JP2009009880A - Co-generation system and storage tank side unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a co-generation system which can start up a fuel cell smoothly, and can prevent the cooling water of a high temperature from flowing into the fuel cell side. <P>SOLUTION: In a pre-heating supply operation mode, a standby heating source 52 in a warming circulation passage D is started up, heat in the warming circulation passage D is taken into the side of an exhausted heat recovering passage C. When hot water introduced in the fuel cell 5 side exceeds a limit during operation in the pre-heating supply operation mode, a three way valve 28 on the side of heating is driven and a part of hot water leaks to a storage tank 10 side. As a result, a part of the hot water is supplied to the storage tank 10, and a small amount of the hot water of a low temperature is taken out of the storage tank 10 and mixed with the hot water flowing in a bypass passage 23 and a temperature as a whole is lowered. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cogeneration system that combines a fuel cell and a storage tank.

There is known a cogeneration system capable of recovering thermal energy of exhaust heat generated by a fuel cell during power generation through a liquid such as hot water and storing it in a storage tank (Patent Documents 1 and 2). The cogeneration system having such a configuration has high energy efficiency because it can effectively use exhaust heat when cooling the fuel cell.
JP 2001-325882 A JP 2007-64526 A

  In the cogeneration systems disclosed in Patent Documents 1 and 2, the temperature of water is raised by the heat generated by the fuel cell, and this hot water is stored in a storage tank.

Since the fuel cell generates heat during power generation as described above, it is necessary to cool the battery in order to maintain power generation. In such a cogeneration system using a fuel cell, it is necessary to take heat away from the fuel cell during normal operation. However, the fuel cell is difficult to start in a low temperature state, and on the contrary, the fuel cell must be warmed up.
Although it is possible to increase the temperature of the fuel cell with an electric heater at startup, the policy to use an electric heater is to use a commercial power supply when starting the cogeneration system, and to adopt the cogeneration system. It will be contrary to.
Therefore, a measure for raising the temperature of the fuel cell by using a preliminary heat source for heating at the time of start-up was considered. In other words, when a cogeneration system using a fuel cell is used for heating floor heating equipment, fan convectors, etc., the amount of heat required for the floor heating equipment may not be provided by the heat generated by the fuel cell alone. There is a thing with preliminary.
In the cogeneration system having such a configuration, a heating heat exchanger is separately attached to an exhaust heat recovery passage through which hot water heated by exhaust heat of the fuel cell circulates. Moreover, the secondary side flow path of the heat exchanger for heating is connected to the heating circulation flow path which circulates a floor heating apparatus etc. The heating circulation channel is provided with a preliminary heat source such as the burner described above.

  In the cogeneration system configured as described above, power is generated by the fuel cell, the temperature of the hot water flowing through the exhaust heat recovery passage is increased by the exhaust heat generated during power generation, and the heating circulation passage is further connected via the heat exchanger for heating. The temperature of the flowing heat medium is raised and supplied to floor heating equipment. Normally, the heating medium is ignited by directly igniting the burner as a preliminary heat source to heat the heating medium flowing in the heating circulation flow path. To contribute.

  In such a cogeneration system equipped with a preliminary heat source, the burner, which is a preliminary heat source, is ignited when the fuel cell is started, and the temperature of the fuel cell is increased by the reverse heat transfer. In other words, when the fuel cell is started, the burner as a preliminary heat source is ignited, the heating medium in the heating circulation passage is heated, and heat is transferred from the heating circulation passage to the exhaust heat recovery passage, contrary to the normal use state. Thus, the temperature of the water on the exhaust heat recovery flow path side can be raised, and the temperature can be raised to a state where the fuel cell can be started. Therefore, as described above, the inventors have invented a configuration in which the temperature of the fuel cell is raised by using a preliminary heat source for heating at the time of start-up, and prototyped the apparatus.

However, there was an unexpected problem here. That is, the heating device includes a device that requires a high-temperature heat medium and a device that requires a low-temperature heat medium.
For example, a floor heating device requires a low-temperature heat medium of about 40 ° C. to 60 ° C., whereas a fan convector requires a high-temperature heat medium of about 80 ° C. Therefore, the required temperature of the heat medium is different between the case of using floor heating and the case of using a fan convector.
Here, as described above, when the burner as a preliminary heat source is ignited and the temperature is raised to start the fuel cell, the heating operation is performed at the same time, and the operation state of the heating operation requires a high-temperature heat medium. If it becomes a situation, a burner etc. will raise the target temperature of the heat medium which flows through a heating circulation flow path according to the request | requirement. As a result, the temperature of the hot water flowing to the fuel cell side also rises and exceeds the temperature range suitable for the operation of the fuel cell.

When fuel cells are operated at high temperatures, their durability is significantly reduced and there is a risk of damage to pumps and other accessories.
As countermeasures, measures such as intermittently operating the burner or switching the valve on the heating circulation flow path side to limit the amount of heat medium flowing to the secondary flow path of the heat exchanger for heating can be considered. Neither is appropriate.
That is, in the former method of intermittently operating the burner, a high-temperature heat medium flows into the heating heat exchanger immediately before stopping the combustion of the burner, and high-temperature hot water flows into the fuel cell. There is a similar problem in the countermeasure for switching the latter valve. That is, in the flow path through which the heat medium is circulated, sudden opening and closing of the valve causes a number of harmful effects. Therefore, a thermally operated valve is used in the heating circulation channel, and its opening / closing operation is very gradual. Therefore, even if the valve on the heating circulation channel side is switched, it is impossible to prevent a high-temperature heat medium from flowing into the secondary channel of the heating heat exchanger.

  The present invention pays attention to the above-mentioned problems of the prior art, can smoothly start the fuel cell, and prevents high temperature cooling water from flowing into the fuel cell side to prevent deterioration of the fuel cell. An object is to provide a cogeneration system that can perform the above and a storage tank side unit that is employed in the cogeneration system.

  The invention described in claim 1 for solving the above-described problem is a cogeneration system for recovering heat generated by the fuel cell, and is in direct communication with the fuel cell in communication with the flow path flowing on the fuel cell side. Alternatively, an exhaust heat recovery passage through which the indirectly heat-exchanged liquid flows is provided, and the exhaust heat recovery passage has a storage tank and a heat exchanger for other uses, and the temperature is raised by the heat generated by the fuel cell. The stored liquid can be stored in a storage tank, and the heat transferred to the secondary side flow path after passing the liquid through the primary side flow path of the heat exchanger for other uses is used for other uses. In a cogeneration system having a preliminary heat source capable of supplying heat to the flow path including the secondary flow path of the heat exchanger for other applications, an operation mode when starting the fuel cell is possible Preheat supply operation mode In the preheating supply operation mode, the auxiliary heat source is operated to raise the temperature of the heat medium flowing through the secondary flow path of the heat exchanger for other uses, and the heat is exhausted via the primary flow path of the heat exchanger for other uses. It is possible to raise the temperature of the liquid flowing through the recovery flow path and allow the heated liquid to reach the fuel cell side. Under certain conditions, the liquid taken out of the storage tank is added to the liquid flowing through the exhaust heat recovery flow path. The cogeneration system is characterized in that the temperature of the liquid mixed and flowing through the exhaust heat recovery flow path can be lowered.

