JP2024113774A - Heat storage system - Google Patents

Abstract

To improve energy efficiency.SOLUTION: A heat storage system (10) includes a boiler (11) which generates steam, a steam turbine (12) to which the steam generated by the boiler is supplied, a condenser (13) for condensing the steam discharged from the steam turbine, and a heat storing and releasing system (21) which heats the condensed water generated by the condenser with a stored heat storage medium so as to generate steam and supplies the steam to the steam turbine. The heat storing and releasing system includes a heater (35) which can heat the stored heat storage medium. The heater heats the heat storage medium with a heat source other than the boiler.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat storage system using a heat storage material.

The system disclosed in Patent Document 1 has a working fluid circuit for circulating a working fluid through a heat exchanger, and a heat storage medium circuit for circulating a heat storage medium. The heat storage medium circuit has a high-temperature storage tank and a low-temperature storage tank connected via a heat exchanger. In the heat exchanger, heat is transferred from the heat storage medium sent from the high-temperature storage tank to the low-temperature storage tank to the working fluid, and the working fluid leaving the heat exchanger enters the turbine.

JP 2013-152073 A

In a system in which the heat storage medium exchanges heat through sensible heat change only in the liquid phase, and the working fluid exchanges heat through sensible heat change and latent heat change, such as steam, as in Patent Document 1, the heat conversion modes of the heat storage medium and the working fluid are different. For this reason, when the heat storage medium is heated only by the working fluid, if the flow rate of the heat storage medium is increased, a temperature zone will arise in which heat cannot be exchanged with the working fluid, and if the flow rate of the heat storage medium is reduced, the working fluid will flow out of the heat exchanger at a high temperature, resulting in a low energy recovery rate.

The present invention was made in consideration of these points, and one of its objectives is to provide a heat storage system that can improve energy efficiency.

The heat storage system of one aspect of the present invention is a heat storage system including a steam generator that generates steam, a steam turbine to which the steam generated by the steam generator is supplied, a condenser that condenses the steam discharged from the steam turbine, and a heat storage and release system that generates steam by heating the condensate generated by the condenser using a stored heat storage material and supplies the steam to the steam turbine, the heat storage and release system including a heating device capable of heating the stored heat storage material, and the heating device heats the heat storage material using a heat source other than the steam generator.

According to the present invention, since the heat storage material of the heat storage and release system can be heated by the heating device, the amount of heat transferred to the heat storage material by the steam generated by the steam generator can be reduced or eliminated by heating the heat storage material. When the amount of heat transferred to the heat storage material by the steam generated by the steam generator is reduced, the flow rate of the heat storage material is increased, so that even if the heat storage material after heating (heat storage) by steam has not yet risen to the desired temperature, the heat storage material can be heated by the heating device, and the heat storage material can be heated to a high temperature in the heat storage and release system to generate steam to be supplied to the steam turbine by the heat storage material. Therefore, it is possible to avoid the occurrence of a temperature zone in which heat exchange with steam cannot be performed in the heat storage material, and the energy recovery rate and energy efficiency can be improved. In addition, when the heat storage material of the heat storage and release system is not heated (heat stored) by the steam generated by the steam generator, it is possible to avoid the steam after heating the heat storage material flowing out at a high temperature, and a decrease in energy efficiency can be suppressed.

1 is a schematic configuration diagram of a heat storage system according to a first embodiment. FIG. 2 is a diagram similar to FIG. 1 showing the heat storage system in a second heat storage operation mode. FIG. 2 is a diagram similar to FIG. 1 showing the heat storage system in a heat dissipation operation mode. 13 is a graph showing the relationship between the amount of heat exchanged and temperature in the comparative structure and the first embodiment. FIG. 11 is a schematic configuration diagram of a heat storage system according to a second embodiment. FIG. 6 is a diagram similar to FIG. 5, illustrating the heat storage system in a heat storage operation mode. 1 is a graph showing the change over time in energy required for power generation.

A heat storage system according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a heat storage system according to an embodiment. As shown in FIG. 1, a heat storage system 10 is used, for example, in a thermal power generation system. The heat storage system 10 includes a boiler (steam generator) 11 that generates steam (superheated steam), a steam turbine (power generation device) 12 that generates power from the steam, and a condenser (condensing device) 13 that condenses the steam to produce condensed water.

The boiler 11 generates steam by heating water through a heat source. Although not limited to this, the heat source of the boiler 11 generates heat from the combustion of fuel for thermal power generation, and the fuel may be fossil fuels such as coal, petroleum, and natural gas, various biomass fuels, hydrogen fuel, ammonia fuel, etc.

The steam turbine 12 is supplied with steam generated in the boiler 11 via piping 15. The steam turbine 12 absorbs the thermal energy of the steam to generate power to rotate the output shaft 12a, and discharges the cooled steam. A generator G is connected to the steam turbine 12 via the output shaft 12a, and the generator G generates electricity by rotating the output shaft 12a.

A pipe 16 is connected to the outlet side of the steam turbine 12, and a condenser 13, a condensate pump 17, a boiler feedwater pump 18, and an ejector 19 are provided on the pipe 16 in this order from upstream to downstream. The condenser 13 recovers the steam discharged from the steam turbine 12, and condenses the steam to condense it. The condensate generated by the condenser 13 is sent by the condensate pump 17 and the boiler feedwater pump 18 toward the ejector 19 and the boiler 11. The ejector 19 and its surrounding structure will be described later.

