U.S. patent application number 14/814644 was filed with the patent office on 2017-02-02 for thermal energy storage facility having functions of heat storage and heat release.
The applicant listed for this patent is SFI Electronics Technology Inc.. Invention is credited to Kuang-Hsin CHU, Ching-Hohn LIEN.
Application Number | 20170030656 14/814644 |
Document ID | / |
Family ID | 57882380 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170030656 |
Kind Code |
A1 |
LIEN; Ching-Hohn ; et
al. |
February 2, 2017 |
THERMAL ENERGY STORAGE FACILITY HAVING FUNCTIONS OF HEAT STORAGE
AND HEAT RELEASE
Abstract
A thermal energy storage facility for use in heat storage and
heat release comprises a heat storage/release mechanism constituted
by multiple heat storage/heat exchange units stacked up, each unit
at least comprises a heat storage board having parallel grooves for
loading phase-change material (PCM) therein and a heat exchange
plate having micro-channel groups for heat transfer fluid (HTF)
flowed through to exchange heat with the PCM; particularly two or
more the thermal energy storage facilities can be worked together
by combination in series or/and in parallel to input of thermal
energy, absorption of thermal energy and both simultaneously from
the PCM, and the thermal energy storage facility capably operating
at a heat storage temperature higher than 1200.degree. C. is suited
for use in solar thermal power generation system to improve overall
efficiency of solar thermal power to reach 35-40%.
Inventors: |
LIEN; Ching-Hohn; (Taoyuan
County, TW) ; CHU; Kuang-Hsin; (New Taipei City,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SFI Electronics Technology Inc. |
Taoyuan County |
|
TW |
|
|
Family ID: |
57882380 |
Appl. No.: |
14/814644 |
Filed: |
July 31, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28D 9/0081 20130101;
F28D 9/0062 20130101; Y02E 70/30 20130101; F28D 2020/0082 20130101;
F28D 20/021 20130101; Y02E 60/145 20130101; Y02E 60/14 20130101;
F28D 9/0093 20130101; F28D 2020/0047 20130101; F28D 2020/0008
20130101; F28D 2020/0013 20130101 |
International
Class: |
F28D 20/02 20060101
F28D020/02; F24J 2/34 20060101 F24J002/34 |
Claims
1. A thermal energy storage facility having functions of heat
storage, heat release and both, using a phase-change material (PCM)
for storing heat and releasing heat, comprising a thermal effect
mechanism and at least two convergence-divergence hoods, wherein
the improvement comprises: the thermal effect mechanism comprises
an external framework functioning as a rigid framework of the
thermal effect mechanism; and a heat storage/release mechanism
hermetically sealed by the external framework and comprising
multiple heat storage/heat exchange units stacked up, each heat
storage/heat exchange unit comprises a heat storage board and a
heat exchange plate stacked up, wherein the heat storage board has
a plurality of parallel grooves for loading the PCM therein, and
the heat exchange plate has one or more micro-channel groups
functioning as a passage of a heat transfer fluid (HTF), each
micro-channel group comprises multiple micro-channel units arranged
in parallel to allow the HTF when passed through to exchange heat
with the PCM of the heat storage board; and the
convergence-divergence hoods each comprise a hollow-core cavity
disposed outside the heat storage/release mechanism of the thermal
effect mechanism and adapted to conceal inlet ends and outlet ends
of micro-channel groups of each said heat storage/heat exchange
unit of the heat storage/release mechanism; and a pipe
communicating with the hollow-core cavity for feeding or
discharging the HTF.
2. The thermal energy storage facility as described in claim 1,
wherein the heat storage boards of the heat storage/heat exchange
units are of a thickness T1 of 5-20 mm, and wherein the grooves of
the heat storage boards are of a bottom thickness T2 of 0.3-3 mm, a
groove width T3 of 5-20 mm, and a groove-to-groove spacing T4 of
0.3-3 mm.
3. The thermal energy storage facility as described in claim 1,
wherein the heat exchange plate has two spaced-apart Z-shaped
micro-channel groups.
4. The thermal energy storage facility as described in claim 2,
wherein the heat exchange plates of the heat storage/heat exchange
units are of a thickness of 1-4 mm.
5. The thermal energy storage facility as described in claim 2,
wherein the micro-channel units of the micro-channel groups of the
heat exchange plates are of a channel depth of 0.5-1.5 mm, a
channel width of 1.0-3.0 mm and a wall thickness of 0.3-1.5 mm
between every two adjacent micro-channel units.
6. The thermal energy storage facility as described in claim 2,
wherein the micro-channel unit of the heat exchange plate is shaped
as a semicircular having a diameter of 1.0-3.0 mm.
