U.S. patent application number 16/704987 was filed with the patent office on 2020-04-09 for heat-storage system and operating method of heat-storage system.
The applicant listed for this patent is PANASONIC CORPORATION. Invention is credited to Atsushi KATO, Yoshiaki KAWAKAMI, Yasufumi TAKAHASHI.
Application Number | 20200109882 16/704987 |
Document ID | / |
Family ID | 64567366 |
Filed Date | 2020-04-09 |
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United States Patent
Application |
20200109882 |
Kind Code |
A1 |
KAWAKAMI; Yoshiaki ; et
al. |
April 9, 2020 |
HEAT-STORAGE SYSTEM AND OPERATING METHOD OF HEAT-STORAGE SYSTEM
Abstract
An operating method of a heat-storage system includes the steps
of executing a first operating mode to supply heat to a first
hydrogen storage alloy in a first tank, to cause movement of
hydrogen from the first hydrogen storage alloy in the first tank to
a second hydrogen storage alloy in a second tank, the second
hydrogen storage alloy being different from the first hydrogen
storage alloy in dissociation pressure characteristic with respect
to an alloy temperature, and executing a second operating mode to
supply cold of outside air to the first hydrogen storage alloy, to
cause movement of hydrogen from the second hydrogen storage alloy
in the second tank to the first hydrogen storage alloy in the first
tank, in which the step of executing the first operating mode
includes a step of storing a temperature generated in the second
hydrogen storage alloy in a heat storage device.
Inventors: |
KAWAKAMI; Yoshiaki; (Tokyo,
JP) ; KATO; Atsushi; (Tokyo, JP) ; TAKAHASHI;
Yasufumi; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PANASONIC CORPORATION |
Osaka |
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JP |
|
|
Family ID: |
64567366 |
Appl. No.: |
16/704987 |
Filed: |
December 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2018/020726 |
May 30, 2018 |
|
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16704987 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24H 4/02 20130101; F25B
2600/2507 20130101; F25B 2400/07 20130101; F24H 1/00 20130101; F24D
19/1054 20130101; F24H 1/18 20130101; F24V 30/00 20180501; F25B
2313/02731 20130101; F25B 2700/19 20130101; F25B 17/12
20130101 |
International
Class: |
F25B 17/12 20060101
F25B017/12; F24D 19/10 20060101 F24D019/10; F24H 4/02 20060101
F24H004/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 2017 |
JP |
2017-111629 |
Claims
1. An operating method of a heat-storage system, comprising the
steps of: executing a first operating mode to supply heat of a heat
source to a first hydrogen storage alloy in a first tank, to cause
movement of hydrogen from the first hydrogen storage alloy in the
first tank to a second hydrogen storage alloy in a second tank, the
second hydrogen storage alloy being different from the first
hydrogen storage alloy in dissociation pressure characteristic with
respect to an alloy temperature; and executing a second operating
mode to supply cold of outside air to the first hydrogen storage
alloy, to cause movement of hydrogen from the second hydrogen
storage alloy in the second tank to the first hydrogen storage
alloy in the first tank, wherein the step of executing the first
operating mode includes a step of storing a temperature generated
in the second hydrogen storage alloy in a heat storage device.
2. The operating method of the heat-storage system according to
claim 1, wherein the step of executing the first operating mode
includes a step of operating a first gas pump that sends hydrogen
from an inside of the first tank to the second tank when a
dissociation pressure of the first hydrogen storage alloy is lower
than a dissociation pressure of the second hydrogen storage
alloy.
3. The operating method of the heat-storage system according to
claim 1, wherein the step of executing the second operating mode
includes a step of operating a second gas pump that sends hydrogen
from the second tank to the first tank when a dissociation pressure
of the second hydrogen storage alloy is lower than a dissociation
pressure of the first hydrogen storage alloy.
4. The operating method of the heat-storage system according to
claim 1, wherein the step of executing the first operating mode
includes a step of supplying hydrogen generated in a water
electrolysis apparatus to the first tank.
5. The operating method of the heat-storage system according to
claim 1, wherein the step of executing the first operating mode
includes a step of supplying hydrogen generated in a water
electrolysis apparatus to the second tank.
6. The operating method of the heat-storage system according to
claim 1, further comprising, after the step of executing the first
operating mode, a step of supplying hydrogen from the first
hydrogen storage alloy in the first tank to a fuel cell apparatus,
and causing the fuel cell apparatus to perform power
generation.
7. The operating method of the heat-storage system according to
claim 6, wherein after the step of supplying hydrogen from the
first hydrogen storage alloy in the first tank to the fuel cell
apparatus and causing the fuel cell apparatus to perform power
generation, the step of executing the second operating mode is
performed.
8. The operating method of the heat-storage system according to
claim 1, further comprising, after the step of executing the second
operating mode, a step of supplying hydrogen from the second
hydrogen storage alloy in the second tank to a fuel cell apparatus,
and causing the fuel cell apparatus to perform power
generation.
9. The operating method of the heat-storage system according to
claim 1, wherein either the step of executing the first operating
mode or the step of executing the second operating mode includes a
step of supplying hydrogen from the first hydrogen storage alloy in
the first tank to a fuel cell apparatus and causing the fuel cell
apparatus to perform power generation when a power failure
occurs.
10. The operating method of the heat-storage system according to
claim 1, wherein either the step of executing the first operating
mode or the step of executing the second operating mode includes a
step of supplying hydrogen from the second hydrogen storage alloy
in the second tank to a fuel cell apparatus and causing the fuel
cell apparatus to perform power generation when a power failure
occurs.
11. The operation method of the heat-storage system according to
claim 1, wherein a dissociation pressure of the first hydrogen
storage alloy becomes higher than a dissociation pressure of the
second hydrogen storage alloy upon receiving supply of heat higher
than an outside air temperature at least in wintertime, and becomes
lower than a dissociation pressure of the second hydrogen storage
alloy upon receiving supply of cold of outside air.
12. The operation method of the heat-storage system according to
claim 1, further comprising having a solar power generation
apparatus, a water electrolysis apparatus using electric power from
the solar power generation apparatus, a fuel cell apparatus, and a
hot water storage tank as the heat storage device, causing hydrogen
generated in the water electrolysis apparatus to be stored in at
least one of the first hydrogen storage alloy or the second
hydrogen storage alloy, generating by the fuel cell apparatus
electric power using hydrogen supplied from at least one of the
first hydrogen storage alloy or the second hydrogen storage alloy,
and causing heat of the second hydrogen storage alloy in the first
operating mode to be stored in the hot water storage tank at least
in wintertime, and causing heat when hydrogen generated in the
water electrolysis apparatus in a period different from at least
the wintertime is stored in at least one of the first hydrogen
storage alloy or the second hydrogen storage alloy, and heat
accompanying power generation of the fuel cell apparatus using
hydrogen supplied from at least one of the first hydrogen storage
alloy or the second hydrogen storage alloy to be stored in the hot
water storage tank.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation application of
International Application No. PCT/JP2018/020726, filed on May 30,
2018, which claims priority to Japanese Patent Application No.
2017-111629, filed on Jun. 6, 2017. The contents of these
applications are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present disclosure relates to a heat-storage system that
covers a hot water supply load at least in the wintertime when
demands for hot water supply increase, a house provided with the
heat-storage system, and an operating method of the heat-storage
system.
Description of Related Art
[0003] A hydrogen storage alloy causes an exothermic reaction when
storing hydrogen, and causes an endothermic reaction when releasing
hydrogen. JP 2002-277095 A discloses a technique for treating a
cold load by a heat pump system using this characteristic of the
hydrogen storage alloy. In the heat pump system of JP 2002-277095
A, a plurality of hydrogen storage alloy tanks are provided, and a
set of heat pump units is formed by a first hydrogen storage alloy
tank and a second hydrogen storage alloy tank, each of which has a
different type of hydrogen storage alloy. The hydrogen storage
alloy tanks in the heat pump unit are connected to each other by
piping, and are configured such that hydrogen released from one of
the hydrogen storage alloy tanks flows into the other of the
hydrogen storage alloy tanks. In JP 2002-277095 A, a cold output
process and a regeneration process are repeatedly performed in such
a heat pump system, and a heat medium circulating between a cold
load and a heat exchanger is cooled by using the endothermic
reaction when hydrogen is released, so as to treat the cold
load.
[0004] However, the conventional heat pump system described above
is a technique for dealing with a cold load, and production of hot
water is not considered.
SUMMARY OF THE INVENTION
[0005] The present disclosure has been made in view of the
above-mentioned situation, and it is an object thereof to perform
hot water production efficiently in a heat-storage system.
[0006] In order to solve the above problem, an aspect according to
an operating method of a heat-storage system of the present
disclosure according to another aspect provides the steps of
executing a first operating mode to supply heat of a heat source to
a first hydrogen storage alloy tank in a first tank, to cause
movement of hydrogen from the first hydrogen storage alloy in the
first tank to a second hydrogen storage alloy in a second tank, the
second hydrogen storage alloy being different from the first
hydrogen storage alloy in dissociation pressure characteristic with
respect to an alloy temperature, and executing a second operating
mode to supply cold of outside air to the first hydrogen storage
alloy, to cause movement of hydrogen from the second hydrogen
storage alloy in the second tank to the first hydrogen storage
alloy in the first tank, in which the step of executing the first
operating mode includes a step of storing a temperature generated
in the second hydrogen storage alloy in a heat storage device.
[0007] According to the present disclosure, hot water production
can be performed more efficiently in a heat-storage system.
[0008] The above and further objects, features and advantages of
the present invention will more fully be apparent from the
following detailed description of preferred embodiment with
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a diagram illustrating a schematic configuration
of a heat-storage system according to a first embodiment of the
present disclosure;
[0010] FIG. 2 is a diagram illustrating a specific example of the
heat-storage system according to the first embodiment of the
present disclosure;
[0011] FIG. 3 is a diagram illustrating a schematic configuration
of a heat-storage system according to a second embodiment of the
present disclosure;
[0012] FIG. 4 is a diagram illustrating a schematic configuration
of a hydrogen unit according to the second embodiment of the
present disclosure;
[0013] FIG. 5 is a chart illustrating alloy characteristics of
hydrogen storage alloys according to the second embodiment of the
present disclosure;
[0014] FIG. 6 is a diagram illustrating an operation pattern of the
heat-storage system according to the second embodiment of the
present disclosure;
[0015] FIG. 7 is a flow diagram of a water electrolysis operation
during a normal operation of the heat-storage system according to
the second embodiment of the present disclosure;
[0016] FIG. 8 is a flow diagram of a fuel cell operation during the
normal operation of the heat-storage system according to the second
embodiment of the present disclosure;
[0017] FIG. 9 is a flow diagram of a hot water supply operation
during a heat pump operation of the heat-storage system according
to the second embodiment of the present disclosure;
[0018] FIG. 10 is a chart for explaining movement of hydrogen
during the hot water supply operation according to the second
embodiment of the present disclosure;
[0019] FIG. 11 is a flow diagram of a regenerative operation during
the heat pump operation of the heat-storage system according to the
second embodiment of the present disclosure, and illustrates a case
where a cooling heat medium circulates through a first tank;
[0020] FIG. 12 is a flow diagram of the regenerative operation
during the heat pump operation of the heat-storage system according
to the second embodiment of the present disclosure, and illustrates
a case where a cooling heat medium circulates through each of the
first tank and a second tank;
[0021] FIG. 13 is a chart for explaining hydrogen movement during
the regenerative operation according to the second embodiment of
the present disclosure;
[0022] FIG. 14 is a flow diagram of a hot water supply operation
during a heat pump operation of a heat-storage system according to
a third embodiment of the present disclosure;
[0023] FIG. 15 is a flow diagram of a fuel cell operation during a
heat pump operation of a heat-storage system according to a fourth
embodiment of the present disclosure;
[0024] FIG. 16 is a chart illustrating alloy characteristics of
hydrogen storage alloys according to a fifth embodiment of the
present disclosure;
[0025] FIG. 17 is a diagram illustrating a schematic configuration
around a hydrogen storage alloy tank of a heat-storage system
according to the fifth embodiment of the present disclosure;
[0026] FIG. 18 is a chart for explaining movement of hydrogen
during a heat pump operation according to the fifth embodiment of
the present disclosure;
[0027] FIG. 19 is a chart illustrating alloy characteristics of
hydrogen storage alloys according to another embodiment of the
present disclosure;
[0028] FIG. 20 is an example of a site layout view of a house in an
urban area;
[0029] FIG. 21 is a diagram illustrating a footprint when only a
lithium ion battery is used as power storage equipment in a house
provided with a heat-storage system; and
[0030] FIG. 22 is a diagram illustrating a footprint when a
hydrogen unit according to the present disclosure is used in a
house provided with a heat-storage system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] As a result of intensive studies on heat output using a heat
pump cycle using a hydrogen tank that stores a hydrogen storage
alloy, the present inventors have conceived the following operating
method of a heat-storage system.
