[0001]The present invention relates to a steam power
generation plant making use of combustion heat of various
fuel, and more particularly, to a technique for accumulating
10 (storing) a part of heat of steam as thermal energy and
supplying the power generation plant with the accumulated (stored) thermal energy as necessary.
BACKGROUND ART
15 [0002]
Patent Literature 1 discloses a solar power system in which heat storage tanks are connected to each other in parallel so as to store and dissipate heat. [0003]
20 Furthermore, there has been known a technique for
storing thermal energy in a heat storage apparatus having two heat storage portions whose temperature characteristics are in different temperature ranges to use the stored thermal energy for an operation of a power generation plant. For
25 example, Patent Literature 2 discloses a solar power
generation plant having a heat storage portion in which a high-temperature heat storage device and a low-temperature heat storage device having different heat storage media are
2

connected to each other in series. In the system disclosed
in Patent Literature 2, in a heat storage operation mode, a
part of superheated steam is stored in the order of the high-
temperature heat storage device and the low-temperature heat
5 storage device. On the other hand, in a heat release
operation mode, water supplied from a feed water pump flows
into in the order of the low-temperature heat storage device
and the high-temperature heat storage device so that the
heat stored in each heat storage device is recovered, thereby
10 generating the superheated steam and supplying the generated
steam with a steam turbine.
CITATION LIST
PATENT LITERATURE
15 [0004]
Patent Literature 1: JP-A-2017-155667
Patent Literature 2: WO-2014-014027
SUMMARY OF INVENTION
20 TECHNICAL PROBLEM
[0005]
According to the technique disclosed in Patent Literature 1, during storage of heat, saturated steam is supplied from the solar power system to each heat storage
25 tank one by one in order. Specifically, the heat storage
tanks are switched therebetween when the temperature of each heat storage tank, which has been monitored, reaches the saturation temperature of a heat medium of each heat storage
3

tank. In the same manner, during dissipation of heat, water
is supplied to each heat storage tank one by one in order so
that gas-liquid two-phase fluid containing the saturated
steam is generated by heat exchange and supplied to the solar
5 power system. However, since sensible heat storage by using
a solid heat storage material such as concrete is performed
in each heat storage layer, the temperature of the heat
storage material is also lowered with heat release, which
makes it difficult to control the temperature of the gas-
10 liquid two-phase fluid.
[0006]
The technique disclosed in Patent Literature 2
includes two types of heat storage devices for high
temperature and low temperature. However, since the high-
15 temperature heat storage device performs sensible heat
storage by using molten salt, in the same manner as the
technique of Patent Literature 1, the output temperature of
steam is lowered with the temperature decrease due to
emission of the molten salt at the time of using the stored
20 heat. In addition, since two types of heat storage devices
for high-temperature and low-temperature are connected to
each other in series, in the case where the temperature of
the steam flowing thereinto is decreased, the steam absorbs
the heat from the high-temperature heat storage device on
25 the contrary and thus the heat cannot be stored efficiently.
[0007]
Latent heat storage makes use of latent heat of phase transformation of a material, and is capable of storing and
4

supplying heat having a fixed temperature corresponding to
a melting point of a heat storage material. However,
generally in the power generation plant, since water and
steam in different temperature ranges flow in each
5 constituent device, and since the technique disclosed in
Patent Literature 2 uses a heat storage material having a temperature characteristic only in one temperature range, water and steam in a plurality of different temperature ranges cannot be supplied to each device of the power
10 generation plant. In addition, since the technique
disclosed in Patent Literature 2 uses only one type of latent heat storage material, an amount of heat storage is determined by the temperature characteristic of the latent heat storage material, and thus heat storage cannot be
15 efficiently performed.
[0008]
The present invention has been made in view of the circumstances above, and an object thereof is to provide a technique for efficiently storing and using, in a plurality
20 of different temperature ranges, excess energy generated in
a power generation plant.
SOLUTION TO PROBLEM
[0009]
25 One of the aspects of the present invention is a heat
storage device (apparatus) including a plurality of heat storage portions, each of which is configured to recover heat from fluid passing through a flow path provided therein
5

to store the recovered, the plurality of heat storage
portions including: a first heat storage portion having a
temperature characteristic in a first temperature range; and
a second heat storage portion having a temperature
5 characteristic in a second temperature range that is lower
than the first temperature range, the flow path including: a first flow path that allows the fluid flowing into the heat storage apparatus to pass through in an order of the first heat storage portion and the second heat storage
10 portion, and discharges the fluid from the heat storage
apparatus; a second flow path that branches at a first branch portion on an upstream of the first heat storage portion of the first flow path, allows the fluid flowing into the heat storage apparatus to pass through the second heat storage
15 portion while bypassing the first heat storage portion, and
discharges the fluid from the heat storage apparatus; and an on-off valve for controlling inflow of the fluid into the flow path, the on-off valve including: a first on-off valve that is provided on the first flow path to control inflow of
20 the fluid into the first heat storage portion; and a second
on-off valve that is provided on the second flow path to control inflow of the fluid into the second heat storage portion, the first on-off valve being configured to be in an open state when temperature of the fluid is equal to or
25 higher than a first temperature threshold determined by the
first temperature range, and the second on-off valve being configured to be in an open state when the temperature of the fluid is less than the first temperature threshold.
6

[0010]
Another one of the aspects of the present invention is
a heat storage apparatus including a plurality of heat
storage portions, each of which is configured to recover
5 heat from fluid passing through a flow path provided therein
to store the recovered heat, the plurality of heat storage portions including: a first heat storage portion having a temperature characteristic in a first temperature range; and a second heat storage portion having a temperature
10 characteristic in a second temperature range that is lower
than the first temperature range, the flow path including: a first flow path that allows the fluid flowing into the heat storage apparatus to pass through the first heat storage portion, and discharges the fluid from the heat storage
15 apparatus; a second flow path that branches at a first branch
portion on an upstream of the first heat storage portion of the first flow path, allows the fluid flowing into the heat storage apparatus to pass through the second heat storage portion, and discharges the fluid from the heat storage
20 apparatus; and an on-off valve for controlling inflow of the
fluid into the flow path, the on-off valve including: a first on-off valve that is provided on the first flow path to control inflow of the fluid into the first heat storage portion; and a second on-off valve that is provided on the
25 second flow path to control inflow of the fluid into the
second heat storage portion, the first on-off valve being configured to be in an open state when temperature of the fluid is equal to or higher than a first temperature
7

threshold determined by the first temperature range, and the
second on-off valve being configured to be in an open state
when the temperature of the fluid is less than the first
temperature threshold.
5 [0011]
Still another one of the aspects of the present invention is a power generation plant including: a boiler that heats supplied water to generate superheated steam; a steam turbine that is rotatably driven by the superheated
10 steam generated in the boiler to drive a generator; and a
feed water line that converts exhaust steam from the steam turbine back to water and supplies the boiler with the water, the power generation plant further including a heat storage apparatus configured to store thermal energy of an excess
15 amount of the superheated steam from among the superheated
steam generated in the boiler, the heat storage apparatus is configured by the heat storage apparatus described above, and the thermal energy stored in the heat storage apparatus is used for an operation of the power generation plant.
20 [0012]
Still another one of the aspects of the present invention is an operation control method during fast cut back in a power generation plant including a steam turbine that drives a generator, a boiler that generates fluid to be
25 supplied to the steam turbine, a heat storage apparatus that
has a plurality of heat storage portions configured to recover heat from the fluid passing through a flow path provided therein to store the recovered heat, a turbine
8

bypass pipe that introduces the fluid generated by the boiler
to the heat storage apparatus while bypassing the steam
turbine, and a turbine bypass on-off valve that controls a
flow rate of the fluid flowing into the turbine bypass pipe,
5 each of the plurality of heat storage portions having a
temperature characteristic in each different temperature range, the flow path including a plurality of branch flow paths each of which introduces the fluid flowing into the heat storage apparatus to each of the plurality of heat
10 storage portions, and each of the plurality of branch flow
paths including each of on-off valves for controlling inflow of the fluid, which is introduced by each of the plurality of branch flow paths, into each of the plurality of the heat storage portions, the operation control method including the
15 steps of: upon receiving an instruction of disconnecting
from a power grid, narrowing down load of the boiler and making the turbine bypass on-off valve in an open state, measuring temperature of the fluid passing through the turbine bypass pipe; making one of the on-off valves provided
20 in one of the plurality of branch flow paths for introducing
the fluid to one of the heat storage portions that has the temperature characteristic in a temperature range to which the temperature of the fluid belongs to be in an open state; and making other ones of the on-off valves to be in close
25 states.
ADVANTAGEOUS EFFECTS OF INVENTION [0013]
9

According to the present invention, it is possible to
efficiently store and use, in a plurality of different
temperature ranges, excess energy generated in a power
generation plant. The problems, configurations, and
5 advantageous effects other than those described above will
be clarified by explanation of the embodiment below.
BRIEF DESCRIPTION OF DRAWINGS [0014]
10 [FIG. 1] FIG. 1A illustrates a system configuration of a
power generation plant according to an embodiment of the present invention. FIG. 1B illustrates a configuration of a controller according to the embodiment of the present invention.
15 [FIG. 2] FIG. 2A and FIG. 2B explain an opening and closing
state of each on-off valve during an operation of the power generation plant according to the embodiment of the present invention. [FIG. 3] FIG. 3 illustrates a configuration of a heat storage
20 apparatus according to the embodiment of the present
invention.
[FIG. 4] FIG. 4A explains change in boiler load and generation of excess steam during a FCB operation. FIG. 4B illustrates a table showing a correlation between boiler
25 load and steam temperature.
[FIG. 5] FIG. 5A illustrates a graph showing a relation between change in steam temperature and operation modes. FIG. 5B illustrates a table showing operation modes and shit
10

conditions based on temperature.
[FIG. 6] FIG. 6A and FIG. 6B explain, for each operation
mode, an opening and closing state of each on-off valve of
the heat storage apparatus according to the embodiment of
5 the present invention.
[FIG. 7] FIG. 7A and FIG. 7B explain, for each operation mode, an opening and closing state of each on-off valve of the heat storage apparatus according to the embodiment of the present invention.
10 [FIG. 8] FIG. 8 explains design temperature of each heat
exchanger of a boiler of a power generation plant.
[FIG. 9] FIG. 9 explains an example of connection at the time of heat recovery from the heat storage apparatus according to the embodiment of the present invention.
15 [FIG. 10] FIG. 10 illustrates a configuration of a heat
storage apparatus according to a modification of the present invention.
[FIG. 11] FIG. 11A and FIG. 11B explain, for each operation mode, an opening and closing state of each on-off valve of
20 the heat storage apparatus according to the modification of
the present invention.
[FIG. 12] FIG. 12A and FIG. 12B explain, for each operation mode, an opening and closing state of each on-off valve of the heat storage apparatus according to the modification of
25 the present invention.
[FIG. 13] FIG. 13A and FIG. 13B illustrate a configuration of a heat storage apparatus according to another modification of the present invention.
11

