JP2018147730A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool down a fuel cell without using a large-sized cooling device, in a fuel cell system that uses a hydrogen tank and a hydrogen storage material as a hydrogen source.SOLUTION: A fuel cell system 10 comprises: a fuel cell 12; a hydrogen tank 16 for storing a hydrogen gas; a reactor 18 inside which a hydrogen storage material is sealed; a cooling device 20 for the fuel cell 12; a first hydrogen gas line 30 for connecting between the fuel cell 12 and the hydrogen tank 16; a second hydrogen gas line 40 for connecting between the reactor 18 and the first hydrogen gas line 30; a first heat exchange line 50 for connecting between the fuel cell 12 and the cooling device 20; and a second heat exchange line 60 for parallel-connecting the reactor 18 with the first heat exchange line 50. The reactor 18 is switched and connected to any one of a first pressure region (P) and a second pressure region (P). A part of cooling medium for cooling down the fuel cell 12 is distributed to the reactor 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system, and more particularly, to a fuel cell system provided with both a hydrogen tank storing hydrogen gas and a reactor enclosing a hydrogen storage material as a fuel source.

In a fuel cell system using hydrogen as a fuel gas, a hydrogen gas tank, a liquid hydrogen tank, a tank filled with a hydrogen storage material, or the like is used as a hydrogen source. Among these, the tank filled with the hydrogen storage material has a high hydrogen storage density per unit volume, so that the system can be miniaturized. Therefore, a fuel cell system using this is particularly suitable as an energy source for moving objects.
Since the fuel cell has an appropriate operating temperature range, it is necessary to maintain the temperature of the fuel cell within an appropriate temperature range in order to obtain high power generation efficiency. In addition, since the hydrogen storage material generates heat when storing hydrogen gas and generates heat when releasing hydrogen gas, thermal management of the hydrogen storage material is necessary to store and release hydrogen in a timely manner.

In order to solve this problem, various proposals have heretofore been made.
For example, in Patent Document 1, at the time of starting the fuel cell system,
(A) Electric power is supplied to the drive motor while the vehicle drive output shaft of the drive motor is fixed, the electric power consumed by the drive motor is released as heat, and the cooling water temperature of the fuel cell is increased using this heat. At the same time
(B) A fuel cell system that warms up the fuel cell stack from the inside by generating the fuel cell stack with a power output lower than the power that can be generated and generating heat by the fuel cell stack itself is disclosed.
This document describes that such a method can promote warm-up of the fuel cell stack without increasing energy loss.

Further, in Patent Document 2, when a single radiator fan is used to simultaneously cool the fuel cell coolant and the other heat dissipating means, the fuel cell coolant is cooled at a predetermined ratio in the radiator direction and the radiator bypass direction. A shunt cooling system control device is disclosed.
This document states that when a radiator fan is used to mainly cool other heat radiating means, the temperature of the fuel cell coolant decreases excessively by flowing more fuel cell coolant in the radiator bypass direction. The point which can be suppressed is described.

Further, in Patent Document 3, a coolant is circulated between the fuel cell and the radiator, and the radiator is cooled by a fan.
(A) A limited rotation speed is provided for the rotation speed of the fan,
(B) The speed limit can be changed according to the use environment of the fuel cell, and
(C) A fuel cell cooling control device is disclosed in which when the use environment of a fuel cell changes and a change in the limit rotation speed is required, the limit rotation speed is changed after the change in the use environment.
This document describes that both the cooling performance and the sound vibration performance can be satisfied by such a method.

  Furthermore, in Non-Patent Document 1, two reactors in which a hydrogen storage alloy is enclosed are installed between a hydrogen tank and a fuel cell, and heat generation / endotherm associated with hydrogen storage / release of the hydrogen storage alloy is used for air conditioning. Has been proposed.

  The temperature control of the fuel cell is generally performed using a radiator. When the coolant is circulated between the fuel cell and the radiator, when the exhaust heat temperature of the fuel cell is relatively low, the temperature difference ΔT between the heat exchanging portion of the radiator and the ambient temperature becomes small. In this case, a large radiator is required in order to efficiently perform the exhaust heat treatment from the fuel cell. However, when a large radiator is used, the degree of freedom of shape of the fuel cell system is lowered.

  On the other hand, Non-Patent Document 1 discloses a system that uses heat generation / heat absorption associated with hydrogen storage / release of a hydrogen storage alloy for air conditioning. However, for example, when the air conditioning requires cooling, the heat of the air conditioning can be used to release hydrogen from the hydrogen storage alloy, but the heat generated during the hydrogen storage cannot be used in the air conditioning. On the other hand, when the air conditioning requires heating, the heat generated during the hydrogen storage can be used in the air conditioning. However, when releasing hydrogen from the hydrogen storage alloy, another heat source is required. Therefore, in a system in which the hydrogen storage alloy and the air conditioner are merely thermally connected, the effective use of heat is insufficient.