[0032] An operating method of a heat-storage system according to a
first aspect of the present disclosure includes the steps of
executing a first operating mode to supply heat of a heat source to
a first hydrogen storage alloy in a first tank, to cause movement
of hydrogen from the first hydrogen storage alloy in the first tank
to a second hydrogen storage alloy in a second tank, the second
hydrogen storage alloy being different from the first hydrogen
storage alloy in dissociation pressure characteristic with respect
to an alloy temperature, and executing a second operating mode to
supply cold of outside air to the first hydrogen storage alloy, to
cause movement of hydrogen from the second hydrogen storage alloy
in the second tank to the first hydrogen storage alloy in the first
tank, in which the step of executing the first operating mode
includes a step of storing a temperature generated in the second
hydrogen storage alloy in a heat storage device.
[0033] In the operating method of the heat-storage system according
to a second aspect of the present disclosure, in the operating
method of the heat-storage system of the first aspect, the step of
executing the first operating mode may include a step of operating
a first gas pump that sends hydrogen from an inside of the first
tank to the second tank when a dissociation pressure of the first
hydrogen storage alloy is lower than a dissociation pressure of the
second hydrogen storage alloy.
[0034] In the operating method of the heat-storage system according
to a third aspect of the present disclosure, in the operating
method of the heat-storage system of the first aspect or the second
aspect, the step of executing the second operating mode may include
a step of operating a second gas pump that sends hydrogen from the
second tank to the first tank when a dissociation pressure of the
second hydrogen storage alloy is lower than a dissociation pressure
of the first hydrogen storage alloy.
[0035] In the operating method of the heat-storage system according
to a fourth aspect of the present disclosure, in the operating
method of the heat-storage system of any one of the first aspect to
the third aspect, the step of executing the first operating mode
may include a step of supplying hydrogen generated in a water
electrolysis apparatus to the first tank.
[0036] In the operating method of the heat-storage system according
to a fifth aspect of the present disclosure, in the operating
method of the heat-storage system of any one of the first aspect to
the fourth aspect, the step of executing the first operating mode
may include a step of supplying hydrogen generated in a water
electrolysis apparatus to the second tank.
[0037] The operating method of the heat-storage system according to
a sixth aspect of the present disclosure may be designed such that
the operating method of the heat-storage system of any one of the
first aspect to the fifth aspect further includes after the step of
executing the first operating mode, a step of supplying hydrogen
from the first hydrogen storage alloy in the first tank to a fuel
cell apparatus, and causing the fuel cell apparatus to perform
power generation.
[0038] The operating method of the heat-storage system according to
a seventh aspect of the present disclosure may be designed such
that the operating method of the heat-storage system of the sixth
aspect includes after the step of supplying hydrogen from the first
hydrogen storage alloy in the first tank to the fuel cell apparatus
and causing the fuel cell apparatus to perform power generation,
the step of executing the second operating mode is performed.
[0039] The operating method of the heat-storage system according to
a eighth aspect of the present disclosure may be designed such that
the operating method of the heat-storage system of any one of the
first aspect to the fifth aspect further includes after the step of
executing the second operating mode, a step of supplying hydrogen
from the second hydrogen storage alloy in the second tank to a fuel
cell apparatus, and causing the fuel cell apparatus to perform
power generation.
[0040] In the operating method of the heat-storage system according
to a ninth aspect of the present disclosure, in the operating
method of the heat-storage system of any one of the first aspect to
the fifth aspect, either the step of executing the first operating
mode or the step of executing the second operating mode may include
a step of supplying hydrogen from the first hydrogen storage alloy
in the first tank to a fuel cell apparatus and causing the fuel
cell apparatus to perform power generation when a power failure
occurs.
[0041] In the operating method of the heat-storage system according
to a tenth aspect of the present disclosure, in the operating
method of the heat-storage system of any one of the first aspect to
the fifth aspect, either the step of executing the first operating
mode or the step of executing the second operating mode may include
a step of supplying hydrogen from the second hydrogen storage alloy
in the second tank to a fuel cell apparatus and causing the fuel
cell apparatus to perform power generation when a power failure
occurs.
[0042] In the operating method of the heat-storage system according
to a eleventh aspect of the present disclosure, in the operating
method of the heat-storage system of the first aspect, a
dissociation pressure of the first hydrogen storage alloy may
become higher than a dissociation pressure of the second hydrogen
storage alloy upon receiving supply of heat higher than an outside
air temperature at least in wintertime, and may become lower than a
dissociation pressure of the second hydrogen storage alloy upon
receiving supply of cold of outside air.
[0043] The operating method of the heat-storage system according to
a twelfth aspect of the present disclosure may be designed such
that the operating method of the heat-storage system of the first
aspect, further includes having a solar power generation apparatus,
a water electrolysis apparatus using electric power from the solar
power generation apparatus, a fuel cell apparatus, and a hot water
storage tank as the heat storage device, causing hydrogen generated
in the water electrolysis apparatus to be stored in at least one of
the first hydrogen storage alloy or the second hydrogen storage
alloy, generating by the fuel cell apparatus electric power using
hydrogen supplied from at least one of the first hydrogen storage
alloy or the second hydrogen storage alloy, and causing heat of the
second hydrogen storage alloy in the first operating mode to be
stored in the hot water storage tank at least in wintertime, and
causing heat when hydrogen generated in the water electrolysis
apparatus in a period different from at least the wintertime is
stored in at least one of the first hydrogen storage alloy or the
second hydrogen storage alloy, and heat accompanying power
generation of the fuel cell apparatus using hydrogen supplied from
at least one of the first hydrogen storage alloy or the second
hydrogen storage alloy to be stored in the hot water storage
tank.
[0044] Hereinafter, embodiments of the present disclosure will be
described with reference to the drawings. Note that in the present
description and drawings, elements having substantially the same
functional configuration are denoted by the same reference
numerals, and redundant descriptions are omitted.
First Embodiment
[0045] FIG. 1 is a diagram illustrating a schematic configuration
of a heat-storage system 1 according to a first embodiment. As
illustrated in FIG. 1, the heat-storage system 1 includes a
hydrogen unit 4 that includes a tank that stores hydrogen, a hot
water storage tank 6 that stores heat supplied from the hydrogen
unit 4, and a controller 7 that controls operation of the
heat-storage system 1. The controller 7 is operative to execute a
hot water supply operation and a regenerative operation described
later. The controller 7 may be one having a control function, and
includes an arithmetic processing unit (not illustrated) and a
storage unit (not illustrated) that stores a control program.
Examples of the arithmetic processing unit include an MPU and a
CPU. An example of the storage unit is a memory. The controller may
be constituted of a single controller that performs centralized
control, or may be constituted of a plurality of controllers that
perform distributed control in cooperation with each other. Here,
the hot water storage tank 6 is an example of a heat storage device
of the present disclosure. Further, the controller 7 is an example
of a controller of the present disclosure.
[0046] In the example illustrated in FIG. 1, the hydrogen unit 4
includes two hydrogen storage alloy tanks 10, 11 as tanks that
store hydrogen. The hot water storage tank 6 is operative to supply
hot water according to a heat load such as a demand for hot water
supply. Further, the hydrogen unit 4 is connected to a water
electrolysis apparatus 8 and stores hydrogen generated in the water
electrolysis apparatus 8. The hydrogen unit 4 is connected to a
fuel cell apparatus 9 and supplies the hydrogen in the hydrogen
unit 4 to the fuel cell apparatus 9. The fuel cell apparatus 9
supplies electric power generated using hydrogen to a power load.
The fuel cell apparatus 9 includes a fuel cell main body (not
illustrated), a power regulator (not illustrated) that adjusts
electric power extracted from the fuel cell main body, and a
controller (not illustrated) that controls the power regulator. The
power regulator is exemplified by an inverter. The hydrogen storage
alloy tank 10 is an example of a first tank of the present
disclosure, and the hydrogen storage alloy tank 11 is an example of
a second tank of the present disclosure.
[0047] FIG. 2 is a diagram illustrating a more specific example of
the heat-storage system in the first embodiment than in FIG. 1.
Respective hydrogen storage alloys in the hydrogen storage alloy
tanks 10, 11 are alloys having different dissociation pressure
characteristics with respect to alloy temperatures (hereinafter,
"temperature-dissociation pressure characteristics"). In the first
embodiment, respective temperature-dissociation pressure
characteristics of the hydrogen storage alloys are different as
illustrated in FIG. 5, and the dissociation pressure of a hydrogen
storage alloy A (hereinafter referred to as "alloy A") is higher
than the dissociation pressure of a hydrogen storage alloy B
(hereinafter referred to as "alloy B") when the alloy temperature
exceeds 20.degree. C. On the other hand, when the alloy temperature
is lower than 20.degree. C., the dissociation pressure of the alloy
A is lower than the dissociation pressure of the alloy B. The
hydrogen storage alloy A is an example of a first hydrogen storage
alloy of the present disclosure. The hydrogen storage alloy B is an
example of a second hydrogen storage alloy of the present
disclosure.
[0048] In other words, in a hot water supply temperature range (for
example, 50 to 70.degree. C.) that can correspond to a hot water
supply load, the dissociation pressure of the alloy A is higher
than the dissociation pressure of the alloy B, and in the outside
air temperature range (for example, 5 to 10.degree. C.) in the
wintertime and surrounding periods thereof (for example, November
to March), the dissociation pressure of the alloy A is lower than
the dissociation pressure of the alloy B. In addition, hydrogen
generated in the water electrolysis apparatus 8 can be stored in at
least one of the alloy A or the alloy B. At least one of the alloy
A or the alloy B that is supplied with hydrogen from the water
electrolysis apparatus 8 has a temperature-dissociation pressure
characteristic of being lower than a pressure of hydrogen supplied
from the water electrolysis apparatus 8 at an alloy temperature
during operation of the water electrolysis apparatus 8.
[0049] Further, hydrogen can be supplied to the fuel cell apparatus
9 from at least one of the alloy A or the alloy B. At this time, at
least one of the alloy A or the alloy B that supplies hydrogen to
the fuel cell apparatus 9 has a temperature-dissociation pressure
characteristic such that a dissociation pressure at an alloy
temperature during power generation of the fuel cell apparatus 9
is, for example, 0.05 MPa (G) or more. In the following
description, the first hydrogen storage alloy tank 10 including the
alloy A will be referred to as "alloy tank 10", and the second
hydrogen storage alloy tank 11 including the alloy B will be
referred to as "alloy tank 11".
[0050] As illustrated in FIG. 2, one end of a gas flow path 12 is
connected to the alloy tank 10, and the other end of the gas flow
path 12 connected to the alloy tank 11. Thus, hydrogen can move
between the alloy A in the alloy tank 10 and the alloy B in the
alloy tank 11 via the gas flow path 12. Further, the gas flow path
12 is provided with a valve 13. The gas flow path 12 and the valve
13 are examples of a hydrogen transfer device of the present
disclosure.
[0051] A first heat medium flow path 14 is a flow path through
which a first heat medium that recovers heat (warm heat) from the
alloy tank 11 flows. The first heat medium flow path 14 is provided
with a heat exchanging unit 14A that recovers heat from the alloy
tank 11. The first heat medium flow path 14, the heat exchanging
unit 14A, and the hot water storage tank 6 are examples of a heat
storage device of the present disclosure. The first heat medium may
be water in the hot water storage tank 6 or a heat medium different
from the water in the hot water storage tank 6. When the first heat
medium is different from the water in the hot water storage tank 6,
in first heat medium flow path 14, the hot water storage tank 6 is
provided with a heat exchanging unit (not illustrated) in which
heat is exchanged between the water in the hot water storage tank 6
and the first heat medium. Note that the heat storage device of the
present disclosure is not limited to this example, and may further
include a secondary heat recovery path that recovers heat from the
first heat medium, as in a second embodiment described later. At
this time, the first heat medium flow path 14 corresponds to a
primary heat recovery path, and the heat exchanging unit 14A
corresponds to a heat exchanging unit in which heat is exchanged
between the first heat medium in the primary heat recovery path and
the alloy B in the alloy tank 11.