The heat storage system 10 further includes a heat storage/discharge system 21 to which steam from the boiler 11 and condensate from the condenser 13 are supplied. The heat storage/discharge system 21 stores and uses a heat storage material HS, and exchanges heat between the heat storage material HS and the steam and condensate. Here, the heat storage material HS is a sensible heat storage material that exchanges heat with steam or water in the liquid phase, and chemically inactive molten salt or the like is used.

The heat storage and release system 21 includes a heat exchanger 23 to which steam is supplied from the boiler 11 via a pipe 22 branching off from a pipe 15 connecting the boiler 11 and the steam turbine 12, and a high-temperature heat storage tank 24 and a low-temperature heat storage tank 25 that contain the heat storage material HS.

The high-temperature heat storage tank 24 contains the heat storage material HS that has been heated by the heat exchanger 23. The low-temperature heat storage tank 25 contains the heat storage material HS that has dissipated heat in the heat exchanger 23. Therefore, the high-temperature heat storage tank 24 contains heat storage material HS that is at a higher temperature than the low-temperature heat storage tank 25.

The high-temperature heat storage tank 24 is connected to the heat exchanger 23 via a high-temperature heat storage tank pipe 27. The high-temperature heat storage tank pipe 27 includes a main pipe 27a that connects the high-temperature heat storage tank 24 and the heat exchanger 23, and a sub-pipe 27b (shown by a dashed line in FIG. 1) that branches off and merges with the main pipe 27a. A pump 28 is provided in the sub-pipe 27b to send the heat storage material HS from the high-temperature heat storage tank 24 through the heat exchanger 23 to the low-temperature heat storage tank 25. Furthermore, a valve 29 is provided in the sub-pipe 27b to block and allow the flow of the heat storage material HS.

The low-temperature heat storage tank 25 is connected to the heat exchanger 23 via a low-temperature heat storage tank pipe 31. The low-temperature heat storage tank pipe 31 includes a main pipe 31a that connects the low-temperature heat storage tank 25 and the heat exchanger 23, and a sub-pipe 31b (shown by a dashed line in FIG. 1) that branches off and merges with the main pipe 31a. The main pipe 31a is provided with a pump 32 that sends the heat storage material HS from the low-temperature heat storage tank 25 through the heat exchanger 23 to the high-temperature heat storage tank 24. Furthermore, the sub-pipe 31b is provided with a valve 33 that blocks and allows the flow of the heat storage material HS.

The heat exchanger 23 is provided so that heat can be exchanged between the heat storage material HS passing through it while being supplied from the low-temperature heat storage tank 25 to the high-temperature heat storage tank 24, and the steam passing through it from the boiler 11 via the piping 22. Through this heat exchange, the heat storage material HS is heated (heat is stored), and the steam supplied from the boiler 11 is cooled, reducing the heat content of the steam. The steam whose heat content has been reduced by the heat exchanger 23 becomes a gas phase, and depending on the temperature and pressure, it becomes two-phase gas-liquid steam (saturated steam) containing water.

The heat storage and release system 21 further includes a heater 35 constituting a heating device capable of heating the stored heat storage material HS, and the heater 35 is a heat source other than the steam generated by the boiler 11. In the illustrated configuration example, the heater 35 is provided in the high-temperature heat storage tank 24 and is capable of heating the heat storage material HS stored (supplied) in the high-temperature heat storage tank 24, but is not limited to this. For example, the heater 35 may be provided in the main pipe 27a of the high-temperature heat storage tank pipe 27, and the heat storage material HS immediately before being stored (supplied) from the low-temperature heat storage tank 25 to the high-temperature heat storage tank 24 may be heated by the heater 35. The heater 35 generates heat by the power generated by the generator G to heat the heat storage material HS, and is preferably controlled by a control unit (not shown) so that surplus power to the required power at a specified power supply destination is supplied from the generator G to generate heat.

The ejector 19 is composed of a steam ejector or the like, and is a device that mixes steam with the liquid flow to transfer its heat and momentum, and obtains a high-pressure ejected fluid from the fluid pressure introduced through the suction side inlet 19b. The ejector 19 has a drive side inlet 19a, a suction side inlet 19b, and a discharge side outlet 19c.

The downstream side of the pipe 16 is connected to the drive side inlet 19a, and condensate pumped by the condensate pump 17 and the boiler feed water pump 18 is supplied to the drive side inlet 19a. A pipe 38 connected to the heat exchanger 23 is connected to the suction side inlet 19b, and steam generated in the boiler 11, which has dissipated heat in the heat exchanger 23 and been discharged is supplied to the suction side inlet 19b through the pipe 38. The pipe 39 connected to the discharge side outlet 19c is connected to the inlet of the boiler 11.

In the ejector 19, when high-pressure condensate is supplied to the drive-side inlet 19a and steam is supplied to the suction-side inlet 19b, the condensate reaches supersonic speed at the drive nozzle outlet inside the ejector 19, and the condensate becomes a gas-liquid two-phase flow, lowering the static pressure and drawing in the steam. In addition, the steam condenses and mixes with the condensate upon contact with the steam, and the pressure rises above the steam pressure supplied from the suction-side inlet 19b, and the steam is discharged from the discharge-side outlet 19c.