JP 2004-247164 A JP 2004-259472 A JP 2006-228629 A

Int. J. Hydrogen Energy 36 (2011) 3215-3221

The problem to be solved by the present invention is that in a fuel cell system using a hydrogen tank and a hydrogen storage material as a hydrogen source, the temperature of the fuel cell can be maintained at an appropriate temperature without using a large cooling device. There is to do.
Further, another problem to be solved by the present invention is that a fuel cell system using a hydrogen tank and a hydrogen storage material as a hydrogen source can reversibly store and release hydrogen without using another heat source or cooling source. There is in making it possible to do.

Another object of the present invention is to provide a fuel cell system that can store exhaust heat from the fuel cell and can be used for warming up or air-conditioning the fuel cell.
Furthermore, another problem to be solved by the present invention is to provide a fuel cell system with high energy efficiency.

In order to solve the above problems, a fuel cell system according to the present invention has the following configuration.
(1) The fuel cell system includes:
A fuel cell using hydrogen gas as fuel;
A hydrogen tank for storing the hydrogen gas;
A reactor in which a hydrogen storage material for discharging the hydrogen gas to be supplied to the fuel cell or storing the hydrogen gas supplied from the hydrogen tank is enclosed;
A cooling device for exchanging heat with the fuel cell by circulating a refrigerant with the fuel cell;
A first hydrogen gas line for connecting a fuel flow path of the fuel cell and the hydrogen tank;
A second hydrogen gas line for connecting the hydrogen flow path of the reactor and the first hydrogen gas line;
A first heat exchange line for connecting the refrigerant flow path (A) of the fuel cell and the refrigerant flow path (B) of the cooling device;
And a second heat exchange line for connecting the refrigerant flow path (C) of the reactor in parallel to the first heat exchange line.
(2) The first hydrogen gas lines include n (n ≧ 2) first hydrogen gas lines so that the pressure of the hydrogen gas gradually increases from the fuel cell toward the hydrogen tank. K-th pressure reducing means (1 ≦ k ≦ n−1) for dividing the pressure region (pressure in the kth pressure region: P _k <pressure in the (k + 1) th pressure region: P _{k +} 1) is provided.
(3) The second hydrogen gas line connects the hydrogen flow path of the reactor by switching to one of the first pressure region or the kth pressure region (2 ≦ k ≦ n), or Hydrogen gas switching means for cutting off the connection with the first hydrogen gas line is provided.
(4) The first heat exchange line is a bypass heat exchange line for returning the refrigerant discharged from the refrigerant flow path (A) of the fuel cell to the refrigerant flow path (A) of the fuel cell as it is. It has.
(5) In the second heat exchange line, when the refrigerant circulates between the fuel cell and the cooling device or between the fuel cell and the bypass heat exchange line, a part of the refrigerant is used as the refrigerant of the reactor. A flow rate adjusting means for flowing through the flow path (C) is provided.

  The fuel cell system according to the present invention includes both a hydrogen tank storing hydrogen gas and a reactor enclosing a hydrogen storage material as fuel sources. Therefore, when hydrogen is supplied from the hydrogen tank to the reactor at the start, the hydrogen storage material occludes hydrogen gas and generates heat. At this time, when the heat exchange line is switched to circulation cooling between the fuel cell and the bypass heat exchange line, and at the same time, when a part of the refrigerant is distributed to the reactor, the refrigerant is not deprived of heat by the cooling device, and the refrigerant The reaction heat accompanying hydrogen storage is added to. As a result, the temperature of the fuel cell can be quickly raised without using an external heat source. After the fuel cell rises to a predetermined temperature, the hydrogen gas line is switched to supply from the hydrogen tank to the fuel cell, and the heat exchange line is switched to circulation cooling between the fuel cell and the cooling device.

  On the other hand, when the temperature of the fuel cell rises excessively after the fuel cell enters the steady operation state, a part of the refrigerant is fed into the reactor while maintaining the heat exchange line in circulation cooling between the fuel cell and the cooling device. Distribute. At the same time, the hydrogen gas line is switched to the supply line from the reactor to the fuel cell. As a result, the hydrogen storage material absorbs the heat of the refrigerant and releases hydrogen gas. Further, the refrigerant is cooled by a hydrogen releasing reaction (endothermic reaction). As a result, the fuel cell can be cooled even when a small cooling device is used.