[0052] A second heat medium flow path 15 is a flow path through
which a second heat medium that supplies heat from a heat source to
the alloy tank 10 flows. The second heat medium flow path 15 is
provided with a heat exchanging unit 15A that supplies heat to the
alloy tank 10. Here, the second heat medium flow path 15 and the
heat exchanging unit 15A are examples of a first heat supply device
of the present disclosure. Further, the heat source may be a heater
such as a combustor or an electric heater, or may be exhaust heat
generated in the home (for example, remaining hot water of a
bathtub), underground heat, or exhaust heat of hot water derived
from a solar heat system, hot water derived from solar power
generation with a function to utilize solar heat, or the like.
Further, the heat supplied from the heat source to the second heat
medium may be of a temperature lower than a hot water supply
temperature range (for example, 50 to 70.degree. C.). Further, the
heat source may be an internal heat source provided in the
heat-storage system 1, or an external heat source provided outside
the heat-storage system 1. Note that the first heat supply device
of the present disclosure is not limited to this example, and may
further include a secondary heat supply path that supplies heat to
the second heat medium, as in a second embodiment described later.
At this time, the second heat medium flow path 15 corresponds to a
primary heat supply path, and the heat exchanging unit 15A
corresponds to a heat exchanging unit in which heat is exchanged
between the second heat medium and the alloy A in the alloy tank
10.
[0053] A third heat medium flow path 16 is a flow path through
which a third heat medium that supplies cold from the outside air
to the alloy tank 10 flows. The third heat medium flow path 16 is
provided with a heat exchanging unit 16A that supplies cold to the
alloy tank 10. The third heat medium flow path 16 and the heat
exchanging unit 16A are examples of a second heat supply device of
the present disclosure. Note that the second heat supply device of
the present disclosure is not limited to this example, and may
further include a primary heat supply path that supplies cold to
the third heat medium, as in a second embodiment described later.
At this time, the third heat medium flow path 16 corresponds to the
primary heat supply path, and the heat exchanging unit 16A
corresponds to a heat exchanging unit in which heat is exchanged
between the third heat medium and the alloy A in the alloy tank
10.
[0054] Further, as a first operating mode, the controller 7
performs control to heat the alloy A with the second heat medium
flowing through the second heat medium flow path 15 via the heat
exchanging unit 15A, and cause movement of hydrogen from the alloy
A in the alloy tank 10 to the alloy B in the alloy tank 11.
[0055] In addition, as a second operating mode, the controller 7
performs control to cool the alloy B with the third heat medium
flowing through the third heat medium flow path 16 via the heat
exchanging unit 16A, and cause movement of hydrogen from the alloy
B in the alloy tank 11 to the alloy A in the alloy tank 10.
[0056] The heat-storage system 1 of the first embodiment is
configured as described above. Next, an operating method of the
heat-storage system 1 will be described.
[0057] The heat-storage system 1 has two operating methods such as
a normal operation and a heat pump operation, and the operating
method is switched according to the season. For example, as
illustrated in FIG. 6, the heat pump operation is performed in the
wintertime and surrounding periods thereof, that is, for example,
from November to March, and the normal operation is performed in
other periods. Switching between the normal operation and the heat
pump operation may be performed manually by a user of the
heat-storage system 1, or a switching time of operation may be
stored in the controller 7 in advance and the operation may be
automatically switched when the switching time comes. Further, the
operation may be switched automatically based on a measured outside
air temperature. Moreover, in this example, the heat pump operation
is performed including the surrounding periods of the wintertime,
but the heat pump operation may be performed in the wintertime (for
example, December to February). That is, it is sufficient that the
heat pump operation is performed at least in the wintertime.
[0058] First, a flow during the normal operation of the
heat-storage system 1 will be described. During the normal
operation, hot water is produced by a water electrolysis operation
and a fuel cell operation.
[0059] (Normal Operation-Water Electrolysis Operation)
[0060] In the water electrolysis operation, electric power from a
power supply device is supplied to the water electrolysis apparatus
8 to perform electrolysis of water. Hydrogen at less than 1 MPa (G)
(for example, 0.9 MPa (G)) produced here is sent to the alloy tank
10. Since the alloy tank 10 generates heat as hydrogen is stored,
when exhaust heat thereof is equal to or higher than a temperature
that can be used for hot water supply (for example, 60.degree. C.),
the exhaust heat is used for hot water storage. In this case, heat
generated in the alloy A is recovered by a heat medium flowing in a
heat medium flow path (not illustrated), and the recovered heat is
stored in the hot water storage tank 6. Here, the power supply
device may be any power supply device as long as it is capable of
supplying power to the water electrolysis apparatus. Examples of
the power supply device include a system power supply, a solar
power generation apparatus, a power storage apparatus, and the
like. The power supply device may be an internal power supply
device provided in the heat-storage system 1, or may be an external
power supply device provided outside the heat-storage system 1.
[0061] Note that hydrogen may be supplied from the water
electrolysis apparatus 8 to the alloy tank 11 during the water
electrolysis operation. In this case, the first heat medium flows
through the first heat medium flow path 14, the heat exchanging
unit 14A recovers heat generated in the alloy B, and the recovered
heat is stored in the hot water storage tank 6.
[0062] (Normal Operation-Fuel Cell Operation)
[0063] While the fuel cell apparatus 9 is in operation, for
example, hydrogen is supplied from the alloy tank 10 to the fuel
cell apparatus 9. At the same time, air in the atmosphere is
supplied to the fuel cell apparatus 9 using a blower or the like
(not illustrated), and power generation is performed. Heat
accompanying power generation of the fuel cell apparatus 9 is
recovered by a heat medium flowing in a heat medium flow path (not
illustrated), and the recovered heat is stored in the hot water
storage tank 6.
[0064] Further, hydrogen may be supplied from the alloy tank 11 to
the fuel cell apparatus 9. At the same time, air in the atmosphere
is supplied to the fuel cell apparatus 9 using the blower or the
like (not illustrated), and power generation is performed. Heat
accompanying power generation of the fuel cell apparatus 9 is
recovered by the heat medium flowing in the heat medium flow path
(not illustrated), and the recovered heat is stored in the hot
water storage tank 6.
[0065] The operating method of heat-storage system 1 during the
normal operation has been described. During the normal operation,
the water electrolysis operation and the fuel cell operation are
alternately repeated to thereby cope with the hot water supply
load.
[0066] Next, a flow during the heat pump operation will be
described. There are two operating methods during the heat pump
operation. One is a "hot water supply operation" that extracts heat
from a heat source to generate heat for hot water storage, and the
other is a "regenerative operation" that returns hydrogen to the
tank where the hydrogen is originally stored by reaction heat
circulation of both the alloy tanks 10, 11. In a period when it is
difficult to achieve energy independence such as, for example, the
wintertime and surrounding periods thereof, that is, November to
March, the "hot water supply operation" and the "regenerative
operation" are alternately repeated to thereby cope with the hot
water supply load. Here, the "hot water supply operation" is an
example of the first operating mode of the present disclosure.
Further, the "regenerative operation" is an example of the second
operating mode of the present disclosure.
[0067] (Heat pump operation-hot water supply operation)
[0068] First, the hot water supply operation after the regenerative
operation is completed will be described. When the regenerative
operation is finished, both the alloy tanks 10, 11 are at a low
temperature (for example, 10.degree. C.). In order to produce hot
water in a hot water supply temperature range (for example,
60.degree. C.) necessary for hot water supply from this low
temperature state, it is necessary to heat both the alloy tanks 10,
11 to a predetermined temperature. Heating of both the alloy tanks
10, 11 during the heat pump operation is performed by supplying
heat from the heat source and using an exothermic reaction
accompanying hydrogen movement between both the alloy tanks 10,
11.
[0069] As illustrated in FIG. 2, heat from the heat source is
supplied to the alloy A in the alloy tank 10 from the second heat
medium flowing through the second heat medium flow path 15 via the
heat exchanging unit 15A. Thus, the alloy A is provided with heat
necessary for hydrogen release. The second heat medium that is
cooled by heat exchange with the alloy A is supplied again with
heat from the heat source, and then supplies heat to the alloy A
via the heat exchanging unit 15A.
[0070] The temperature of the alloy A in the alloy tank 10 rises
due to heat supplied from the heat source, and when the
dissociation pressure of the alloy A in the alloy tank 10 becomes
higher than the dissociation pressure of the alloy B in the alloy
tank 11 accompanying the temperature rise, hydrogen begins to move
from the alloy tank 10 to the alloy tank 11 through the gas flow
path 12. At this time, the controller 7 controls the valve 13 to
open. When hydrogen moves to the alloy tank 11, a hydrogen storage
reaction occurs in the alloy B in the alloy tank 11 to generate
heat. Heat generated in the alloy tank 11 is transmitted to the
first heat medium flowing through the first heat medium flow path
14 via the heat exchanging unit 14A, and finally stored in the hot
water storage tank 6.
[0071] The alloy B generates heat by the hydrogen storage reaction
and is deprived of heat by the first heat medium. However, in the
initial stage of the hot water supply operation, since the
dissociation pressure difference between the alloy A and the alloy
B is large, hydrogen easily moves and the amount of heat generated
by the hydrogen storage reaction is large. For this reason, the
temperature of the alloy B rises until reaching a steady state. On
the other hand, the temperature of the alloy A decreases
accompanying a hydrogen release reaction, but the temperature of
the alloy A increases until reaching a steady state since the
supply of heat from the heat source is continued.
[0072] Note that immediately after the hot water supply operation
is started, it is necessary to supply more heat from the heat
source than in a steady time until temperatures of the alloys A and
B in both the alloy tanks 10, 11 reach a design temperature. For
this reason, for the amount of heat necessary for the heat source,
it is necessary to take into account the amount of sensible heat
from a state that the hot water supply operation is started until
both the alloy tanks 10, 11 reach a steady temperature, and it is
necessary to note that heat of the amount of sensible heat cannot
be extracted when the temperature is increased by reaction heat of
the alloy. A heat source may be used for heating the alloy B in the
alloy tank 11. In this manner, hot water that can be extracted for
hot water supply when the same amount of hydrogen moves increases.
However, it is necessary to note that the heat amount of the heat
source to be secured also increases in that case.
[0073] By heating in the initial stage of the hot water supply
operation, when the temperature of the alloy A in the alloy tank 10
becomes the temperature of the heat source, 35.degree. C. for
example, and the temperature of the alloy B in the alloy tank 11
becomes a temperature in the hot water supply temperature range,
60.degree. C. for example, and reaches a steady state, the
dissociation pressure at the temperature of the heat source of the
alloy A in the alloy tank 10 has become higher than the
dissociation pressure at the temperature in the hot water supply
temperature range of the alloy B in the alloy tank 11. For this
reason, during the hot water supply operation, hydrogen continues
to move from the alloy tank 10 to the alloy tank 11, and the alloy
tank 11 continues to generate heat due to the hydrogen storage
reaction. Thus, hot water which has a temperature in the hot water
supply temperature range can be produced continuously.
[0074] The hot water supply operation during the heat pump
operation in the first embodiment is performed in this manner.
Next, the regenerative operation after the hot water supply
operation is completed will be described.
[0075] (Heat Pump Operation-Regenerative Operation)
[0076] When the hot water supply operation is finished, the alloys
A and B in both the alloy tanks 10, 11 are at high temperatures
(for example, 35.degree. C. and 60.degree. C.). In order to have
temperatures necessary for the regenerative operation (for example,
10.degree. C.) from this state, it is necessary to first cool the
alloys A and B of both the alloy tanks 10, 11 to a predetermined
temperature. Cooling of the alloys A and B in both the alloy tanks
10, 11 during the heat pump operation is performed by releasing
heat to the outside air and using an endothermic reaction
accompanying hydrogen movement between both the alloy tanks 10,
11.
[0077] Releasing heat to the outside air is performed by that the
third heat medium supplied with cold of the outside air flows
through the third heat medium flow path 16 and supplies cold to the
alloy A in the alloy tank 10 via the heat exchanging unit 16A. The
third heat medium heated by heat exchange with the alloy A in the
alloy tank 10 is cooled again by outside air, and then supplies
cold to the alloy A via the heat exchanging unit 16A.