7. The thermal energy storage facility as described in claim 1,
wherein the PCM is one or more molten salts selected from the group
consisting of Li.sub.2CO.sub.3, LiF, NaF, KF, MgF.sub.2, CaF.sub.2,
CaO, mixture of 46.5% LiF/11.5% NaF/42% KF, mixture of 80.5%
LiF/19.5% CaF.sub.2 and mixture of 66.3% NaNO.sub.3/33.7%
KNO.sub.3, afore clamed PCMs materials in combination with graphite
form, afore clamed PCMs encapsules.
8. The thermal energy storage facility as described in claim 6,
wherein the PCM further contains graphite or metal added.
9. The thermal energy storage facility as described in claim 6,
wherein the thermal energy storage facility operates at a heat
storage temperature equal to or higher than of 1000.degree. C.
10. The thermal energy storage facility as described in claim 6,
wherein the thermal energy storage facility operates at a heat
storage temperature ranged from 700.degree. C. to 1500.degree.
C.
11. The thermal energy storage facility as described in claim 6,
wherein the thermal energy storage facility operates at a heat
storage temperature higher than 1500.degree. C.
12. A large-scale thermal energy storage facility for use in a
solar power generation system to effectuate thermal energy storage,
comprising two or more thermal energy storage facilities of claim 1
are connected in parallel, connected in series or connected by a
combination of both.
Description
BACKGROUND OF THE PRESENT INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to thermal energy storage
facilities, and more particularly to thermal energy storage
facilities having functions of heat storage and heat release and
suited for increasing the efficiency of solar power generation
system.
[0003] 2. Description of Related Art
[0004] Electrical power can be continuously generated by a solar
power generation process in combination with a thermal energy
storage system. The solar power plants collect solar energy and
store part of the solar-derived thermal energy in thermal energy
storage systems, to generate electrical power continuously through
day and night, or during cloudy and rainy periods. Hence, solar
power is presently one of the most promising renewable energy
resources. In this regard, thermal energy storage technology is
crucial to solar power generation. According to the prior art,
solar-derived thermal energy storage is typically implemented by
one of the three following materials: a sensible heat storage
material, a latent heat storage material, and a thermochemical
reaction-based heat storage material.
[0005] Solar power generation most often requires the sensible heat
storage material in the presence of a molten salt which has a
melting point of 221.degree. C. and comprises 66.3% NaNO.sub.3 and
33.7% KNO.sub.3. However, the currently conventional molten salts
solar heat storage systems, only use the sensible heat of molten
salts. The molten salt also served as heat transfer fluids
(hereinafter referred to as the HTF).
[0006] Thus, the conventional molten salts solar thermal energy
storage systems use only the sensible heat of the molten salts.
Resulted in the HTF has drawbacks as follows: [0007] 1. The
sensible heat molten salts freeze and solidify at low temperature,
thereby clogging a pipe; and [0008] 2. The sensible heat molten
salts may undergo decomposition and degradation at high temperature
and thus corrodes metallic pipes.
[0009] To avoid clog and corrosion of metallic pipes, the sensible
heat molten salts HTF used in a solar power generation system has
to operate from 290.degree. C. to 565.degree. C., and thus
inevitably leads to the following limitations: [0010] 1. The heat
storage temperature of the solar power generation system ranges
from 290.degree. C. to 565.degree. C. only; [0011] 2. in
consequence the thermal energy released from the solar power
generation system can bring about steam of a maximum temperature
less than 565.degree. C.; and [0012] 3. Since the steam temperature
cannot be higher than 600.degree. C., the steam turbine efficiency
will be less than 34%. The sensible heat molten salts HTF is
conventionally in conjunction with tube solar receivers, which are
made of vertical metallic pipes. Subject to the limitation on
thermal stress of the metallic pipes, the maximum intensity of
sunlight concentrated by the tube solar receivers, equal to the
irradiation intensity of a few hundreds of the Suns and thus the
overall receiver efficiency achieved is just 57%. The overall solar
power generation efficiency of the solar power generation system
equals 19.5% (=0.57.times.0.34), i.e., less than 20%.
[0013] Latent heat is energy absorbed or released by materials
during phase transition. A phase-change material (hereinafter
referred to as the PCM) is a latent heat storage material
characterized by a large heat of fusion. The PCM effectuates heat
storage by absorbing and releasing heat at constant temperature
during phase transition, such as phase changed from solid state to
liquid state to gas state, or reversibly. At a phase-transition
temperature, the PCM absorbs heat when melting, and releases heat
when solidifying, without significant change of temperature.