In the piping 16, between the boiler feedwater pump 18 and the ejector 19, a valve 41 is provided to block and allow the flow of condensate discharged from the boiler feedwater pump 18. In addition, in the piping 38, between the heat exchanger 23 and the ejector 19, a valve 42 is provided to block and allow the flow of steam that has been dissipated heat by the heat exchanger 23.

The thermal storage system 10 further includes a bypass pipe 43 (shown by a dashed line in FIG. 1) connected to the pipes 16 and 39 so as to bypass the ejector 19. One end (upstream end) of the bypass pipe 43 is connected between the boiler feedwater pump 18 in the pipe 16 and the drive side inlet 19a of the ejector 19, and more specifically, between the boiler feedwater pump 18 in the pipe 16 and the valve 41. The other end (downstream end) of the bypass pipe 43 is connected between the discharge side outlet 19c of the ejector 19 in the pipe 39 and the inlet of the boiler 11.

The bypass pipe 43 is provided with a valve 44 that blocks and allows the flow of condensate sent from the boiler feedwater pump 18.

The heat storage system 10 further includes a pipe 46 (shown by a dashed line in FIG. 1) that connects the pipe 16 and the pipe 38 and through which the condensate flows. The specific connection position of the pipe 46 is such that one end is between the condensate pump 17 and the boiler feedwater pump 18 on the pipe 16, and the other end is between the heat exchanger 23 and the valve 42 on the pipe 38.

A pump 47 is provided in the piping 46 to send the condensate flowing from the condenser 13 to the piping 16 to the piping 38 and the heat exchanger 23. In addition, a valve 48 is provided in the piping 46 to block and allow the flow of the condensate.

Here, the heat exchanger 23 is provided so as to be able to exchange heat between the condensate passing from the condenser 13 through the pipes 16, 46, and 38 and the heat storage material HS passing through while being supplied from the high-temperature heat storage tank 24 to the low-temperature heat storage tank 25 (see FIG. 3). Through this heat exchange, the heat storage material HS is dissipated, and the condensate is heated to generate steam, in other words, the heat quantity of the condensate (steam) is increased. The steam generated in the heat exchanger 23 is supplied to the steam turbine 12 through the pipes 22 and 15. Here, the heat exchanger 23 functions as an auxiliary boiler (auxiliary steam generator) capable of generating steam to be supplied to the steam turbine 12.

The heat storage system 10 of the first embodiment is selectively operated in a first heat storage operation mode, a second heat storage operation mode, and a heat dissipation operation mode. In the first heat storage operation mode and the second heat storage operation mode, thermal energy is stored in the heat storage material HS, and the output from the generator G to a specified power supply destination is relatively low. In the heat dissipation operation mode, thermal energy is released from the heat storage material HS, and the output from the generator G to a specified power supply destination is relatively high. Below, the first heat storage operation mode will be described with reference to FIG. 1, the second heat storage operation mode will be described with reference to FIG. 2, and the heat dissipation operation mode will be described with reference to FIG. 3. In addition, in FIG. 1 to FIG. 3, pipes that are not used in each operation mode are illustrated with dashed lines.

[First heat storage operation mode: Figure 1]
In the first heat-storage operation mode, the valves 29, 33, 44, and 48 are closed, and the valves 41 and 42 are open. In addition, the condensate pump 17, the boiler feedwater pump 18, and the pump 32 are operated, and the pumps 28 and 47 are stopped.

When the pump 32 of the heat storage and release system 21 is operated, the heat storage material HS in the low-temperature heat storage tank 25 flows into the heat exchanger 23 via the main pipe 31a of the low-temperature heat storage tank piping 31. In the heat exchanger 23, the heat storage material HS is heated by heat exchange with the steam generated in the boiler 11 and the temperature is increased. The heat storage material HS heated in the heat exchanger 23 is stored in the high-temperature heat storage tank 24 via the main pipe 27a of the high-temperature heat storage tank piping 27 by the power of the pump 32.

As a result, the amount of heat storage material HS that becomes high temperature increases in the high-temperature heat storage tank 24, and the amount of heat storage material HS that becomes low temperature decreases in the low-temperature heat storage tank 25. This increases the heat storage energy of the heat storage system 10.

In the first heat storage operation mode, the steam (superheated steam) generated in the boiler 11 is distributed to the heat exchanger 23 and the steam turbine 12 via the pipes 15 and 22. The steam that flows into the heat exchanger 23 from the pipe 22 is cooled by dissipating heat to the heat storage material HS sent from the low-temperature heat storage tank 25 to the high-temperature heat storage tank 24, and is sucked into the suction side inlet 19b of the ejector 19 via the pipe 38.

In the first heat storage operation mode, the steam that flows into the steam turbine 12 from the pipe 15 is converted into power to rotate the output shaft 12a by the thermal energy in the steam turbine 12, and is discharged with a reduced temperature. The generator G generates electricity using the rotational power of the output shaft 12a, and supplies the electricity to a specified power supply destination. The steam discharged from the steam turbine 12 is condensed in the condenser 13. This condensate is supplied to the ejector 19 via the pipe 16 by the condensate pump 17 and the boiler feed water pump 18, and flows into the drive side inlet 19a.

Condensate is supplied to the ejector 19 from the drive side inlet 19a, and steam that has dissipated heat in the heat exchanger 23 and been discharged is supplied from the suction side inlet 19b. Inside the ejector 19, the condensate and steam come into contact with each other, causing the steam to condense and mix, and the condensate, which has a higher temperature than before it flowed into the ejector 19, is supplied to the boiler 11 via the discharge side outlet 19c and piping 39.