[0078] If the dissociation pressure of the alloy A in the alloy
tank 10 becomes smaller than the dissociation pressure of the alloy
B in the alloy tank 11 as the alloy A in the alloy tank 10 is
cooled, hydrogen begins to move from the alloy tank 11 to the alloy
tank 10 through the gas flow path 12. At this time, the controller
7 controls the valve 13 to open. When hydrogen begins to move from
the alloy tank 11 to the alloy tank 10, an endothermic reaction
accompanying release of hydrogen occurs in the alloy B in the alloy
tank 11, and the temperature of the alloy B gradually decreases. On
the other hand, the alloy A in the alloy tank 10 causes an
exothermic reaction due to hydrogen storage, but since cold is
supplied to the alloy A in the alloy tank 10 via the heat
exchanging unit 16A, the temperature of the alloy A also gradually
decreases.
[0079] Note that immediately after the regenerative operation is
started, it is necessary to dissipate more heat than in a steady
time until temperatures of the alloy tanks 10, 11 reach the design
temperature. However, it is only necessary to discard this heat
because it is heat that is only to be discarded. When the
temperatures of both the alloy tanks 10, 11 reach the design
temperature (for example, 10.degree. C.), hydrogen can be moved by
reaction heat circulation between both the alloy tanks 10, 11. At
this time, heat from the heat source may be supplied to the alloy B
in the alloy tank 11 from a heat medium flowing through a heat
medium path (not illustrated), so that the temperature of the alloy
B does not decrease too much.
[0080] When the temperatures of the alloys A and B in the alloy
tanks 10, 11 become steady at, for example, 10.degree. C. due to
cooling in the initial stage of the regenerative operation, as
illustrated in FIG. 13, the dissociation pressure of the alloy A in
the alloy tank 10 is smaller than the dissociation pressure of the
alloy B in the alloy tank 11. For this reason, hydrogen continues
to move from the alloy tank 11 to the alloy tank 10 during the
regenerative operation, and hydrogen is stored in the alloy tank 10
for the next hot water supply operation.
[0081] The regenerative operation during the heat pump operation in
the first embodiment is performed in this manner. After the
regenerative operation, the hot water supply operation is performed
again to produce hot water. A cycle in which the hot water supply
operation and the regenerative operation are repeated alternately
is performed at least once a day. For example, the regenerative
operation may be performed when the outside air temperature is low
at night, and the hot water supply operation may be performed
during the day. In addition, this cycle may be performed multiple
times a day. For example, when two cycles are performed, the
regenerative operation and the hot water supply operation are
performed at night, and the regenerative operation and the hot
water supply operation are performed during the day. By increasing
the number of cycles, it becomes possible to increase the amount of
heat that can be used as hot water for hot water supply or the
like.
[0082] As described above, in the heat-storage system 1 of the
first embodiment, by using the alloy A and the alloy B having
different temperature-dissociation pressure characteristics of
hydrogen storage alloys from each other, during the heat pump
operation, hot water can be produced by performing the hot water
supply operation using the heat source and the regenerative
operation using heat release to the outside air. If the heat source
is a heat source that is previously unused or difficult to use,
such as exhaust heat generated in the home or underground heat, the
heat-storage system 1 can produce hot water more efficiently even
in a period when it is difficult to achieve energy
independence.
[0083] The alloy A used in the alloy tank 10 and the alloy B used
in the alloy tank 11 are appropriately selected according to the
purpose of using hot water, the temperature of the heat source, the
outside air temperature, and so on. For example, an MmNi (Misch
Metal Nickel)-based alloy, a TiFe-based alloy, a TiV-based BCC
alloy, a TiVCr-based BCC alloy, or a TiCr-based BCC alloy is used.
An example of the MmNi-based alloy is an MmNiMn-based alloy.
Further, the alloy B in the alloy tank 11 may have a low
dissociation pressure in the entire temperature range and may have
a pressure change with respect to a temperature change as small as
possible.
[0084] Note that the lower the temperature zone of heat supplied to
the alloy tank 10 needed during the hot water supply operation, the
more the choices of available heat sources. Thus, an intersection
of the temperature-dissociation pressure characteristics of both
the alloys A, B may be lower as long as it does not fall below the
temperature during the regenerative operation (the temperature that
can be cooled by releasing heat to the outside air). Further, the
smaller the difference between the "alloy temperature during hot
water supply" and the "alloy temperature during regeneration" on
the alloy A side, the lower the sensible heat loss when the
operation is switched, and thus the more efficient in terms of
energy.
[0085] Further, rather than using up all hydrogen for power
generation according to electric power demand, power generation is
not performed in a specific period to leave the hydrogen even if
there is power demand, and low-temperature exhaust heat that cannot
be used and has been originally discarded is used to perform the
heat pump operation, so as to obtain high-temperature water. Thus,
a large amount of hot water can be obtained by up to 70%, compared
to cases of not performing the heat pump operation. In addition, by
setting the minimum storage amount of hydrogen, the capacity of the
hydrogen storage alloy can be reduced by up to 20% per heat pump
operation, as compared to the case where the minimum storage amount
is not set.
Second Embodiment
[0086] FIG. 3 is a diagram illustrating a schematic configuration
of a heat-storage system 1 provided in a house. As illustrated in
FIG. 3, the heat-storage system 1 includes a solar power generation
apparatus 2, a power storage apparatus 3 such as a lithium ion
battery, a hydrogen unit 4 that generates power and produces hot
water using hydrogen, a water heater 5 that produces hot water
using electric power, a hot water storage tank 6 that temporarily
stores hot water supplied from the hydrogen unit 4 and the water
heater 5, and a controller 7 that controls operation of the solar
power generation apparatus 2, the power storage apparatus 3, the
hydrogen unit 4, and the water heater 5, and the hot water storage
tank 6. In an example illustrated in FIG. 3, the solar power
generation apparatus 2 is provided on the roof of a house 100. The
power storage apparatus 11. the hydrogen unit 4, the hot water
heater 5, and the hot water storage tank 6 are provided within the
same site space as the house 100, and the controller 7 is provided
in the house 100. The heat-storage system 1 according to the first
embodiment is operative to include the water electrolysis apparatus
8 and the fuel cell apparatus 9 separately from the hydrogen unit
4. In the heat-storage system 1 according to the second embodiment,
the hydrogen unit 4 includes a water electrolysis apparatus 8, a
fuel cell apparatus 9, and two hydrogen storage alloy tanks (alloy
tanks) 10, 11. Further, the hot water storage tank 6 is operative
to supply hot water according to a heat load such as a demand for
hot water supply in the house 100.
[0087] In the heat-storage system 1 according to the second
embodiment, electric power generated in the solar power generation
apparatus 2 is supplied to a power load of the house 100, and
remaining power is supplied to the power storage apparatus 3, or
the water electrolysis apparatus 8 of the hydrogen unit 4, or the
water heater 5. Still remaining power flows back to the system
power 80. If the flowing back is not possible, output suppression
or the like is performed. When electric power generated in the
solar power generation apparatus 2 is lower than the electric power
demand in the home, the electric power from the power storage
apparatus 3 or the electric power from the fuel cell apparatus 9 is
supplied to the house 100. The controller 7 of the heat-storage
system 1 also controls power supply according to such electric
power demand. For example, when "electric power of solar power
generation <electric power demand" holds, insufficient power is
first supplied from the power storage apparatus 3, and if it is
still not enough, electric power is supplied by power generation
with the fuel cell apparatus 9. The power generation with the fuel
cell apparatus 9 is performed not only for responding to power
demand, but also for increasing the amount of power stored in the
power storage apparatus 3 in preparation for a time zone when the
electric power demand is large. For example, charging from the fuel
cell apparatus 9 to the power storage apparatus 3 is performed in a
time zone when it is not necessary to discharge from the power
storage apparatus 3. The reason for charging the power storage
apparatus 3 from the fuel cell apparatus 9 in this manner is that
the power storage apparatus 3 has better responsiveness than the
fuel cell apparatus 9 in response to electric power demand
fluctuation or peak electric power demand. Thus, the operating rate
of the hydrogen-related devices (the water electrolysis apparatus
8, the fuel cell apparatus 9, and the hydrogen storage alloy tanks
10, 11) is considerably lower than the operating rate of the power
storage apparatus 3.
[0088] FIG. 4 is a diagram illustrating a schematic configuration
of the hydrogen unit 4 in the second embodiment. As described
above, the hydrogen unit 4 includes the water electrolysis
apparatus 8, the fuel cell apparatus 9, and the two hydrogen
storage alloy tanks (alloy tanks) 10, 11. The hydrogen storage
alloys (alloys A, B) in the alloy tanks 10, 11 are alloys having
different temperature-dissociation pressure characteristics with
respect to alloy temperatures. In the second embodiment, the
temperature-dissociation pressure characteristics of the hydrogen
storage alloys (alloys A, B) differ as illustrated in FIG. 5, and
when the alloy temperature exceeds 20.degree. C., the dissociation
pressure of the alloy A is higher than the dissociation pressure of
the alloy B. On the other hand, when the alloy temperature is lower
than 20.degree. C., the dissociation pressure of the alloy A is
lower than the dissociation pressure of the alloy B.
[0089] In other words, in a hot water supply temperature range (for
example, 50 to 70.degree. C.) that can correspond to a hot water
supply load, the dissociation pressure of the alloy A is higher
than the dissociation pressure of the alloy B, and in the outside
air temperature range (for example, 5 to 10.degree. C.) in the
wintertime and surrounding periods thereof (for example, November
to March), the dissociation pressure of the alloy A is lower than
the dissociation pressure of the alloy B. Further, both the alloys
A and B have a characteristic that the dissociation pressure at the
alloy temperature during the water electrolysis operation is lower
than the pressure of hydrogen generated in the water electrolysis
apparatus 8 so that the alloys can store hydrogen generated in the
water electrolysis apparatus 8. Moreover, both the alloys A and B
have a characteristic that the dissociation pressure at the alloy
temperature during the fuel cell operation is, for example, 0.05
MPa (G) or more so that the alloys can supply hydrogen to the fuel
cell apparatus 9.
[0090] As illustrated in FIG. 4, one end of a pipe 50 is connected
to the alloy tank 10, and the other end of the pipe 50 is connected
to a valve V8. One end of another pipe 51 is connected to the valve
V8, and the other end of the pipe 51 is connected to one end of a
pipe 54. One end of a pipe 52 is connected to the alloy tank 11,
and the other end of the pipe 52 is connected to a valve V9. One
end of another pipe 53 is connected to the valve V9, and the other
end of the pipe 53 is connected to the pipe 54. The other end of
the pipe 54 is connected to a dehumidifier 20. One end of another
pipe 55 is connected to the dehumidifier 20, and one end of a pipe
56 is connected to the other end of the pipe 55. The other end of
the pipe 56 is connected to a valve V7. One end of another pipe 57
is connected to the valve V7, and the other end of the pipe 57 is
connected to the water electrolysis apparatus 8. One end of a pipe
58 is connected to a middle part of the pipe 55, and the other end
of the pipe 58 is connected to a valve V10. One end of another pipe
59 is connected to the valve V10, and the other end of the pipe 59
is connected to the fuel cell apparatus 9. Hydrogen flows through
the above pipes 50 to 59.
[0091] One end of another pipe 30 is connected to the fuel cell
apparatus 9, and the other end of the pipe 30 is connected to a
three-way valve V1. One end of another pipe 31 is connected to the
three-way valve V1, and the other end of the pipe 31 is connected
to a pump P1. One end of another pipe 32 is connected to the pump
P1, and the other end of the pipe 32 is connected to one end of a
pipe 33. The other end of the pipe 33 is connected to a three-way
valve V2. One end of another pipe 34 is connected to the three-way
valve V2, and the pipe 34 extends through a heat exchanger 21 to a
radiator 22 with a fan. The other end of a pipe 35 having one end
connected to the three-way valve V2 is connected between the heat
exchanger 21 and the radiator 22 in the pipe 34. The other end of
the pipe 34 is connected to one end of a pipe 36. The other end of
the pipe 36 is connected to one end of a pipe 47, and a valve V5 is
provided in a middle part of the pipe 36. One end of a pipe 37 is
connected to a middle part of the pipe 36, and one end of a pipe 38
is connected to the other end of the pipe 37. The other end of the
pipe 38 is connected to the three-way valve V3. One end of another
pipe 39 is connected to the three-way valve V3, and the other end
of the pipe 39 is connected to the alloy tank 10. A heat medium
such as water flows in the pipes 30 to 39.