Therefore, the PCM is capable of storing and releasing a large
amount of thermal energy.
[0014] At low temperature, the PCM is in the solid state and thus
unable to function directly as the HTF in the solar power
generation system; as a result, a solar power generation system
which relies upon a latent heat storage material is confronted with
intricate design of a heat storage and heat release system.
However, latent heat storage materials have much higher latent heat
storage density than sensible heat storage materials and thus are
more advantageous than sensible heat storage materials in terms of
heat storage level and volume.
[0015] The higher the power generation system temperature, the
higher is the solar power generation efficiency of the solar power
generation system. High-temperature PCM heat storage system, can
link with a volume solar receiver, with a gas HTF, such as air or
supercritical CO2. The maximum intensity of sunlight concentrated
by the volume receivers may equal to the irradiation intensity of
more than a thousand of the Suns. The efficiency of volume solar
heat receiver can be 70-80%, and can achieve a maximum temperature
of 1200.degree. C. The heat released can be used to heat up gas fed
into a gas turbine and thus drive a gas turbine combined cycle
generator. The waste heat of gas discharged from the gas turbine
still reaches 600.degree. C., can be used to drive a steam turbine
to achieve an overall power generation efficiency of 50%. The solar
power generation system will achieve an overall solar power
generation efficiency of 35-40% (=0.7.times.0.5-0.8.times.0.5).
Thus, when a combined power block combined with a high-temperature
heat storage device. Overall efficiency of 50% can be achieved
constantly, and can be served as a base load power cycle.
[0016] Hence, the solar power generation efficiency is enhanced by
developing a heat storage device which uses a latent heat storage
material and features high heat storage level, high heat storage
temperature, withstand to high HTF pressure, and high efficiency of
heat storage/heat release heat exchange.
[0017] According to the prior arts, a heat storage facility with
multi-channel PCM heat storage boards stacked alternately with
printed circuit heat exchanger (abbreviated as the PCHE) plates,
was developed. In order to achieve high heat storage, high heat
exchange efficiency and can withstand high HTF pressure.
[0018] Referring to FIG. 1, a conventional micro-channel heat
exchanger 90 comprises multiple heat exchange units 91 stacked up.
The heat exchange units 91 each comprise a first heat exchange
plate 93 and a second heat exchange plate 95. The first heat
exchange plates 93 and the second heat exchange plates 95 are
stacked up, coupled together by diffusion bonded, and arranged in a
manner that the first heat exchange plate 93 alternates with the
second heat exchange plate 95. A plurality of first micro-channels
94 is disposed on the surface of each of the first heat exchange
plates 93 to function as passages of a heat transfer fluid F1. A
plurality of second micro-channels 96 is disposed on the surface of
each of the second heat exchange plates 95. The second
micro-channels 96 of the second heat exchange plates 95 cross the
first micro-channels 94 of the first heat exchange plates 93 at 90
degrees and function as passages of a heat transfer fluid F2. When
the heat transfer fluid F1 passes through the first micro-channels
94, the heat transfer fluid F1 undergoes heat exchange, at high
heat transfer speed, with the heat transfer fluid F2 which passes
through the second micro-channels 96 in a manner that the direction
of the flow of the heat transfer fluid F1 crosses the direction of
the flow of the heat transfer fluid F2 at 90 degrees.
[0019] The aforesaid technical features of the micro-channel heat
exchanger 90, coupled with the first heat exchange plate 93 or the
second heat exchange plate 95 which is very thin and serves to
space apart the first micro-channels 94 and the second
micro-channels 96, achieve a heat exchange efficiency of 94%.
[0020] Both the micro-channel heat exchanger and the PCHE exhibit
high heat transfer rate, high heat exchange efficiency and
withstand high pressure but are not capable of heat storage.
SUMMARY OF THE INVENTION
[0021] In view of the aforesaid drawbacks of the prior art, the
motive of the present invention is to couple together a
conventional micro-channel heat exchanger (or PCHE) and latent heat
storage material to thereby build a thermal energy storage facility
at least having functions of both heat storage and heat
release.
[0022] The primary objective of the present invention is to provide
a thermal energy storage facility using a latent heat storage
material and having functions of both heat storage and heat
release, characterized in that: the thermal energy storage facility
is a single block, or multiple blocks of thermal energy storage
facilities are connected in parallel, connected in series, or
connected by a combination of parallel connection and series
connection, to be applied to a solar power generation system to
effectuate thermal energy storage; thermal energy from the volume
solar receivers is absorbed by air or the other HTF; and operate in
conjunction with a gas turbine combined cycle generator. Hence, the
thermal energy storage facility of the present invention is
conducive to increasing the overall solar power generation
efficiency to 35-40%.