1 is a schematic diagram of a fuel cell system according to the present invention. It is an example of a reactor. It is a schematic diagram of a hydrogen gas line and a heat exchange line when performing warm-up operation. It is a schematic diagram of the hydrogen gas line and heat exchange line in the case of cooling a fuel cell using a reactor.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Fuel cell system]
FIG. 1 shows a schematic diagram of a fuel cell system according to the present invention. In FIG. 1, the fuel cell system 10 includes:
A fuel cell 12 using hydrogen gas as fuel;
A hydrogen tank 16 for storing hydrogen gas;
A reactor 18 that discharges hydrogen gas to be supplied to the fuel cell 12 or encloses a hydrogen storage material for storing hydrogen gas supplied from the hydrogen tank 16;
A cooling device 20 for exchanging heat with the fuel cell 12 by circulating a refrigerant with the fuel cell 12, and
A first hydrogen gas line 30 for connecting the fuel flow path of the fuel cell 12 and the hydrogen tank 16;
A second hydrogen gas line 40 for connecting the hydrogen flow path of the reactor 18 and the first hydrogen gas line 30;
A first heat exchange line 50 for connecting the refrigerant channel (A) of the fuel cell 12 and the refrigerant channel (B) of the cooling device 20;
And a second heat exchange line 60 for connecting the refrigerant flow path (C) of the reactor 18 in parallel to the first heat exchange line 50.

[1.1. Fuel cell]
In the present invention, the fuel cell 12 only needs to use hydrogen as a fuel, and the type of the fuel cell 12 is not particularly limited. In particular, the polymer electrolyte fuel cell has a maximum exhaust heat temperature (T _max ) lower than that of other fuel cells, and a temperature difference ΔT from the ambient temperature is relatively small. Therefore, a relatively large cooling device 20 is required for efficient cooling. On the other hand, when the present invention is applied to the polymer electrolyte fuel cell, the cooling device 20 can be reduced in size.

  Inside the fuel cell 12, there are a fuel flow path for flowing fuel, an oxidant flow path for flowing oxidant gas, and a refrigerant flow path (A) for flowing a refrigerant (both not shown). Is provided. An air compressor 14 for supplying air to the air electrode is connected to the oxidant flow path of the fuel cell 12.

[1.2. Hydrogen tank]
The hydrogen tank 16 is for storing hydrogen gas. In the present invention, the structure, capacity, etc. of the hydrogen tank 16 are not particularly limited. The hydrogen gas in the hydrogen tank 16 may be supplied to the fuel cell 12 or supplied to the reactor 18. This point will be described later.

[1.3. Reactor]
The reactor 18 is for enclosing a hydrogen storage material. The reactor 18 includes a storage space for a hydrogen storage material, a refrigerant flow path (C) for flowing a refrigerant, and a hydrogen flow path (not shown) for flowing hydrogen. The structure of the reactor 18 is not particularly limited as long as it can occlude / release hydrogen and exchange heat with the refrigerant. Details of the reactor 18 and the hydrogen storage material will be described later.

[1.4. Cooling system]
The cooling device 20 is for releasing the exhaust heat from the fuel cell 12 to the outside. In the present invention, the cooling device 20 includes the fuel cell 12 and the reactor 18 via the first heat exchange line 50 and the second heat exchange line 60 that can switch the refrigerant circulation path according to the temperature of the fuel cell 12. It is connected to the. Therefore, the cooling device 20 can be downsized as compared with the case where the refrigerant is simply circulated between the fuel cell 12 and the cooling device 20.
The composition of the refrigerant is not particularly limited.

[1.5. First hydrogen gas line]
The first hydrogen gas line 30 is for connecting the fuel flow path of the fuel cell 12 and the hydrogen tank 16. The first hydrogen gas line 30 includes n (n ≧ 2) pressure regions (first ≧ 2) so that the hydrogen gas pressure gradually increases from the fuel cell 12 toward the hydrogen tank 16. A total of (n−1) k-th decompression means (1 ≦ k ≦ n−1) for dividing the pressure in the k pressure region: P _k <(k + 1) th pressure region: P _{k + 1} ) I have. The configuration of the first hydrogen gas line is not particularly limited as long as it exhibits such a function.

[1.5.1. Number of divisions (n)]
The division number (n) of the first hydrogen gas line 30 may be two or more. In the example illustrated in FIG. 1, the first hydrogen gas line 30 includes a first main gas pipe 32, a first decompression unit 34 a, and a second decompression unit 34 b. That is, the first hydrogen gas line 30 extends from the fuel cell 12 toward the hydrogen tank 16 in the first pressure region 32a (pressure: P ₁ ), the second pressure region 32b (pressure: P ₂ > P ₁ ), and the first The three pressure regions 32c (pressure: P ₃ > P ₂ ) are divided into a total of three pressure regions.

The first main gas pipe 32 is for connecting a fuel flow path (not shown) of the fuel cell 12 and the hydrogen tank 16. The first pressure reducing means 34a is for reducing the pressure from P ₂ to P ₁ and simultaneously supplying and stopping hydrogen gas from the hydrogen tank 16 to the fuel cell 12. Examples of the decompression means having the decompression function and the opening / closing function include an injector.
The second pressure reducing means 34b is for reducing the pressure from P ₃ to P ₂ . The second decompression means 34b only needs to have a decompression function, and the opening / closing function is not necessarily required. An example of the decompression means having only the decompression function is a decompression valve.

