JP4497396B2 - Fuel cell heat recovery device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat recovery apparatus in a fuel cell cogeneration system that uses heat generated during fuel cell operation for hot water supply or the like.
[0002]
[Prior art]
Conventionally, in a fuel cell cogeneration system that uses both the electric power generated in the fuel cell and the heat generated by the operation of the fuel cell (for example, as hot water), as shown in FIG. The heat recovery heat exchanger 3 is interposed in the water circuit to take out the exhaust heat on the fuel cell side (cooling of the fuel cell, heat of condensation, or heat generation of the reformer).
That is, heat recovery water circuits L1 and L2 that return from the hot water tank 2 through the heat exchanger 3 to the hot water tank 2 are provided, and the heat recovery water flowing through the circuits L1 and L2 exchanges heat with the fuel cell side in the heat exchanger 3. Therefore, heat is stored in the hot water tank 2 (hot water is stored).
[0003]
In such a system, sufficient heat is stored in the hot water tank 2 (so-called “full tank”), and when the circulating heat recovery water becomes high temperature (over about 40 degrees), it is insufficient for cooling the fuel cell 1. Thus, the fuel cell 1 cannot continue operation. Therefore, a radiator 15 is provided in parallel with the heat recovery water circuit L1 from the hot water tank 2 to the heat exchanger 3, and when the control unit 10 determines that cooling is necessary, the three-way valve 16 is operated to switch the flow path, and at the same time the radiator 15 The cooling is performed by operating (see Patent Document 1).
[0004]
However, the above-described conventional techniques have the following problems.
(1) Radiator mounting space is required.
(2) Electric power is consumed for cooling in the radiator, and the effective use of the power generated by the fuel cell is reduced.
(3) A detection device such as a temperature sensor, a control unit, or a three-way valve for switching the flow path is necessary for determining the necessity of cooling, and the configuration is complicated.
(4) Wiring work to the radiator power supply and control unit is required.
(5) It is necessary to take measures against freezing of the radiator.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-325982
[Problems to be solved by the invention]
The present invention is proposed in order to cope with the above-described problems, and does not require a space for installing a radiator and driving power, and does not require a detection / control device for determining the necessity of cooling, or is simple and compact. An object of the present invention is to provide a heat recovery device for a fuel cell configured with a simple system.
[0007]
[Means for Solving the Problems]
The fuel cell heat recovery apparatus of the present invention includes a heat recovery heat exchanger (3) interposed in a cooling circuit of the fuel cell (1), and passes through the heat exchanger (3) from the hot water tank (2) to store hot water. In the heat recovery device for a fuel cell, in which a heat recovery water circuit (L1, L2) returning to the tank (2) is provided, and heat generated in the fuel cell (1) by the heat recovery water is stored in the hot water storage tank (2). The heat recovery water circuit (L1) from the hot water storage tank (2) to the heat recovery heat exchanger (3) is provided with a heat radiating means (4) for exchanging heat with the outside, and the heat radiating means (4) is connected to the hot water tank. A heat dissipating pipe (4A) is disposed in a space between (2) and the installation base (5) to dissipate heat (Claim 1).
[0008]
In general, fuel cell cogeneration systems
(1) Consume relatively large energy at startup,
(2) It takes some time to start and stop,
It has the characteristic.
Therefore, as a result of various researches, the inventor does not need to stop the fuel cell if the operation is continued with the output kept at the lowest level until there is a demand for hot water, even when the hot water tank is full of hot water, It has been found that the above characteristics (1) and (2) can be accommodated. It was also found that if the fuel cell is operated at the lowest level output that does not stop, the heat recovery circuit requires less heat to continue operation and the heat dissipation means can be simplified.
This finding has led to the present invention.
[0009]
Therefore, according to the above-described configuration, the heat recovery water sent to the heat recovery heat exchanger always passes through the heat dissipating means for exchanging heat with the outside, and is naturally cooled when the temperature is high. Further, special power for cooling is not required, and a detection device and a control unit for determining the necessity for cooling, or a three-way valve for switching the flow path are not required.