In this way, in the first heat storage operation mode, a circulation system can be configured in which steam and water (condensate) circulate in the following flow: boiler 11 → heat exchanger 23 → ejector 19 → boiler 11. Also, in the first heat storage operation mode, the heat storage material HS can be heated via the heat exchanger 23 by the steam generated in the boiler 11, thereby increasing the heat quantity of the heat storage material HS.

[Second heat storage operation mode: Figure 2]
In the second heat storage operation mode, the valves 29, 33, 41, 42, and 48 are closed, and the valve 44 is opened. In addition, the condensate pump 17 and the boiler feed water pump 18 are operated, and the pumps 28, 32, and 47 are stopped. As a result, in the second heat storage operation mode, the operation of the heat storage and release system 21 is stopped. Therefore, the movement of the heat storage material HS between the high temperature heat storage tank 24 and the low temperature heat storage tank 25 is stopped, and the heat exchange by the heat storage material HS in the heat exchanger 23 is also stopped.

In the second heat storage operation mode, all of the steam (superheated steam) generated in the boiler 11 is supplied to the steam turbine 12 via the pipe 15. The steam that flows into the steam turbine 12 from the pipe 15 is converted into thermal energy by the steam turbine 12 to power that rotates the output shaft 12a, and is discharged with a reduced temperature. The generator G generates electricity using the rotational power of the output shaft 12a, and the electricity is supplied to a specified power supply destination, and the surplus electricity relative to the required power at the power supply destination is supplied to the heater 35. This causes the heater 35 to generate heat, and the heat storage material HS stored in the high-temperature heat storage tank 24 is heated by the heater 35, raising the temperature of the heat storage material HS.

The steam discharged from the steam turbine 12 is condensed in the condenser 13. This condensate is pumped by the condensate pump 17 and the boiler feedwater pump 18 through the pipe 16, the bypass pipe 43, and the pipe 39 to the boiler 11.

In this way, in the second heat storage operation mode, the heat storage material HS can be heated by the heater 35, which is a heat source other than the steam generated by the boiler 11, to increase the heat quantity of the heat storage material HS. In addition, in the first embodiment, by selectively implementing the first heat storage operation mode and the second heat storage operation mode, the heat exchanger 23 and the heater 35 can be selectively used to heat the heat storage material HS.

[Heat dissipation operation mode: Figure 3]
In the heat dissipation operation mode, the valves 41 and 42 are closed, and the valves 29, 33, 44, and 48 are opened. In addition, the condensate pump 17, the boiler feed water pump 18, and the pumps 28 and 47 are operated, and the pump 32 is stopped.

When the pump 28 is operated, the heat storage material HS in the high-temperature heat storage tank 24 flows into the heat exchanger 23 via the sub-pipe 27b of the high-temperature heat storage tank piping 27. In the heat exchanger 23, the heat storage material HS exchanges heat with the condensate generated in the condenser 13, lowering its temperature and dissipating heat. The heat storage material HS that has dissipated heat in the heat exchanger 23 is stored in the low-temperature heat storage tank 25 via the sub-pipe 31b of the low-temperature heat storage tank piping 31 by the power of the pump 28.

As a result, the amount of low-temperature heat storage material HS stored in the low-temperature heat storage tank 25 increases, and the amount of high-temperature heat storage material HS stored in the high-temperature heat storage tank 24 decreases. As a result, the heat storage energy of the heat storage system 10 decreases.

In the heat dissipation operation mode, all of the steam (superheated steam) generated in the boiler 11 is supplied to the steam turbine 12 via the pipe 15. The steam that flows into the steam turbine 12 from the pipe 15 is converted into thermal energy by the steam turbine 12 to power that rotates the output shaft 12a, and is discharged with a reduced temperature. The generator G generates electricity using the rotational power of the output shaft 12a, and supplies the electricity to a specified power supply destination. The steam discharged from the steam turbine 12 is condensed by the condenser 13. The condensate is sent through the pipe 16 by the condensate pump 17, the boiler feedwater pump 18, and the pump 47, and is distributed at the branch point of the pipes 16 and 46.

The condensate that flows through pipe 16 without being distributed through pipe 46 is supplied to boiler 11 via bypass pipe 43 and pipe 39.

The condensate flowing into pipe 46 is supplied to heat exchanger 23 via pipe 38. The condensate flowing into heat exchanger 23 is heated by heat radiation from heat storage material HS sent from high-temperature heat storage tank 24 to low-temperature heat storage tank 25 in heat exchanger 23, and steam is generated in heat exchanger 23. The steam generated in heat exchanger 23 flows into pipe 15 via pipe 22, merges with steam generated in boiler 11, and is supplied to steam turbine 12.

In this way, in the heat dissipation operation mode, thermal energy is supplied not only from the boiler 11 but also from the heat storage material HS, and the output of the steam turbine 12 can be increased compared to each heat storage operation mode. Therefore, the heat dissipation operation mode can be a mode that can respond to cases where the output of the power supply destination of the generator G becomes relatively high. On the other hand, in the first heat storage operation mode, thermal energy is stored in the heat storage material HS in the heat exchanger 23 to which the steam from the boiler 11 is distributed, and in the second heat storage operation mode, thermal energy is stored in the heater 35 to which surplus power is supplied. Therefore, each heat storage operation mode can be a mode that can respond to cases where the output of the power supply destination of the generator G becomes relatively low. As a result, the output of the generator G can be adjusted according to the power generation output request by switching between each heat storage operation mode and heat dissipation operation mode.