[0092] One end of another pipe 40 is connected to the alloy tank
10, and the other end of the pipe 40 is connected to a three-way
valve V4. One end of another pipe 41 is connected to the three-way
valve V4, and the other end of the pipe 41 is connected to a pump
P2. One end of another pipe 42 is connected to the pump P2, and the
other end of the pipe 42 is connected to the three-way valve V3 via
a heat exchanger 23. One end of another pipe 43 is connected to a
connection point between the pipe 37 and the pipe 38, and the other
end of the pipe 43 is connected to a valve V6. One end of another
pipe 44 is connected to the valve V6, and the other end of the pipe
44 is connected to the alloy tank 11. A heat medium such as water
flows in the pipes 40 to 44 described above.
[0093] One end of another pipe 45 is connected to the alloy tank
11, and one end of a pipe 46 is connected to the other end of the
pipe 45. The other end of the pipe 46 is connected to one end of
the pipe 47, and the other end of the pipe 47 is connected to the
fuel cell apparatus 9. One end of a pipe 48 is connected to a
connection point between the pipe 45 and the pipe 46, and the other
end of the pipe 48 is connected to the three-way valve V4. Further,
one end of a pipe 49 is connected to a middle part of the pipe 47,
and the other end of the pipe 49 is connected to the three-way
valve V1. A heat medium such as water flows in the pipes 45 to 49
above.
[0094] Inside the heat exchanger 21, a pipe 70 leading to the hot
water storage tank 6 is passed, and water flowing in the pipe 70
exchanges heat with the heat medium in the pipe 34 in the heat
exchanger 21. Inside the heat exchanger 23, a pipe 71 leading to an
external heat source (not illustrated) is passed, and a heat medium
flowing in the pipe 71 exchanges heat with the heat medium in the
pipe 42 in the heat exchanger 23. Note that the "external heat
source" refers to a heat source that is not normally used such as
exhaust heat generated in the home, or underground heat, and does
not include a heating device provided for the purpose of heating a
hydrogen storage alloy tank. As the external heat source, for
example, various energy sources can be used including unused energy
of remaining hot water of a domestic bathtub (for example,
35.degree. C.), underground heat, hot water derived from a solar
heat system, hot water derived from solar power generation with a
function to utilize solar heat, and wastewater. Further, a
plurality of external heat sources may be combined, or tap water
may be used depending on the alloy specifications. Although a heat
medium may be heated using a heat source other than the external
heat source, the external heat source as those described above may
be used from the viewpoint of producing hot water with higher
energy efficiency.
[0095] By the hydrogen unit 4 having the piping configuration
described above, in the heat-storage system 1, a device that
supplies hydrogen (hereinafter, "hydrogen supply device") from the
water electrolysis apparatus 8 to at least one of the alloy tanks
10, 11 is formed by the water electrolysis apparatus 8, both the
alloy tanks 10, 11, and the pipes 50 to 57 that connect them to
each other.
[0096] Further, in the heat-storage system 1, by the pipes 40, 48,
46, 47, 49, 31 to 39 provided so that the heat medium circulates
between the alloy tank 10 and the heat exchanger 21 and by the
pipes 45 to 47, 49, 31 to 37, 43, 44 provided so that the heat
medium circulates between the alloy tank 11 and the heat exchanger
21, a device that gives heat generated in at least one of both the
alloy tanks 10, 11 to water supplied from the outside through the
heat exchanger 21 is formed (hereinafter referred to as "first heat
supply device").
[0097] Further, in the heat-storage system 1, by the fuel cell
apparatus 9, both the alloy tanks 10, 11, and the pipes 50 to 55,
58, 59 that connect them to each other, and by the pipes 30 to 36,
47 provided so that the heat medium circulates between the fuel
cell apparatus 9 and the heat exchanger 21, a device that supplies
hydrogen from at least one of both the alloy tanks 10, 11 to the
fuel cell apparatus 9, and gives heat accompanying fuel cell power
generation to water supplied from the outside through the heat
exchanger 21 is formed (hereinafter referred to as "second heat
supply device").
[0098] In addition, in the heat-storage system 1, a device in which
hydrogen can move between both the alloy tanks 10, 11 is formed by
the alloy tank 10, the alloy tank 11, and the pipes 50 to 54
connecting them (hereinafter referred to as "hydrogen transfer
device").
[0099] Further, in the heat-storage system 1, a heat circulation
device (first heat supply device and second heat supply device) is
formed that heats or cools a heat medium and circulates the heat
medium through the hydrogen storage alloy tank (the alloy tanks 10,
11). In the present embodiment, as a heat circulation device that
heats a heat medium and circulates the heat medium through a
hydrogen storage alloy tank, a device (first heat supply device) is
formed in which the pipes 40 to 42, 39 are provided so that the
heat medium circulates between the alloy tank 10 and the heat
exchanger 23, so as to circulate the heat medium having exchanged
heat with the external heat source through the heat exchanger 23 to
pass through the alloy tank 10. In addition, as a heat circulation
device that cools a heat medium and circulates the heat medium
through a hydrogen storage alloy tank, a device (second heat supply
device) is formed in which the pipes 40, 48, 46, 47, 49, 31 to 39
are provided so that the heat medium circulates between the alloy
tank 10 and the radiator 22, and the pipes 45 to 47, 49, 31 to 37,
43, 44 are provided so that the heat medium circulates between the
alloy tank 11 and the radiator 22, so as to circulate the heat
medium having exchanged heat with the outside air through the
radiator 22 to pass through both the alloy tanks 10, 11.
[0100] Note that the configurations of the hydrogen supply device,
the first heat supply device, the hydrogen transfer device, the
first heat supply device, and the second heat supply device are not
limited to the piping configuration described in the second
embodiment. For example, in the second embodiment, the hydrogen
supply device and the first heat supply device share part of the
piping through which hydrogen passes, but other piping may be
used.
[0101] The heat-storage system 1 of the second embodiment is
configured as described above. Next, an operating method of the
heat-storage system 1 of the second embodiment will be
described.
[0102] The heat-storage system 1 of the second embodiment has two
operating methods such as a normal operation and a heat pump
operation, and the operating method is switched according to the
season. For example, as illustrated in FIG. 6, the heat pump
operation is performed in the wintertime and surrounding periods
thereof, that is, for example, from November to March, and the
normal operation is performed in other periods. Switching between
the normal operation and the heat pump operation may be performed
manually by a user of the heat-storage system 1, or a switching
time of operation may be stored in the controller 7 in advance and
the operation may be automatically switched when the switching time
comes. Further, the operation may be switched automatically based
on a measured outside air temperature.
[0103] First, a flow during the normal operation of the
heat-storage system 1 of the second embodiment will be described.
During the normal operation, hot water is produced by a water
electrolysis operation and a fuel cell operation.
[0104] (Normal Operation-Water Electrolysis Operation)
[0105] In the water electrolysis operation, electric power from the
solar power generation apparatus 2 (FIG. 3) is supplied to the
water electrolysis apparatus 8 to perform electrolysis of water.
Hydrogen produced here at less than 1 MPa (G) (for example, 0.9 MPa
(G)) is sent to the dehumidifier 20 through the pipe 57, the valve
V7, and the pipes 56, 55 as illustrated in FIG. 7. Hydrogen whose
dew point is decreased therein is sent to the alloy tank 10. At
this time, the valve V8 is opened. Here, the valves V7 and V8 are
examples of a first supply device of the present disclosure. Since
the alloy tank 10 generates heat as hydrogen is stored, if exhaust
heat thereof is equal to or higher than a temperature that can be
used for hot water supply (for example, 60.degree. C.), the exhaust
heat is used in the heat exchanger 21 for hot water storage. In
this case, the heat medium having recovered heat generated by a
hydrogen storage reaction is sent to the pipe 40, the three-way
valve V4, the pipes 48, 46, 47, 49, the three-way valve V1, the
pipe 31, the pump P1, the pipes 32, 33, the three-way valve V2, and
the pipe 34, and exchanges heat with water in the pipe 70 the heat
exchanger 21. The heat medium that is cooled here is returned from
the pipe 34 to the alloy tank 10 through the radiator 22, the pipes
36, 37, 38, the three-way valve V3, and the pipe 39, and recovers
heat again. The radiator 22 operates appropriately as
necessary.
[0106] Note that hydrogen may be supplied from the water
electrolysis apparatus 8 to the alloy tank 11 during the water
electrolysis operation. In this case, the hydrogen produced by the
water electrolysis apparatus 8 is sent to the alloy tank 11 via the
pipe 57, the valve V7, the pipes 56, 55, the dehumidifier 20, the
pipes 54, 53, the valve V9, and the pipe 52. Here, the valves V7
and V9 are examples of a second supply device of the present
disclosure. The heat medium having recovered heat generated in the
alloy tank 11 is sent to the pipes 45, 46, 47, 49, the three-way
valve V1, the pipe 31, the pump P1, the pipes 32, 33, the three-way
valve V2, and the pipe 34, and exchanges heat with water in the
pipe 70 in the heat exchanger 21. The heat medium that is cooled
here is returned to the alloy tank 11 from the pipe 34 through the
radiator 22, the pipes 36, 37, 43, the valve V6, and the pipe 44,
and recovers heat again. The radiator 22 operates appropriately as
necessary.
[0107] (Normal Operation-Fuel Cell Operation)
[0108] During operation of the fuel cell apparatus 9, for example,
as illustrated in FIG. 8, hydrogen is supplied from the alloy tank
10 to the fuel cell apparatus 9 through the pipe 50, the valve V8,
the pipes 51, 54, the dehumidifier 20, the pipes 55, 58, the valve
V10, and the pipe 59. At the same time, air in the atmosphere is
supplied to the fuel cell apparatus 9 using the blower or the like
(not illustrated), and power generation is performed. The
controller 7 instructs a controller (not illustrated) in the fuel
cell apparatus 9 to perform power generation during actual
operation. In response to this instruction, the controller (not
illustrated) in the fuel cell apparatus 9 causes the fuel cell
apparatus 9 to perform power generation. Here, the valves V8 and
V10 are examples of a third supply device of the present
disclosure. Note that when hydrogen passes through the dehumidifier
20, moisture adsorbed during dehumidification can be removed by
heating the dehumidifier 20 to, for example, about 200.degree. C.
with an electric heater or the like. Thus, the dehumidifier 20 can
exhibit a predetermined dehumidifying performance even during the
next water electrolysis operation. The heat medium having recovered
heat generated by fuel cell power generation passes through the
pipe 30, the three-way valve V1, the pipe 31, the pump P1, the
pipes 32, 33, the three-way valve V2, and the pipe 34, and
exchanges heat with water in the pipe 70 through the heat exchanger
21. Thereafter, the heat medium in the pipe 34 is sent to the alloy
tank 10 through the radiator 22, the pipes 36, 37, 38, the
three-way valve V3, and the pipe 39, and is used for heat
absorption when the alloy A releases hydrogen. Thereafter, the heat
medium is sent from the alloy tank 10 to the fuel cell apparatus 9
through the pipe 40, the three-way valve V4, and the pipes 48, 46,
47, and recovers heat again.
[0109] Note that when heating for hot water storage is not
necessary, a fan of the radiator 22 is turned on, and heat whose
amount is equal to or larger than the amount to be supplied to the
alloy is released to the atmosphere. Further, when hydrogen is
supplied from the alloy tank 11 to the fuel cell apparatus 9, the
hydrogen is sent to the dehumidifier 20 through the pipe 52, the
valve V9, and the pipes 53, 54, and hydrogen is supplied through
the pipes 55, 58, the valve V10, and the pipe 59. Here, the valves
V9 and V10 are examples of a fourth supply device of the present
disclosure. In addition, the heat medium having recovered heat
accompanying power generation of the fuel cell apparatus 9 passes
through the pipe 30, the three-way valve V1, the pipe 31, the pump
P1, the pipes 32, 33, the three-way valve V2, and the pipe 34, and
exchanges heat with water in the pipe 70 through the heat exchanger
21. The heat medium having finished heat exchange in the heat
exchanger 21 is sent to the alloy tank 11 through the pipe 34, the
radiator 22, the pipes 36, 37, 43, the valve V6, and the pipe 44,
and is used for heat absorption when the hydrogen storage alloy
(alloy B) releases hydrogen. Thereafter, the heat medium is sent
from the alloy tank 11 to the fuel cell apparatus 9 via the pipes
45, 46, 47, and recovers heat again. The radiator 22 is
appropriately operated as necessary.