[FIG. 14] FIG. 14A and FIG. 14B illustrate a configuration of a heat storage apparatus according to still another modification of the present invention.
[FIG. 15] FIG. 15A and FIG. 15B illustrate a configuration
5 of a heat storage apparatus according to still another
modification of the present invention.
[FIG. 16] FIG. 16A and FIG. 16B illustrate a system of a modification of the present invention.
[FIG. 17] FIG. 17 explains an example of connection at the
10 time of heat recovery from the heat storage apparatus
according to the embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS [0015]
15 An example of a power generation plant to which a heat
storage device (apparatus) according to an embodiment of the present invention is applied will be described. The heat storage apparatus of the present embodiment is used, for example, in a power generation plant 100 illustrated in FIG
20 1.
[0016]
FIG. 1A illustrates a fluid system of the power generation plant 100 of the present embodiment. The power generation plant 100 of the present embodiment includes a
25 boiler 110 that burns fuel to generate steam by heat of the
combustion, a steam turbine 120 that drives a generator 101 by rotating a turbine using the steam generated from the boiler 110 so as to generate electricity, a feed water line
12

130 that supplies the boiler 110 with water, a heat storage
apparatus 140 that stores thermal energy of the steam
superheated by the boiler 110, and a controller 150 (FIG.
1B).
5 [0017]
The boiler 110 includes an economizer (ECO) 111, a furnace water cooled wall 112, a steam separator 113, a superheater 114, and a reheater 115. The boiler 110 may include a plurality of superheaters 114 in a plurality of
10 stages from downstream to upstream.
[0018]
The steam turbine 120 includes a high-pressure steam turbine (HPT) 121, an intermediate-pressure steam turbine (IPT) 122, and a low-pressure steam turbine (LPT) 123, each
15 of which performs predetermined works for driving the
generator 101. [0019]
The feed water line 130 is provided with a condenser 131, a condensate pump 132, a low-pressure feed water
20 superheater (low-pressure heater) 133, a deaerator 134, a
feed water pump 135, and a high-pressure feed water superheater (high-pressure heater) 136. [0020]
In the power generation plant 100 designed with the
25 structure above, the economizer 111 preheats the supplied
water by heat exchange with the combustion gas. In the furnace water cooled wall 112, the water preheated in the economizer 111 passes through a furnace wall tube (not
13

illustrated) formed on its wall so that water-steam two-
phase fluid is generated. The water-steam two-phase fluid
generated in the furnace water cooled wall 112 is sent to
the steam separator 113 to be separated into saturated steam
5 and saturated water. Here, the saturated steam is introduced
to the superheater 114 while the saturated water is made to pass through a first pipe 161 and then introduced to the condenser 131. [0021]
10 The superheater 114 superheats, by heat exchange with
the combustion gas, the steam that has been separated by the steam separator 113, and the superheated steam is introduced into the high-pressure steam turbine 121 via a main steam pipe 162. The steam that has performed predetermined works
15 in the high-pressure steam turbine 121 passes through a low-
temperature reheat steam pipe 163, and is introduced to the reheater 115. The reheater 115 heats the steam that has performed predetermined works in the high-pressure steam turbine 121. The steam that has been superheated in the
20 reheater 115 passes through a high-temperature reheat steam
pipe 164, and is supplied to the intermediate-pressure steam turbine 122 and the low-pressure steam turbine 123. The steam performs works in the intermediate-pressure steam turbine 122 and the low-pressure steam turbine 123,
25 respectively, thereby driving the generator 101. The main
steam pipe 162 includes a first stop valve 176, and the high-temperature reheat steam pipe 164 includes a second stop valve 177.
14

[0022]
The main steam pipe 162 and the low-temperature reheat
steam pipe 163 are connected to each other via a high-
pressure bypass steam pipe 165 having a first on-off valve
5 171.
[0023]
The steam that has finished the works in the low-pressure steam turbine 123 passes through a first exhaust steam pipe 166, and is introduced into the condenser 131.
10 The condensate pump 132 makes the condensate water that has
condensed by the condenser 131 pass through the low-pressure heater 133 together with the saturated water sent from the steam separator 113. Thereafter, the condensate water is sent to the deaerator 134, whereby gas components in the
15 condensate water are removed. The feed water pump 135
further boosts the condensate water that has passed through the deaerator 134. Thereafter, the condensate water that has been boosted is supplied to the high-pressure heater 136 to be heated therein, and finally is returned to the boiler
20 110.
[0024]
The power generation plant 100 further includes a turbine bypass steam pipe 167 that branches from the high-temperature reheat steam pipe 164 and introduces the steam
25 to the condenser 131 while bypassing the intermediate-
pressure steam turbine 122. The turbine bypass steam pipe 167 includes a turbine bypass on-off valve 172. [0025]
15

The heat storage apparatus 140 of the present
embodiment is disposed on the turbine bypass steam pipe 167.
The heat storage apparatus 140 stores thermal energy of the
steam that is introduced to the heat storage apparatus 140
5 through the turbine bypass steam pipe 167. The steam after
heat exchange performed by the heat storage apparatus 140 is introduced into the condenser 131. [0026]
The turbine bypass steam pipe 167 may further include
10 a second bypass steam pipe 168 that introduces the steam to
the condenser 131 while bypassing the heat storage apparatus 140. In this case, on the downstream of a branch point between the turbine bypass steam pipe 167 and the second bypass steam pipe 168, each of a third on-off valve 173 and
15 a fourth on-off valve 174 is provided.
[0027]
In addition, the turbine bypass steam pipe 167 includes a temperature sensor 181 configured to detect temperature of the steam passing through the inside of the turbine bypass
20 steam pipe 167.
[0028]
As illustrated in FIG. 1B, the controller 150 is configured to control opening and closing operations of each on-off valve in response to instructions from the outside
25 (for example, a control console 151 installed in the power
generation plant), or signals output from various sensors including the temperature sensor 181, which are installed in the power generation plant 100.
16

[0029]
The power generation plant 100 of the present
embodiment includes, for example, two types of operation
modes: a normal operation mode for supplying the steam
5 turbine 120 with steam to drive the generator 101; and a
heat storage operation mode for storing thermal energy of steam generated by the boiler 110 in the heat storage apparatus 140 without supplying the steam turbine 120 with the steam.
10 [0030]
Upon receiving a command for performing an operation in the normal operation mode from such as the control console 151, as illustrated in FIG. 2 A, the controller 150 outputs closing commands to the turbine bypass on-off valve 172 and
15 the first on-off valve 171. Since the turbine bypass on-off
valve 172 and the first on-off valve 171 are closed, steam and water are circulated between the boiler 110, the steam turbine 120, and the feed water line 130, whereby the generator 101 is driven.
20 [0031]
On the other hand, upon receiving a command for performing an operation in the heat storage operation mode, as illustrated in FIG. 2B, the controller 150 outputs opening commands to the turbine bypass on-off valve 172, the third
25 on-off valve 173, and the first on-off valve 171.
Furthermore, the controller 150 outputs closing commands to the fourth on-off valve 174, the first stop valve 176, and the second stop valve 177. Since the turbine bypass on-off
17

valve 172 and the third on-off valve 173 are opened, the
steam in the high-temperature reheat steam pipe 164 is
introduced to the heat storage apparatus 140.
[0032]
5 Furthermore, the controller 150 of the present
embodiment controls opening and closing operations of on-off valves included in respective flow paths of the heat storage apparatus 140, which will be described later. Details of the control will be described later, too.
10 [0033]
[Heat Storage Apparatus]
Next, the heat storage apparatus 140 of the present embodiment will be described with reference to FIG. 3. Hereinafter, in this specification, steam, water, and the
15 like circulating in the power generation plant 100 are
referred to as fluid when there is no need to distinguish them from each other. [0034]
The heat storage apparatus 140 of the present
20 embodiment includes a plurality of heat storage layers, each
of which is formed of a heat storage material having a temperature characteristic (melting point) in each different temperature range. Each of the heat storage layers includes at least one heat exchanger.
25 [0035]
Within the heat storage apparatus 140, flow paths are provided in a manner that heat exchangers in the respective heat storage layers are connected to each other in series
18

and in parallel. Upon storing heat in the heat storage
apparatus 140, flow paths through which the fluid passes are
changed over depending on temperature of the fluid supplied
to the heat storage apparatus 140, thereby enabling efficient
5 heat storage. Changing paths is realized by a command output
from the controller 150 to the on-off valve provided in each path, which will be described later. [0036]
Hereinafter, in the present embodiment, an example in
10 which three heat storage layers are provided as the heat
storage layers will be described. The three heat storage layers include: a high-temperature heat storage layer 210 (hereinafter, also simply referred to as a high-temperature layer 210) formed of a heat storage material having a
15 temperature characteristic (melting point) in a temperature
range around 580°C (first temperature range); an intermediate-temperature heat storage layer 220 (intermediate-temperature layer 220) formed of a heat storage material having a temperature characteristic in a
20 temperature range around 500°C (second temperature range);
and a low-temperature heat storage layer 230 (low-temperature layer 230) formed of a heat storage material having a temperature characteristic in a temperature range around 400°C (third temperature range).
25 [0037]
The heat storage apparatus 140 includes, as flow paths used for storing heat, a first flow path 241, a second flow path 242, and a third flow path 243. The first flow path
19