Next, the effects of the first embodiment will be described below using a comparative structure. The comparative structure is configured without the heater 35 in the first embodiment. In addition, in both the first embodiment and the comparative structure, liquid phase molten salt is used as the heat storage material.

Figure 4 is a graph showing the relationship between the amount of heat exchanged and temperature in the comparative structure and the first embodiment. In Figure 4, the horizontal axis is the amount of heat exchanged (MW), and the vertical axis is the temperature (°C). In the graph in Figure 4, since molten salt is used as the heat storage material, the heat storage material changes temperature between the high temperature TH and the low temperature TL during normal operation and maintains a liquid phase. Therefore, the heat storage material undergoes sensible heat change, and the temperature change with respect to the change in heat amount changes linearly (with a uniform slope) in each of the arrow lines GHa and GH1 during heat storage and the arrow line GL during heat release in the comparative structure.

On the other hand, as shown by the dashed line GW in Figure 4, water (steam) changes into saturated steam, which is a two-phase gas-liquid state where water and steam are mixed, and the temperature remains constant as a result of latent heat changes. Also, in the dashed line GW, when the heat quantity becomes greater than that of saturated steam, the temperature changes linearly according to the heat quantity as the superheated steam changes into sensible heat, and when the heat quantity becomes greater than that of saturated steam, the temperature changes linearly according to the heat quantity as the compressed water changes into sensible heat.

When heating the heat storage material, it is necessary to maintain the temperature of the heat storage material lower than that of the steam during heat exchange so that heat exchange can take place between the steam and the heat storage material. Then, the arrow lines GHa and GH1, which show the temperature change when the heat storage material at the low temperature TL is heated, approach each other most closely at the boundary point of the dashed line GW between saturated steam and superheated steam, as shown in the figure. The arrow line GHa shows the temperature change when priority is given to a higher temperature in the heat storage material after heating, and the amount of change in the horizontal axis of the arrow line GHa during this temperature change is the amount of heat exchanged during heat storage in the heat storage material Q1.

When releasing heat from the heat storage material, it is necessary to satisfy the condition (hereinafter referred to as "temperature condition for heat release") that maintains the temperature of the heat storage material higher than the steam (water) during heat exchange so that heat can be exchanged between the steam (water) and the heat storage material. Then, the arrow line GL showing the temperature change during heat exchange when releasing heat from the heat storage material at high temperature TH approaches closest at the boundary point of the dashed line GW between saturated steam and compressed water, as shown in the figure. The amount of change in the horizontal axis of such arrow line GL is the amount of heat exchanged Q2 during heat release in the heat storage material.

Comparing the amount of heat exchanged Q2 during heat release and the amount of heat exchanged Q1 during heat storage shown by the arrow line GHa, the amount of heat exchanged Q1 during heat storage is significantly smaller. Moreover, when heat storage shown by the arrow line GHa is performed, the energy of the steam (water) cannot be sufficiently transferred to the heat storage material for the amount of heat exchanged Q3 of steam (water) in the range to the left of the range shown by the amount of heat exchanged Q1 in Figure 4. As a result, the comparative structure has a problem in that, depending on the operating conditions, the steam may flow out of the heat exchanger in the form of high-pressure steam and be discarded, resulting in low energy efficiency. Furthermore, because the amount of heat exchanged Q1 is small, it takes a long time to store the heat that is insufficient for the amount of heat exchanged Q2 during heat release, resulting in a problem of reduced adjustment of power generation during times when power generation output demand is high (e.g., daytime, etc.).

On the other hand, the arrow line GH1 shows the temperature change when priority is given to increasing the amount of heat exchanged by the heat storage material after heating, and the amount of change in the horizontal axis direction of the arrow line GH1 due to this temperature change is the amount of heat exchanged Q4 during heat storage in the heat storage material. In the heat storage shown by the arrow line GH1, the amount of heat exchanged Q4 approaches the amount of heat exchanged Q2 during heat release described above, and compared to the heat storage shown by the arrow line GHa, the energy recovery rate can be increased and energy efficiency can be improved.

However, the slope (temperature change relative to change in heat quantity) of the arrow line GH1 during heat storage is smaller than that of the arrow line GL during heat dissipation, and the slope is proportional to the flow rate of the heat storage material, so the flow rate of the heat storage material is significantly greater during heat storage than during heat dissipation. However, in a heat storage and dissipation system using a high-temperature heat storage tank and a low-temperature heat storage tank, the volumetric capacity of each heat storage tank must be the same, and if the flow rate of the heat storage material is significantly greater during heat storage, the volumetric capacity of the heat storage material in the high-temperature heat storage tank will continue to increase, making it impossible to continue operating the entire heat storage system.

Therefore, in the first embodiment, a first heat storage operation mode and a second heat storage operation mode are implemented during heat storage. In the first embodiment, heat storage is performed in the first heat storage operation mode as indicated by the arrow line GH1 described above, and then heat storage is performed in the second heat storage operation mode as indicated by the arrow line GH2. Note that in the heat release operation mode in the first embodiment, heat release is performed as indicated by the arrow line GL described above.