[1.5.2. Pressure in the pressure area]
The first pressure region 32 a is directly connected to the fuel flow path of the fuel cell 12. If the pressure P _{1 in} the first pressure region 32 a is too low, hydrogen cannot flow toward the fuel cell 12. Accordingly, P ₁ is preferably 0.1 MPa or more. P ₁ is preferably 0.11 MPa or more, and more preferably 0.13 MPa or more.
On the other hand, if P ₁ becomes too high, the fuel cell 12 may be damaged. Therefore, P ₁ is preferably 0.3 MPa or less. P ₁ is preferably 0.28 MPa or less, and more preferably 0.25 MPa or less.

Any one of the kth pressure regions (2 ≦ k ≦ n) (in the example shown in FIG. 1, the second pressure region 32b) is connected to the hydrogen flow of the reactor 18 via the second hydrogen gas line 40 described later. Connected to the road. If the pressure P _{k in} the kth pressure region (2 ≦ k ≦ n) connected to the reactor 18 is too low, it is difficult to store hydrogen in the hydrogen storage material. Therefore, P _k is preferably 0.3 MPa or more. P _k is preferably 0.6 MPa or more, and more preferably 0.9 MPa or more.
On the other hand, if P _k becomes too high, the reactor 18 may be damaged. Accordingly, P _k is preferably 2.0 MPa or less. P _k is preferably 1.7 MPa or less, more preferably 1.5 MPa or less.

When the first hydrogen gas line 30 is divided into three or more pressure regions, the pressure P _j (j ≠ 1, k) other than P ₁ and P _k is P _j <P _{j + 1} . As long as the above is satisfied, there is no particular limitation.

[1.6. Second hydrogen gas line]
The second hydrogen gas line 40 is for connecting the hydrogen flow path of the reactor 18 and the first hydrogen gas line 30. The second hydrogen gas line 40 is used to supply hydrogen gas from the hydrogen tank 16 to the reactor 18 when storing hydrogen, and to supply hydrogen gas from the reactor 18 to the fuel flow path of the fuel cell 12 when releasing hydrogen. Therefore, the second hydrogen gas line 40 is connected by switching the hydrogen flow path of the reactor 18 to either the first pressure region 32a or the kth pressure region (2 ≦ k ≦ n) 32k, or the first Hydrogen gas switching means for cutting off the connection with the hydrogen gas line 30 is provided. The configuration of the hydrogen gas switching means is not particularly limited as long as it has such a function.

  In the example shown in FIG. 1, the second hydrogen gas line 40 includes a second main gas pipe 42, a first branch pipe 44a, a second branch pipe 44b, a first on-off valve 46a, and a second on-off valve 46b. It has. One end of the second main gas pipe 42 is connected to the hydrogen flow path of the reactor 18, and the other end is connected to one end of the first branch pipe 44a and one end of the second branch pipe 44b.

The other end of the first branch pipe 44 a is connected to the second pressure region 32 b of the first main gas pipe 32. The first branch pipe 44a is provided with a first opening / closing valve 46a.
The other end of the second branch pipe 44 b is connected to the first pressure region 32 a of the first main gas pipe 32. The second branch pipe 44b is provided with a second opening / closing valve 46b.
In the example shown in FIG. 1, the first branch pipe 44a, the second branch pipe 44b, the first on-off valve 46a, and the second on-off valve 46b connect the reactor 18 to either the first pressure region 32a or the second pressure region 32b. A hydrogen gas switching means for switching to either one of them or connecting to the first hydrogen gas line is configured.

[1.7. First heat exchange line]
The first heat exchange line 50 connects the refrigerant flow path (A) of the fuel cell 12 and the refrigerant flow path (B) of the cooling device 20 to circulate the refrigerant between the fuel cell 12 and the cooling device 20. Is. Furthermore, in this invention, in order to improve energy efficiency, the 1st heat exchange line 50 is provided with the bypass heat exchange line. The bypass heat exchange line is for returning the refrigerant discharged from the refrigerant channel (A) of the fuel cell 12 to the refrigerant channel (A) of the fuel cell 12 as it is. That is, the refrigerant may circulate between the fuel cell 12 and the cooling device 20 and may circulate between the fuel cell 12 and the bypass heat exchange line. The configuration of the first heat exchange line is not particularly limited as long as it exhibits such a function.

  In the example shown in FIG. 1, the first heat exchange line 50 includes a first main water pipe 52a, a second main water pipe 52b, a first refrigerant pump 54, a bypass water pipe 56, and a three-way valve 58. One end of the first main water pipe 52 a is connected to the outlet of the refrigerant channel (A) of the fuel cell 12, and the other end is connected to the inlet of the refrigerant channel (B) of the cooling device 20. One end of the second main water pipe 52 b is connected to the outlet of the refrigerant channel (B) of the cooling device 20, and the other end is connected to the inlet of the refrigerant channel (A) of the fuel cell 12.