241 allows the fluid to pass through the high-temperature
layer 210, the intermediate-temperature layer 220, and the
low-temperature layer 230 in this order. The fluid passing
through the first flow path 241 performs heat exchange at
5 each heat storage layer so that heat is stored in each heat
storage layer. The second flow path 242 allows the fluid to pass through the intermediate-temperature layer 220 and the low-temperature layer 230 in this order. The fluid passing through the second flow path 242 performs heat exchange in
10 each heat storage layer so that heat is stored in each heat
storage layer. The third flow path 243 allows the fluid to pass only through the low-temperature layer 230. The fluid passing through the third flow path 243 exchanges heat in the low-temperature layer 230 so that heat is stored in the
15 low-temperature layer 230.
[0038]
Heat exchange is performed at each heat exchanger provided in each heat storage layer. In the present embodiment, as illustrated in FIG. 3, the high-temperature
20 layer 210 includes a high-temperature heat exchanger 211,
the intermediate-temperature layer 220 includes a first intermediate-temperature heat exchanger 221 and a second intermediate-temperature heat exchanger 222, and the low-temperature layer 230 includes a first low-temperature heat
25 exchanger 231, a second low-temperature heat exchanger 232,
and a third low-temperature heat exchanger 233, respectively. [0039]
Each heat exchanger (high-temperature heat exchanger
20

211, the first intermediate-temperature heat exchanger 221,
the second intermediate-temperature heat exchanger 222, the
first low-temperature heat exchanger 231, the second low-
temperature heat exchanger 232, and the third low-
5 temperature heat exchanger 233) performs heat exchange with
fluid that flows in each heat storage layer. Each heat
exchanger functions as a heat storage portion for storing
thermal energy in each heat storage layer in which each heat
exchanger is disposed when fluid having temperature equal to
10 or higher than a melting point of each heat storage layer
flows in each heat storage layer. On the other hand, when
fluid having temperature lower than the melting point of
each heat storage layer flows in each heat storage layer,
each heat exchanger dissipates the thermal energy stored in
15 each heat storage layer.
[0040]
The first flow path 241 branches from the turbine
bypass steam pipe 167 at a branch point 271, connects the
high-temperature heat exchanger 211, the first intermediate-
20 temperature heat exchanger 221, and the first low-
temperature heat exchanger 231 in this order, and then joins
the turbine bypass steam pipe 167 at a merging point 272.
The first flow path 241 allows the fluid flowing into the
heat storage apparatus 140 to pass through the high-
25 temperature heat exchanger 211, the first intermediate-
temperature heat exchanger 221, and the first low-
temperature heat exchanger 231 in this order, and then
discharges the fluid from the heat storage apparatus 140.
21

When the temperature of the supplied fluid is higher than
the melting point of the high-temperature layer 210, the
thermal energy of the fluid is stored in the high-temperature
layer 210, the intermediate-temperature layer 220, and the
5 low-temperature layer 230 in this order.
[0041]
The second flow path 242 branches from the turbine bypass steam pipe 167 at the branch point 271, connects the second intermediate-temperature heat exchanger 222 and the
10 second low-temperature heat exchanger 232 in this order, and
joins the turbine bypass steam pipe 167 at the merging point 272. The second flow path 242 allows the fluid flowing into the heat storage apparatus 140 to pass through the second intermediate-temperature heat exchanger 222 and the second
15 low-temperature heat exchanger 232 in this order, and then
discharges the fluid from the heat storage apparatus 140. When the temperature of the supplied fluid is higher than the melting point of the intermediate-temperature layer 220, the thermal energy of the fluid is stored in the
20 intermediate-temperature layer 220 and the low-temperature
layer 230 in this order. [0042]
The third flow path 243 branches from the turbine bypass steam pipe 167 at the branch point 271, and joins the
25 turbine bypass steam pipe 167 at the merging point 272 via
the third low-temperature heat exchanger 233. The third flow path 243 allows the fluid flowing into the heat storage apparatus 140 to pass only through the third low-temperature
22

heat exchanger 233, and then discharges the fluid from the
heat storage apparatus 140. When the temperature of the
supplied fluid is higher than the melting point of the low-
temperature layer 230, the thermal energy of the fluid is
5 stored in the low-temperature layer 230.
[0043]
At the inlet side of the heat storage apparatus 140, the first flow path 241, the second flow path 242, and the third flow path 243 include a high-temperature on-off valve
10 251, an intermediate-temperature on-off valve 252, and a
low-temperature on-off valve 253, respectively. These on-off valves are configured to be opened and closed in response to a command output from the controller 150 in accordance with the temperature of the fluid flowing, in the turbine
15 bypass steam pipe 167, on the upstream side of the heat
storage apparatus 140. [0044]
The controller 150 detects temperature of the fluid flowing into the heat storage apparatus 140, and opens and
20 closes the respective on-off valves in accordance with the
detected temperature so as to control inflow paths of the fluid. For example, the controller 150 controls opening and closing operations of the valves in accordance with the temperature of the flowing fluid such that heat in a heat
25 storage layer whose heat storage material has a melting point
that is lower than the temperature of the fluid while being closest to the temperature of the fluid is stored. A specific example of controlling the on-off valves will be
23

described later. [0045]
As the heat storage material used for each heat storage
layer, for example, a latent heat storage material making
5 use of latent heat of phase transformation of a material may
be employed. The temperature characteristic of the heat storage layer is determined based on a melting temperature (melting point) of this latent heat storage material. Furthermore, as the heat storage material used for each heat
10 storage layer, an alloy material whose heat storage
temperature (melting point) exceeds 500°C may be employed. Still further, as the heat storage material, a structure in which the alloy material is included by ceramics or metal may be employed. For example, latent-heat storage body
15 microcapsules disclosed in WO 2017/200021 can be used.
[0046]
By using, for each heat storage layer, the heat storage material having the structure in which a latent heat storage material is included by such as ceramics, it is possible to
20 obtain a heat storage portion making use of phase
transformation of the latent heat storage material, which is operated only by input and output of heat. Since the melting temperature can be controlled by composition at the time of manufacturing the latent heat storage material, a
25 temperature range of the fluid can be more finely set.
[0047]
As the heat storage material used for each heat storage layer, in accordance with a temperature range of thermal
24

energy to be stored in the heat storage apparatus 140, one
having a melting point in the temperature range is selected.
A heat storage capacity of each heat storage layer is also
determined based on an assumed amount of excess thermal
5 energy. As a result, it is possible to efficiently store
heat without wasting the generated excess energy, which also leads to optimization of facility investment. [0048]
Within the heat storage apparatus 140, as flow paths
10 used for heat recovery, flow paths for connecting the heat
exchangers disposed in the same heat storage layer are further provided. As the flow paths for heat recovery, the heat storage apparatus 140 includes a first heat recovery pipe 261 passing through the high-temperature heat exchanger
15 211 of the high-temperature layer 210, a second heat recovery
pipe 262 passing through the first intermediate-temperature heat exchanger 221 and the second intermediate-temperature heat exchanger 222 of the intermediate-temperature layer 220, and a third heat recovery pipe 263 passing through the first
20 low-temperature heat exchanger 231, the second low-
temperature heat exchanger 232, and the third low-temperature heat exchanger 233 of the low-temperature layer 230. [0049]
25 The first heat recovery pipe 261 allows the fluid to
pass only through the high-temperature layer 210 at the time of heat recovery so as to recover heat only from the high-temperature layer 210. The second heat recovery pipe 262
25

allows the fluid to pass only through the intermediate-
temperature layer 220 so as to recover heat only from the
intermediate-temperature layer 220. The third heat recovery
pipe 263 allows the fluid to pass only through the low-
5 temperature layer 230 so as to recover heat only from the
low-temperature layer 230.
[0050]
As described above, according to the heat storage apparatus 140 of the present embodiment, the thermal energy
10 of a plurality of different temperature corresponding to the
melting points of the heat storage layers can be recovered independently and separately to each other at the time of heat recovery. The recovered thermal energy of different temperature can be supplied to utilization places in
15 accordance with the required temperature. That is,
according to the heat storage apparatus 140 of the present embodiment, it is possible to realize selective use of heat in accordance with purposes. [0051]
20 [Example of Use]
Hereinafter, an example of use of the power generation plant 100 provided with the heat storage apparatus 140 of the present embodiment will be described. [0052]
25 For example, in the power generation plant 100, when
there is an accident in a power transmission line system, so-called a Fast Cut Back (FCB) operation, in which the generator 101 is disconnected from the power grid to decrease
26

the generated power to in-plant auxiliary power
corresponding to a few percent of the generated power in the
normal operation, is performed. When an operation of the
plant 100 is shifted to this FCB operation, the steam turbine
5 120 that drives the generator 101 is made in an unloaded
state. By rapidly narrowing down the input of water feed to the boiler 110 to the lowest load, the operation of the plant 100 is shifted to in-plant individual load operation. [0053]
10 An outline of control during the FCB operation in the
power generation plant 100 provided with the heat storage apparatus 140 of the present embodiment will be described with reference to FIG. 4A. [0054]
15 After disconnection from the power grid, for example,
in a coal combustion plant, operations of mills that supply the boiler 110 with coal are stopped one by one at the timing indicated by the asterisks on the broken line illustrated in FIG. 4A so that the load of the boiler 110 is narrowed down
20 to such as about 5%. Even when the mills are stopped in
this manner, steam to be generated by the boiler 110 continues to be generated as excess energy as indicated by the diagonal lines illustrated in FIG. 4A. [0055]
25 When the load of the boiler 110 is narrowed down, the
temperature of the steam passing through the turbine bypass steam pipe 167 is also decreased. For example, FIG. 4B illustrates change in the temperature of steam passing
27

through the turbine bypass steam pipe 167 when the load of
the boiler 110 is gradually narrowed down.
[0056]
The present embodiment is configured to, after
5 disconnection from the power grid, store an amount of heat
of excess energy that continues to be generated in the heat storage apparatus 140. At this time, in accordance with the temperature of the steam flowing in the turbine bypass steam pipe 167, control of opening and closing each on-off valve
10 is performed so that heat is stored in a heat storage layer
whose heat storage material has a melting point that is lower than the temperature of the fluid while being closest to the temperature of the fluid. [0057]
15 Furthermore, the present embodiment is configured to,
after reconnection to the power grid, recover the thermal energy stored in the heat storage apparatus 140 and use the recovered energy for operating the boiler 110. At this time, in accordance with the design temperature of each heat
20 exchanger (the furnace water cooled wall 112, the steam
separator 113, and the superheater 114) included in the boiler 110, a part of the fluid supplied to each heat exchanger is branched so that the thermal energy from a heat storage layer whose heat storage material has a melting point
25 corresponding to the design temperature is recovered and
returned to the boiler 110. [0058]
Hereinafter, a flow of control relating to heat storage
28