Here, the heat exchanger for other uses is used, for example, for heating or reheating a bath.
The present invention improves a cogeneration system that preheats a fuel cell with a preliminary heat source. The operation when preheating the fuel cell is as described above. In the preheating supply operation mode, a preliminary heat source such as a burner is operated to raise the temperature of the heat medium flowing through the secondary flow path of the heat exchanger for other applications. Then, the temperature of the liquid flowing through the exhaust heat recovery flow path via the primary flow path of the heat exchanger for other uses is raised, and the heated liquid is brought to the fuel cell side.
However, if the temperature of the liquid that reaches the fuel cell side is too high or is likely to rise, mix the liquid extracted from the storage tank with the liquid that flows through the exhaust heat recovery flow path. Reduce the temperature of the flowing liquid. As a result, the temperature of the liquid reaching the fuel cell side is lowered, and the fuel cell is not damaged.

  The invention according to claim 2 is a cogeneration system that recovers heat generated by the fuel cell, and is a liquid that is directly or indirectly heat-exchanged with the fuel cell in communication with the flow path flowing through the fuel cell side. A storage for storing liquid in a state in which a temperature stratification is formed inside the exhaust heat recovery passage through which the heat flows, a heating circulation passage for supplying a heating medium to the heating device, and an upper connection portion and a lower connection portion A tank and a heat exchanger for other uses for exchanging heat between the exhaust heat recovery flow path and the heating circulation flow path, the exhaust heat recovery flow path from the fuel cell side to the upper side connection portion of the storage tank And a bypass passage for bypassing the storage tank, and the primary side passage for the heat exchanger for other uses is the exhaust heat recovery passage. It is a part of the fuel cell side of the bypass flow path. In the cogeneration system having a heating source in the heating circulation channel, a preheating supply operation mode is provided as one of the operation modes, and in the preheating supply operation mode, the heating medium that operates the preliminary heat source and flows through the heating circulation channel is provided. The temperature rises, the temperature of the liquid flowing through the exhaust heat recovery flow path via the primary flow path of the heat exchanger for other uses is increased, and the heated liquid passes through the bypass flow path to the exhaust heat recovery flow path The cogeneration system is characterized in that a part of the liquid flowing through the exhaust heat recovery passageway under a certain condition is circulated to the circulation passage via the tank.

The cogeneration system of the present invention also improves the cogeneration system that preheats the fuel cell with a preliminary heat source.
The storage tank employed in the present invention stores liquid in a state where temperature stratification is formed, and has an upper side connection portion and a lower side connection portion. This tank is always filled with liquid. Prior to the start of operation of the cogeneration system, some or all of the liquid in the storage tank is cold. And the hot water etc. which operated the cogeneration system and was heated by the fuel cell are introduce | transduced in a storage tank from an upper side connection part. As a result, hot water accumulates in the upper layer of the low-temperature liquid. Excess liquid is pushed out from the lower side connecting portion.
In the preheating supply operation mode in the cogeneration system of the present invention, the preliminary heat source is operated to raise the temperature of the heat medium flowing through the heating circulation flow path, and the exhaust heat recovery is performed via the primary flow path of the heat exchanger for other uses. The temperature of the liquid flowing in the flow path is raised, and the heated liquid is circulated to the exhaust heat recovery flow path via the bypass flow path and supplied to the fuel cell side.
In the operation in the preheating supply operation mode, the liquid flowing through the exhaust heat recovery flow path flows through the bypass flow path, so that the liquid heated indirectly by the preliminary heat source flows into the fuel cell side as it is without accumulating in the storage tank. Therefore, the temperature of the fuel cell is raised to a startable state.
On the other hand, when the temperature of the liquid reaching the fuel cell side is too high or may be increased, a part of the liquid flowing through the exhaust heat recovery passage is circulated through the circulation passage via the tank. As a result, the low-temperature liquid is pushed out from the lower side connection portion of the storage tank and mixed into the exhaust heat recovery flow path. The temperature of the liquid flowing through the exhaust heat recovery flow path is lowered by mixing of the low temperature liquid, and the fuel cell is protected.

  As a measure for distributing a part of the liquid flowing through the exhaust heat recovery flow path to the circulation path via the tank, a valve is provided at a part of the bypass flow path or at the branch point of the bypass flow path, and this valve is controlled to discharge the liquid. It is conceivable that a part of the heat medium flowing through the heat recovery flow path is circulated to the circulation flow path via the tank.

  In the invention according to claim 4, the temperature detection means is provided in the flow path downstream of the heat exchanger for other uses in the exhaust heat recovery flow path and reaching the fuel cell side. The cogeneration system according to any one of claims 1 to 3, wherein the temperature detected by the temperature detecting means is equal to or higher than a predetermined temperature.

In the present invention, the actual temperature of the liquid in the exhaust heat recovery flow path is measured, and a part of the liquid flowing through the exhaust heat recovery flow path is caused to flow to the tank side accordingly. In the present invention, the temperature detecting means is located on the downstream side of the heat exchanger for other uses in the exhaust heat recovery passage and reaches the fuel cell side, so that the temperature is raised by the heat exchanger for other uses. The temperature of the liquid after being applied can be detected.
The position of the temperature detecting means is desirably downstream of the bypass flow path.

  The invention according to claim 5 includes a heating operation mode for supplying a heating medium to the heating device as an operation mode, and in the heating operation mode, a high-temperature heat medium and a low-temperature heat medium can be supplied according to the heating device. 4. The cogeneration system according to claim 2, wherein one of the predetermined conditions is a case where the heating apparatus is operating in the heating operation mode and a high-temperature heat medium is supplied to the heating device.

  When operating in the preheating supply operation mode as described above, the heating operation mode is set, and when a high-temperature heat medium is supplied to the heating equipment, or during the supply of the high-temperature heat medium to the heating equipment, preheating is performed. In the supply operation mode, the temperature of the liquid flowing to the fuel cell side becomes excessive. Therefore, in the present invention, the case where the heating medium is being operated in the heating operation mode and a high-temperature heat medium is supplied to the heating device is set as one of the constant conditions.