[0110] The operating method of heat-storage system 1 during the
normal operation has been described. During the normal operation,
the water electrolysis operation and the fuel cell operation are
alternately repeated to thereby cope with the hot water supply
load.
[0111] Next, a flow during the heat pump operation will be
described. There are two operating methods during the heat pump
operation. One is a "hot water supply operation" that extracts heat
from an external heat source to generate heat for hot water
storage, and the other is a "regenerative operation " that returns
hydrogen to the tank where the hydrogen is originally stored by
reaction heat circulation of both the alloy tanks 10, 11. Here, the
"hot water supply operation" is an example of the first operating
mode of the present disclosure. Further, the "regenerative
operation" is an example of the second operating mode of the
present disclosure. In a period when it is difficult to achieve
energy independence such as, for example, the wintertime and
surrounding periods thereof, that is, November to March, the "hot
water supply operation" and the "regenerative operation" are
alternately repeated to thereby cope with the hot water supply
load.
[0112] (Heat Pump Operation-Hot Water Supply Operation)
[0113] First, the hot water supply operation after the regenerative
operation is completed will be described. When the regenerative
operation is finished, both the alloy tanks 10, 11 are at a low
temperature (for example, 10.degree. C.). In order to produce hot
water in the hot water supply temperature range (for example,
60.degree. C.) necessary for hot water supply from the above state,
it is necessary to heat both the alloy tanks 10, 11 to a
predetermined temperature. Heating of both the alloy tanks 10, 11
during the heat pump operation is performed by recovering heat from
the external heat source and using an exothermic reaction
accompanying hydrogen movement between both the alloy tanks 10,
11.
[0114] As illustrated in FIG. 9, heat from the external heat source
is recovered from the heat medium in the pipe 71 through the heat
exchanger 23. The heat medium in the pipe 42 having recovered the
heat of the external heat source is sent to the alloy tank 10 via
the three-way valve V3 and the pipe 39, and thus heat necessary for
releasing hydrogen is given to the alloy tank 10. The heat medium
cooled by heat exchange with the alloy tank 10 is sent to the heat
exchanger 23 via the pipe 40, the three-way valve V4, the pipe 41,
and the pump P2, and recovers heat again from the external heat
source.
[0115] The temperature of the alloy A in the alloy tank 10 rises
due to the heat supplied from the external heat source, and when
the dissociation pressure of the alloy A in the alloy tank 10
becomes higher than the dissociation pressure of the alloy B in the
alloy tank 11 as the temperature rises, hydrogen begins to move
from the alloy tank 10 to the alloy tank 11 through the pipe 50,
the valve V8, the pipes 51, 53, the valve V9, and the pipe 52.
Accompanying the movement, a hydrogen storage reaction occurs in
the alloy B in the alloy tank 11 to generate heat. The heat
generated in the alloy tank 11 is sent to the pipes 45, 46, 47, 49,
the three-way valve V1, the pipe 31, the pump P1, the pipes 32, 33,
the three-way valve V2, the pipe 34, and the heat exchanger 21
through the heat medium, and heat exchange with a heat medium in
the pipe 70 leading to the hot water storage tank 6 is performed.
The heat medium after exchanging heat is sent to the alloy tank 11
through the pipe 34, the radiator 22, the pipes 36, 37, 43, the
valve V6, and the pipe 44, and recovers heat again in the tank.
[0116] The alloy B in the alloy tank 11 generates heat due to the
hydrogen storage reaction, and heat is taken away by the heat
medium passing through the alloy tank 11. However, in the initial
stage of the hot water supply operation, since the dissociation
pressure difference between the alloy A and the alloy B is large,
hydrogen easily moves and the amount of heat generated by the
hydrogen storage reaction is large. Accordingly, the temperature of
the alloy B in the alloy tank 11 increases until reaching a steady
state. On the other hand, the temperature of the alloy A in the
alloy tank 10 decreases accompanying a hydrogen release reaction,
but since the heat medium having recovered heat of the external
heat source in the heat exchanger 23 circulates through the alloy
tank 10, the temperature rises until reaching a steady state.
[0117] Note that immediately after the hot water supply operation
is started, it is necessary to recover more heat from the external
heat source than in a steady time until temperatures of the alloys
A and B in the alloy tanks 10, 11 reach a design temperature. For
this reason, for the amount of heat necessary for the external heat
source, it is necessary to take into account the amount of sensible
heat from a state that the hot water supply operation is started
until both the alloy tanks 10, 11 reach a steady temperature, and
it is necessary to note that heat of the amount of sensible heat
cannot be extracted when the temperature is increased by reaction
heat of the alloy. Note that an external heat source may be used
for heating the alloy B in the alloy tank 11. In this manner, hot
water that can be extracted for hot water supply when the same
amount of hydrogen moves increases. In this case, however, it is
necessary to note that the amount of heat of the external heat
source to be secured also increases.
[0118] By heating in the initial stage of the hot water supply
operation, as illustrated in FIG. 10, when the temperature of the
alloy A in the alloy tank 10 becomes the temperature of the
external heat source, 35.degree. C. for example, and the
temperature of the alloy B in the alloy tank 11 becomes a
temperature in the hot water supply temperature range, 60.degree.
C. for example, and reaches a steady state, the dissociation
pressure at the temperature of the external heat source of the
alloy A in the alloy tank 10 has become higher than the
dissociation pressure at the temperature in the hot water supply
temperature range of the alloy B in the alloy tank 11. For this
reason, during the hot water supply operation, hydrogen continues
to move from the alloy tank 10 to the alloy tank 11, and the alloy
tank 11 continues to generate heat due to the hydrogen storage
reaction. Thus, hot water which has a temperature in the hot water
supply temperature range can be produced continuously.
[0119] The hot water supply operation during the heat pump
operation in the second embodiment is performed in this manner.
Next, the regenerative operation after the hot water supply
operation is completed will be described.
[0120] (Heat Pump Operation-Regenerative Operation)
[0121] When the hot water supply operation is finished, the alloys
A and B in both the alloy tanks 10, 11 are at high temperatures
(for example, 35.degree. C. and 60.degree. C.). In order to have
temperatures necessary for the regenerative operation (for example,
10.degree. C.) from this state, it is necessary to first cool the
alloys A and B of both the alloy tanks 10, 11 to a predetermined
temperature. Cooling of the alloys A and B in both the alloy tanks
10, 11 during the heat pump operation is performed by releasing
heat to the outside air and using an endothermic reaction
accompanying hydrogen movement between both the alloy tanks 10,
11.
[0122] Releasing heat to the outside air is performed by heat
exchange between the heat medium in the pipe and the outside air
via the radiator 22. Then, the heat medium cooled by the radiator
22 is sent to the alloy tank 10 via the pipes 36, 37, 38, the
three-way valve V3, and the pipe 39 as illustrated in FIG. 11.
Thus, the alloy A in the alloy tank 10 is cooled. The heat medium
heated by heat exchange with the alloy tank 10 is sent to the pipe
40, the three-way valve V4, the pipes 48, 46, 47, 49, the three-way
valve V1, the pipe 31, the pump P1, the pipes 32, 33, the three-way
valve V2, the pipe 34, and the radiator 22, and is cooled again by
the outside air.
[0123] Then, when the dissociation pressure of the alloy A in the
alloy tank 10 becomes smaller than the dissociation pressure of the
alloy B in the alloy tank 11 accompanying cooling of the alloy A in
the alloy tank 10, hydrogen begins to move from the alloy tank 11
to the alloy tank 10 through the pipe 52, the valve V9, the pipes
53, 51, the valve V8, and the pipe 50. Consequently, an endothermic
reaction accompanying release of hydrogen occurs in the alloy B in
the alloy tank 11, and the temperature of the alloy B in the alloy
tank 11 gradually decreases. On the other hand, the alloy A in the
alloy tank 10 causes an exothermic reaction due to hydrogen
storage, but since the heat medium cooled by the outside air
circulates through the alloy tank 10 through the radiator 22, the
temperature of the alloy A in the alloy tank 10 also decreases
gradually.
[0124] Note that immediately after the regenerative operation is
started, it is necessary to dissipate more heat than in a steady
time until temperatures of the alloy tanks 10, 11 reach the design
temperature. However, it is only necessary to discard this heat
because it is heat that is only to be discarded. When the
temperatures of both the alloy tanks 10, 11 reach the design
temperature (for example, 10.degree. C.), hydrogen can be moved by
reaction heat circulation between both the alloy tanks 10, 11.
Therefore, the valve V6 may be opened to circulate the heat medium
through the alloy tank 11 as illustrated in FIG. 12, so that the
temperature of the alloy tank 11 does not drop too much. When it is
no longer necessary to discard heat to the outside, the fan of the
radiator 22 may be stopped. Of course, the valve V6 may be opened
from the beginning of the regenerative operation to release
heat.
[0125] When the temperatures of the alloys A and B in the alloy
tanks 10, 11 become steady at, for example, 10.degree. C. due to
cooling in the initial stage of the regenerative operation, as
illustrated in FIG. 13, the dissociation pressure of the alloy A in
the alloy tank 10 is smaller than the dissociation pressure of the
alloy B in the alloy tank 11. For this reason, hydrogen continues
to move from the alloy tank 11 to the alloy tank 10 during the
regenerative operation, and hydrogen is stored in the alloy tank 10
for the next hot water supply operation.
[0126] The regenerative operation during the heat pump operation in
the second embodiment is performed in this manner. After the
regenerative operation, the hot water supply operation is performed
again to produce hot water. A cycle in which the hot water supply
operation and the regenerative operation are repeated alternately
is performed at least once a day. For example, the regenerative
operation may be performed when the outside air temperature is low
at night, and the hot water supply operation may be performed
during the day. In addition, this cycle may be performed multiple
times a day. For example, when two cycles are performed, the
regenerative operation and the hot water supply operation are
performed at night, and the regenerative operation and the hot
water supply operation are performed during the day. By increasing
the number of cycles, it becomes possible to increase the amount of
heat that can be used as hot water for hot water supply or the
like.
[0127] As described above, in the heat-storage system 1 of the
second embodiment, by using the alloy A and the alloy B having
different temperature-dissociation pressure characteristics of the
hydrogen storage alloys from each other, during the heat pump
operation, hot water can be produced by performing the hot water
supply operation using the external heat source and the
regenerative operation using heat release to the outside air. The
external heat source is a heat source that is previously unused or
difficult to use, such as exhaust heat generated in the home or
underground heat. Thus, according to the heat-storage system 1 of
the second embodiment that uses the external heat source, hot water
can be more efficiently produced even in the period when it is
difficult to achieve energy independence.
[0128] Note that the alloy A used in the alloy tank 10 and the
alloy B used in the alloy tank 11 are appropriately selected
according to the purpose of using hot water, the temperature of the
external heat source, the outside air temperature, and so on. For
example, an MmNi-based alloy, a TiFe-based alloy, a TiV-based BCC
alloy, a TiVCr-based BCC alloy, a TiCr-based BCC alloy, or the like
is used. Further, the alloy B in the alloy tank 11 may have a low
dissociation pressure in the entire temperature range and may have
a pressure change with respect to a temperature change as small as
possible.
[0129] Note that the lower the temperature zone of heat supplied to
the alloy tank 10 needed during the hot water supply operation, the
more the choices of available external heat sources. Thus, an
intersection of the temperature-dissociation pressure
characteristics of both the alloys A, B may be lower as long as it
does not fall below the temperature during the regenerative
operation (the temperature that can be cooled by heat release to
the outside air). Further, the smaller the difference between the
"alloy temperature during hot water supply" and the "alloy
temperature during regeneration" on the alloy A side, the lower the
sensible heat loss when the operation is switched, and thus the
more efficient in terms of energy.
[0130] Further, rather than using up all hydrogen for power
generation according to electric power demand, power generation is
not performed in a specific period to leave the hydrogen even if
there is power demand, and low-temperature exhaust heat that cannot
be used and has been originally discarded is used to perform the
heat pump operation, so as to obtain high-temperature water. Thus,
a large amount of hot water can be obtained by up to 70%, compared
to cases of not performing the heat pump operation. In addition, by
providing the minimum storage amount of hydrogen, the capacity of
the hydrogen storage alloy can be reduced by up to 20% per heat
pump operation, as compared to the case where the minimum storage
amount is not provided.