in the heat storage apparatus 140 performed by the controller
150 during the FCB operation will be described.
[0059]
Upon receiving an instruction of disconnecting from
5 the power grid, the controller 150 narrows down the load of
the boiler 110 while outputting an opening operation instruction to the turbine bypass on-off valve 172 to make the turbine bypass on-off valve 172 be in an open state. Thus, the fluid generated in the boiler 110 is introduced to
10 the heat storage apparatus 140 via the turbine bypass steam
pipe 167. [0060]
Thereafter, the controller 150 detects temperature of the fluid flowing in the turbine bypass steam pipe 167, and
15 controls the opening and closing operations of the high-
temperature on-off valve 251, the intermediate-temperature on-off valve 252, and the low-temperature on-off valve 253 in accordance with the detected temperature. [0061]
20 In this case, a temperature range of each heat storage
layer is determined in accordance with the bypass steam temperature after a predetermined time has elapsed after disconnection from the power grid. Furthermore, a heat storage capacity of each heat storage layer shall be capable
25 of storing an excess energy amount after each time has
elapsed. [0062]
Hereinafter, a case in which a latent heat storage
29

material whose melting point is 580°C is used for the high-
temperature layer 210, a latent heat storage material whose
melting point is 500°C is used for the intermediate-
temperature layer 220, and a latent heat storage material
5 whose melting point is 400°C is used for the low-temperature
layer 230 will be described as a specific example of opening and closing operation instructions that are output from the controller 150 to each on-off valve. Here, the second bypass steam pipe 168 will also be described.
10 [0063]
It is assumed that the steam temperature in the turbine bypass steam pipe 167 (turbine bypass steam temperature) varies with decrease in the load of the boiler 110 as illustrated in FIG. 5A.
15 [0064]
Here, as temperature thresholds T1 and T2, values in which about 10°C is added as a margin to the melting point of each latent heat storage material are set. For example, T1 is set to 590°C, and T2 is set to 510°C. Furthermore, T3
20 (=410°C) is set as a temperature threshold for bypassing the
heat storage apparatus 140 via the second bypass steam pipe 168 without storing heat in the heat storage apparatus 140. [0065]
The controller 150 of the present embodiment is
25 configured to control the opening and closing operations of
each on-off valve of the heat storage apparatus 140 every time the turbine bypass steam temperature reaches the temperature threshold. In the present embodiment,
30

operations in different opening and closing modes of the on-
off valves are respectively referred to as operation modes.
In other words, the controller 150 shifts the operation modes
every time the turbine bypass steam temperature reaches the
5 temperature threshold.
[0066]
FIG. 5B illustrates, in the table, the relation between the turbine bypass steam temperature T (hereinafter, referred to as bypass steam temperature T) and the
10 temperature thresholds T1, T2, T3 when each operation mode
is executed. As illustrated in FIG. 5B, an operation mode 1 is the operation mode when the bypass steam temperature T is the first temperature threshold T1 or more. An operation mode 2 is the operation mode when the bypass steam
15 temperature T is the second temperature threshold T2 or more
while being less than the first temperature threshold T1. An operation mode 3 is the operation mode when the bypass steam temperature T is the third temperature threshold T3 or more while being less than the second temperature threshold
20 T2. An operation mode 4 is the operation mode when the
bypass steam temperature T is less than the third temperature threshold T3. Note that the operation mode 4 corresponds to, for example, an emergency such as breakdown of the power generation plant 100.
25 [0067]
In the operation mode 1, in other words, when the bypass steam temperature T is T1 or more, as illustrated in FIG. 6A, the controller 150 opens only the high-temperature
31

on-off valve 251 while closing the other on-off valves 252,
253, 174. Thus, as illustrated in FIG. 6A by the thick lines,
the fluid flowing into the heat storage apparatus 140 flows
into the high-temperature heat exchanger 211, the first
5 intermediate-temperature heat exchanger 221, and the first
low-temperature heat exchanger 231 in this order. [0068]
In this case, the fluid whose temperature is reduced by heat exchange in the high-temperature heat exchanger 211
10 flows into the first intermediate-temperature heat exchanger
221. The fluid whose temperature is further reduced by heat exchange in the first intermediate-temperature heat exchanger 221 flows into the first low-temperature heat exchanger 231. Then, the fluid whose temperature is further
15 reduced by heat exchange in the first low-temperature heat
exchanger 231 is discharged from the heat storage apparatus 140 to the condenser 131 via the turbine bypass steam pipe 167. [0069]
20 In the operation mode 2, in other words, when the
bypass steam temperature T is T2 or more while being less than T1, as illustrated in FIG. 6B, the controller 150 opens only the intermediate-temperature on-off valve 252 while closing the other on-off valves 251, 253, 174. Thus, as
25 illustrated in FIG. 6B by the thick lines, the fluid flowing
into the heat storage apparatus 140 flows into the second intermediate-temperature heat exchanger 222 and the second low-temperature heat exchanger 232 in this order.
32

[0070]
In this case, the fluid whose temperature is reduced
by heat exchange in the second intermediate-temperature heat
exchanger 222 flows into the second low-temperature heat
5 exchanger 232. Then, the fluid whose temperature is further
reduced by heat exchange in the second low-temperature heat exchanger 232 is discharged from the heat storage apparatus 140 to the condenser 131 via the turbine bypass steam pipe 167.
10 [0071]
In the operation mode 3, in other words, when the bypass steam temperature T is T3 or more while being less than T2, as illustrated in FIG. 7A, the controller 150 opens only the low-temperature on-off valve 253 while closing the
15 other on-off valves 251, 252, 174. Thus, as illustrated in
FIG. 7A by the thick lines, the fluid flowing into the heat storage apparatus 140 flows into the third low-temperature heat exchanger 233. [0072]
20 In this case, the fluid whose temperature is reduced
by heat exchange in the third low-temperature heat exchanger 233 is discharged from the heat storage apparatus 140 to the condenser 131 via the turbine bypass steam pipe 167. [0073]
25 In the operation mode 4, in other words, when the
bypass steam temperature T is less than T3, as illustrated in FIG. 7B, the controller 150 opens only the fourth on-off valve 174 while closing the other on-off valves 251, 252,
33

253. Thus, as illustrated in FIG. 7B by the thick lines,
the fluid in the turbine bypass steam pipe 167 is discharged
to the condenser 131 via the second bypass steam pipe 168
without flowing into the heat storage apparatus 140.
5 [0074]
[Heat Recovery]
Next, an example of heat recovery from the heat storage apparatus 140 will be described. As described above, the heat storage apparatus 140 of the present embodiment can
10 store thermal energy in a plurality of temperature ranges.
Accordingly, heat can also be recovered from the heat storage apparatus 140 for each temperature range, and then provided to utilization places. In the following, an example in which each heat exchanger of the boiler 110 is supplied with the
15 thermal energy recovered from each heat storage layer in
accordance with its design temperature. [0075]
FIG. 8 illustrates an example of design temperature of each heat exchanger of the boiler 110. Here, it is assumed
20 that the boiler 110 includes a primary superheater 114a and
a secondary superheater 114b. [0076]
As illustrated in FIG. 8, the design temperature on inlet and outlet sides of each of the furnace water cooled
25 wall 112, the primary superheater 114a, and the secondary
superheater 114b are 330°C, 430°C, 430°C, 470°C, 460°C, and 560°C, respectively. [0077]
34

Accordingly, in the present embodiment, a part of the
fluid supplied to the furnace water cooled wall 112 is made
to pass through the low-temperature layer 230 to be heated
therein, and then supplied to the outlet side of the furnace
5 water cooled wall 112. Furthermore, a part of the fluid
supplied to the primary superheater 114a is made to pass through the intermediate-temperature layer 220 to be heated therein, and then supplied to the outlet side of the primary superheater 114a. Still further, a part of the fluid
10 supplied to the secondary superheater 114b is made to pass
through the high-temperature layer 210 to be heated therein, and then supplied to the outlet side of the secondary superheater 114b. [0078]
15 In this case, as illustrated in FIG. 9, the inlet side
of the third heat recovery pipe 263 for recovering the thermal energy from the low-temperature layer 230 of the heat storage apparatus 140 is connected to a pipe on the inlet side of the furnace water cooled wall 112. The outlet
20 side of the third heat recovery pipe 263 is connected to a
pipe on the outlet side of the furnace water cooled wall 112. The inlet side of the second heat recovery pipe 262 for recovering the thermal energy from the intermediate-temperature layer 220 is connected to a pipe on the inlet
25 side of the primary superheater 114a. The outlet side of
the second heat recovery pipe 262 is connected to a pipe on the outlet side of the primary superheater 114a. The inlet side of the first heat recovery pipe 261 for recovering the
35

thermal energy from the high-temperature layer 210 is
connected to a pipe on the inlet side of the secondary
superheater 114b. The outlet side of the first heat recovery
pipe 261 is connected to a pipe of the outlet of the secondary
5 superheater 114b.
[0079]
As described above, the power generation plant 100 of the present embodiment is equipped with the heat storage apparatus 140 that includes a plurality of heat storage
10 layers formed of latent heat storage materials having
different melting points. When excess energy is generated, the heat storage apparatus 140 stores, each heat storage layer, the thermal energy corresponding to a melting point of a latent heat storage material forming each heat storage
15 layer.
[0080]
Since the power generation plant 100 includes the heat storage apparatus 140 configured as above, excess energy can be stored independently for each temperature zone. As a
20 result, at the time of heat recovery from the heat storage
apparatus 140, it is possible to recover the heat from a heat storage layer that stores thermal energy corresponding to temperature required by a heat exchanger of a utilization place, thereby allowing the excess energy to be efficiently
25 used. For example, by using this excess energy when
reconnecting to the power grid after a FCB operation, it is possible to supply each heat exchanger of the boiler 110 with optimum thermal energy, thereby enabling quick start of
36