[0023] The thermal energy storage facility comprises a thermal
effect mechanism and at least two convergence-divergence hoods. The
thermal effect mechanism further comprises an external framework
and a heat storage and heat release mechanism. The external
framework forms a rigid framework of the thermal effect mechanism
and contains the heat storage/release mechanism. The heat
storage/release mechanism comprises multiple heat storage/heat
exchange units stacked up. The heat storage/heat exchange units
each comprise a heat storage board and a heat exchange plate
stacked up. The heat storage board has a plurality of parallel
grooves for holding therein the PCM. The heat exchange plate has at
least one micro-channel group, preferably two spaced-apart Z-shaped
micro-channel groups functioning as passages of the HTF. The
micro-channel groups each comprise multiple micro-channel units
arranged in parallel such that the HTF passing through the heat
exchange plate exchanges heat with the PCM of the heat storage
board.
[0024] The convergence-divergence hoods each comprise a hollow-core
cavity and a pipe, wherein the hollow-core cavities are disposed
outside the heat storage/release mechanism of the thermal effect
mechanism and adapted to conceal inlet ends and outlet ends of
micro-channel groups of each said heat storage/heat exchange unit
of the heat storage/release mechanism, with the pipe communicating
with the hollow-core cavity and functioning as the pipe for feeding
or discharging the HTF.
[0025] The heat storage boards of the heat storage/heat exchange
units are of a thickness T1 of 5-20 mm. The parallel grooves are of
a bottom thickness T2 of 0.3-3 mm and a groove width T3 of 5-20 mm.
Every two adjacent ones of the grooves are separated by a
groove-to-groove spacing T4 of 0.3-3 mm.
[0026] The heat exchange plates of the heat storage/heat exchange
units are of a thickness of 1-4 mm. The micro-channel units of the
micro-channel groups are of a channel depth of 0.5-1.5 mm and a
channel width of 1.0-3.0 mm. The least wall thickness between every
two adjacent micro-channel units is 0.3-1.5 mm. Preferably, each
micro-channel unit of the micro-channel groups is shaped as a
semicircular having a diameter of 1.0-3.0 mm.
[0027] The PCM is selectively a molten salt of a mixture of
Li.sub.2CO.sub.3, LiF, NaF, KF, MgF.sub.2, CaF.sub.2, CaO, 46.5%
LiF/11.5% NaF/42% KF, a molten salt of a mixture of 80.5% LiF/19.5%
CaF.sub.2, or a molten salt of a mixture of 66.3% NaNO.sub.3/33.7%
KNO.sub.3. Preferably, graphite or metal is added to the PCM.
[0028] The thermal energy storage facility operates at a heat
storage temperature of 1000.degree. C. or higher, preferably
1200.degree. C.-1500.degree. C., and most preferably 1500.degree.
C. or higher, in order to effectuate thermal energy storage in the
solar power generation system.
[0029] Advantages of the thermal energy storage facility of the
present invention are as follows: [0030] 1. The thermal energy
storage facility is capable of input of thermal energy, absorption
of thermal energy and both simultaneously. [0031] 2. The thermal
energy storage facility uses a latent heat storage material and is
capable of heat storage and heat release to thereby overcome a
drawback of the prior art, that is, both conventional micro-channel
heat exchanger and PCHE are not capable of heat storage. [0032] 3.
The thermal energy storage facility is standalone, or the thermal
energy storage facilities are connected in parallel, connected in
series, or connected by a combination of parallel connection and
series connection, operated at a heat storage temperature of
1200.degree. C. or higher, and applied to the solar power
generation system to effectuate thermal energy storage. Hence, the
thermal energy storage facility is conducive to increasing the
overall solar power generation efficiency to 35-40%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a schematic view of a prior conventional
micro-channel heat exchanger;
[0034] FIG. 2 is a schematic view of a thermal energy storage
facility having functions of heat storage and heat exchange
according to the present invention;
[0035] FIG. 3 is a cutaway view of the thermal energy storage
facility of FIG. 2;
[0036] FIG. 4 includes an exploded view and partial enlarged
cross-sectional views of a heat storage/release mechanism and heat
storage/heat exchange units of the thermal energy storage facility
of FIG. 2; and
[0037] FIG. 5 is a schematic view of a large-scale thermal energy
storage system comprising two or more thermal energy storage
facilities of FIG. 2 connected in parallel or in series.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Referring to from FIG. 2 to FIG. 4, a thermal energy storage
facility 10 of the present invention exhibits heat storage
efficiency of 94% or higher and heat storage temperature of
1200.degree. C. or higher and comprises a thermal effect mechanism
15 and at least two (that is, two, four or multiple)
convergence-divergence hoods 70.