[0010]
The heat recovery device for a fuel cell of the present invention includes a heat recovery heat exchanger (3) interposed in a cooling circuit of the fuel cell (1), and the heat exchanger (3) from the hot water tank (2). In a heat recovery device for a fuel cell, heat recovery water circuits (L1, L2) that return to the hot water storage tank (2) are provided, and heat generated in the fuel cell (1) by the heat recovery water is stored in the hot water storage tank (2). the hot water tank heat recovery heat exchanger (2) heat dissipation means for performing external heat exchanger to the heat recovery water circuit (L1) leading to (3) (4) is provided, heat radiating means (4), the hot water storage The present invention is characterized in that a heat radiating pipe (4B) is embedded in the concrete foundation (5A ) on which the tank (2) is installed (claim 2).
[0011]
Alternatively, the heat recovery device for a fuel cell of the present invention includes a heat recovery heat exchanger (3) interposed in a cooling circuit of the fuel cell (1), and the heat exchanger (3) from the hot water tank (2). In the heat recovery apparatus for a fuel cell, in which the heat recovery water circuit (L1, L2) is returned to the hot water storage tank (2) and the heat generated by the heat recovery water in the fuel cell is stored in the hot water storage tank (2). The heat recovery water circuit (L1) from the tank (2) to the heat recovery heat exchanger (3) is provided with heat dissipating means (4) for exchanging heat with the outside, and the heat dissipating means (4) The heat dissipating pipe (4C) is disposed in the soil in the vicinity of the installation base (5) of 2) (Claim 3).
[0012]
In the heat recovery apparatus for a fuel cell according to the present invention, a temperature sensor (T1 or T2) is provided in the heat recovery water circuit (L1), and the heat recovery water supplied to the heat recovery heat exchanger (3) is provided. It is preferable to have control means (control unit 10) configured to perform control to reduce the output of the fuel cell (1) if the temperature is equal to or higher than a predetermined value (claim 4).
A control method of a fuel cell having such a heat recovery device (a fuel cell heat recovery device according to claim 4) is provided by a temperature sensor (T1 or T2) provided in the heat recovery water circuit (L1). A step of measuring the temperature of the heat recovery water supplied to the recovery heat exchanger (3), and a step of reducing the output of the fuel cell (1) if the heat recovery water is a predetermined value or more. Is preferred.
[0013]
By adopting such a configuration, the temperature of the heat recovery water supplied to the heat exchanger can be controlled to a predetermined value or less, so that the operation of the fuel cell can be reliably continued. And it is realizable with a simple control system.
[0014]
In such a cogeneration system, when the outside air temperature is low in winter, it is necessary to prevent the pipe from being damaged due to freezing. For internal pipes and the like, a method has been adopted in which an electric heater is energized when the detected temperature falls below a set value. Conventionally, independent anti-freezing control has been required for external pipes such as radiators. On the other hand, the present invention does not require an independent anti-freezing device, can use the anti-freezing control of the internal piping, and can simplify the system configuration.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
In addition, the same code | symbol is attached | subjected to the components similar to the prior art demonstrated in the said FIG. 10, and the overlapping description is abbreviate | omitted.
[0016]
In FIG. 1, the hot water tank 2 is cylindrical and is relatively vertically long, and hot water is stored in a stratified manner in which the upper layer is high temperature and the lower layer is low temperature. That is, hot water of 60 to 70 degrees C recovered from the fuel cell 1 is introduced into the upper part of the hot water tank 2 by the circuit L2, and is taken out from the upper part of the hot water tank 2 through the flow path L3 for use of hot water. . Further, the heat recovery water flowing through the circuit L1 to the heat exchanger 3, in other words, the heat recovery water used for cooling the fuel cell 1 is taken out from the lower part of the hot water storage tank 2 having a low temperature.
The circuit L1 exiting the hot water tank 2 is provided with a heat dissipating means 5, and the heat recovery water dissipates heat to the outside and is cooled and sent to the heat exchanger 3.
[0017]
2 and 3 show details of an embodiment of the heat dissipation means.