the plant. [0081]
Furthermore, the heat storage apparatus 140 of the
present embodiment uses, as a heat storage material of each
5 heat storage layer, a latent heat storage material making
use of latent heat of phase transformation of a material. As a result, it is possible to realize a heat storage portion capable of high-density heat storage, which is operated only by input and output of heat. In addition, when an alloy
10 system material with a high melting point is used as the
latent heat storage material, high heat storage temperature can be realized. As a result, for example, it is possible to store high-temperature fluid such as turbine bypass steam while keeping its temperature at the high level, and produce
15 steam in the highest temperature range even during heat
release. [0082]
Still further, the heat storage apparatus 140 of the present embodiment includes flow paths allowing, in
20 accordance with the temperature of the fluid flowing into
the heat storage apparatus 140, the fluid to flow into a heat storage layer whose heat storage material has a melting point lower than and closest to the temperature above. As a result, heat storage for each of a plurality of temperature
25 ranges can be realized with a simple structure.
[0083]
Still further, each flow path in the heat storage apparatus 140 is configured such that, after the fluid passes
37

through a heat storage layer whose heat storage material has
the highest melting point, when there is another heat storage
layer formed of a heat storage material whose melting point
is high next to the heat storage material having the highest
5 melting point, it allows the fluid to pass through this
another heat storage layer. In other words, since one flow path is provided with the high-temperature, intermediate-temperature, and low-temperature heat storage layers in this order, it is possible to recover the heat of the fluid
10 without leaving residual heat. According to the power
generation plant 100 including the heat storage apparatus 140 of the present embodiment, it is possible to realize an efficient operation of the power generation plant 100 by fully using the recovered thermal energy for startup or the
15 like.
[0084]
Still further, the heat storage apparatus 140 of the present embodiment includes, for each temperature range of the fluid, a heat storage layer having an sufficient
20 capability with respect to the corresponding temperature
range. For example, in the case of using the heat storage layers for storing excess energy during a FCB operation, a temperature range of each heat storage layer is determined in accordance with the bypass steam temperature after a
25 predetermined time has elapsed after disconnection from the
power grid. Furthermore, the heat storage capacity of each heat storage layer is determined in accordance with an amount of excess energy after each time has elapsed.
38

[0085]
The heat storage layers configured as above enable
efficient heat recovery. For example, in the case of
preparing a heat storage portion for a highest expected
5 temperature of fluid flowing into the heat storage apparatus
140, the specification thereof is too high so that waste is caused in heat recovery of intermediate-temperature or low-temperature fluid. On the other hand, since the present embodiment is configured to store heat in an appropriate
10 heat storage layer for each temperature range, such waste
can be avoided. [0086]
Still further, in the power generation plant 100 provided with the heat storage apparatus 140 of the present
15 embodiment, since the heat storage apparatus 140 fully
recovers heat of the fluid, the temperature of the fluid discharged from the heat storage apparatus 140 to the condenser 131 is reduced. As a result, an amount of heat to be returned to the condenser 131 can be suppressed.
20 [0087]
Especially, during a FCB operation, an amount of heat of excess steam is large. If the power generation plant 100 is a conventional plant, a FCB function provided therein makes all the generated excess steam return to the condenser
25 131, which not only causes waste, but also requires the
condenser 131 to receive a large amount of excess stem. Realizing the condenser 131 having a large capacity for receiving excess stem requires large-scale construction. On
39

the other hand, since the present invention is configured to
store, in the heat storage apparatus 140, a large part of
the heat amount of the fluid to be returned to the condenser
131, it is sufficient that the capability of the condenser
5 131 is substantially equivalent to the condenser 131 used in
a plant without being provided with the FCB function. As a result, it is possible to suppress the facility cost. [0088]
The power generation plant 100 provided with the heat
10 storage apparatus 140 of the present embodiment can
efficiently store heat during a FCB operation, and can efficiently recover the stored thermal energy when reconnecting to the power grid. Furthermore, not only at the time of reconnecting to the power grid after the FCB
15 operation, but also at the time of normal startup or rapid
increase in the load of the power generation plant 100, it is possible to make use of the thermal energy stored in the heat storage apparatus 140. As a result, it is possible to shorten the startup time and the load increase time.
20 [0089]
Note that the time of rapid load increase corresponds to a case of, for example, requiring load change faster than load change from startup to stop in the normal operation. For example, the time of rapid load increase includes cases
25 where the power grid side requires load increase higher than
that in the normal startup such as at the time of recovery after the power grid is in an unstable state. For example, in the case of the boiler 110, the time of rapid load increase
40

corresponds to a rate of increase of 5% per minute or more,
and in the case of the gas turbine, it corresponds to a rate
of increase of 10% to 20% per minute or more.
[0090]
5 In addition, in the case of equipment constituting the
power generation plant 100, the time of rapid load increase corresponds to a case where its load change rate exceeds a rate determined by a limit corresponding to change in an amount of heat of the equipment other than the steam turbine
10 120, or a case where load change that is not allowable to
the boiler 110 is requested from the power grid. [0091]
Still further, in the power generation plant 100 of the present embodiment, since the heat storage apparatus 140
15 is disposed on the turbine bypass steam pipe 167 having the
turbine bypass on-off valve 172, a mode can be switched to the heat storage operation mode immediately only by providing an opening and closing operation instruction to the turbine bypass on-off valve 172. As a result, it is possible to
20 perform the switching processing when the system must be
inevitably disconnected from the power grid such as in the case of performing a FCB, thereby making it possible to easily recover the generated excess energy. [0092]
25 For example, in the case of making use of the heat
storage apparatus 140 of the present embodiment to startup and stop a steam power generation plant in the DSS (Daily Start & Stop), startup and stop times thereof can be
41

shortened. Furthermore, when the present steam power
generation plant and a regenerative energy power generation
plant are used together, the heat storage apparatus 140 of
the present embodiment can totally level the fluctuation in
5 an amount of power supply that is derived from regenerative
energy. As a result, it is possible to reduce the possibilities in which the total amount of power supply exceeds an amount required by the power grid. [0093]
10
[Modification of Heat Storage Apparatus]
In the embodiment described above, the heat storage apparatus 140 is configured such that the heat storage portions serving as the heat exchangers of the respective
15 heat storage layers are connected to each other in series
and in parallel by the respective internal flow paths. Meanwhile, the present invention is not limited thereto as long as the heat storage apparatus 140 is configured to store heat in an optimum heat storage layer in accordance with the
20 temperature of the fluid flowing thereinto, and also store
the heat in a manner that the stored heat is available for each temperature at the time of heat release. In the following, a modification of the heat storage apparatus 140 will be described.
25 [0094]
FIG. 10 illustrates another example of the heat storage apparatus 140 (hereinafter referred to as a heat storage apparatus 140a) of the embodiment described above. Here, in
42

the same manner as the embodiment described above, an example
of including three heat storage layers which are the high-
temperature layer 210, the intermediate-temperature layer
220, and the low-temperature layer 230 will be described.
5 As illustrated in FIG. 10, the heat storage apparatus 140a
is configured such that the heat exchangers of the respective heat storage layers are connected to each other in series. [0095]
The heat storage apparatus 140a includes the high-
10 temperature heat exchanger 211, the first intermediate-
temperature heat exchanger 221, the first low-temperature
heat exchanger 231, the first flow path 241, a second flow
path 342, a third flow path 343, the high-temperature on-off
valve 251, a first intermediate-temperature on-off valve 352,
15 a low-temperature on-off valve 353, a second intermediate-
temperature on-off valve 354, the first heat recovery pipe
261, the second heat recovery pipe 262, and the third heat
recovery pipe 263.
[0096]
20 The high-temperature heat exchanger 211, the first
intermediate-temperature heat exchanger 221, and the first
low-temperature heat exchanger 231 are configured in the
same manner as those of the heat storage apparatus 140,
respectively. The first flow path 241 and the high-
25 temperature on-off valve 251 are also configured in the same
manner as those of the heat storage apparatus 140. In the
following, the elements configured differently from those of
the heat storage apparatus 140 are focused on and described.
43

[0097]
The second flow path 342 branches from the turbine
bypass steam pipe 167 at the branch point 271, and joins the
first flow path 241 at a merging point 375 on the downstream
5 of the high-temperature heat exchanger 211 while bypassing
the high-temperature heat exchanger 211. The second flow path 342 allows the fluid flowing into the heat storage apparatus 140a to pass through in the order of the first intermediate-temperature heat exchanger 221 and the first
10 low-temperature heat exchanger 231, and discharges the fluid
from the heat storage apparatus 140a. [0098]
The third flow path 343 branches from the second flow path 342 at a branch point 372 on the downstream of the first
15 intermediate-temperature on-off valve 352, and joins the
first flow path 241 at a merging point 376 on the downstream of the first intermediate-temperature heat exchanger 221 while bypassing the first intermediate-temperature heat exchanger 221. The third flow path 343 allows the fluid
20 flowing into the heat storage apparatus 140a to pass only
through the first low-temperature heat exchanger 231, and discharges the fluid from the heat storage apparatus 140a. [0099]
On the downstream of each branch point 271, 372, the
25 high-temperature on-off valve 251, the first intermediate-
temperature on-off valve 352, the second intermediate-temperature on-off valve 354, and the low-temperature on-off valve 353 are provided. These valves are opened and closed
44

based on commands from the controller 150, and configured to
perform control as to which flow path to be selected for
flowing the fluid. The controller 150 outputs opening and
closing operation commands to the respective on-off valves
5 in accordance with the temperature of the fluid flowing, in
the turbine bypass steam pipe 167, on the upstream side of the heat storage apparatus 140a. [0100]
In the following, the temperature thresholds T1 and T2
10 are used for explanation in the same manner as the case of
the heat storage apparatus 140. When the temperature of the fluid flowing, in the turbine bypass steam pipe 167, on the upstream side of the heat storage apparatus 140a is the first temperature threshold T1 or more, the controller 150 makes
15 the high-temperature on-off valve 251 be in an open state
while making the first intermediate-temperature on-off valve 352 be in a close state. When the temperature of this fluid is less than T1, the controller 150 makes the high-temperature on-off valve 251 be in a close state while making
20 the first intermediate-temperature on-off valve 352 be in an
open state. When the temperature of this fluid is the second temperature threshold T2 or more, the controller 150 makes the second intermediate-temperature on-off valve 354 be in an open state while making the low-temperature on-off valve
25 353 be in a close state. When the temperature of this fluid
is less than the second temperature threshold T2, the controller 150 makes the second intermediate-temperature on-off valve 354 be in a close state while making the low-
45