Third Embodiment
[0131] A heat-storage system 1 of a third embodiment is configured
similarly to the heat-storage system 1 of the second embodiment,
but differs in hot water supply operation method during a heat pump
operation. In the third embodiment, a hot water supply operation
during the day when surplus power of solar power generation occurs
even in a period when it is difficult to achieve energy
independence will be described.
[0132] (Heat Pump Operation-Hot Water Supply Operation)
[0133] FIG. 14 is a flow diagram of a hot water supply operation
during a heat pump operation in the third embodiment. In the third
embodiment, hydrogen is produced by the water electrolysis
apparatus 8 using surplus power of solar power generation even
during the hot water supply operation of the heat pump operation.
The hydrogen produced at this time is supplied to the alloy tank 11
via the pipe 57, the valve V7, the pipes 56, 55, the dehumidifier
20, the pipes 54, 53, the valve V9, and the pipe 52. Thus, a
storage reaction of hydrogen occurs in the alloy B in the alloy
tank 11, and the temperature of the alloy B in the alloy tank 11
rises. On the other hand, also in the third embodiment, hydrogen
released from the alloy tank 10 is supplied to the alloy tank 11
during the hot water supply operation, as in the first and second
embodiments. Thus, in the hot water supply operation of the third
embodiment, since hydrogen is supplied from the alloy tank 10 and
the water electrolysis apparatus 8 to the alloy tank 11, even if
the amount of hydrogen released from the alloy tank 10 is
restricted, the temperature of the alloy B in the alloy tank 11 can
be increased. That is, it is not necessary to facilitate hydrogen
release from the alloy tank 10 as compared to the case where the
alloy B in the alloy tank 11 is heated only with hydrogen supplied
from the alloy tank 10. Accordingly, the amount of the heat medium
in the pipe 42 that has recovered heat from the external heat
source and is to be supplied to the alloy tank 10 can be reduced,
and as a result, pump motive power for sending the heat medium can
be reduced. Thus, hot water can be produced still more efficiently.
Note that when the charging amount of hydrogen in the alloy tank 11
reaches a predetermined charging amount, water electrolysis is
stopped, and the system shifts to the regenerative operation.
Fourth Embodiment
[0134] In a heat-storage system 1 of a fourth embodiment, a fuel
cell operation is performed between a hot water supply operation of
a heat pump operation and a regenerative operation.
[0135] (Heat Pump Operation-Hot Water Supply Operation)
[0136] The hot water supply operation of the heat pump operation in
the fourth embodiment produces hydrogen in the water electrolysis
apparatus 8 using surplus power of solar power generation during a
hot water supply operation, similarly to the hot water supply
operation of the heat pump operation in the third embodiment
illustrated in FIG. 14. Further, the hydrogen produced at this time
is supplied to the alloy tank 11. However, the heat-storage system
1 according to the fourth embodiment is different in that supply of
hydrogen to the alloy tank 10 is started without shifting to the
regenerative operation after the hydrogen reaches a predetermined
charging amount in the alloy tank 11. When hydrogen is fully
charged in the alloy tank 10, water electrolysis is stopped even if
there is still surplus power. When hydrogen is stored in both the
alloy tanks 10, 11 by the water electrolysis apparatus 8 during the
heat pump operation, the alloy tank 10 is fully charged when the
hot water supply operation is finished. Thus, hydrogen cannot be
moved from the alloy tank 11 to the alloy tank 10, and the
regenerative operation cannot be performed. Accordingly, in the
fourth embodiment, the fuel cell operation is performed between the
hot water supply operation and the regenerative operation.
[0137] (Heat Pump Operation-Fuel Cell Operation)
[0138] As illustrated in FIG. 15, hydrogen remaining in the alloy
tank 10 is sent to the fuel cell apparatus 9 via the pipe 50, the
valve V8, the pipes 51, 54, the dehumidifier 20, the pipes 55, 58,
the valve V10, and the pipe 59. The hydrogen moved here is used for
power generation for power demand when the relationship of "power
by solar power generation<electric power demand of house" is
satisfied (particularly after the evening). Then, heat generated
from the fuel cell apparatus 9 is sent to the pipe 30, the
three-way valve V1, the pipe 31, the pump P1, the pipes 32, 33, the
three-way valve V2, the pipe 34, and the heat exchanger 21 through
the heat medium, and heat exchange with water in the pipe 70 is
performed. Thus, hot water is produced. Thereafter, the heat medium
in the pipe 34 is sent to the fuel cell apparatus 9 through the
radiator 22, the pipe 36, the valve V5, and the pipe 47, and
recovers heat again. Note that if the hot water storage tank 6 has
sufficient capacity and hot water can be stored in the hot water
storage tank 6, heat generated from the fuel cell apparatus 9 may
be used for production of hot water as described above, but if the
hot water cannot be stored, the heat may be released by the
radiator 22.
[0139] During the fuel cell operation, the temperature of the alloy
tank 10 decreases due to an endothermic reaction accompanying
release of hydrogen. Thus, it is possible to reduce motive power
and cold for cooling the alloy tank 10 required for the
regenerative operation after the fuel cell operation, and it is
possible to produce hot water more efficiently.
[0140] As a method of using hydrogen stored in the alloy tank 10,
it is conceivable that remaining hydrogen in the alloy tank 10 is
retained as it is in order to reduce the amount of hydrogen that
moves during the regenerative operation. In this case, motive power
and heat release to the outside air necessary for the regenerative
operation can be reduced, but since hydrogen remains in the alloy
tank 11 when the regenerative operation is finished, there is a
risk that sufficient hydrogen cannot be moved during the next hot
water supply operation, and the amount of heat necessary for hot
water supply cannot be obtained. Here, as the amount of heat per
unit amount of hydrogen obtained from one of alloys accompanying
hydrogen movement between the alloys and the amount of heat per
unit amount of hydrogen generated accompanying fuel cell power
generation, the amount of heat accompanying the fuel cell power
generation is about 4 times larger. Thus, when there is surplus
hydrogen in the alloy tank 11, by performing the fuel cell power
generation using hydrogen in the alloy tank 11, and performing
heating for hot water storage and heating of the alloy tank 11 as
necessary while covering the electric power demand of the house, a
necessary amount of stored hot water can be secured without
performing the hot water supply operation. Of course, depending on
the remaining amount of hydrogen in the alloy tank 11, by combining
the fuel cell operation and the hot water supply operation, a
necessary amount of stored hot water can be secured.
[0141] In this way, the method of using hydrogen stored more than
necessary is basically using when the amount of solar generated
power is less than the electric power demand of the house, and
using as fuel for fuel cell operation instead of hot water supply
operation is most suitable. Note that even if hot water storage is
completed, as long as there is electric power demand, power
generation with surplus amount of hydrogen may be continued, and
when the surplus runs out, the fuel cell operation is finished
regardless of the electric power demand. Further, it is not
necessary to forcibly consume the surplus hydrogen, and there is no
problem in moving hydrogen between the tanks any number of times
while the hot water supply operation and the regenerative operation
are repeated.
Fifth Embodiment
[0142] In a fifth embodiment, a heat-storage system 1 in a case
where temperature-dissociation pressure characteristics of the
alloy A in the alloy tank 10 and the alloy B in the alloy tank 11
are similar to each other as illustrated in FIG. 16 will be
described. The dissociation pressure of the alloy A is higher than
the dissociation pressure of the alloy B over the entire
temperature range. Thus, for example, even when the temperature of
the alloy tank 10 becomes 35.degree. C. and the temperature of the
alloy tank 11 becomes 60.degree. C. as in the hot water supply
operation of the first embodiment and the second embodiment, the
dissociation pressure of alloy A is lower than the dissociation
pressure of alloy B, and thus hydrogen movement from the alloy tank
10 to the alloy tank 11 does not occur. Further, even when the
temperatures of both the alloy tanks 10, 11 are both 10.degree. C.
as in the regenerative operation of the first embodiment and the
second embodiment, the dissociation pressure of the alloy A is
higher than the dissociation pressure of the alloy B, and thus
hydrogen movement from the alloy tank 11 to the alloy tank 10 does
not occur. That is, when the relationship between the
temperature-dissociation pressure characteristics of the hydrogen
storage alloys in both the alloy tanks 10, 11 is as illustrated in
FIG. 16, it is difficult to perform the heat pump operation in the
first embodiment and the second embodiment.
[0143] On the other hand, the hydrogen unit 4 of the fifth
embodiment has a configuration as illustrated in FIG. 17. Note that
while only a configuration around both the alloy tanks 10, 11 is
illustrated in FIG. 17, the other configuration is the same as that
of the hydrogen unit 4 of the first to fourth embodiments.
[0144] In the hydrogen unit 4 in the fifth embodiment, one end of a
pipe 60 is connected to a middle part of the pipe 50 connecting the
alloy tank 10 and the valve V8, and the other end of the pipe 60 is
connected to a middle part of the pipe 52 connecting the alloy tank
11 and the valve V9. This pipe 60 is provided with a valve V11 and
a gas pump P3 that sends hydrogen from the alloy tank 10 to the
alloy tank 11. Similarly, one end of another pipe 61 is connected
in a middle part of the pipe 50, and the other end of the pipe 61
is connected in a middle part of the pipe 52. The pipe 61 is
provided with a gas pump P4 that sends hydrogen from the alloy tank
11 toward the alloy tank 10 and a valve V 12.
[0145] In the hydrogen unit 4 having such a configuration, even if
movement of hydrogen does not occur by a difference in dissociation
pressure between the alloys A, B of both the alloy tanks 10, 11,
hydrogen can be moved from the side of the alloy having a low
dissociation pressure to the side of the alloy having a high
dissociation pressure as illustrated in FIG. 18 by using pressures
given by the gas pumps P3, P4 as force to move hydrogen.
[0146] When hydrogen is moved by the pressures given by the gas
pumps P3, P4, the temperature and the dissociation pressure of the
alloy on the side where hydrogen is released first decrease as
hydrogen is released. Thus, it becomes difficult for hydrogen to be
released. Accordingly, unless the alloy on the hydrogen release
side is heated so that the temperature becomes constant and
hydrogen is easily released, the pressure necessary for suction of
the gas pumps P3, P4 continues to increase, and there is a risk
that eventually hydrogen can no longer be sucked. Also in the fifth
embodiment, there is no difference from the case of using the
dissociation pressure difference between both the alloys A, B in
that it is necessary to give the amount of heat absorbed
accompanying release of hydrogen from the outside, but a
temperature zone thereof is relatively wide, and it is possible to
use a low-temperature heat source that could not be used when an
external heat source is used as a driving force.
[0147] Next, the temperature and the dissociation pressure of the
alloy on the hydrogen receiving side rise as hydrogen is stored.
Thus, it becomes difficult for hydrogen to be stored. Accordingly,
unless heat is removed so that the alloy on the hydrogen storage
side has a constant temperature and thus hydrogen is stored easily,
hydrogen cannot be pushed in by the pressures applied by the gas
pumps P3, P4. Thus, although it is necessary to remove the amount
of heat generated as hydrogen is stored, a temperature zone thereof
just needs to be determined according to the purpose of using hot
water, and the heat can also be recovered as hot water that cannot
be obtained when the dissociation pressure difference between both
the alloys A, B is used.
[0148] In the heat-storage system 1 of the fifth embodiment as
described above, providing the gas pump P3 that sends hydrogen from
the alloy tank 10 toward the alloy tank 11 and the gas pump P4 that
sends hydrogen from the alloy tank 11 toward the alloy tank 10 has
the following merits.
[0149] (1) The temperature-dissociation pressure characteristics of
both the alloys A, B do not necessarily have to have an
intersection.
[0150] (2) Choices of the temperature zone of the external heat
source to be given or removed for hydrogen absorption and release
can be expanded as compared to the case of moving hydrogen using
the dissociation pressure difference between the alloys A, B.
[0151] However, in both cases of storage and release, as lifts of
the gas pumps P3, P4 increase, power consumption is increased, and
it is necessary to raise specifications of the gas pumps P3, P4.
For this reason, alloy characteristics or an operating temperature
zone may be selected so that a discharge lift and a suction lift of
the gas pumps P3, P4 are small. Based on this idea, for example,
the temperature of the external low-temperature heat source during
the hot water supply operation and the operating temperature during
the regenerative operation can be the same. Specifically, this
operating method is conceivable when geothermal heat is used.