  The invention according to claim 6 is a storage tank side unit constituting a cogeneration system for recovering heat generated by the fuel cell, and is connected to a flow path flowing through the fuel cell side, directly or indirectly with the fuel cell. The exhaust heat recovery channel through which the heat-exchanged liquid flows is provided, and the exhaust heat recovery channel has a storage tank and a heat exchanger for other uses, and is heated by the heat generated by the fuel cell. The liquid can be stored in a storage tank, and the heat transferred to the secondary side flow path after passing the liquid through the primary side flow path of the heat exchanger for other uses can be used for other uses. In a storage tank side unit equipped with a preliminary heat source capable of supplying heat to the flow path including the secondary side flow path of the heat exchanger for other applications, preheating as an operation mode when starting the fuel cell is possible. Preheating supply with supply operation mode In the reversal mode, the auxiliary heat source is operated to raise the temperature of the heat medium flowing through the secondary flow path of the heat exchanger for other uses, and the exhaust heat recovery flow passes through the primary flow path of the heat exchanger for other uses. It is possible to raise the temperature of the liquid flowing through the passage and bring the heated liquid to the fuel cell side. Under certain conditions, the liquid taken out from the storage tank is mixed with the liquid flowing through the exhaust heat recovery passage. The storage tank side unit is characterized in that the temperature of the liquid flowing through the exhaust heat recovery flow path can be lowered.

  In the present invention, a part of a cogeneration system is unitized.

  In the cogeneration system of the present invention, preheating when starting the fuel cell is possible, and the fuel cell is not excessively heated. Therefore, the fuel cell can be started up smoothly and the fuel cell is not damaged. The same effect can be obtained for the storage tank side unit.

Embodiments of the present invention will be further described below.
FIG. 1 is a piping diagram of the cogeneration system of the present embodiment. FIG. 2 is a piping system diagram shown in FIG. 1 and shows the flow of auxiliary hot water in the circulation path through the tank and the storage mode. FIG. 3 is a piping system diagram shown in FIG. 1 and shows the flow of auxiliary hot water in the bypass circulation passage and the heating operation mode.
In FIG. 1, 1 is the cogeneration system of this embodiment. The cogeneration system 1 is roughly composed of a power generation device 2 and a storage tank side unit 3, and is a combination of these.

  The power generation device 2 includes the fuel cell 5 as a main component, and is used to recover the exhaust heat generated during power generation by cooling the fuel cell 5 that generates heat accompanying power generation and the fuel cell 5. The battery side heat exchanger 6 and the circulation pump 7 are provided. The circulation pump 7 is provided in order to circulate hot water in the exhaust heat recovery flow path C described later.

  The power generation apparatus 2 has a function as a power generation device for supplying power to an electric power load E provided outside and a function as a thermal energy generation device for heating hot water (liquid). .

  On the other hand, the storage tank side unit 3 is mainly configured of a storage tank 10 for storing hot water. The upper side connection portion 11 provided at the top of the storage tank 10 and the lower side provided at the bottom. The connection portion 12 is connected to the pipes that constitute the exhaust heat recovery passage C and the hot water / water supply passage H.

  The storage tank 10 constitutes temperature stratification inside to store hot water, and a plurality of (four in the present embodiment) temperature sensors 13a to 13d in the height direction, that is, the level of rising hot water stored inside. 13d is attached. The temperature sensors 13a to 13d function as temperature detecting means for detecting the temperature of the hot water in the storage tank 10, respectively, and the remaining amount for detecting the remaining amount of hot water within a predetermined temperature or temperature range in the storage tank 10. Also serves as a quantity detection means.

  More specifically, in the cogeneration system 1 of the present embodiment, the hot water taken out from the bottom of the storage tank 10 is discharged to the exhaust heat recovery flow path C and passes through the battery side heat exchanger 6 of the power generator 2. Thus, heat is exchanged and heated, and the storage tank 10 is slowly returned to the top side.

  Here, in general, when a liquid is stored in a tank, if the temperature difference between the liquids is equal to or greater than a predetermined threshold (about 10 ° C. in hot water), the liquid is divided into layers for each temperature. Therefore, the hot water passing through the exhaust heat recovery passage C is heated to a temperature higher than the threshold temperature with respect to the temperature of the hot water in the storage tank 10 and slowly returned to the extent that the hot water in the storage tank 10 is not disturbed. Then, the hot water stored in the storage tank 10 is divided into layers for each temperature (temperature stratification). Therefore, it is possible to detect how much hot water heated to a desired temperature range is stored in the storage tank 10 by checking the detection temperature of the temperature sensors 13 a to 13 d installed in the storage tank 10.

  The exhaust heat recovery flow path C is formed by combining a plurality of pipes, and can constitute a circulation path 15 via a tank and a bypass circulation flow path 16. More specifically, the exhaust heat recovery flow path C includes a heating forward flow path 21 that connects the lower side connection portion 12 of the storage tank 10 and the battery side heat exchanger 6 in the power generation device 2, and battery side heat exchange. It has a heating return side flow path 22 that connects the outlet side of the vessel 6 and the upper side connection portion 11. Further, the exhaust heat recovery flow path C has a bypass flow path 23 that bypasses both flow paths at an intermediate portion between the heating forward flow path 21 and the heating return flow path 22. The bypass channel 23 and the heating return side channel 22 are connected via a heating side three-way valve 28. The end side of the bypass flow path 23 and the heating forward flow path 21 are connected by, for example, a tee 27.

The flow path on the storage tank 10 side from the tee 27 is referred to as a heating upstream flow path 31, and the flow path on the power generation device 2 side from the tee 27 is referred to as a heating forward downstream flow path 32.
The heating forward flow path 21 is a flow path for supplying hot water discharged from the bottom side of the storage tank 10 to the battery side heat exchanger 6 of the fuel cell 5.

  A pressure sensor 24 and a temperature sensor 26 are provided in the middle of the heating forward flow path 21 and downstream of the tee 27 in the hot water flow direction, that is, in the heating forward downstream flow path 32. The pressure sensor 24 is provided for detecting the supply pressure of the hot water flowing through the exhaust heat recovery passage C, and the temperature sensor 26 is provided for detecting the temperature of the hot water flowing through the exhaust heat recovery passage C. It has been. The temperature of hot water detected by the temperature sensor 26 is the temperature of hot water immediately before being introduced to the fuel cell 5 side of the power generation device 2.