[0039] The thermal effect mechanism 15 comprises an external
framework 20 and a heat storage/release mechanism 30. In an
embodiment of the present invention, the infrastructure of the
thermal effect mechanism 15 includes a metallic material which is
resistant to high temperature such that the thermal effect
mechanism 15 is can withstand atmospheric pressure of 500-1000 atm
at 900.degree. C.
[0040] The external framework 20 comprises a top panel 21, a bottom
panel 22, a front panel 23 and a rear panel 24 which together form
a rigid framework of the thermal effect mechanism 15. In an
embodiment of the present invention, the thermal effect mechanism
15 comprises the external framework 20 and the heat storage/release
mechanism 30 and allows the heat storage/release mechanism 30 to be
hermetically sealed and thus disposed inside the external framework
20.
[0041] The external framework 20 is made of a metallic material
good at thermal insulation and resistant to high temperature. It is
also feasible for the external framework 20 to be made of a
sensible heat storage material in order to enhance the heat storage
heat release capability of the thermal effect mechanism 15. Upon
the production of the external framework 20, it is enclosed by a
thermally insulating material.
[0042] Referring to FIG. 3 and FIG. 4, the heat storage/release
mechanism 30 comprises multiple heat storage/heat exchange units 40
which are stacked up and alternate with each other. The heat
storage/heat exchange units 40 each comprise a heat storage board
50 and a heat exchange plate 60 which are stacked up and form a
block unit by a pressing process.
[0043] The heat storage board 50 is made of a sensible heat storage
material and has a plurality of parallel grooves 52. The heat
storage board 50 is of a thickness T1 of 5-20 mm. The grooves 52
are of a bottom thickness T2 of 0.3-3 mm and a groove width T3 of
5-20 mm. Every two adjacent ones of the grooves 52 are separated by
a groove-to-groove spacing T4 of 0.3-3 mm.
[0044] The two ends of each of the grooves 52 of the heat storage
board 50 are closed or open. The two ends of each of the grooves 52
are hermetically sealed with the top panel 21 and the bottom panel
22 of the external framework 20.
[0045] Further referring to FIG. 4, the opening of each of the
grooves 52 of the heat storage board 50 is hermetically sealed with
the other heat storage/heat exchange unit 40 which is stacked
alternately by a diffusion bonding process. The outermost heat
storage/heat exchange unit(s) 40 use the front panel 23 or the rear
panel 24 of the external framework 20 to hermetically seal the
opening of each of the grooves 52.
[0046] Therefore, the PCM is placed inside each groove 52 of the
heat storage board 50 so that the heat storage board 50 is capable
of heat storage and heat release. The PCM is selectively a molten
salt of a mixture of Li.sub.2CO.sub.3, LiF, NaF, KF, MgF.sub.2,
CaF.sub.2, CaO, 46.5% LiF/11.5% NaF/42% KF, 80.5% LiF/19.5%
CaF.sub.2 or a molten salt of a mixture of 66.3% NaNO.sub.3/33.7%
KNO.sub.3. To augment the coefficient of thermal conductivity of
the PCM, a material with high coefficient of thermal conductivity,
such as graphite or metal, is added to the PCM as appropriate.
[0047] Referring to FIG. 4, the heat exchange plate 60 is of a
thickness of 1-4 mm and is made of a sensible heat storage
material. At least one (including one, two or multiple)
micro-channel group 62 is disposed on one side of the heat exchange
plate 60. Preferably, two spaced-apart Z-shaped micro-channel
groups 62 are disposed on one side of the heat exchange plate 60.
The micro-channel groups 62 each comprise multiple micro-channel
units 63 arranged in parallel. The channel cross-sections of the
micro-channel units 63 are of any appropriate shape and are,
preferably, characterized by a channel depth of 0.5-1.5 mm and a
channel width of 1.0-3.0 mm, wherein the least wall thickness
between every two adjacent ones of the micro-channel units 63 is
0.3-1.5 mm. Preferably, the micro-channel unit 63 is shaped as a
semicircular having a diameter of 1.0-3.0 mm.
[0048] Referring to FIG. 3, the convergence-divergence hoods 70
each have a hollow-core cavity 71 and a pipe 72 in communication
with the hollow-core cavity 71. The convergence-divergence hoods 70
are disposed outside the heat storage/release mechanism 30 of the
thermal effect mechanism 15. The hollow-core cavities 71 of the
convergence-divergence hoods 70 conceal inlet ends and outlet ends
of the micro-channel groups 62 of each heat storage/heat exchange
unit 40 of the heat storage/release mechanism 30 thoroughly.