An intermediate part of the first main water pipe 52 a and an intermediate part of the second main water pipe 52 b are connected by a bypass water pipe 56. A three-way valve 58 for switching the direction of the refrigerant flow to either the cooling device 20 side or the bypass water pipe 56 side is provided at the connection point between the first main water pipe 52 a and the bypass water pipe 56.
Furthermore, the second main water pipe 52b is provided with a refrigerant pump 54 for circulating the refrigerant in one direction. The first refrigerant pump 54 is provided between the coupling point between the bypass water pipe 56 and the second main water pipe 52b and the fuel cell 12 (that is, the second main water pipe 52b on the fuel cell 12 side of the bypass water pipe 56). It has been.
In the example shown in FIG. 1, the bypass water pipe 56 and the three-way valve 58 constitute a bypass heat exchange line.

[1.8. Second heat exchange line]
The second heat exchange line 60 is for connecting the refrigerant flow path (C) of the reactor 18 in parallel to the first heat exchange line 50. “Connected in parallel” means that one end of the refrigerant flow path (C) of the reactor 18 is connected to the first main water pipe 52a and the other end is connected to the second main water pipe 52b.
Furthermore, when the refrigerant circulates between the fuel cell 12 and the cooling device 20 or between the fuel cell 12 and the bypass heat exchange line, the second heat exchange line 60 allows a part of the refrigerant to pass through the refrigerant flow path (C ) Is provided. The configuration of the second heat exchange line is not particularly limited as long as it exhibits such a function.

In the example shown in FIG. 1, the second heat exchange line 60 includes a first branch water pipe 62 a, a second branch water pipe 62 b, and a second refrigerant pump 64. One end of the first branch water pipe 62a is connected to the outlet of the refrigerant channel (C) of the reactor 18, and the other end is connected to the second main water pipe 52b. The first branch water pipe 62 a is connected between the connection point of the second main water pipe 52 b and the bypass water pipe 56 and the first refrigerant pump 54.
One end of the second branch water pipe 62b is connected to the first main water pipe 52a, and the other end is connected to the inlet of the refrigerant flow path (C) of the reactor 18. The second branch water pipe 62 b is connected between the fuel cell 12 and the three-way valve 58. Further, the second branch water pipe 62b is provided with a second refrigerant pump 64 (flow rate adjusting means) for distributing the refrigerant to the reactor 18.

  The second refrigerant pump 64 may be installed in the first branch water pipe 62a. Further, instead of or in addition to the second refrigerant pump 64, a flow rate adjusting valve (flow rate adjusting means) may be installed in the first branch water pipe 62a and / or the second branch water pipe 62b. Further, the first branch water pipe 62a may be connected to the first main water pipe 52a, and the second branch water pipe 62b may be connected to the second main water pipe 52b.

[2. Reactor]
[2.1. Reactor structure]
An example of the reactor 18 is shown in FIG. In FIG. 2, the reactor 18 includes a casing 18a and a refrigerant flow path (C) 18b provided on the outer periphery and inside of the casing 18a. The refrigerant flow path (C) 18b has a hollow inside so that the refrigerant can flow inside. A refrigerant inlet 18c and a refrigerant outlet 18d are provided on the upper surface of the housing 18a. Each refrigerant flow path (C) 18b is connected to a refrigerant inlet 18c and a refrigerant outlet 18d, respectively. Therefore, the refrigerant supplied from the refrigerant inlet 18c passes through the cooling channel (C) 18b and is discharged from the refrigerant outlet 18d.

  The refrigerant flow path (C) 18b also serves as an outer wall and a partition wall of the casing 18a. The space between the refrigerant flow paths (C) 18b is a hydrogen flow path 18e for flowing hydrogen gas, and the space is filled with the hydrogen storage material 22. Details of the hydrogen storage material 22 will be described later.

The refrigerant channel (C) 18b is for exchanging heat between the refrigerant flowing through the refrigerant channel (C) 18b and the hydrogen storage material 22. Therefore, the refrigerant flow path (C) 18b may include heat transfer fins for promoting heat exchange with the refrigerant-hydrogen storage material 22.
For example, heat transfer fins (A) (not shown) are provided on the inner surface of the refrigerant flow path (C) 18b to promote heat exchange between the refrigerant and the refrigerant flow path (C) 18b. Also good.
Alternatively, heat transfer for promoting heat exchange between the refrigerant flow path (C) 18b and the hydrogen storage material 22 is performed on the outer surface of the refrigerant flow path (C) 18b (that is, the filling portion of the hydrogen storage material 22). Fins (B) (not shown) may be provided.