temperature on-off valve 353 be in an open state. [0101]
In the following, control of the on-off valves
performed by the controller 150 for each operation mode 1 to
5 4 according to the present modification will be described
with reference to FIG. 11A to FIG. 12B. Here, the operations
of the second bypass steam pipe 168 and the fourth on-off
valve 174 will be also described. In the heat storage
apparatus 140a of the present modification, the second bypass
10 steam pipe 168 branches at a branch point 373 on the third
flow path 343, and joins the first flow path 241 (turbine
bypass steam pipe 167) at the merging point 272 while
bypassing the first low-temperature heat exchanger 231.
[0102]
15 In the operation mode 1, in other words, when the
bypass steam temperature T is T1 or more, the controller 150
controls the opening and closing operations of each on-off
valve so as to allow the fluid to pass through the first
flow path 241. That is, as illustrated in FIG. 11A, the
20 controller 150 outputs command signals for opening only the
high-temperature on-off valve 251 while closing the other
on-off valves 174, 352, 353, 354. Thus, as illustrated in
FIG. 11A by the thick lines, the fluid flowing into the heat
storage apparatus 140a flows in the order of the high-
25 temperature heat exchanger 211, the first intermediate-
temperature heat exchanger 221, and the first low-
temperature heat exchanger 231, and is discharged from the
heat storage apparatus 140a.
46

[0103]
In the operation mode 2, in other words, when the
bypass steam temperature T is T2 or more while being less
than T1, the controller 150 controls the opening and closing
5 operations of each on-off valve so as to allow the fluid to
pass through the second flow path 342. That is, as illustrated in FIG. 11B, the controller 150 outputs command signals for opening the first intermediate-temperature on-off valve 352 and the second intermediate-temperature on-off
10 valve 354 while closing the other on-off valves 251, 353,
174. Thus, as illustrated in FIG. 11B by the thick lines, the fluid flowing into the heat storage apparatus 140a flows in the order of the first intermediate-temperature heat exchanger 221 and the first low-temperature heat exchanger
15 231, and is discharged from the heat storage apparatus 140a.
[0104]
In the operation mode 3, in other words, when the bypass steam temperature T is T3 or more while being less than T2, the controller 150 controls the opening and closing
20 operations of each on-off valve so as to allow the fluid to
pass through the third flow path 343. That is, as illustrated in FIG. 12A, the controller 150 outputs command signals for opening the first intermediate-temperature on-off valve 352 and the low-temperature on-off valve 353 while
25 closing the other on-off valves 251, 354, 174. Thus, as
illustrated in FIG. 12A by the thick lines, the fluid flowing into the heat storage apparatus 140a passes only through the first low-temperature heat exchanger 231, and is discharged
47

from the heat storage apparatus 140a. [0105]
In the operation mode 4, in other words, when the
bypass steam temperature T is less than T3, the controller
5 150 performs control so as to allow the bypass steam to pass
through the second bypass steam pipe 168 while bypassing
each heat storage layer of the heat storage apparatus 140a.
That is, as illustrated in FIG. 12B, the controller 150
outputs command signals for opening the first intermediate-
10 temperature on-off valve 352 and the fourth on-off valve 174
while closing the other on-off valves 251, 354, 353. Thus,
as illustrated in FIG. 12B by the thick lines, the fluid
flowing into the heat storage apparatus 140a is introduced
to the condenser 131 without dissipating heat to the heat
15 storage apparatus 140a.
[0106]
According to the present modification, in the same
manner as the embodiment described above, thermal energy can
be stored in a plurality of heat storage layers having
20 different temperature characteristics. Furthermore, at the
time of using the stored thermal energy, it can be recovered
for each temperature level of the stored heat. As a result,
it is possible to efficiently store and recover the excess
energy.
25 [0107]
[Other Modifications of Heat Storage Apparatus]
Furthermore, the heat storage apparatus 140 may be configured such that the heat exchangers are disposed in
48

parallel to each other in the respective heat storage layers.
FIG. 13A illustrates a configuration example of a heat
storage apparatus 140b according to the present modification.
As illustrated in FIG. 13A, in the same manner as the heat
5 storage apparatus 140, the heat storage apparatus 140b
includes the first flow path 241, the second flow path 242, and the third flow path 243. The first flow path 241 allows the fluid to pass only through the high-temperature heat exchanger 211 and discharges the fluid after heat exchange
10 from the heat storage apparatus 140. The second flow path
242 allows the fluid to pass only through the second intermediate-temperature heat exchanger 222 and discharges the fluid after heat exchange from the heat storage apparatus 140. The third flow path 243 allows the fluid to pass only
15 through the third low-temperature heat exchanger 233 and
discharges the fluid after heat exchange from the heat storage apparatus 140, in the same manner as the embodiment described above. [0108]
20 The heat storage apparatus 140b can realize the same
advantageous effects as those of the heat storage apparatus 140 with a simple configuration. [0109]
Furthermore, each one heat exchanger of the heat
25 storage apparatus 140 may be provided in each heat storage
layer such that they are connected to each other in series and in parallel in the same manner as the embodiment described above. That is, each flow path may share each
49

heat exchanger in each heat storage layer. FIG. 13B
illustrates a configuration example of a heat storage
apparatus 140c according to the present modification.
[0110]
5 As illustrated in FIG. 13B, the first flow path 241
passes through the high-temperature heat exchanger 211, the first intermediate-temperature heat exchanger 221, and the first low-temperature heat exchanger 231. The second flow path 242 passes through the first intermediate-temperature
10 heat exchanger 221 and the first low-temperature heat
exchanger 231. The third flow path 243 passes through the first low-temperature heat exchanger 231. In other words, the first intermediate-temperature heat exchanger 221 receives the fluid flowing from the first flow path 241 and
15 the second flow path 242. The first low-temperature heat
exchanger 231 receives the fluid flowing from the first flow path 241, the second flow path 242, and the third flow path 243. [0111]
20 In the present modification, each heat storage portion
is not provided individually for each flow path but is shared therebetween, thereby making it possible to obtain the same advantageous effects as those of the heat storage apparatus 140 with a simple configuration.
25 [0112]
The number of heat storage layers is not be limited as long as it is more than one. For example, it may be two as illustrated in FIG. 14A. FIG. 14A illustrates an example of
50

a heat storage apparatus in which two heat storage layers
are provided and the heat exchangers in the respective heat
storage layers are connected to each other in parallel.
[0113]
5 A heat storage apparatus 140d illustrated in FIG. 14A
includes the high-temperature heat exchanger 211 that is
provided in the high-temperature layer 210 and performs heat
exchange therein, and the second intermediate-temperature
heat exchanger 222 that is provided in the intermediate-
10 temperature layer 220 and performs heat exchange therein.
Furthermore, the heat storage apparatus 140d includes the
first flow path 241 that allows the fluid flowing into the
heat storage apparatus 140d to pass through the high-
temperature heat exchanger 211 and discharges it from the
15 heat storage apparatus 140d, and the second flow path 242
that branches at the branch point 271 on the upstream of the
high-temperature heat exchanger 211 of the first flow path
241, allows the fluid flowing into the heat storage apparatus
140d to pass through the second intermediate-temperature
20 heat exchanger 222, and discharges it from the heat storage
apparatus 140d. Still further, the heat storage apparatus
140d includes the high-temperature on-off valve 251 that is
provided on the first flow path 241 and controls the fluid
flowing into the high-temperature heat exchanger 211, and
25 the intermediate-temperature on-off valve 252 that is
provided on the second flow path 242 and controls the fluid
flowing into the second intermediate-temperature heat
exchanger 222.
51

[0114]
In the heat storage apparatus 140d, when the
temperature of the fluid is the predetermined first
temperature threshold T1 or more, the high-temperature on-
5 off valve 251 is made in an open state in response to a
command from the controller 150. When the temperature of
the fluid is less than the first temperature threshold T1,
the intermediate-temperature on-off valve 252 is made in an
open state in response to a command from the controller 150.
10 [0115]
In the following, control of the opening and closing operations performed by the controller 150 in the case where the power generation plant 100 includes the second bypass steam pipe 168 and the fourth on-off valve 174 will be
15 described with reference to a heat storage apparatus 140e of
FIG. 14B. [0116]
The heat storage apparatus 140e illustrated in FIG. 14B is configured in the same manner as the heat storage
20 apparatus 140d. The difference therebetween can be found in
that, in the heat storage apparatus 140e, the second bypass steam pipe 168 branches at the branch point 271 and joins the turbine bypass steam pipe 167 at the merging point 272. Furthermore, in the heat storage apparatus 140e, the second
25 bypass steam pipe 168 is provided with the fourth on-off
valve 174. [0117]
In the heat storage apparatus 140e, in the same manner
52

as the heat storage apparatus 140d, when the temperature of
the fluid is the predetermined first temperature threshold
T1 or more, the high-temperature on-off valve 251 is made in
an open state in response to a command from the controller
5 150. When the temperature of the fluid is less than the
first temperature threshold T1, the intermediate-temperature on-off valve 252 is made in an open state in response to a command from the controller 150. [0118]
10 Furthermore, in the heat storage apparatus 140e, even
when the temperature of the fluid is less than the first temperature threshold T1, if it is less than the second temperature threshold T2, the intermediate-temperature on-off valve 252 is made in a close state in response to a
15 command from the controller 150. When the temperature of
the fluid is less than the second temperature threshold T2, the controller 150 makes the fourth on-off valve 174 be in an open state so as to make the fluid flowing in the turbine bypass steam pipe 167 bypass the heat storage apparatus 140e
20 (the high-temperature heat exchanger 211 and the second
intermediate-temperature heat exchanger 222). [0119]
FIG. 15A illustrates an example of a heat storage apparatus in which two heat storage layers are provided and
25 the heat exchangers in the respective heat storage layers
are connected to each other in series. [0120]
A heat storage apparatus 140f illustrated in FIG. 15A
53