[0049] Referring to FIG. 5, when the convergence-divergence hoods
70 are disposed at the inlet ends for concealing the micro-channel
groups 62, the pipes 72 of the convergence-divergence hoods 70
function as a feed pipe 73 of the HTF. Likewise, when the
convergence-divergence hoods 70 are disposed at the outlet ends for
concealing the micro-channel groups 62, the pipes 72 of the
convergence-divergence hoods 70 function as a discharge pipe 74 of
the HTF.
[0050] Referring to from FIG. 2 to FIG. 5, the inlet ends and
outlet ends of the micro-channel groups 62 of the heat exchange
plate 60 are only connected to the convergence-divergence hoods 70,
respectively, to form self-contained channels.
[0051] Referring to FIG. 5, in practice the thermal energy storage
facility 10 of the present invention is optionally allowed either a
high-temperature homogenous HTF or a low-temperature homogenous HTF
to enter the feed pipe 73 of all the convergence-divergence hoods
70. In another embodiment, the thermal energy storage facility 10
of the present invention is also optionally allowed a
high-temperature homogenous or heterogeneous HTF and/or a
low-temperature homogenous or heterogeneous HTF to respectively
enter the feed pipe 73 of two or more different
convergence-divergence hoods 70 simultaneously.
[0052] After the homogenous and/or heterogeneous HTF provided with
high or low temperature entered the feed pipe 73 of all the
convergence-divergence hoods 70, the HTF goes from the hollow-core
cavities 71 of the convergence-divergence hoods 70 to the
micro-channel groups 62 of the heat storage/heat exchange units 40,
undergoes thermal conduction-based heat exchange with the PCM
placed inside each groove 52 of the heat storage board 50 of the
heat storage/heat exchange units 40, exits the outlet ends of the
micro-channel groups 62, then passes through the hollow-core
cavities 71 which conceal the outlet ends of the micro-channel
groups 62, and is eventually discharged from the discharge pipes 74
of the convergence-divergence hoods 70.
[0053] Hence, according to the present invention, the micro-channel
groups 62 of the thermal energy storage facility 10 are either
fully used to input of thermal energy transmitted heat from HTF to
PCM or fully used to absorption of thermal energy transmitted heat
from PCM to HTF. Alternatively, according to the present invention,
one of two or more different micro-channel groups 62 of the thermal
energy storage facility 10 is further used to input of thermal
energy and the rest are used to absorption of thermal energy
simultaneously.
[0054] Accordingly, the thermal energy storage facility 10 of the
present invention in use therefore has basic functions capable of
heat storage, heat release and both simultaneously.
[0055] More detailed speaking, after the HTF has been heated up
with concentrated solar energy, the passage of the high-temperature
HTF through the micro-channel units 63 of the micro-channel groups
62 is accompanied by the process of transferring (by heat
conduction) the thermal energy to the PCM disposed at the heat
storage board 50. Conversely, the passage of the low-temperature
HTF through the micro-channel units 63 of the micro-channel groups
62 is accompanied by the process of absorbing (by heat conduction)
the heat extract released from the PCM of the heat storage board 50
to thereby effectuate heating.
[0056] When passing through the micro-channel groups 62 of the heat
exchange plate 60 of each heat storage/heat exchange unit 40, the
HTF is only separated from the PCM of the heat storage board 50 of
each heat storage/heat exchange unit 40 by a thin wall to enable
heat exchange to take place therebetween. Hence, the thermal energy
storage facility 10 of the present invention has a high heat
transfer efficiency, exhibits a heat storage efficiency of 92% or
higher, and achieves a heat storage temperature of 1000.degree. C.
or higher, preferably a heat storage efficiency of 94% or higher, a
heat storage temperature of 1200.degree. C.-1500.degree. C., most
preferably a heat storage efficiency of 99% or higher and a heat
storage temperature of 1500.degree. C. or higher, which are much
higher than the 80% heat storage efficiency of a conventional heat
storage device operating in conjunction with a conventional
shell-and-tube heat exchanger.
[0057] Referring to FIG. 5, the discharge pipe 74 of a thermal
energy storage facility 10 and the feed pipe 73 of another thermal
energy storage facility 10 are connected in series. By analogy,
multiple thermal energy storage facilities 10 of the same
specification are connected in series to form a large-scale thermal
energy storage facility.