In the heat storage indicated by the arrow line GH2, heat storage by steam (water) is stopped, and the heater 35 is heated by the surplus power supplied from the generator G to heat the heat storage material. Therefore, the heat storage indicated by the arrow line GH2 can increase the temperature of the heat storage material without increasing or decreasing the amount of heat exchanged, and can heat the heat storage material until it reaches the arrow line GL during heat release to satisfy the above-mentioned heat release temperature condition. As a result, in the first embodiment, the flow rate of the heat storage material during heat release and heat storage can be made close to the same, and the operation of the entire heat storage system 10 including the heat storage and release system 21 using the high-temperature heat storage tank 24 and the low-temperature heat storage tank 25 can be continued.

According to the first embodiment, in the first heat storage operation mode, which is the first step of heat storage, the steam generated in the boiler 11 is distributed to the heat storage and release system 21 and the steam turbine 12, and the heat storage material HS of the volume capacity required in the heat release operation mode can be stored in the high-temperature heat storage tank 24. After that, in the second heat storage operation mode, which is the second step of heat storage, the distribution is stopped and all steam from the boiler 11 is supplied to the steam turbine 12, and the heat storage material HS in the high-temperature heat storage tank 24 can be heated (heat stored) to the target temperature by the heater 35 using surplus electricity generated by the generator G.

As described above, in the first embodiment, the volumetric capacity of the heat storage material HS during heat storage and heat release can be made nearly the same, while the heat exchange amounts Q2 and Q4 during heat storage and heat release can also be made nearly the same, thereby reducing energy loss and improving the energy efficiency of the heat storage system 10. In addition, by making the heat exchange amounts Q2 and Q4 during heat storage and heat release nearly the same, the heating time by the heater 35 can be shortened, and the ability to adjust the generated power can be effectively demonstrated.

[Second embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the same reference numerals may be used for the same or equivalent components as those in the first embodiment, and the description may be omitted or simplified.

A second embodiment of the present invention will be described with reference to Figs. 5 to 7. Fig. 5 is a schematic diagram of a heat storage system according to the second embodiment, showing the heat dissipation operation mode. Fig. 6 is a diagram similar to Fig. 5, showing the heat storage system in the heat storage operation mode. As shown in Figs. 5 and 6, the second embodiment includes a heat storage and release system 51 which is a modified version of the heat storage and release system 21 of the first embodiment.

The heat storage and release system 51 in the second embodiment is supplied with superheated steam from the boiler 11 and condensate from the condenser 13 via piping 52. The piping 52 connects the piping 15 and 16, with the downstream end of the piping 52 connected to the piping 15 between the boiler 11 and the steam turbine 12, and the upstream end of the piping 52 connected to the piping 16 between the condensate pump 17 and the boiler feedwater pump 18. A feedwater pump 53 is provided on the piping 52 downstream of the heat storage material boiler 63 described later.

The heat storage and release system 51 includes a high-temperature heat storage tank 54 and a low-temperature heat storage tank 55 that store heat storage material HS, as in the first embodiment. The heat storage and release system 51 also includes a pipe 57 and a heat storage material supply pump 58 that supply the heat storage material HS from the high-temperature heat storage tank 54 to the low-temperature heat storage tank 55, and a pipe 61 and a heat storage material transfer pump 62 that supply the heat storage material HS from the low-temperature heat storage tank 55 to the high-temperature heat storage tank 54.

Furthermore, the heat storage and release system 51 includes a heat storage material boiler (auxiliary steam generator) 63 provided in the pipe 57, and a heating furnace 64 provided in the pipe 61 and constituting a heating device.

The heat storage material boiler 63 is provided so as to be capable of exchanging heat between the heat storage material HS passing therethrough while being supplied from the high-temperature heat storage tank 54 to the low-temperature heat storage tank 55 and the condensate passing therethrough from the condenser 13 via the pipes 16 and 52. Through this heat exchange, the condensate is heated and undergoes a phase change to steam (superheated steam), and the heat storage material HS is released. The steam generated by heating in the heat storage material boiler 63 is supplied to the steam turbine 12 via the pipes 52 and 15.

The heating furnace 64 is provided so as to be capable of heating the heat storage material HS sent (supplied) from the low-temperature heat storage tank 55 to the high-temperature heat storage tank 54. As the heating furnace 64, a boiler using a known fuel as a heat source can be adopted as long as it can heat the heat storage material HS, which maintains a liquid phase before and after heating, to the target temperature. However, in consideration of the environmental load, etc., it is preferable to use natural energy such as biomass fuel or sunlight. The heating furnace 64 becomes a heat source other than the steam generated by the boiler 11.

The heat storage material supply pump 58 provided in the piping 57 is provided downstream of the high-temperature heat storage tank 54 and upstream of the heat storage material boiler 63. The flow rate of the heat storage material HS supplied to the heat storage material boiler 63 by the heat storage material supply pump 58 is controlled by a control unit (not shown). The heat storage material transfer pump 62 provided in the piping 61 is provided downstream of the low-temperature heat storage tank 55 and upstream of the heating furnace 64.

The heat storage and release system 51 further includes a heater 65 constituting a heating device capable of heating the stored heat storage material HS, similar to the heater 35 in the first embodiment, and the heater 65 is a heat source other than the steam generated by the boiler 11. In the illustrated configuration example, the heater 65 is provided in the high-temperature heat storage tank 54 and is capable of heating the heat storage material HS stored (supplied) in the high-temperature heat storage tank 54, but is not limited to this. For example, the heater 65 may be provided in the piping 61, and the heat storage material HS immediately before being stored (supplied) from the low-temperature heat storage tank 55 to the high-temperature heat storage tank 54 may be heated by the heater 65. The heater 65 generates heat by the power generated by the generator G to heat the heat storage material HS, and preferably generates heat by being supplied with surplus power relative to the required power at a specified power supply destination.