[2.2. Composition of hydrogen storage material]
A hydrogen storage material 22 is enclosed in the reactor 18. In the present invention, the composition of the hydrogen storage material 22 is not particularly limited as long as hydrogen gas can be occluded and released.
As will be described later, the first hydrogen gas line 30 for supplying hydrogen gas from the hydrogen tank 16 to the fuel cell 12 is divided into a plurality of pressure regions having different pressures using a decompression unit. On the other hand, the maximum exhaust heat temperature (T _max ) of the fuel cell 12 varies depending on the type. In order to release hydrogen using only the exhaust heat of the fuel cell 12, the hydrogen storage material 22 is such that the equilibrium hydrogen pressure at the maximum exhaust heat temperature (T _max ) of the fuel cell 12 satisfies a predetermined condition. preferable. This point will be described later.

  The hydrogen storage material 22 generates heat when storing hydrogen and absorbs heat when releasing hydrogen. Therefore, in order to efficiently store and release hydrogen, the hydrogen storage material 22 preferably has a high thermal conductivity. However, the hydrogen storage material 22 generally has a low thermal conductivity. In such a case, it is preferable to add a heat conduction aid to the hydrogen storage material 22. Examples of the heat conduction aid include carbon fiber, carbon nanotube, graphite, aluminum nitride, and silicon carbide.

[2.3. Equilibrium pressure of hydrogen storage material]
When the temperature of the fuel cell 12 rises excessively, hydrogen is supplied from the reactor 18 to the fuel cell 12 through the second hydrogen gas line 40. In order to release hydrogen from the reactor 18 using only the exhaust heat of the fuel cell 12, the hydrogen storage material must have an equilibrium hydrogen pressure at the maximum exhaust heat temperature (T _max ) of the fuel cell 12 greater than P _1. preferable.

On the other hand, when the fuel cell 12 is started, hydrogen is supplied from the hydrogen tank 16 to the reactor 18 via the second hydrogen gas line 40. In order for the hydrogen storage material to occlude hydrogen gas only by the pressure difference between the first hydrogen gas line 30 and the reactor 18, the hydrogen storage material has an equilibrium hydrogen pressure at the maximum exhaust heat temperature (T _max ) of the fuel cell 12. Is preferably less than the pressure P _{k in} the k-th pressure region (2 ≦ k ≦ n) connected to the reactor 18.

[3. Operation method of fuel cell system]
Hereinafter, a specific example of the operation method of the fuel cell system 10 in which the reactor 18 is connected in parallel to the refrigerant circulation path will be described. In the following description, a hydrogen storage alloy having the following equilibrium characteristics was used as the hydrogen storage material enclosed in the reactor 18.
Equilibrium temperature of hydrogen pressure 0.1 MPa: 10 ° C
Equilibrium temperature of hydrogen pressure 2.0MPa: 90 ° C

A hydrogen tank 16 having a maximum pressure (P ₃ ) of 70 MPa was used. Further, the pressure (P ₂ ) in the second pressure region 32b is reduced to 2 MPa using the pressure reducing valve (second pressure reducing unit 34b), and the pressure in the first pressure region 32a is further used using the injector (first pressure reducing unit 34a). (P ₁ ) was depressurized to 0.1 MPa.
Further, the maximum exhaust heat temperature (T _max ) of the fuel cell 12 was 90 ° C. Further, a radiator was used as the cooling device 20, and the refrigerant was cooled by heat exchange with the outside air.

[3.1. Warm-up operation]
FIG. 3 is a schematic diagram of a hydrogen gas line and a heat exchange line when performing warm-up operation. First, at the time of starting, both the first pressure reducing means 34a and the second pressure reducing means 34b are opened, and the air compressor 14 is operated. As a result, hydrogen gas is supplied to the fuel electrode of the fuel cell 12, air is supplied to the air electrode, and power generation by the fuel cell 12 is started.
At the same time, when the first opening / closing valve 46a is opened and the second opening / closing valve 46b is closed, hydrogen gas is supplied to the reactor 18 from the second pressure region 32b (hydrogen pressure: 2 MPa). In the reactor 18, the hydrogen storage material absorbs hydrogen and generates heat (90 ° C.).

  Further, the three-way valve 58 is switched to the bypass water pipe 56 side, and the first refrigerant pump 54 and the second refrigerant pump 64 are operated. Thereby, the refrigerant circulates between the fuel cell 12 and the bypass water pipe 56. Further, a part of the refrigerant discharged from the fuel cell 12 is distributed to the reactor 18 and the temperature rises. The refrigerant whose temperature has risen returns to the fuel cell 12 via the second main water pipe 52b. As a result, the fuel cell 12 (5 ° C.) can be warmed up without causing loss due to the cooling device 20.

  For example, when the circulating cooling by the cooling device 20 is started simultaneously with the start of the fuel cell 12, the heat loss by the cooling device 20 is large. Therefore, at the time of start-up, if the temperature of the fuel cell 12 is low, it takes a long time for the warm-up operation. On the other hand, when hydrogen is allowed to flow in the reactor 18 in addition to the fuel cell 12 and the refrigerant circulation path is switched to the bypass heat exchange line, the reaction heat from the reactor 18 is generated without causing loss due to the cooling device 20. Thus, the temperature of the fuel cell 12 can be quickly raised.