[0058] Likewise the feed pipes 73 of two thermal energy storage
facilities 10 are connected in parallel, and the corresponding
discharge pipes 74 of the two thermal energy storage facilities 10
are connected in parallel. By analogy, multiple thermal energy
storage facilities 10 of the same specification are connected in
parallel to form another kind of a large-scale thermal energy
storage facility. Furthermore, the thermal energy storage
facilities 10 are connected by a combination of parallel connection
and series connection to further form another kind of a large-scale
thermal energy storage facility. Hence, according to the present
invention, multiple thermal energy storage facilities 10 of the
same specification can be connected in parallel, or connected in
series, or connected by a combination of parallel connection and
series connection.
[0059] The thermal energy storage facility 10 of the present
invention not only uses the PCM of the thermal effect mechanism 15
to effectuate heat storage, but also uses the infrastructure of the
thermal effect mechanism 15 further made of a sensible heat storage
material to enhance an additional heat storage.
EMBODIMENT
[0060] The embodiments below illustrate the thermal energy storage
facility 10 having functions of heat storage and heat release
according to the present invention and applied to the solar power
generation system for thermal energy storage to achieve an overall
solar power generation efficiency of 35-40%.
Embodiment 1
[0061] The thermal energy storage facility 10 of FIG. 2 is produced
and configured to resist pressure of at least 500 atm and has the
highest operating temperature of 1095.degree. C. and the lowest
operating temperature of 565.degree. C., with further details
provided below.
TABLE-US-00001 volume (width .times. depth .times. = 65.32 cm
.times. 64.4 cm .times. 103 cm = 433 L length) of thermal effect
mechanism 15 volume of PCM = 60 cm .times. 50 cm .times. 103 cm =
309 L accounts for 71.4% of volume of thermal effect mechanism 15
volume of structure of = 433 L - 309 L = 124 L thermal effect
accounts for 28.6% of volume of thermal mechanism 15 effect
mechanism 15
[0062] The PCM is NaF which has a melting point of 996.degree. C.,
density of 2780 kg/m.sup.3, specific heat of 3.336
MJ/m.sup.3.degree. C., latent heat (996.degree. C.) of 2208
MJ/m.sup.3, where M is 10.sup.6.
[0063] The structure (infrastructure) of the thermal effect
mechanism 15 is made of INCONEL 600 alloy which is resistant to a
maximum temperature of 1095.degree. C. and has a density of 8470
kg/m.sup.3 and specific heat of 5.32 MJ/m.sup.3.degree. C., where M
is 10.sup.6.
[0064] At an operating temperature of 565.degree. C.-1095.degree.
C., heat storage level per cubic meter (m.sup.3) of the thermal
energy storage facility 10 in this embodiment equals the sum of
three heat levels as follows: 1262 MJ+1577 MJ+806 MJ=3645 MJ.
TABLE-US-00002 sensible heat of PCM = 0.714 m.sup.3 .times. 3.336
MJ/m.sup.3.degree. C. .times. (1095-565) .degree. C. = 1262 MJ
latent heat = 0.714 m.sup.3 .times. 2208 MJ/m.sup.3 (996.degree.
C.) of PCM = 1577 MJ sensible heat of = 0.286 m.sup.3 .times. 5.32
MJ/m.sup.3.degree. C. .times. (1095-565) .degree. C. structure of
thermal = 806 MJ effect mechanism 15
Embodiment 2
[0065] The thermal energy storage facility 10 of embodiment 1 is
applied to the solar power generation system and coupled to the
volume-dependent solar receivers and supercritical CO.sub.2 gas
turbine generator.
[0066] The high-temperature HTF F1 of the volume-dependent solar
receivers passes through a Z-shaped micro-channel of the thermal
energy storage facility 10 to thereby store thermal energy in the
PCM of the thermal energy storage facility 10.
[0067] A supercritical CO.sub.2 working fluid F2 which operates at
a pressure of 199.7 Bar, and another Z-shaped micro-channel passing
through the thermal energy storage facility 10 takes up the thermal
energy of the PCM of thermal energy storage facility 10, so as to
drive the supercritical CO.sub.2 gas turbine generator when the
temperature reaches 485.8.degree. C.
[0068] The efficiency of the supercritical CO.sub.2 gas turbine
generator is 44.2%. The efficiency of the volume-dependent solar
receivers is 80%. The overall efficiency of the solar power
generation system is 35.4%.
Embodiment 3
[0069] The thermal energy storage facility 10 of FIG. 2 is produced
and configured to resist pressure of at least 500 atm and has the
highest operating temperature of 1500.degree. C. and the lowest
operating temperature of 1200.degree. C., with further details
provided below.