On the other hand, the heating return side flow path 22 is a flow path for returning the hot water passing through the battery side heat exchanger 6 to the top side of the storage tank 10. The heating side three-way valve 28 is provided in the middle of the heating return side flow path 22.
Two of the three ports constituting the heating side three-way valve 28 are connected to the heating return side flow path 22, and the bypass flow path 23 is connected to the remaining ports. That is, the heating side three-way valve 28 includes a channel on the storage tank 10 side of the heating side three-way valve 28 in the heating return side channel 22 (hereinafter referred to as a heating return downstream channel 35 if necessary), It is connected to the flow path on the power generation device 2 side of the side three-way valve 28 (hereinafter referred to as a heating return upstream flow path 36 if necessary) and the bypass flow path 23.

  The heating return side flow path 22 has a main flow path and a branch path which will be described later. The heating return upstream flow path 36 of the main flow path of the heating return side flow path 22 has a heat exchanger for heating (heat exchanger for other uses). 37 is connected, and a temperature sensor 38 is connected downstream of the heating heat exchanger 37.

The heating return side flow path 22 is provided with a bypass branch flow path 40 that bypasses the heating heat exchanger 37, the temperature sensor 38, and the heating side three-way valve 28 as a branch path. In other words, the heating return upstream flow path 36 of the heating return flow path 22, the upstream side of the heating heat exchanger 37 is branched, and the bypass branch flow path 40 is provided, and the end of the bypass return flow path 40 is the heating return downstream. A tee 41 is connected to the side flow path 35.
The bypass branch channel 40 is a channel that returns hot water from the fuel cell 5 side to the storage tank 10 side without passing through the heating heat exchanger 37. An electromagnetic valve 43 is provided in the bypass branch channel 40.
A temperature sensor 45 for detecting the temperature of hot water flowing toward the storage tank 10 side is provided on the downstream side of the heating return downstream channel 35 and downstream of the junction (tee 41) of the bypass branch channel 40. Yes.
A temperature sensor 34 is also provided between the power generation device 2 in the heating return side flow path 22 and the branch point of the bypass branch flow path 40. The temperature sensor 34 measures the temperature of hot water immediately after being discharged from the power generation device 2.

The exhaust heat recovery channel C can be configured as a tank-by-tank circulation channel 15 or a bypass circulation channel 16 by adjusting a heating side three-way valve 28 provided in the middle of the heating return side channel 22. More specifically, when two ports connected to the heating return side flow path 22 among the three ports constituting the heating side three-way valve 28 are opened, as shown by hatching in FIG. A tank-based circulation flow path 15 that can circulate hot water with the power generation device 2 can be configured.
Further, among the three ports constituting the heating side three-way valve 28, when the port connected to the heating return upstream flow path 36 and the port connected to the bypass flow path 23 are opened, as shown in FIG. In addition, a bypass circulation channel 16 that can bypass the storage tank 10 and circulate hot water can be formed.

The heating circulation channel D is a channel for circulating a heat medium such as antifreeze between the storage tank unit 3 and the two heating terminals 50 and 51 installed outside the cogeneration system 1.
Of the two heating terminals 50 and 51, one heating terminal 50 is a fan convector and requires a high-temperature heat medium. The other heating terminal 51 is a floor heating device and requires a low-temperature heat medium.
A preliminary heat source 52 is connected to the heating circulation channel D. The preliminary heat source 52 includes a burner 53 and a heat exchanger 55.
The flow paths for supplying the heat medium to the heating terminals 50 and 51, that is, the high temperature heat medium supply flow path 57 and the low temperature heat medium supply flow path 58 are both branched downstream of the preliminary heat source 52. However, the high-temperature heat medium supply channel 57 and the low-temperature heat medium supply channel 58 are different in branching portions for taking out the heat medium required by the respective heating terminals 50 and 51. That is, the low-temperature heat medium supply flow path 58 is branched downstream of the heat exchanger 55 of the preliminary heat source 52, but the branch pipe 61 of the return side pipe 60 that returns to the heat exchanger 55 is a low-temperature heat medium supply flow path. 58. For this reason, the heat medium supplied from the low-temperature heat medium supply channel 58 is mixed with a low-temperature heat medium, and the temperature becomes relatively low.

On the other hand, the high-temperature heat medium supply channel 57 is branched from a position where the heat medium that has exited the preliminary heat source 52 directly flows, and the high-temperature heat medium that has exited the preliminary heat source 52 flows.
One ends of the high temperature heat medium supply channel 57 and the low temperature heat medium supply channel 58 are connected to the heating terminals 50 and 51. The return side flow paths from the heating terminals 50 and 51 are aggregated in the heating return side flow path 62 and connected to the upstream side of the preliminary heat source 52.

  On the upstream side of the preliminary heat source 52, a circulation pump 65 is provided for circulating the heat medium in the heating circulation passage D and feeding the heat medium to the heating terminals 50 and 51. The heating circulation channel D is further connected to the secondary side channel of the heating heat exchanger 37 described above. The heating heat exchanger 37 is a so-called liquid-liquid heat exchanger, and the heat medium circulating in the heating circulation channel D is exchanged with the hot water flowing through the heating return side channel 22. It is provided for heating.

The secondary side of the heating heat exchanger 37 is connected to the downstream side of the auxiliary heat source 52 by the heat exchange upstream pipe 66, and the outlet side of the heating heat exchanger 37 is connected to the downstream side of the heat exchange. The side pipe 67 is connected to the upstream side of the circulation pump 65.
Further, the heat exchange upstream pipe 66 and the heat exchange downstream pipe 67 are short-circuited by a heat exchange bypass pipe 69.
The heat exchange upstream piping 66 is provided with a heat exchange upstream thermal valve 68, and the heat exchange bypass piping 69 is provided with a bypass thermal valve 72.

The hot water supply / water supply flow path H is for supplying hot water from the hot water supply flow path 73 connected to the upper side connection portion 11 of the storage tank 10 to the hot water supply / water supply flow path H side and the exhaust heat recovery flow path C side from the outside. The water supply flow path 74 is provided.
Since the hot water supply / water supply flow path H is a known one, it is not shown in the figure and will not be described in detail.

  The cogeneration system 1 has a control means (not shown) on the power generation device 2 side and a control means 75 of the storage tank side unit 3, and both of them communicate with each other to cooperate with each other in the cogeneration system 1. Control is in progress. The operation of the storage tank side unit 3 is controlled by the control means 75 as described above. The control means 75 is the same as that provided in a conventionally known cogeneration system, and can be configured to include, for example, a CPU and a memory in which a predetermined control program is incorporated. The control means 75 operates the valves, the fuel cell 5, the preliminary heat source 52, etc. provided in each part of the cogeneration system 1 based on the detection signals of the sensors provided in each part, the data stored in the memory, etc. Is controlled to optimize the total energy efficiency of the cogeneration system 1.