The hot water tank 2 is installed on the concrete foundation 5 via (three in the illustrated example) support legs 6, and the leg 6 is placed in the gap δ between the foundation 5 and the lower surface of the hot water tank 2 by the support legs 6. A heat radiating pipe 4A that is bent and folded a plurality of times is provided.
[0018]
Conventionally, the space in which the heat radiating pipe 4A is disposed is a dead space, and a radiator cannot be disposed. Moreover, it is below the bottom part where the water temperature of the hot water tank 2 is low, the ambient temperature is low, and the heat dissipation effect is great.
Reference numeral 7 denotes an auxiliary heat source unit. When the hot water temperature is low, such as insufficient heat recovered from the fuel cell 1, the auxiliary operation is performed to maintain an appropriate water temperature.
[0019]
Although not shown, it is more effective to provide fins in the heat radiation pipe 4A. Of course, the cross-sectional shape of the heat radiating pipe 4A is not limited to a circular pipe, and a modified pipe having various cross-sectional shapes with an increased surface area may be employed to improve the cooling effect, or a pipe with a large surface area such as a bellows pipe may be used. It may be used.
[0020]
Moreover, in embodiment shown in FIG. 4 and FIG. 5, the heat radiating means has the heat radiating piping 4B embedded in the concrete foundation 5A. With such a configuration, the concrete foundation 5A has a large heat capacity, so that a sufficient heat dissipation effect can be obtained.
In such a household fuel cell cogeneration system, the time from when the hot water tank is filled with hot water until there is a demand for hot water is relatively short. The problem of reduction does not occur.
[0021]
Furthermore, other embodiment is shown in FIG. 6 and FIG.
FIG. 6 shows an example in which a heat radiating pipe 4C is buried in the ground near the foundation 5. FIG. At the time of installation of the equipment, simple civil engineering work such as foundation work is carried out, and such a radiating pipe embedding work does not particularly increase the man-hours.
[0022]
In the embodiment shown in FIG. 7, a heat radiating means is provided on one side surface of the casing C of the unit including the hot water tank. In this case, the heat radiating means may be provided either inside or outside the casing C using, for example, a folded heat radiating pipe 4D. And it is preferable to provide it below the casing C because the environmental temperature is low and the connection distance can be shortened.
[0023]
In each of the embodiments described above, natural heat dissipation is performed without using a complicated detection device or control unit. Next, an embodiment in which operation control with a simple configuration is performed will be described with reference to FIG. To do.
In FIG. 8, the heat recovery water circuit L1 communicating with the heat recovery heat exchanger 3 from below the hot water tank 2 is provided with a heat radiating means 4, and the circuit L1 detects the temperature of the heat recovery water. A temperature sensor T1 is provided.
[0024]
In FIG. 8, the temperature sensor T2 is also attached to the lower part of the hot water tank 2, but as will be described later, the temperature sensor may be either T1 or T2, and is appropriate for each. A comparative determination is made at a predetermined temperature.
[0025]
A control unit 10 is provided, and detection data is input from the temperature sensor T1 (or T2), and a control signal is sent from the control unit 10 to the fuel cell 1 based on the data. .
In the control, when cooling is necessary, natural cooling is enabled by performing operation control so as to suppress the output of the fuel cell and reducing a necessary heat radiation amount.
[0026]
The following methods can be selected for determining the necessity of cooling.
(1) When the temperature of the heat recovery water sent from the hot water tank to the fuel cell is high (detected by the sensor T1).
(2) When the temperature of the hot water at the lower part of the hot water tank is high (detected by the sensor T2).
(3) Alternatively, in the operation control system that predicts the user's heat and power demands and determines the fuel cell operation time and output, it is predicted that the hot water storage tank will be filled with hot water by the next predicted heat demand occurrence time. If so, the output of the fuel cell is reduced until the heat demand is generated.
[0027]
The mode of control according to the above (1) or (2) will be described with reference to the flowchart of FIG.
First, the water temperature t is detected by the temperature sensor T1 (or T2) (step S1), and it is determined whether the detected water temperature t is equal to or higher than a predetermined value (step S2). If No, the process jumps to Step S4, and if Yes, the output of the fuel cell (FC) 1 is reduced (Step S3). Then, in step S4, it is determined whether or not the control is finished. If No, the process returns to step S1.