TABLE-US-00003 volume (width .times. depth .times. = 65.32 cm
.times. 83.07 cm .times. 103 cm = 558.9 L length) of thermal effect
mechanism 15 volume of PCM = 60 cm .times. 51 cm .times. 103 cm =
315.2 L accounts for 56.4% of volume of thermal effect mechanism 15
volume of structure = 558.9 L - 315.2 L = 243.7 L of thermal effect
accounts for 43.6% of volume of thermal mechanism 15 effect
mechanism 15
[0070] The PCM is MgF.sub.2 and has a melting point of 1263.degree.
C., a density of 3148 kg/m.sup.3, specific heat of 3.463
MJ/m.sup.3.degree. C., and latent heat (1263.degree. C.) of 2956
MJ/m.sup.3, where M is 10.sup.6.
[0071] The structure of the thermal effect mechanism 15 is made of
silicon carbide (SiC) and has a density of 3100 kg/m.sup.3, a
melting point of 2837.degree. C., an operating temperature of
1700.degree. C., rupture modulus of 110 Mpa, specific heat of 7.874
MJ/m.sup.3.degree. C., and coefficient of thermal conductivity of
125 W/m-K (20.degree. C.)-40 W/m-K (1000.degree. C.), where M is
10.sup.6.
[0072] At an operating temperature of 1200.degree. C.-1500.degree.
C., heat storage level per cubic meter (m.sup.3) of the thermal
energy storage facility 10 in this embodiment equals the sum of
three heat levels as follows: 586 MJ+1667 MJ+1030 MJ=3283 MJ
TABLE-US-00004 sensible heat of = 0.564 m.sup.3 .times. 3.463
MJ/m.sup.3.degree. C. .times. (1500-1200).degree. C. PCM = 586 MJ
latent heat = 0.564 m.sup.3 .times. 2956 MJ/m.sup.3 (1263.degree.
C.) of PCM = 1667 MJ sensible heat of = 0.436 m.sup.3 .times. 7.874
MJ/m.sup.3.degree. C. .times. (1500-1200).degree. C. structure of
thermal = 1030 MJ effect mechanism 15
Embodiment 4
[0073] The thermal energy storage facility of embodiment 3 is
applied to the solar power generation system of embodiment 2 and
substitutes for the thermal energy storage facility of embodiment
1.
[0074] The efficiency of the supercritical CO.sub.2 gas turbine
generator is 50%. The efficiency of the volume-dependent solar
receivers is 80%. The overall efficiency of the solar power
generation system is 40%.
Comparative Example
[0075] A conventional heat storage system with two heat storage
tanks is built in the solar power generation system and configured
to operate in conjunction with area-dependent solar receivers and a
steam turbine in power generation.
[0076] As regards the heat storage system, its high-temperature
heat storage tank operates at a temperature of 565.degree. C., and
its low-temperature heat storage tank operates at a temperature of
290.degree. C. The heat storage system stores heat by sensible heat
of a molten salt rather than by phase-transition heat of the molten
salt.
[0077] The HTF comes in the form of a molten salt which comprises a
mixture of 66.3% NaNO.sub.3 and 33.7% KNO.sub.3 and has a melting
point of 221.degree. C., and its latent heat at the melting point
(221.degree. C.) is 232 MJ/m.sup.3, where M is 10.sup.6.
[0078] At an operating temperature of 290.degree. C.-565.degree.
C., heat storage level per cubic meter (m.sup.3) of the heat
storage system=molten salt specific heat (1.6 kJ/kg.degree.
C..sup.-1).times.molten salt density 1870
(kg/m.sup.3).times.(565.degree. C.-290.degree. C.)=823
MJ/m.sup.3.
[0079] The efficiency of the steam turbine is 34%. The efficiency
of the area-dependent solar receivers is 57%. The overall
efficiency of the solar power generation system is 19.5%, that is,
less than 20%.
Results
[0080] 1. Embodiment 1 has a heat storage level of 3645 MJ/m.sup.3
which is 4.43 times of 66.3% NaNO.sub.3/33.7% KNO.sub.3 molten salt
sensible heat storage (823 MJ/m.sup.3) of the comparative
example.
[0081] 2. Embodiment 3 has a heat storage level of 3283 MJ/m.sup.3
which is 3.99 times of 66.3% NaNO.sub.3/33.7% KNO.sub.3 molten salt
sensible heat storage (823 MJ/m.sup.3) of the comparative
example.
[0082] 3. The solar power generation systems of embodiment 2 and
embodiment 4 use the thermal energy storage facilities of
embodiment 1 and embodiment 3 to thereby attain a power generation
efficiency of 35.4% and 40%, respectively, which is higher than the
power generation efficiency of less than 20% in the comparative
example.
* * * * *