Further, when the gas pumps P3, P4 are provided, energy efficiency
decreases by the amount of motive power for driving the gas pumps
P3, P4 as compared to a case where the gas pumps P3, P4 are not
provided. However, the heat-storage system 1 provided with the gas
pumps P3, P4 has higher energy efficiency than conventional
heat-storage systems in which heat of the external heat source is
not used and discarded. That is, it is possible to produce hot
water more efficiently than the conventional heat-storage systems.
In addition, it is advantageous in terms of energy efficiency when
the gas pumps P3, P4 are not provided. Accordingly, in order to
make hydrogen movement using only the dissociation pressure
difference between the alloys A, B in the alloy tanks 10, 11 easily
occur, the alloys A and B may be of a combination such that the
temperature zone where the temperature-dissociation pressure
characteristics intersect is of temperatures (for example, around
20.degree. C.) between the outside air temperature in the
wintertime and surrounding periods thereof and the external heat
source temperatures.
[0152] In addition, as one that exerts a force to move hydrogen, it
is also possible to use a combination of the dissociation pressure
difference and the gas pumps P3, P4 according to an operating state
or a power situation. In this manner, there are merits as
follows.
[0153] (1) Even when the heat-storage system 1 is basically
designed to move hydrogen using the dissociation pressure
difference, by using the gas pumps P3, P4 as a force to move
hydrogen when the necessary amount of external heat source cannot
be secured, the heat pump operation can be performed efficiently
and more reliably according to conditions of the external heat
source.
[0154] (2) When the heat-storage system 1 is basically designed to
move hydrogen using the dissociation pressure difference, a need
may arise such that it is desired to complete hot water storage
operation in a short time on the demand side, or to store hot water
at a higher temperature. When such a need arises, movement of
hydrogen from the alloy tank 10 to the alloy tank 11 can be
facilitated.
[0155] (3) A heat-storage system according to alloy characteristics
or external heat source conditions can be built, such as moving
hydrogen using a dissociation pressure difference during the hot
water supply operation and moving hydrogen by driving the gas pumps
P3, P4 during the regenerative operation.
[0156] As described above, by combining the dissociation pressure
difference between both the alloys A, B and the gas pumps P3, P4 as
the force to move hydrogen, restrictions on the alloy
specifications or the external heat source when the heat pump
operation is performed can be further reduced, making it possible
to cope with a case where the operation must be performed under
conditions that deviate from design values in operation.
[0157] What to use as the force to move hydrogen is mostly
determined by the alloy characteristics, the external heat source
temperature, and the hot water supply temperature desired to be
extracted. However, depending on the day, the temperature of the
external heat source may fluctuate, or a predetermined amount of
external heat source may not be ensured. In such a case, if the gas
pumps can be driven to move hydrogen, the heat pump operation
itself can be established, and energy efficient operation can be
performed by moving hydrogen by the dissociation pressure
difference in a normal time.
[0158] In addition, when the heat pump operation is performed one
cycle per day, a basic operation is to perform a regenerative
operation when the outside air temperature is low at night and to
perform the hot water supply operation during the day. For example,
when the heat pump operation is performed two cycles a day, it is
necessary to perform the regenerative operation and the hot water
supply operation at night, and perform the regenerative operation
and the hot water supply operation during the day. In this case,
for example, in the regenerative operation during the day, the
outside air temperature becomes high, and thus the temperature
during the regenerative operation may become higher than the design
value. Accordingly, it is possible that hydrogen cannot be moved
only by the dissociation pressure difference, but by providing the
gas pumps, it becomes possible to move hydrogen.
[0159] Further, there is a possibility that the external heat
source is insufficient in the hot water supply operation during the
day, there is a possibility that a supply temperature from the
external heat source in the hot water supply operation becomes
lower than the design value. In this case, it is possible that
hydrogen cannot be moved only by the dissociation pressure
difference, but hydrogen can be moved by having the gas pumps.
Further, surplus power of solar power generation may occur during
the day depending on the day. In this case, the gas pumps can be
driven by this surplus power, and the heat pump operation can be
performed during the day. By having the gas pumps, it is possible
to cope with various situations that can be assumed in practice,
and thus both the dissociation pressure difference and the gas
pumps may be secured as the force to move hydrogen. This is
particularly effective when it is desired to perform multiple heat
pump cycles per day.
[0160] Note that if the direction of moving hydrogen with a gas
pump is one direction, "installing two gas pumps" or "making a
piping route switching circuit so that the direction of hydrogen
movement can be changed with one gas pump" is no longer necessary,
which has a merit in practice. In order to have one direction of
moving hydrogen, if the external heat source conditions are within
an assumable range, the characteristics of both the alloys may be
selected so that hydrogen can always be moved by the dissociation
pressure difference in either operation.
[0161] Table 1 illustrates examples of combinations of forces to
move hydrogen during the heat pump operation.
TABLE-US-00001 TABLE 1 Other Hot water application supply examples
operation Regenerative operation [1] Dissociation Gas pump [2]
pressure Dissociation pressure difference + difference Gas pump [3]
Gas pump Dissociation pressure difference [4] Dissociation pressure
difference + Gas pump [5] Dissociation Dissociation pressure
difference [6] pressure Gas pump [7] difference + Dissociation
pressure difference + gas pump Gas pump
[0162] In the embodiments described above, the heat-storage system
1 is configured by using the alloy tanks 10, 11 having different
alloy characteristics. However, the number of hydrogen storage
alloy tanks is not limited to the two described above, and more
hydrogen storage alloy tanks may be provided. In an example
illustrated in FIG. 19, a hydrogen storage alloy tank having an
alloy C having characteristics different from those of the alloy A
and the alloy B is provided. Here, assuming that the temperature in
the hot water supply temperature range is 60.degree. C., the
dissociation pressure of the alloy C at the temperature in the hot
water supply temperature range is lower than the dissociation
pressure of the alloy A and higher than the dissociation pressure
of the alloy B. Further, if the temperature of the external heat
source is 35.degree. C., the dissociation pressure of the alloy C
at the temperature of the external heat source is lower than the
dissociation pressure of the alloy A and higher than the
dissociation pressure of the alloy B. On the other hand, when the
outside air temperature is 10.degree. C., the dissociation pressure
of the alloy C at the outside air temperature is higher than the
dissociation pressure of the alloy A and lower than the
dissociation pressure of the alloy B. For the alloy A, the alloy B,
and the alloy C in this example, an MmNi-based alloy, a TiFe-based
alloy, a TiV-based BCC alloy, a TiVCr-based BCC alloy, a TiCr-based
BCC alloy, or the like is used.
[0163] Here, the hydrogen storage alloy tank having a relatively
high dissociation pressure in the hot water supply temperature
range is defined as a first hydrogen storage alloy tank (first
tank), and the hydrogen storage alloy tank having a relatively low
dissociation pressure in the hot water supply temperature range is
defined as a second hydrogen storage alloy tank (second tank). For
example, if the first alloy tank is the tank of the alloy A, the
second alloy tank is the tank of the alloy B or the tank of the
alloy C. Further, if the first alloy tank is the tank of the alloy
C, the second alloy tank is the tank of the alloy B. In this case,
hydrogen moves from the first alloy tank to the second alloy tank
by supplying heat from the external heat source to the first alloy
tank. Consequently, a hydrogen storage reaction occurs in the
hydrogen storage alloy (alloy B or alloy C) in the second alloy
tank, and at that time, the hot water supply operation can be
performed using heat. On the other hand, if the heat medium is
circulated so that the hydrogen storage alloy (alloy A or alloy C)
in the first alloy tank is cooled to the outside air temperature,
hydrogen moves from the second alloy tank to the first alloy tank.
Thus, the regenerative operation in which hydrogen is stored in the
first alloy tank can be performed. Thus, even when the number of
hydrogen storage alloy tanks increases, the hot water supply
operation and the regenerative operation of the heat-storage system
1 can be performed.
[0164] In the example illustrated in FIG. 19, during the hot water
supply operation, hydrogen moves sequentially in the order of the
alloy A tank, the alloy C tank, and the alloy B tank. Further,
during the regenerative operation, hydrogen moves sequentially in
the order of the alloy B tank, the alloy C tank, and the alloy A
tank. As illustrated in FIG. 19, the amount of heat that can be
taken out when there are three alloy tanks is almost doubled with
reference to a case where there are two alloy tanks. Furthermore,
when there are four alloy tanks, the amount of heat is almost
tripled. That is, the amount of heat that can be taken out can be
increased every time the number of alloy tanks is increased. As the
number of alloy tanks increases, the amount of heat from the
external heat source necessary for hydrogen release increases, but
since the energy to be obtained is larger, it is possible to
produce hot water more efficiently than hitherto.
[0165] Further, in the embodiments described above, the
configuration as illustrated in FIG. 1 or 2 is exemplified as the
heat-storage system 1, but the configuration of the heat-storage
system 1 is not limited to this. For example, the heat-storage
system 1 includes a plurality of hydrogen storage alloy tanks
having different dissociation pressure characteristics with respect
to alloy temperatures, and is operative to supply heat generated in
the hydrogen storage alloy tank to water supplied from the outside.
Then, the heat-storage system 1 is operative to be capable of
performing a hot water supply operation to circulate a heated heat
medium through a first alloy tank, and cause movement of hydrogen
from the first alloy tank to a second alloy tank, and a
regenerative operation to circulate a cooled heat medium in the
heat circulation device through the first alloy tank, and cause
movement of hydrogen from the second alloy tank to the first alloy
tank. With such a configuration, even at a time when energy
independence is difficult, hot water can be efficiently produced
using heat generated by movement of hydrogen between the hydrogen
storage alloy tanks.
[0166] In addition, in the heat-storage system 1, during the heat
pump operation, even when there is an emergency that no power is
sent from the system power 80 due to a disaster or the like for
example, fuel cell power generation can be performed with hydrogen
reserved for the heat pump operation. By using power of the
separately installed power storage apparatus 3, power from the fuel
cell apparatus 9, and hot water while it is raining or in the
nighttime when no power can be obtained from solar power
generation, although it depends on the scale of the heat-storage
system 1, it is possible to supply energy to the house 100 as usual
for several days.
[0167] In addition, when the heat-storage system 1 according to the
above embodiments is installed in a house, it is possible to expand
the effective space in the site. The reason will be described
below.
[0168] FIG. 20 is a diagram illustrating an example of a house in
an urban area, and is a site layout view illustrating the
positional relationship of a house and a garden, and so on. The
house exemplified in FIG. 20 has a land area of 100 m.sup.2 and a
building coverage ratio of 50%. In the site layout as illustrated
in FIG. 20, power storage equipment included in the heat-storage
system 1 is arranged in a space on the north side of the house.
[0169] Here, if the power storage equipment included in the
heat-storage system constituted only of lithium ion batteries (LiB)
with a storage capacity of 10 kWh, assuming that 50 kWh of energy
is to be stored as a power storage apparatus, five lithium ion
batteries are arranged as illustrated in FIG. 21. That is, when
only the lithium ion battery is used, it occupies most of the space
on the north side of the house as a footprint of the power storage
apparatus. In addition, as the size of the lithium ion battery, a
general value of a lithium ion battery having a storage capacity of
10 kWh that is currently commercially available is used. The height
of the lithium ion battery is about 1 m. In addition, an interval
of 0.3 m is provided as a space for performing maintenance between
the lithium ion batteries.
[0170] On the other hand, in the case of the heat-storage system 1
according to the present disclosure, in order to secure 50 kWh of
energy with a combined output of electric power and heat, it is
only necessary to arrange one hydrogen unit 4 having a size as
illustrated in FIG. 22. That is, the heat-storage system 1
according to the present disclosure makes it possible to reduce the
footprint of the power storage equipment to half or less as
compared to the case where only the lithium ion battery is used as
the power storage equipment. The height of the hydrogen unit 4 is
about 1.5 m.
[0171] As described above, by the heat-storage system 1 according
to the present disclosure, hot water can be produced more
efficiently than hitherto, the footprint of the power storage
equipment can be greatly reduced, and a vacant space by that amount
can be effectively utilized.
[0172] As mentioned above, although embodiments of the present
disclosure have been described, the present disclosure is not
limited to such examples. It is obvious to those skilled in the art
that various changes or modifications are conceivable within the
scope of the technical idea described in the claims, and it is
understood that such changes or modifications belong of course to
the technical scope of the present disclosure.
[0173] The present disclosure is useful for heat-storage systems
for houses and commercial facilities.
* * * * *