includes the high-temperature heat exchanger 211 that is
provided in the high-temperature layer 210 and performs heat
exchange therein, and the first intermediate-temperature
heat exchanger 221 that is provided in the intermediate-
5 temperature layer 220 and performs heat exchange therein.
Furthermore, the heat storage apparatus 140f includes the
first flow path 241 that allows the fluid flowing into the
heat storage apparatus 140f to pass through in the order of
the high-temperature heat exchanger 211 and the first
10 intermediate-temperature heat exchanger 221 and discharges
it from the heat storage apparatus 140f, and the second flow path 342 that branches at the branch point 271 on the upstream of the high-temperature heat exchanger 211 of the first flow path 241, allows the fluid flowing into the heat
15 storage apparatus 140f to pass through the first
intermediate-temperature heat exchanger 221 while bypassing the high-temperature heat exchanger 211, and discharges it from the heat storage apparatus 140f. Still further, the heat storage apparatus 140f includes the high-temperature
20 on-off valve 251 that is provided on the first flow path 241
and controls the fluid flowing into the high-temperature heat exchanger 211, and the first intermediate-temperature on-off valve 352 that is provided on the second flow path 242 and controls the fluid flowing into the first
25 intermediate-temperature heat exchanger 221.
[0121]
In the heat storage apparatus 140f, when the temperature of the fluid is the predetermined first
54

temperature threshold T1 or more, the high-temperature on-
off valve 251 is made in an open state in response to a
command from the controller 150. When the temperature of
the fluid is less than the first temperature threshold T1,
5 the first intermediate-temperature on-off valve 352 is made
in an open state in response to a command from the controller 150. [0122]
In the following, control of the opening and closing
10 operations performed by the controller 150 in the case where
the power generation plant 100 includes the second bypass steam pipe 168 and the fourth on-off valve 174 will be described with reference to a heat storage apparatus 140g of FIG. 15B.
15 [0123]
The heat storage apparatus 140g illustrated in FIG. 15B is configured substantially in the same manner as the heat storage apparatus 140f. The difference therebetween can be found in that, in the heat storage apparatus 140f,
20 the second bypass steam pipe 168 branches at the branch point
372 on the downstream of the first intermediate-temperature on-off valve 352 of the second flow path 342 and joins the turbine bypass steam pipe 167 at the merging point 272. Furthermore, in the heat storage apparatus 140f, the second
25 bypass steam pipe 168 is provided with the fourth on-off
valve 174. Still further, on the downstream of the branch point 372 of the second flow path 342, the second intermediate-temperature on-off valve 354 is provided.
55

[0124]
In the heat storage apparatus 140g, in the same manner
as the heat storage apparatus 140f, when the temperature of
the fluid is the predetermined first temperature threshold
5 T1 or more, the high-temperature on-off valve 251 is made in
an open state in response to a command from the controller 150. When the temperature of the fluid is less than the first temperature threshold T1, the first intermediate-temperature on-off valve 352 is made in an open state.
10 [0125]
When the temperature of the fluid is the second temperature threshold T2 or more, the second intermediate-temperature on-off valve 354 is made in an open state in response to a command from the controller 150. When the
15 temperature of the fluid is less than the second temperature
threshold T2, the fourth on-off valve 174 is made in an open state. [0126]
As described above, in the heat storage apparatus 140,
20 the number (size) of heat storage layers and paths can be
optimized in accordance with a required temperature and an amount of steam. According to the heat storage apparatus 140, it is possible to realize heat storage for every temperature level by a simple configuration having heat
25 exchangers installed in respective heat storage layers so as
to control the paths of steam by opening and closing on-off valves. [0127]
56

[Modification of Heat Storage Fluid]
In the embodiment described above, the heat storage
apparatus 140 is configured to acquire and store thermal
energy from fluid passing through the turbine bypass steam
5 pipe 167. Meanwhile, a target of heat storage is not limited
to the thermal energy of the fluid. For example, the thermal energy of saturated water returned from the steam separator 113 to the condenser 131 may be stored. FIG. 16A illustrates a system of the power generation plant 100 according to the
10 present modification.
[0128]
As illustrated in FIG. 16A, a heat storage pipe 161a is provided on the first pipe 161 for returning the saturated water from the steam separator 113 to the condenser 131.
15 The heat storage pipe 161a branches from the first pipe 161,
passes through the heat storage apparatus 140, and joins the first pipe 161. [0129]
The heat storage pipe 161a is provided with a fifth
20 on-off valve 175 on the upstream side of the heat storage
apparatus 140. The fifth on-off valve 175 is provided for controlling whether to return the saturated water supplied from the steam separator 113, via the heat storage apparatus 140, to the condenser 131 or return it directly to the
25 condenser 131. In the case of making the saturated water
flow into the heat storage apparatus 140, the controller 150 outputs a command for making the fifth on-off valve 175 be in an open state.
57

[0130]
At this time, the heat storage apparatus for storing
the thermal energy of the saturated water returned from the
steam separator 113 to the condenser 131 may be another heat
5 storage apparatus 141 that is provided separately and
independently from the heat storage apparatus 140 provided on the turbine bypass steam pipe 167. FIG. 16B illustrates an example of piping according to the present modification. [0131]
10 As illustrated in FIG. 16B, the heat storage apparatus
141 is provided on, for example, the first pipe 161. In this case as well, a bypass flow path used for bypassing the heat storage apparatus 141 and returning the saturated water to the condenser 131 may be further provided.
15 [0132]
As described above, since these modifications are configured to store heat further from the saturated water returned from the steam separator 113 to the condenser 131, it is possible to fully store the excess thermal energy
20 generated in the system, thereby allowing the stored thermal
energy to be used when reconnecting to the power grid, etc. [0133] [Modification in Heat Recovery]
In the power generation plant 100 according to the
25 embodiment described above, since the thermal energy stored
in the heat storage apparatus 140 is supplied, for each heat storage layer, to the heat exchangers of the boiler 110 which correspond to the temperature ranges of the respective heat
58

storage layers, it is possible to efficiently support energy supply at the time of rapid load increase of the boiler 110. [0134]
Meanwhile, a heat recovery method from the heat storage
5 apparatus 140 is not limited thereto. For example, as
illustrated in FIG. 17, a heat recovery method of allowing
the fluid to pass through each heat storage layer in the
order from the low-temperature layer 230 so as to recover
the whole thermal energy stored in the heat storage apparatus
10 140, and thereafter, making the fluid return to the system
of the power generation plant 100 may be employed. [0135]
A return destination of the fluid after thermal energy
recovery is, for example, the main steam pipe 162. The fluid
15 to the heat storage apparatus 140 is supplied from, for
example, the feed water line 130. In this case, for example,
a fourth heat recovery pipe 264 that connects the feed water
line 130 and the main steam pipe 162 is provided, and the
heat storage apparatus 140 is disposed on the fourth heat
20 recovery pipe 264.
[0136]
Since the pipes are arranged in the manner as described
above, water input to the heat storage apparatus 140 is
heated in the low-temperature layer 230, the intermediate-
25 temperature layer 220, and the high-temperature layer 210 in
this order. Thus, high-temperature and high-pressure steam
is generated only within the heat storage apparatus 140,
which can be fed directly into the high-pressure steam
59

turbine 121. [0137]
In the present modification, during a high-load
operation, the return destination of the fluid after thermal
5 energy recovery in the heat storage apparatus 140 may be a
low-temperature reheat steam pipe 163. [0138]
It should be noted that the present invention is not
limited to the embodiment and modifications described above.
10 Various modifications can be made in accordance with design
or the like within the scope of the technical concept of the
present invention.
REFERENCE SIGNS LIST
15 [0139]
100: power generation plant, 101: generator, 110: boiler, 111: economizer, 112: furnace water cooled wall, 113: steam separator, 114: superheater, 114a: primary superheater,
20 114b: secondary superheater, 115: reheater, 120: steam
turbine, 121: high-pressure steam turbine, 122: intermediate-pressure steam turbine, 123: low-pressure steam turbine, 130: feed water line, 131: condenser, 132: condensate pump, 133: low-pressure heater, 134: deaerator,
25 135: feed water pump, 136: high-pressure heater,
140: heat storage apparatus, 140a: heat storage apparatus, 140b: heat storage apparatus, 140c: heat storage apparatus, 140d: heat storage apparatus, 140e: heat storage
60

apparatus, 140f: heat storage apparatus, 140g: heat storage apparatus, 141: heat storage apparatus,
150: controller, 151: control console,
161: first pipe, 161a: heat storage pipe, 162: main
5 steam pipe, 163: low-temperature reheat steam pipe, 164:
high-temperature reheat steam pipe, 165: high-pressure
bypass steam pipe, 166: first exhaust steam pipe, 167:
turbine bypass steam pipe, 168: second bypass steam pipe,
171: first on-off valve, 172: turbine bypass on-off
10 valve, 173: third on-off valve, 174: fourth on-off valve,
175: fifth on-off valve, 176: first stop valve, 177: second stop valve,
181: temperature sensor
210: high-temperature heat storage layer (high-
15 temperature layer), 211: high-temperature heat exchanger,
220: intermediate-temperature layer (intermediate-
temperature layer), 221: first intermediate-temperature heat
exchanger, 222: second intermediate-temperature heat
exchanger, 230: low-temperature heat storage layer (low-
20 temperature layer), 231: first low-temperature heat
exchanger, 232: second low-temperature heat exchanger, 233:
third low-temperature heat exchanger, 241: first flow path,
242: second flow path, 243: third flow path, 251: high-
temperature on-off valve, 252: intermediate-temperature on-
25 off valve, 253: low-temperature on-off valve, 261: first
heat recovery pipe, 262: second heat recovery pipe, 263:
third heat recovery pipe, 264: fourth heat recovery pipe,
271: branch point, 272: merging point,
61

342: second flow path, 343: third flow path, 352: first
intermediate-temperature on-off valve, 353: low-temperature
on-off valve, 354: second intermediate-temperature on-off
valve, 372: branch point, 373: branch point, 375: merging
5 point, 376: merging point