[3.2. Steady operation]
During steady operation of the fuel cell 12, normally, no heat generation / heat absorption from the reactor 18 is required. For this reason, when the temperature of the fuel cell 12 rises sufficiently, both the first on-off valve 46a and the second on-off valve 46b are closed, and the supply of hydrogen gas to the reactor 18 is stopped. Further, the three-way valve 58 is switched to the cooling device 20 side, and the second refrigerant pump 64 is stopped. Thereby, the refrigerant circulates between the fuel cell 12 and the cooling device 20, and the reactor 18 stops operating.

[3.3. Fuel cell cooling]
FIG. 4 is a schematic diagram of a hydrogen gas line and a heat exchange line when the fuel cell is cooled using a reactor. When the temperature of the fuel cell 12 rises excessively after the fuel cell 12 shifts to the steady operation state, the second refrigerant pump 64 is operated while the three-way valve 58 remains on the cooling device 20 side. At the same time, the first decompression means 34a, the second decompression means 34b, and the first opening / closing valve 46a are all closed, and the second opening / closing valve 46b is opened.

  When the second refrigerant pump 64 is operated, a part of the refrigerant is distributed to the reactor 18 and the flow rate of the refrigerant flowing through the cooling device 20 is reduced. Therefore, even if the cooling device 20 is small, the refrigerant can be sufficiently cooled. Further, since the temperature difference ΔT between the refrigerant flowing from the fuel cell 12 into the cooling device 20 and the outside remains relatively large, the cooling efficiency is not lowered.

On the other hand, when the refrigerant is distributed to the reactor 18 and the second opening / closing valve 46b is opened at the same time, hydrogen gas (pressure: 0.1 MPa) is released from the reactor 18 to the fuel cell. Moreover, the temperature of a refrigerant | coolant falls by the hydrogen releasing reaction (endothermic reaction) of a hydrogen storage material (10 degreeC). The refrigerant cooled by the reactor 18 flows into the second main water pipe 52b and merges with the refrigerant cooled by the cooling device 20. That is, the fuel cell 12 (90 ° C.) is cooled by the refrigerant cooled in each of the cooling device 20 and the reactor 18.
In FIG. 4, hydrogen gas is supplied from only the reactor 18 to the fuel cell 12, but hydrogen gas may be supplied from both the reactor 18 and the hydrogen tank 18 during cooling.

[4. Action]
The fuel cell system 10 according to the present invention includes both a hydrogen tank 16 storing hydrogen gas and a reactor 18 enclosing a hydrogen storage material as fuel sources. Therefore, when hydrogen is supplied from the hydrogen tank 16 to the reactor 18 at the start, the hydrogen storage material occludes hydrogen gas and generates heat. At this time, when the heat exchange line is switched to the circulation cooling between the fuel cell 12 and the bypass heat exchange line, and at the same time, when a part of the refrigerant is distributed to the reactor 18, the refrigerant is not deprived of heat by the cooling device 20, And the reaction heat accompanying hydrogen occlusion is added to a refrigerant | coolant. As a result, the temperature of the fuel cell 12 can be quickly raised without using an external heat source. After the fuel cell 12 rises to a predetermined temperature, the hydrogen gas line is switched to supply from the hydrogen tank 16 to the fuel cell 12, and the heat exchange line is switched to circulation cooling between the fuel cell 12 and the cooling device 20.

  On the other hand, when the temperature of the fuel cell 12 rises excessively after the fuel cell 12 enters the steady operation state, a part of the refrigerant is maintained while maintaining the heat exchange line in circulation cooling between the fuel cell 12 and the cooling device 20. Is distributed to the reactor 18. At the same time, the hydrogen gas line is switched to the supply line from the reactor 18 to the fuel cell 12. As a result, the hydrogen storage material absorbs the heat of the refrigerant and releases hydrogen gas. Further, the refrigerant is cooled by a hydrogen releasing reaction (endothermic reaction). As a result, the fuel cell 12 can be cooled even when the small cooling device 20 is used.

Furthermore, the fuel cell system 10 according to the present invention has the following effects.
(1) Since the exhaust heat treatment of the fuel cell 12 can be realized by the small cooling device 20, the degree of freedom of shape of the system is improved.
(2) By storing the exhaust heat of the fuel cell 12 in the reactor 18, air conditioning becomes possible in addition to warming up and cooling the fuel cell 12. This also improves the energy efficiency of the system.