Then, operation | movement of the cogeneration system 1 of this embodiment is demonstrated. The cogeneration system 1 can operate by selecting an operation mode from an operation mode group including a storage mode, a hot water supply mode, a heating operation mode, a warm-up / detour operation mode, and a preheat supply operation mode.
Hereinafter, description will be made sequentially.

(Storage mode)
In the storage mode, by operating the circulation pump 7, a water flow is generated in the circulation route 15 via the tank of the exhaust heat recovery passage C, and the exhaust heat (thermal energy) generated with the operation of the power generation device 2 is generated. In this operation mode, the hot water is collected and heated, and the hot water is stored in the storage tank 10.
When the cogeneration system 1 operates in the storage mode, the heating side three-way valve 28 is closed with respect to the bypass flow path 23 based on the control signal transmitted from the control means 75, the heating return upstream flow path 36 and the heating return downstream. The side channel 35 is adjusted to be open.
Therefore, the circulation path 15 via the tank as shown by the hatching in FIG. 2 is opened.

  When the circulation pump 7 is operated in the state where the opening degree of the heating side three-way valve 28 is adjusted as described above, a circulating flow of hot water is generated in the circulation path 15 via the tank indicated by hatching in FIG. More specifically, when the cogeneration system 1 operates in the storage mode, the low-temperature hot water stored on the bottom side of the storage tank 10 with the operation of the circulation pump 7 is heated from the lower side connection portion 12. Sucked into the forward flow path 21 and supplied to the power generator 2. As a result, hot water sucked out from the storage tank 10 is supplied to the battery-side heat exchanger 6 in the power generation device 2, the fuel cell 5 of the power generation device 2 is cooled, and is generated along with the operation of the power generation device 2. The heat energy thus absorbed is absorbed by the hot water supplied to the battery-side heat exchanger 6. Hot water heated by exchanging heat in the battery side heat exchanger 6 is returned from the upper side connection portion 11 into the storage tank 10 via the heating return side flow path 22. Thereby, the hot water in the storage tank 10 is heated gradually.

In the present embodiment, a bypass branch channel 40 is provided in the heating return side channel 22. Although the bypass valve 40 is provided with an electromagnetic valve 43, the electromagnetic valve 43 is a normally open electromagnetic valve and is open in the storage mode. Therefore, in the present embodiment, hot water flows through the bypass branch channel 40 and reaches the storage tank 10 in the storage mode as indicated by an arrow in FIG.
In the storage mode, both hot water passing through the heating heat exchanger 37 serving as the main flow path and hot water passing through the bypass branch flow path 40 serving as the branch path reach the storage tank 10. That is, in the storage mode, all of the hot water discharged from the power generator 2 flows into the storage tank 10.

(Hot water supply mode)
The hot water supply mode is an operation mode in which hot water is supplied using high-temperature hot water stored in the storage tank 10 in the above-described storage mode, but detailed description thereof is omitted because it is a known operation.

(Heating operation mode)
The heating operation mode is an operation mode in which the heat medium in the heating circulation passage D is heated by exchanging heat in the heating heat exchanger 37 and supplied to the heating terminals 50 and 51. When the heating operation mode is selected, as shown by hatching or arrows in FIG. 3, a circulating flow of hot water or a heat medium is generated.
That is, in the heating operation mode, hot water is mainly supplied to the bypass circulation channel 16 and only a part of the hot water is supplied to the storage tank 10.

  More specifically, when the cogeneration system 1 operates in the heating operation mode, the control means 75 controls the heating side three-way valve 28 provided in the middle of the heating return side passage 22 of the exhaust heat recovery passage C. Of the three ports constituting the port, the port connected to the heating return upstream flow path 36 and the port connected to the bypass flow path 23 are opened, the heating return downstream flow path 35 is closed, and hatching is shown in FIG. Through such a bypass channel 23, the bypass circulation channel 16 that bypasses the storage tank 10 and can circulate hot water is opened.

  When the circulation pump 7 is started in a state where the opening degree of the heating side three-way valve 28 is adjusted in this way, a circulating flow of hot water is generated in the flow path (detour circulation flow path 16) indicated by hatching in FIG. . That is, a hot water circulation flow is generated in the bypass circulation passage 16 that passes through the primary side of the heating heat exchanger 37, passes through the bypass passage 23, and returns to the power generator 2.

On the other hand, in the present embodiment, a bypass branch channel 40 is provided in the heating return side channel 22, and an electromagnetic valve 43 is provided in the bypass branch channel 40. However, the solenoid valve 43 is always open. The electromagnetic valve 43 is open even in the heating operation mode. Therefore, in the present embodiment, hot water flows into the bypass branch channel 40 even in the heating operation mode as indicated by an arrow in FIG.
Since the bypass branch passage 40 bypasses the bypass passage 23 described above, the hot water flowing through the bypass branch passage 40 enters the heating return downstream passage 35 and reaches the storage tank 10.
Here, in the storage mode described above, all of the hot water discharged from the power generator 2 flows into the storage tank 10, whereas in the heating operation mode described this time, it passes through the heating heat exchanger 37 that is the main channel. Hot water that has flowed through the flow path flows through the bypass flow path 23 to bypass the storage tank 10, and only hot water that has flowed through the bypass branch flow path 40 that is an auxiliary flow path flows into the storage tank 10.

Looking at the heating circulation flow path D, the control means 75 activates the circulation pump 65 provided in the heating circulation flow path D and generates a circulation flow of the heat medium in the heating circulation flow path D. As a result, the heat medium flows to the secondary side of the heat exchanger 37 for heating. As described above, since the hot water heated by the power generator 2 flows on the primary side of the heating heat exchanger 37, the heat of the hot water circulating in the exhaust heat recovery passage C in the heating heat exchanger 37. Energy is released to the heating circulation channel D side by heat exchange, and the heat medium circulating in the heating circulation channel D is heated. The heat medium heated and exchanged in the heat exchanger 37 for heating is supplied to the heating terminals 50 and 51 and used as a heat source for heating.
When the temperature of the heat medium flowing through the heating circulation channel D is lowered, the burner 53 of the preliminary heat source 52 is ignited to raise the temperature of the heat medium flowing through the heating circulation channel D.