In the second embodiment, the system is selectively operated in a heat storage operation mode and a heat dissipation operation mode. In the following, the case where the boiler 11 and the heating furnace 64 are operated at a constant output as rated operation in both the heat storage operation mode and the heat dissipation operation mode will be described, but this does not prevent the output from being adjusted under various conditions.

[Common to heat storage operation mode and heat dissipation operation mode]
In both the heat storage operation mode and the heat release operation mode, all of the steam (superheated steam) generated in the boiler 11 is supplied to the steam turbine 12 via the pipe 15. The thermal energy of the steam that flows into the steam turbine 12 from the pipe 15 is converted into power for rotating the output shaft 12a in the steam turbine 12, and the temperature of the steam is reduced before it is discharged. Electricity is generated by the generator G using the rotational power of the output shaft 12a, and the electric power is supplied to a predetermined power supply destination.

The steam discharged from the steam turbine 12 is condensed in the condenser 13. This condensate is supplied to the boiler 11 via the piping 16 by the condensate pump 17 and the boiler feedwater pump 18, in other words, returned to the boiler 11 and circulated.

In both the heat storage operation mode and the heat release operation mode, the heat storage material transfer pump 62 of the heat storage and release system 51 is operated, causing the heat storage material HS in the low-temperature heat storage tank 55 to flow through the piping 61 into the heating furnace 64. After the heat storage material HS is heated to a predetermined temperature in the heating furnace 64, the heated heat storage material HS is supplied to the high-temperature heat storage tank 54. Next, the heat release operation mode and the heat storage operation mode will be described in that order.

[Heat dissipation operation mode: Figure 5]
In the heat dissipation operation mode, the heat storage material supply pump 58 is operated to cause the heat storage material HS in the high-temperature heat storage tank 54 to flow into the heat storage material boiler 63 via the pipe 57. The water feed pump 53 is operated to cause the condensate generated in the condenser 13 to flow into the heat storage material boiler 63 via the pipe 52, and the condensate exchanges heat with the heat storage material HS. The condensate is heated by this heat exchange, and steam is generated. The generated steam flows into the pipe 15 via the pipe 52, merges with the steam generated in the boiler 11, and is supplied to the steam turbine 12.

Here, the operation of the heat storage material supply pump 58 is controlled by a control unit (not shown) to adjust the flow rate of the heat storage material HS supplied to the heat storage material boiler 63. This makes it possible to adjust the amount of heat exchanged (amount of energy) of the steam supplied from the heat storage material boiler 63 to the steam turbine 12.

In the heat storage material boiler 63, the heat storage material HS that has been heat exchanged with the condensate generated in the condenser 13 drops in temperature and dissipates heat. The heat storage material HS that has dissipated heat in the heat storage material boiler 63 is stored in the low-temperature heat storage tank 55 via piping 57. Therefore, in the heat dissipation operation mode, the amount of heat storage material HS that becomes low temperature in the low-temperature heat storage tank 55 increases, and the amount of heat storage material HS that becomes high temperature in the high-temperature heat storage tank 54 decreases. This results in a decrease in the stored heat energy of the heat storage system 10.

[Heat storage operation mode: Figure 6]
In the heat storage operation mode, unlike the heat dissipation operation mode, the water supply pump 53 and the heat storage material supply pump 58 are stopped, and the inflow of the heat storage material HS and condensate to the heat storage material boiler 63 is stopped. On the other hand, the generator G generates power, and while power is supplied to a specified power supply destination, surplus power to the power required by the power supply destination is supplied to the heater 65. This causes the heater 65 to generate heat, and the heat storage material HS stored in the high-temperature heat storage tank 54 is heated by the heater 65, thereby increasing the temperature of the heat storage material HS.

In addition, while the discharge of the heat storage material HS from the high-temperature heat storage tank 54 is stopped, the heating of the heat storage material HS in the heating furnace 64 and the supply to the high-temperature heat storage tank 54 continue. Therefore, in the heat storage operation mode, the amount of heat storage material HS stored in the low-temperature heat storage tank 55 decreases, and the amount of heat storage material HS stored in the high-temperature heat storage tank 54 increases. This increases the heat storage energy of the heat storage system 10.

In this way, in the second embodiment, the heat storage material HS can be heated by the heating furnace 64 constituting the heating device in the heat dissipation operation mode, and the heat storage material HS can be heated by both the heating furnace 64 and the heater 65 constituting the heating device in the heat storage operation mode.

Figure 7 is a graph showing the change over time in the energy required for power generation. In Figure 7, the horizontal axis is time (hr) and the vertical axis is the energy (%) required for power generation by generator G. The graph in Figure 7 assumes that the energy required for power generation is greater during the day than at night, with the peak occurring just before noon.

As shown in the graph in Figure 7, the average energy value over a 24-hour period is set to 100%, as indicated by the dashed line, and the assumed condition is that the constant energy value at night is 60% of the average value (100%).