(3) When the first hydrogen gas line 30 is divided into three or more pressure regions, the reactor 18 can be connected to the low pressure region and the medium pressure region. Therefore, excessive pressure resistance is not required for the reactor 18 and the hydrogen gas line system. In addition, this makes it possible to reduce the size and cost of the reactor 18 and the hydrogen gas line system equipment.
(4) Occlusion / release of hydrogen is performed using the differential pressure from the hydrogen tank 16 to the fuel cell 12, and accompanying the occlusion / release of hydrogen using the heat exchange line between the cooling device 20 and the fuel cell 12. Since the reaction heat is released and absorbed, the addition of valves associated with the installation of the reactor 18 can be minimized.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

  The fuel cell system according to the present invention can be used for a stationary power generation system, an energy source of a moving body, and the like.

DESCRIPTION OF SYMBOLS 10 Fuel cell system 12 Fuel cell 16 Hydrogen tank 18 Reactor 20 Cooling device 30 1st hydrogen gas line 40 2nd hydrogen gas line 50 1st heat exchange line 60 2nd heat exchange line

Claims (10)

A fuel cell system having the following configuration.
(1) The fuel cell system includes:
A fuel cell using hydrogen gas as fuel;
A hydrogen tank for storing the hydrogen gas;
A reactor in which a hydrogen storage material for discharging the hydrogen gas to be supplied to the fuel cell or storing the hydrogen gas supplied from the hydrogen tank is enclosed;
A cooling device for exchanging heat with the fuel cell by circulating a refrigerant with the fuel cell;
A first hydrogen gas line for connecting a fuel flow path of the fuel cell and the hydrogen tank;
A second hydrogen gas line for connecting the hydrogen flow path of the reactor and the first hydrogen gas line;
A first heat exchange line for connecting the refrigerant flow path (A) of the fuel cell and the refrigerant flow path (B) of the cooling device;
And a second heat exchange line for connecting the refrigerant flow path (C) of the reactor in parallel to the first heat exchange line.
(2) The first hydrogen gas lines include n (n ≧ 2) first hydrogen gas lines so that the pressure of the hydrogen gas gradually increases from the fuel cell toward the hydrogen tank. K-th pressure reducing means (1 ≦ k ≦ n−1) for dividing the pressure region (pressure in the kth pressure region: P _k <pressure in the (k + 1) th pressure region: P _{k +} 1) is provided.
(3) The second hydrogen gas line connects the hydrogen flow path of the reactor by switching to one of the first pressure region or the kth pressure region (2 ≦ k ≦ n), or Hydrogen gas switching means for cutting off the connection with the first hydrogen gas line is provided.
(4) The first heat exchange line is a bypass heat exchange line for returning the refrigerant discharged from the refrigerant flow path (A) of the fuel cell to the refrigerant flow path (A) of the fuel cell as it is. It has.
(5) In the second heat exchange line, when the refrigerant circulates between the fuel cell and the cooling device or between the fuel cell and the bypass heat exchange line, a part of the refrigerant is used as the refrigerant of the reactor. A flow rate adjusting means for flowing through the flow path (C) is provided. The first hydrogen gas line includes a first decompression unit and a second decompression unit for dividing the first hydrogen gas line into three pressure regions (P ₁ <P ₂ <P ₃ ),
The second hydrogen gas line is configured to switch the reactor to either the first pressure region (pressure: P ₁ ) or the second pressure region (pressure: P ₂ ), or to connect the first hydrogen gas line. The fuel cell system according to claim 1, further comprising hydrogen gas switching means for cutting off the connection with the hydrogen gas line. The second heat exchange line includes a first branch water pipe and a second branch water pipe connected to the inlet side and the outlet side of the refrigerant flow path (C) of the reactor,
3. The fuel cell system according to claim 1, wherein the flow rate adjusting means is provided in the first branch water pipe or the second branch water pipe. The fuel cell system according to any one of claims 1 to 3, wherein the P ₁ is not less than 0.1 MPa and not more than 0.3 MPa. 5. The pressure P _k in the _k- th pressure region (2 ≦ k ≦ n) connected to the hydrogen flow path of the reactor is 0.3 MPa or more and 2.0 MPa or less. 5. The fuel cell system according to item. The water storage material, the fuel cell system according to any one of claims 1 to 5 in which the equilibrium hydrogen pressure at maximum exhaust heat temperature of the fuel cell is comprised of greater than the P _1. The hydrogen storage material is less than the pressure P _k of the k-th pressure region equilibrium hydrogen pressure at maximum exhaust heat temperature of the fuel cell is connected to the hydrogen flow path of the reactor (2 ≦ k ≦ n) The fuel cell system according to any one of claims 1 to 6, comprising:   The heat transfer fin (A) for promoting the heat exchange between the refrigerant and the refrigerant channel (C) is provided on the inner surface of the refrigerant channel (C) of the reactor. 8. The fuel cell system according to any one of 1 to 7.   The heat transfer fin (B) for promoting heat exchange between the refrigerant flow path (C) and the hydrogen storage material is provided in the hydrogen storage material filling portion of the reactor. 9. The fuel cell system according to any one of 1 to 8.   The fuel cell system according to any one of claims 1 to 9, wherein the hydrogen storage material includes a heat conduction aid.

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