Returning to the description of the exhaust heat recovery flow path C side, in the heating operation mode, the hot water passing through the heating heat exchanger 37 flows through the bypass flow path 23 and bypasses the storage tank 10. The reason for selecting such a flow path is that it does not want to disturb the temperature stratification in the storage tank 10. That is, in the heating operation mode, the hot water that has passed through the heating heat exchanger 37 is deprived of heat by the heating circulation channel D, and the temperature of the hot water that has exited the heating heat exchanger 37 is lowered. Therefore, when this hot water is returned to the storage tank 10, low temperature hot water is injected from the upper part of the storage tank, and the low temperature hot water is mixed in the portion where the high temperature hot water stays. Therefore, in the present embodiment, in the heating operation mode, hot water flowing through the main flow path (flow path that passes through the heating heat exchanger 37) is caused to flow to the bypass flow path 23 to bypass the storage tank 10 and to the power generator 2 side. I decided to return it.
However, in the present embodiment, in order to prevent the fuel cell 5 from being damaged, the bypass branch channel 40 is provided, and only a part of the hot water flows into the storage tank 10.

  The reason for adopting such a configuration in which a part of hot water flows through the storage tank 10 is as follows. That is, even if the cogeneration system 1 side is in the heating operation mode, heat exchange may not be sufficiently performed by the heating heat exchanger 37 depending on the opening / closing state of the valves on the heating terminals 50 and 51 side. In such a case, the temperature of the hot water discharged from the primary side of the heating heat exchanger 37 is not sufficiently lowered. Therefore, if this hot water is returned to the power generation device 2 as it is, the fuel cell 5 may not be sufficiently cooled.

Therefore, in this embodiment, a part of hot water is supplied to the storage tank 10 and only a small amount of low-temperature hot water is taken out from the storage tank 10. That is, hot water passing through the bypass branch channel 40 is caused to flow to the storage tank 10. As a result, the low-temperature hot water stored on the bottom side of the storage tank 10 is sucked out from the lower side connecting portion 12 to the small flow rate, heating-out side flow path 21, and the bypass flow path 23 is passed through the portion of the tee 27. Mixed with flowing hot water. Therefore, low temperature hot water is mixed with the hot water flowing through the bypass passage 23, and the entire temperature is lowered.
Therefore, the temperature of the hot water supplied to the battery-side heat exchanger 6 in the power generator 2 does not become excessively high, the fuel cell 5 can be cooled, and the fuel cell 5 is not damaged.
The hot water flowing through the bypass branch channel 40 is considerably hot because it bypasses the heat exchanger 37 for heating, and even if it is introduced into the storage tank 10, the temperature stratification is not disturbed.

(Warm-up / detour operation mode)
The warm-up / bypass operation mode is an operation mode in which hot water is circulated through a flow path that bypasses the storage tank 10 while the fuel cell 5 of the power generation device 2 is operated to generate heat. The warm-up / bypass operation mode is an operation mode that is selected when the temperature of the hot water flowing through the exhaust heat recovery flow path C is low. The warm-up operation in the initial operation stage of the cogeneration system or exhaust heat for some reason. This is an operation mode that is executed when the temperature of the hot water flowing through the recovery channel C decreases.
When the cogeneration system 1 operates in the warm-up / detour operation mode, all hot water flows through the detour circulation flow path 16.

More specifically, when the cogeneration system 1 is operated in the warm-up / detour operation mode, the control means 75 is arranged on the heating side three sides provided in the middle of the heating return side channel 22 of the exhaust heat recovery channel C. Of the three ports constituting the valve 28, the port connected to the heating return upstream flow path 36 and the port connected to the bypass flow path 23 are opened, the heating return downstream flow path 35 is closed, and FIG. A detour circulation passage 16 that bypasses the storage tank 10 indicated by hatching and can circulate hot water is opened.
When operating in the warm-up / bypass mode, the bypass branch channel 40 of the heating return side channel 22 is closed. That is, the normally open solenoid valve 43 is energized and the solenoid valve 43 is closed.

When the circulation pump 7 is operated with the heating side three-way valve 28 and the electromagnetic valve 43 adjusted as described above, a circulating flow of hot water is generated only in the hatched portion of FIG. That is, when the cogeneration system 1 operates in the warm-up / bypass mode, all of the hot water flowing through the heating return side flow path 22 flows into the bypass flow path 23 as the circulation pump 7 is operated, Is returned to the power generation device 2 side through the heating-out side flow path 21.
That is, the hot water discharged from the battery side heat exchanger 6 returns to the battery side heat exchanger 6 as it is, and the temperature of the circulating hot water rises early.

(Preheating supply operation mode)
FIG. 4 is a piping system diagram shown in FIG. 1 and shows the flow of hot water and heat medium in the preheating supply operation mode. FIG. 5 is a piping diagram showing the principle of the heating-side three-way valve and the flow of hot water in the preheating supply operation mode. FIG. 6 is a piping system diagram showing an irregular posture of the heating side three-way valve and a flow of hot water in the preheating supply operation mode.
The preheating supply operation mode is an operation mode executed at a stage before the start of the cogeneration system. The preheating supply operation mode is executed when the fuel cell is cold and start-up is not easy.

In the preheating supply operation mode, the preliminary heat source 52 in the heating circulation channel D is activated, the temperature of the heat medium in the heating circulation channel D is raised, and this heat is taken into the exhaust heat recovery channel C side, so that the fuel cell 5 It is a mode to circulate to the side.
The flow path on the exhaust heat recovery flow path C side in the preheating supply operation mode is basically the same as the warm-up / detour operation mode described above. That is, when the cogeneration system is operated in the preheat supply operation mode, the entire amount of hot water is circulated in principle in the flow path that bypasses the storage tank 10.
Specifically, when the cogeneration system 1 operates in the preheat supply operation mode, the control means 75 configures the heating side three-way valve 28 provided in the middle of the heating return side passage 22 of the exhaust heat recovery passage C. Among the three ports, the port connected to the heating return upstream flow path 36 and the port connected to the bypass flow path 23 are opened, the heating return downstream flow path 35 is closed, and the storage shown by hatching in FIG. A bypass circulation channel 16 that bypasses the tank 10 and can circulate hot water is opened.
When operating in the preheat supply operation mode, the bypass branch channel 40 of the heating return side channel 22 is closed. That is, the normally open solenoid valve 43 is energized and the solenoid valve 43 is closed.
When the circulation pump 7 is started with the heating-side three-way valve 28 and the electromagnetic valve 43 adjusted in this manner, the hot water circulates in the flow path (detour circulation flow path 16) indicated by hatching in FIG. A flow is generated. That is, a hot water circulation flow is generated only in the bypass circulation passage 16 that passes through the primary side of the heating heat exchanger 37, passes through the bypass passage 23, and returns to the power generator 2.