Under these assumed conditions, the nighttime energy value (60%) is set to be equal to the load on the boiler 11 (see the dotted area in Figure 7). In addition, the load on the heating furnace 64 is set to be equal to the value (40%) obtained by subtracting the nighttime energy value (60%) from the average 24-hour energy value (100%) (see the area between the dotted area and the dashed line in Figure 7).

Under the above conditions, during the nighttime hours when the energy is constant, the energy required for power generation can be met by the load of the boiler 11 alone. Therefore, the heat storage operation mode is implemented, and the energy generated by the load of the heating furnace 64 is stored in the heat storage material HS (see the hatched area in Figure 7).

In addition, under the above conditions, the value of the required energy increases or decreases within a range of 60% to approximately 150% except during the hours when the nighttime energy is constant. In this range, the heat dissipation operation mode is implemented, and the energy generated by the load on the heating furnace 64 is dissipated from the heat storage material HS through heat exchange with the condensate in the heat storage material boiler 63 and supplied. Then, depending on the increase or decrease in the required energy, the flow rate of the heat storage material HS supplied to the heat storage material boiler 63 is adjusted by the heat storage material supply pump 58, and the amount of heat dissipated from the heat storage material HS to the condensate is adjusted.

When the required energy value is in the range of 60% to 100%, the amount of energy stored in the heat storage and release system 51 is greater than the energy released to the heat storage material HS. When the required energy value exceeds 100%, the amount of energy released to the heat storage material HS is greater than the energy stored in the heat storage and release system 51.

In the second embodiment, the heat source for heating the heat storage material HS of the heat storage and release system 51 is the heating furnace 64 and the heater 65. This makes it possible to provide energy for storing heat in the heat storage material HS without using steam generated in the boiler 11, and prevents the steam from flowing out at a high temperature. Therefore, even in the second embodiment, it is possible to increase the energy recovery rate and improve energy efficiency.

The embodiments of the present invention are not limited to the above-mentioned embodiments, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in a different way due to technological advances or derived other technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of the present invention.

For example, in the heat storage/dissipation system 51 of the second embodiment, the heat storage material HS can be heated by the heater 65, but the heat storage material HS may be heated only by the heating furnace 64 without providing the heater 65.

The energy changes in the graph in Figure 7 are merely an example, and it is possible to reverse the day and night output or change the timing of increase and decrease in the same way as described above.

The boiler 11 may also be another steam generator as long as it is capable of generating and supplying steam in the same manner as in each of the above embodiments.

In addition to providing heaters for heating the heat storage material HS in the high-temperature heat storage tanks 24 and 54, there is no prohibition on providing heaters in the low-temperature heat storage tanks 25 and 55 and the above-mentioned piping for the purpose of heat retention, etc., and these may be made to generate heat using electricity from the generator G.

10: Heat storage system 11: Boiler (steam generator)
12: Steam turbine 13: Condenser 21: Heat storage and release system 23: Heat exchanger (auxiliary steam generator)
24: High-temperature heat storage tank 25: Low-temperature heat storage tank 35: Heater (heating device)
51: Heat storage and release system 54: High-temperature heat storage tank 55: Low-temperature heat storage tank 58: Heat storage material supply pump 63: Heat storage material boiler (auxiliary steam generator)
64: Heating furnace (heating device)
65: Heater (heating device)
G: Generator HS: Heat storage material

Claims (6)

A steam generator for generating steam;
a steam turbine to which the steam generated in the steam generator is supplied;
a condenser that condenses steam discharged from the steam turbine;
a heat storage system that heats condensate generated in the condenser by a stored heat storage material to generate steam and supplies the steam to the steam turbine,
The heat storage and release system includes a heating device capable of heating the stored heat storage material,
The heat storage system according to claim 1, wherein the heating device heats the heat storage material with a heat source other than the steam generator. The heat storage and release system includes a high-temperature heat storage tank and a low-temperature heat storage tank that accommodate a heat storage material,
an auxiliary steam generator that generates steam by heating condensate using a heat storage material supplied from the high-temperature heat storage tank to the low-temperature heat storage tank;
The heat storage system according to claim 1, wherein the heating device heats the heat storage material supplied from the low-temperature heat storage tank to the high-temperature heat storage tank. The heat storage system according to claim 2, characterized in that the heating device is equipped with a heating furnace that heats the heat storage material supplied from the low-temperature heat storage tank to the high-temperature heat storage tank. The steam turbine further includes a generator that generates electricity from the power generated by the steam turbine.
4. The heat storage system according to claim 2, wherein the heating device includes a heater that heats the heat storage material stored in the high-temperature heat storage tank with the electric power generated by the generator. The steam turbine further includes a generator that generates electricity from the power generated by the steam turbine.
the heating device includes a heater that heats the heat storage material stored in the high-temperature heat storage tank by using the electric power generated by the generator,
The heat storage and release system further includes a heat exchanger that heats a heat storage material supplied from the low-temperature heat storage tank to the high-temperature heat storage tank by steam generated by the steam generator,
3. The heat storage system according to claim 2, wherein the heat storage material of the heat storage/dissipation system is heated by selectively using the heat exchanger and the heater. the heat storage/release system includes a heat storage material supply pump capable of adjusting a flow rate of the heat storage material supplied from the high-temperature heat storage tank to the low-temperature heat storage tank;
4. The heat storage system according to claim 2, wherein the amount of energy supplied to the steam turbine by the steam generated by the auxiliary steam generator is adjusted by adjusting the flow rate of the heat storage material by the heat storage material supply pump.

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