WE CLAIMS

1.A heat storage device comprising a plurality of heat
storage portions, each of which is configured to recover
5 heat from fluid passing through a flow path provided therein
to store the recovered heat,
the plurality of heat storage portions including:
a first heat storage portion having a temperature
characteristic in a first temperature range; and
10 a second heat storage portion having a
temperature characteristic in a second temperature range that is lower than the first temperature range, the flow path including:
a first flow path that allows the fluid flowing
15 into the heat storage device to pass through in an
order of the first heat storage portion and the second
heat storage portion, and discharges the fluid from
the heat storage device;
a second flow path that branches at a first
20 branch portion on an upstream of the first heat storage
portion of the first flow path, allows the fluid
flowing into the heat storage device to pass through
the second heat storage portion while bypassing the
first heat storage portion, and discharges the fluid
25 from the heat storage device; and
an on-off valve for controlling inflow of the fluid into the flow path, the on-off valve including:
63

a first on-off valve that is provided on the first flow path to control inflow of the fluid into the first heat storage portion; and
a second on-off valve that is provided on the
5 second flow path to control inflow of the fluid into
the second heat storage portion,
the first on-off valve being configured to be in an
open state when temperature of the fluid is equal to or
higher than a first temperature threshold determined by the
10 first temperature range, and
the second on-off valve being configured to be in an open state when the temperature of the fluid is less than the first temperature threshold.
15 2. The heat storage device according to claim 1, wherein
the on-off valve further includes a third on-off valve
provided on a downstream of a second branch portion that is
on a downstream of the second on-off valve of the second
flow path,
20 a bypass flow path including a bypass on-off valve
branches from the second branch portion and discharges the fluid flowing into the second flow path while bypassing the second heat storage portion,
the third on-off valve is configured to be in an open
25 state when the temperature of the fluid is equal to or higher
than a second temperature threshold determined by the second temperature range, and
the bypass on-off valve is configured to be in an open
64

state when the temperature of the fluid is less than the second temperature threshold.
3. A heat storage device comprising a plurality of heat
5 storage portions, each of which is configured to recover
heat from fluid passing through a flow path provided therein to store the recovered heat,
the plurality of heat storage portions including:
a first heat storage portion having a temperature
10 characteristic in a first temperature range; and
a second heat storage portion having a
temperature characteristic in a second temperature
range that is lower than the first temperature range,
the flow path including:
15 a first flow path that allows the fluid flowing
into the heat storage device to pass through the first heat storage portion, and discharges the fluid from the heat storage device;
a second flow path that branches at a first
20 branch portion on an upstream of the first heat storage
portion of the first flow path, allows the fluid
flowing into the heat storage device to pass through
the second heat storage portion, and discharges the
fluid from the heat storage device; and
25 an on-off valve for controlling inflow of the
fluid into the flow path, the on-off valve including:
a first on-off valve that is provided on the
65

first flow path to control inflow of the fluid into the first heat storage portion; and
a second on-off valve that is provided on the
second flow path to control inflow of the fluid into
5 the second heat storage portion,
the first on-off valve being configured to be in an
open state when temperature of the fluid is equal to or
higher than a first temperature threshold determined by the
first temperature range, and
10 the second on-off valve being configured to be in an
open state when the temperature of the fluid is less than the first temperature threshold.
4. The heat storage device according to claim 3, wherein
15 even when the temperature of the fluid is less than
the first temperature threshold, in a case of being less than a second temperature threshold determined by the second temperature range, the second on-off valve is configured to be in a close state, and
20 when the temperature of the fluid is less than the
second temperature threshold, a bypass on-off valve, which is provided on a bypass flow path that branches at the first branch portion and allows the fluid to flow therein while bypassing the first heat storage portion and the second heat
25 storage portion, is configured to be in an open state.
5. The heat storage device according to claim 3, wherein
the plurality of heat storage portions further
66

includes a fourth heat storage portion having a temperature characteristic in the second temperature range, and
the first flow path allows the fluid that has passed
through the first heat storage portion to further pass
5 through the fourth heat storage portion, and discharges the
fluid from the heat storage device.
6. The heat storage device according to claim 3, wherein
the first flow path allows the fluid that has passed
10 through the first heat storage portion to further pass
through the second heat storage portion, and discharges the fluid from the heat storage device.
7. The heat storage device according to any one of claim
15 1 to claim 6, wherein
each of the plurality of heat storage portion includes a latent heat storage material making use of latent heat of phase transformation of a material, and
the temperature characteristic is determined based on
20 a melting temperature of the latent heat storage material.
8. A power generation plant comprising:
a boiler that heats supplied water to generate
superheated steam;
25 a steam turbine that is rotatably driven by the
superheated steam generated in the boiler to drive a
generator; and
a feed water line that converts exhaust steam from the
67

steam turbine back to water and supplies the boiler with the water,
the power generation plant further comprising a heat
storage device configured to store thermal energy of an
5 excess amount of the superheated steam from among the
superheated steam generated in the boiler,
the heat storage device is configured by the heat
storage device according to any one of claim 1 to claim 7,
and
10 the thermal energy stored in the heat storage device
is used for an operation of the power generation plant.
9. The power generation plant according to claim 8,
wherein
15 the operation includes a power grid reconnection
operation after disconnection from a power gird, and
the thermal energy stored in the heat storage device is recovered from the heat storage device for each of the temperature ranges.
20
10. The power generation plant according to claim 8,
wherein
the steam turbine includes a high-pressure steam
turbine and an intermediate-and-low-pressure steam turbine,
25 the boiler includes a reheater that reheats steam after
rotational drive of the high-pressure steam turbine,
the feed water line includes a condenser that condenses the steam which has finished a work in the steam turbine and
68

stores the condensed steam as water,
the power generation plant further includes:
a turbine bypass pipe that introduces the steam
reheated by the reheater to the condenser while
5 bypassing the intermediate-and-low-pressure steam
turbine; and
a controller configured to control opening and closing operations of the on-off valve,
the heat storage device is disposed on the turbine
10 bypass pipe, and
the controller is configured to, in accordance with steam temperature in the turbine bypass pipe, control the opening and closing operations of the on-off valve.
15 11. The power generation plant according to claim 10,
wherein
the boiler includes:
a furnace that heats the water to generate water-
steam two-phase fluid; and
20 a steam separator that separates the water-steam
two-phase fluid superheated in the furnace into saturated steam and saturated water,
the power generation plant includes a first pipe that
introduces the saturated water generated in the steam
25 separator to the condenser, and
the heat storage device is supplied with the saturated water further from the first pipe.
69

12. The power generation plant according to claim 10,
wherein
the boiler includes:
a furnace that heats the water to generate water-
5 steam two-phase fluid; and
a steam separator that separates the water-steam
two-phase fluid superheated in the furnace into
saturated steam and saturated water,
the power generation plant includes:
10 a second heat storage device that is configured
by the heat storage device according to any one of claim 1 to claim 7; and
a first pipe that introduces the saturated water
generated in the steam separator to the condenser, and
15 the second heat storage device is disposed on the first
pipe.
13. The power generation plant according to claim 8,
wherein
20 the thermal energy stored in the heat storage device
is used for heating the water in the boiler during the
operation of the power generation plant, and
the boiler includes:
a first heat exchanger configured to generate
25 fluid having temperature of the first temperature
range by heat exchange;
a second heat exchanger configured to generate
fluid having temperature of the second temperature
70

range by heat exchange;
a second heat recovery pipe configured to, during
the operation of the power generation plant, introduce
a part of the fluid generated by the second heat
5 exchanger to the second heat storage portion, and after
recovering the thermal energy in the second heat storage portion, introduce the fluid to the first heat exchanger; and
a first heat recovery pipe configured to, during
10 the operation of the power generation plant, introduce
a part of the fluid generated by the first heat exchanger to the first heat storage portion, and after recovering the thermal energy in the first heat storage portion, introduce the fluid to an outlet side of the
15 first heat exchanger.
14. The power generation plant according to claim 8,
wherein
the thermal energy stored in the heat storage device
20 is used for rotationally driving the steam turbine during
the operation of the power generation plant, and
a fourth heat recovery pipe configured to, during the
operation of the power generation plant, introduce a part of
the water in the feed water line to the steam turbine via
25 the heat storage device is provided.
15. The power generation plant according to claim 10,
further comprising a turbine bypass on-off valve for
71

controlling inflow of the steam into the turbine bypass pipe, wherein
at a time of disconnection from a power grid, the
controller makes the turbine bypass on-off valve be in an
5 open state, and
each of the first temperature range and the second
temperature range of the heat storage device is determined
in association with temperature of steam on an outlet side
of the boiler which corresponds to load of the boiler after
10 a first time and a second time have elapsed after
disconnection from the power grid.
16. The power generation plant according to claim 15,
wherein
15 a capacity of each of the first heat storage portion
and the second heat storage portion is determined in accordance with the thermal energy generated within the first time and the second time after disconnection from the power grid.
20
17. An operation control method during fast cut back in a
power generation plant including a steam turbine that drives
a generator, a boiler that generates fluid to be supplied to
the steam turbine, a heat storage device that has a plurality
25 of heat storage portions configured to recover heat from the
fluid passing through a flow path provided therein to store the recovered heat, a turbine bypass pipe that introduces the fluid generated by the boiler to the heat storage device
72

while bypassing the steam turbine, and a turbine bypass on-off valve that controls a flow rate of the fluid flowing into the turbine bypass pipe,
each of the plurality of heat storage portions having
5 a temperature characteristic in each different temperature
range,
the flow path including a plurality of branch flow
paths each of which introduces the fluid flowing into the
heat storage device to each of the plurality of heat storage
10 portions, and
each of the plurality of branch flow paths including
each of on-off valves for controlling inflow of the fluid,
which is introduced by each of the plurality of branch flow
paths, into each of the plurality of the heat storage
15 portions,
the operation control method comprising the steps of:
upon receiving an instruction of disconnecting from a
power grid, narrowing down load of the boiler and making the
turbine bypass on-off valve in an open state;
20 measuring temperature of the fluid passing through the
turbine bypass pipe;
making one of the on-off valves provided in one of the
plurality of branch flow paths for introducing the fluid to
one of the heat storage portions that has the temperature
25 characteristic in a temperature range to which the
73

temperature of the fluid belongs to be in an open
state; and
making other ones of the on-off valves to be in close states.