On the other hand, in the heating circulation channel D, the burner 53 of the preliminary heat source 52 is ignited to raise the temperature of the heat medium flowing through the heating circulation channel D, and the heating medium is passed to the secondary side of the heating heat exchanger 37. .
Specifically, as shown in the figure, the heat exchange upstream side thermal valve 68 of the heat exchange upstream side pipe 66 is opened, and the bypass thermal valve 72 of the heat exchange bypass pipe 69 is closed.
In this state, the circulation pump 65 of the heating circulation channel D is started.
As a result, in the heating circulation flow path D, the heat medium discharged from the circulation pump 65 passes through the heat exchanger 55 of the auxiliary heat source 52 and rises in temperature, and then passes through the heat exchange upstream pipe 66 to be the heating heat exchanger. 37 on the secondary side. Then, the heat medium exiting the primary side of the heating heat exchanger 37 returns to the circulation pump 65 via the return side pipe 60.

In the preheating supply operation mode, the high-temperature heat medium passes through the secondary side of the heating heat exchanger 37, and the low-temperature hot water passes through the primary side of the heating heat exchanger 37. Heat moves to the exhaust heat recovery passage C, and the hot water in the exhaust heat recovery passage C is heated. Then, the heated hot water flows into the power generation device 2 through the bypass channel 23. In this state, all of the hot water flowing to the power generation device 2 has passed through the heating heat exchanger 37, and the cold water in the storage tank 10 is not mixed.
Therefore, the fuel cell 5 of the power generation device 2 is appropriately preheated and can be activated.

Next, a case where there is an operation request for the heating operation mode during the operation in the preheating supply operation mode will be described.
When there is an operation request for the heating operation mode during operation in the preheating supply operation mode, a heat medium is supplied to these in response to the request from the heating terminals 50 and 51. Therefore, the preliminary heat source 52 proportionally controls the combustion amount of the burner 53 so as to supply a heat medium having a temperature required by the heating terminals 50 and 51.
Here, when only the heating terminal (low temperature side) 51 is functioning, the burner 53 burns with a relatively low combustion amount, and when the heating terminal (high temperature side) 50 is functioning, a relatively high combustion amount. The burner 53 burns. Therefore, the water temperature of the exhaust heat recovery passage C also rises with the temperature rise on the heating circulation passage D side.

Therefore, when there is an operation request for the heating operation mode during the operation in the preheating supply operation mode, the control means 75 monitors the temperature of the hot water flowing through the exhaust heat recovery passage C. Specifically, the temperature sensor 26 monitors the temperature of hot water immediately before being introduced to the fuel cell 5 side of the power generation device 2.
When the temperature of hot water just before being introduced to the fuel cell 5 exceeds a certain limit temperature, for example, 80 ° C., the heating side three-way valve 28 is operated to leak a part of the hot water to the storage tank 10 side. .

That is, the heating side three-way valve 28 has a valve body 64 built in the housing 63 as shown in FIGS. 5 and 6, and opens and closes three ports depending on the position of the valve body 64.
During operation in the preheating supply operation mode, in principle, the port connected to the heating return upstream flow path 36 and the port connected to the bypass flow path 23 among the three ports as shown in FIG. The heating return downstream flow path 35 is closed.
However, the temperature of the hot water just before being introduced to the fuel cell 5 side is monitored by the temperature sensor 26, and when this exceeds a certain temperature, the valve body is moved as shown in FIG. 6 so that all three ports are in communication. To do. More desirably, the bypass passage 23 is a large opening, and the valve body is moved to a position where the storage tank 10 side is a small opening.

As a result, a part of hot water is supplied to the storage tank 10 as shown by the arrows in the figure, and only a small amount of low-temperature hot water is taken out from the storage tank 10. As a result, a small amount of cold water is sucked out from the lower side connecting portion 12 of the storage tank 10 to the heating forward side flow path 21 and mixed with hot water flowing through the bypass flow path 23 at the tee 27 site. Therefore, low temperature hot water is mixed with the hot water flowing through the bypass passage 23, and the entire temperature is lowered.
As a result, the temperature of the hot water supplied to the battery-side heat exchanger 6 in the power generator 2 is lowered, and the fuel cell 5 is not damaged.

  The above description assumes that there is a request for operation in the heating operation mode during operation in the preheating supply operation mode, but there are also cases where operation in the preheating supply operation mode is performed when operating in the heating operation mode. It is the same.

FIG. 7 is a flowchart showing a desirable operation when starting the cogeneration system.
When starting the cogeneration system 1 according to the present embodiment, an activation request is awaited in step 1, and if there is an activation request, it is determined in step 2 whether the fuel cell 5 can be activated. That is, the outside air temperature and the temperature of each part of the cogeneration system 1 are detected to determine whether or not the fuel cell 5 is in a startable state.
If the fuel cell 5 can be started, the routine proceeds to step 8 where the fuel cell 5 is immediately started, warm-up / detour operation is performed, and the startup step is completed.

If the temperature of each part is low and the fuel cell 5 cannot be started, the process proceeds to step 3 to start the operation in the preheat supply operation mode. That is, the preliminary heat source 52 in the heating circulation channel D is activated, the temperature of the heat medium in the heating circulation channel D is raised, and this heat is taken into the exhaust heat recovery channel C and circulated to the fuel cell 5 side.
The situation of the heating side three-way valve 28 at this time is as shown in FIG. 5, and the port connected to the heating return upstream flow path 36 and the port connected to the bypass flow path 23 are opened, and the heating return downstream side The flow path 35 is closed.

Then, the process proceeds to step 4 to determine whether or not it is in the heating operation mode and whether or not there is a request for high-temperature heating.
If it is not in the heating operation mode or there is no request for high temperature even in the heating operation mode, the process returns to step 2 to determine again whether or not it can be started. These series of operations are repeated until the temperature reaches a startable temperature.

On the other hand, when it is in the heating operation mode and there is a request for high-temperature heating, the process proceeds to step 5 where the detection value of the temperature sensor 26 is confirmed, and whether or not this temperature exceeds a certain limit temperature such as 80 ° C. Determine whether. If the temperature exceeds the limit temperature, it is unsuitable for operating the fuel cell 5. Therefore, the heating side three-way valve 28 is operated, and the port on the storage tank 10 side is slightly opened as shown in FIG. Leaks to the storage tank 10 side.
As a result, the low-temperature hot water taken out from the storage tank 10 is mixed with the hot water flowing through the bypass passage 23, and the temperature of the hot water reaching the power generation device 2 side is lowered.
Therefore, the fuel cell 5 is not excessively heated, and the durability of the fuel cell 5 is maintained.

