinable; and a plurality of heat storage elements, the heat storage elements ing a phase change material stored in a containment vessel; wherein each heat storage element is in thermal contact with the block of heat- absorbing material, each storage element being received in a tive hole 10 machined in the block.
- 2. A thermal energy storage apparatus according to claim 1, wherein the block of heat-absorbing material includes a heat e region having a first plurality of holes formed therein, the heat storage elements being seated in respective ones of 15 said holes.
- 3. A thermal energy storage apparatus according to claim 1 or claim 2, wherein the holes are formed with predetermined intervals therebetween. 20
- 4. A thermal energy e apparatus according to claim 3, wherein the predetermined intervals are chosen to optimise heat transport in the heat e region.
- 5. A thermal energy e apparatus according to any one of the preceding claims, 25 r including one or more heating elements in thermal contact with the heat storage region.
- 6. A thermal energy storage apparatus according to claim 5, wherein the one or more heating elements are seated in a second plurality of holes in the heat storage region.
- 7. A thermal energy storage apparatus ing to claim 5 or claim 8, wherein the H:\pl\\\Iulcmorcn\NRPonbl\DCC\.PL\V\. l Ul)‘)};5‘)2_ l ,doc-S/US/Ztl 16 —l6- heating elements are electric g ts.
- A thermal energy storage apparatus ing to any one of claims 5 to 7, wherein the heating elements are individually controllable to supply different amounts of heat to different areas of the heat storage region.
- A thermal energy e apparatus according to claim 8, further including one or more temperature sensors associated with each of the different areas of the heat storage region.
- 10. A thermal energy storage apparatus according to any one of the preceding claims, further including means for ting heat from the heat storage elements.
- 11. A l energy storage apparatus according to claim 10, wherein the means for 15 extracting heat is a closed—cycle heat engine coupled to the heat storage region.
- 12. A thermal energy storage apparatus ing to claim 11, wherein the closed— cycle heat engine is a Stirling engine, and the Stirling engine is coupled to the heat storage region Via a wick. . A thermal energy storage apparatus according to any one of the preceding claims, wherein the phase change material includes silicon metalloid or a eutectic, hypereutectic or hypoeutectic silicon composition. 25 l4. A l energy storage apparatus ntially as hereinbefore described with reference to the accompanying drawings. 102 /
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201161521487P | 2011-08-09 | 2011-08-09 | |
US61/521,487 | 2011-08-09 | ||
PCT/AU2012/000938 WO2013020176A1 (en) | 2011-08-09 | 2012-08-09 | Thermal energy storage apparatus |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ620848A NZ620848A (en) | 2016-06-24 |
NZ620848B2 true NZ620848B2 (en) | 2016-09-27 |
Family
ID=
Similar Documents
Publication | Publication Date | Title |
---|---|---|
AU2012292959B2 (en) | Thermal energy storage apparatus | |
Li et al. | Properties enhancement of phase-change materials via silica and Al honeycomb panels for the thermal management of LiFeO4 batteries | |
Li et al. | Preparation of novel copper-powder-sintered frame/paraffin form-stable phase change materials with extremely high thermal conductivity | |
EP1730460B1 (en) | Method and apparatus for storing heat energy | |
AU2018262109B2 (en) | Thermal energy storage apparatus | |
Sharaf et al. | Year-round energy and exergy performance investigation of a photovoltaic panel coupled with metal foam/phase change material composite | |
Fraas | Economic potential for thermophotovoltaic electric power generation in the steel industry | |
Naplocha et al. | Effects of cellular metals on the performances and durability of composite heat storage systems | |
Wani et al. | A review of phase change materials as an alternative for solar thermal energy storage | |
Reid et al. | Computational evaluation of a latent heat energy storage system | |
NZ620848B2 (en) | Thermal energy storage apparatus | |
McClelland et al. | End‐point density of hot‐pressed alumina | |
JP6042888B6 (en) | Heat storage device | |
Mao et al. | Enhancement of power generation of thermoelectric generator using phase change material | |
EP3942240A1 (en) | An energy conversion, storage and retrieval device and method | |
Gokon et al. | Thermal storage/discharge performances of Cu-Si alloy for solar thermochemical process | |
Sharaf et al. | Efficiency Enhancement of Photovoltaic Module Using An Aluminum Foam Matrix Filled With Phase Change Material (PCM) Under Hot Climate Conditions | |
Boubou et al. | ASSESSMENT OF DIFFERENT SANDS POTENTIALITY TO FORMULATE AN EFFECTIVE THERMAL ENERGY STORAGE MATERIAL (TESM). | |
CN104236358B (en) | Detector phase change material device | |
Kubatík et al. | Compaction of lithium-silicate ceramics using spark plasma sintering | |
YAZICI | The Effect of Phase Change Temperature of Graphite Matrix Composite on Small-Scale Li-Ion Package Performance Under Square Wave Load | |
Nilsson et al. | Zone Plates for Hard X‐Ray FEL Radiation | |
Dalle Donne et al. | Research and development work for the lithium orthosilicate pebbles for the Karlsruhe ceramic breeder blanket | |
Li et al. | Preparation and performance improvement of phase change materials with Skin-Flesh structure inspired by loofah | |
Jin et al. | Study on fabrication technology and melting heat transfer process of salt/ceramic composite phase change energy storage materials |