[0028]
In such a configuration, in operation when the output is reduced,
Q1 (exchange heat amount of heat exchanger) ≤ Q2 (heat dissipation heat dissipation heat amount)
What is necessary is just to set the thermal radiation means 4 so that it may become.
[0029]
It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.
[0030]
【The invention's effect】
The effects of the present invention are as follows.
(1) Since the special space required for installing the radiator is not required, the system can be made compact.
(2) Cooling is possible without using special power.
(3) A detector / control unit such as a sensor for determining the necessity of cooling can be omitted or simplified, and a three-way valve or the like for switching the flow path is unnecessary, thereby simplifying the system configuration.
(4) No power supply or control wiring for water cooling is required.
(5) It is not necessary to prepare the freeze prevention control for the heat radiation part independently, and the system configuration can be simplified and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a side view showing an embodiment of the heat dissipating means of the present invention.
FIG. 3 is a plan view taken along the line aa in FIG. 2;
FIG. 4 is a side view showing another embodiment of the heat dissipating means.
5 is a cross-sectional view taken along the line bb in FIG. 4;
FIG. 6 is a side view showing still another embodiment of the heat dissipating means.
FIG. 7 is a side view showing still another embodiment of the heat dissipating means.
FIG. 8 is a configuration diagram illustrating an embodiment combined with control.
FIG. 9 is a flowchart showing a control function according to the configuration of FIG. 8;
FIG. 10 is a diagram showing a configuration of a conventional heat recovery device for a fuel cell.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Hot water tank 3 ... Heat exchanger 4 for heat recovery 4, 4A, 4B ... Radiation means 5 ... Base 7 ... Auxiliary heat source machine 10 ... Control unit 15 ... Radiator 16 ... Three-way valve T1, T2 ... Temperature sensor

Claims (4)

  A heat recovery heat exchanger is installed in the cooling circuit of the fuel cell, and a heat recovery water circuit that returns from the hot water tank to the hot water tank through the heat exchanger is provided, and the heat generated in the fuel cell by the heat recovery water is stored as hot water. In a heat recovery device for a fuel cell that stores heat in a tank, a heat recovery water circuit extending from the hot water storage tank to a heat exchanger for heat recovery is provided with a heat radiating means for exchanging heat with the outside. A heat recovery apparatus for a fuel cell, characterized in that a heat radiating pipe is disposed in a space between the installation foundation and radiates heat. A heat recovery heat exchanger is installed in the cooling circuit of the fuel cell, and a heat recovery water circuit that returns from the hot water storage tank to the hot water storage tank is provided, and the heat generated in the fuel cell is stored by the heat recovery water. In a heat recovery device for a fuel cell that stores heat in a tank, a heat recovery means for exchanging heat with the outside is provided in a heat recovery water circuit from the hot water storage tank to a heat recovery heat exchanger, and the heat dissipation means is provided with a hot water storage tank . A heat recovery device for a fuel cell, characterized in that a heat radiating pipe is embedded in a concrete foundation.   A heat recovery heat exchanger is installed in the cooling circuit of the fuel cell, and a heat recovery water circuit that returns from the hot water tank to the hot water tank through the heat exchanger is provided, and the heat generated in the fuel cell by the heat recovery water is stored as hot water. In a heat recovery device for a fuel cell that stores heat in a tank, a heat recovery water circuit extending from the hot water storage tank to a heat exchanger for heat recovery is provided with a heat dissipation means for performing heat exchange with the outside, and the heat dissipation means is installed in the hot water tank A heat recovery device for a fuel cell, characterized in that a heat radiating pipe is arranged in the soil near the foundation.   A control configured to provide a temperature sensor in the heat recovery water circuit and perform control to reduce the output of the fuel cell if the temperature of the heat recovery water supplied to the heat recovery heat exchanger is equal to or higher than a predetermined value. The heat recovery apparatus for a fuel cell according to any one of claims 1 to 3, further comprising means.

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