In the embodiment described above, hot water is supplied to the storage tank 10 side by moving the valve body 64 of the heating side three-way valve 28 provided in the bypass flow path 23 to an intermediate position. It is also possible to guide cold water.
For example, the electromagnetic valve 43 may be opened in the bypass branch channel 40 to supply hot water to the storage tank 10 side, and cold water may be led out from the storage tank 10.
A plurality of two-way valves may be combined in place of the three-way valve.

It is a piping system diagram of the cogeneration system of this embodiment. It is a piping system diagram shown in Drawing 1, and shows the flow of auxiliary hot water in a circulation route via a tank and storage mode. It is a piping system diagram shown in FIG. 1, Comprising: The flow of the auxiliary hot water in a detour circulation flow path and heating operation mode is shown. It is a piping system diagram shown in FIG. 1, Comprising: The flow of the hot water and heat medium in the preheating supply operation mode is shown. It is a piping system diagram which shows the principal attitude | position of the heating side three-way valve in the preheating supply operation mode, and the flow of hot water. It is a piping system diagram which shows the unusual attitude | position of the heating side three-way valve in the preheating supply operation mode, and the flow of hot water. It is a flowchart which shows the desirable operation | movement at the time of starting a cogeneration system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cogeneration system 2 Power generation device 3 Storage tank side unit 5 Fuel cell 6 Battery side heat exchanger 10 Storage tank 11 Upper side connection part 12 Lower side connection part 15 Recirculation flow path 16 via tank Detour circulation flow path 23 Bypass flow path 26 Temperature sensor 28 Heating side three-way valve 37 Heat exchanger for heating (heat exchanger for other applications)
40 Detour branch flow path 43 Solenoid valves 50 and 51 Heating terminal 52 Preliminary heat source C Waste heat recovery flow path D Heating circulation flow path

Claims (6)

  A cogeneration system for recovering heat generated by a fuel cell, comprising a waste heat recovery flow path through which a liquid that is directly or indirectly heat-exchanged with the fuel cell is communicated with a flow path flowing through the fuel cell side The waste heat recovery flow path has a storage tank and a heat exchanger for other applications, and can store the liquid heated by the heat generated by the fuel cell in the storage tank. It is possible to use the heat transferred to the secondary side flow path by passing the liquid through the primary side flow path of the heat exchanger and used for other purposes, and the secondary side of the heat exchanger for other uses In a cogeneration system equipped with a preliminary heat source capable of supplying heat to the flow path including the flow path, a preheat supply operation mode is provided as an operation mode when starting the fuel cell, and the preliminary heat source is operated in the preheat supply operation mode. Heat for other applications The temperature of the heat medium flowing through the secondary side flow path of the exchanger is raised, the temperature of the liquid flowing through the exhaust heat recovery flow path via the primary side flow path of the heat exchanger for other uses is raised, and the heated liquid is It is possible to reach the fuel cell side, and under certain conditions, the liquid taken out from the storage tank is mixed with the liquid flowing through the exhaust heat recovery flow path to lower the temperature of the liquid flowing through the exhaust heat recovery flow path A cogeneration system characterized by being capable of   A cogeneration system for recovering the heat generated by the fuel cell, the exhaust heat recovery flow path through which the liquid directly or indirectly exchanged with the fuel cell is communicated with the flow path flowing through the fuel cell side; A heating circulation channel for supplying a heat medium to the heating device, a storage tank that has an upper side connection portion and a lower side connection portion and stores liquid in a state where temperature stratification is formed therein, and the exhaust heat recovery channel And a heat exchanger for other applications for exchanging heat between the heating circulation passage and the exhaust heat recovery passage entering the upper connection portion of the storage tank from the fuel cell side to the fuel cell from the lower connection portion A circulation path through the tank that returns to the side and a bypass flow path that bypasses the storage tank, and the primary flow path of the heat exchanger for other uses is a part of the exhaust heat recovery flow path, Is also in the area on the fuel cell side. The cogeneration system has a preheating supply operation mode as one of the operation modes, and in the preheating supply operation mode, the preliminary heat source is operated to raise the temperature of the heat medium flowing through the heating circulation flow path, and heat for other purposes. The temperature of the liquid flowing through the exhaust heat recovery flow path via the primary flow path of the exchanger is raised, and the heated liquid is circulated to the exhaust heat recovery flow path via the bypass flow path to the fuel cell side. A cogeneration system characterized in that a part of the liquid that is supplied and flows through the exhaust heat recovery passageway under a certain condition is circulated through the circulation passage via the tank.   A valve is provided at a part of the bypass channel or at a branch point of the bypass channel, and the valve is controlled to circulate a part of the heat medium flowing through the exhaust heat recovery channel into the circulation channel via the tank. The cogeneration system according to claim 2.   The temperature detection means is provided in the flow path downstream of the heat exchanger for other applications in the exhaust heat recovery flow path and to the fuel cell side. One of the constant conditions is that the temperature detected by the temperature detection means is a predetermined temperature. The cogeneration system according to any one of claims 1 to 3, wherein the cogeneration system is at a temperature or higher.   A heating operation mode that supplies a heat medium to the heating equipment is provided as an operation mode. In the heating operation mode, a high-temperature heat medium and a low-temperature heat medium can be supplied according to the heating equipment. The cogeneration system according to claim 2 or 3, wherein the cogeneration system is operating in a mode and supplying a high-temperature heat medium to a heating device.   A storage tank side unit that constitutes a cogeneration system that recovers heat generated by a fuel cell, and is connected to a flow path that flows on the fuel cell side to flow a liquid that is directly or indirectly heat-exchanged with the fuel cell. It has a waste heat recovery flow path, has a storage tank and a heat exchanger for other uses in the waste heat recovery flow path, and can store the liquid heated by the heat generated by the fuel cell in the storage tank The heat transferred to the secondary side flow path by passing the liquid through the primary side flow path of the heat exchanger for other uses can be used for other uses, and for the other uses. In the storage tank side unit equipped with a preliminary heat source capable of supplying heat to the flow path including the secondary flow path of the heat exchanger, a preheat supply operation mode is provided as an operation mode when starting the fuel cell, and a preheat supply operation is performed. Reserved in mode The temperature of the heat medium flowing through the secondary flow path of the heat exchanger for other applications is increased by operating the source, and the liquid flowing through the exhaust heat recovery flow path via the primary flow path of the heat exchanger for other applications It is possible to raise the temperature and bring the heated liquid to the fuel cell side. Under certain conditions, the liquid flowing through the exhaust heat recovery passage is mixed with the liquid taken out from the storage tank, and the exhaust heat recovery flow is A storage tank side unit characterized in that the temperature of the liquid flowing through the passage can be lowered.

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