JP2002373690A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the generating efficiency of a fuel cell system. SOLUTION: The fuel cell system comprises a hydrogen storage device 14, disposed in a second passage 21 branching from a first passage 20 interconnecting a hydrogen supply device 3 to a fuel cell 1 and for storing a hydrogen storage alloy, a third passage 24 for circulating cooling water for the fuel cell, and a radiator 15 interposed in the third passage. The hydrogen storage alloy has the characteristics of storing and not releasing hydrogen, during a fuel cell system stop before a warm-up. The hydrogen storage device 14 is disposed, so as to develop heat exchange with the cooling water downstream of the radiator in the third passage. A means 16 detects the temperature of the cooling water downstream of the radiator in the third passage, and a means 18 controls or makes the temperature of the cooling water, by releasing the hydrogen from the hydrogen storage alloy, when the detected cooling water temperature reaches an operational upper limit temperature of the fuel cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel cell system.

[0002]

2. Description of the Related Art A fuel cell system provided with a hydrogen storage alloy is disclosed in Japanese Patent Application Laid-Open No. H6-106, which heats the hydrogen storage alloy by using exhaust heat from the fuel cell to release hydrogen.
There are techniques described in JP-A-260202 and JP-A-8-144858.

The technique described in Japanese Patent Application Laid-Open No. 6-260202 is to supplement the amount of heat absorbed by the hydrogen storage alloy when releasing hydrogen with the exhaust heat of the fuel cell held by the cooling water.

The technique described in Japanese Patent Application Laid-Open No. 8-144858 relates to a hydrogen engine. When the temperature of the engine cooling water is low, the set value of the hydrogen pressure is set to a lower value than when the temperature of the engine cooling water is high. This technology prevents the supply of cooling water to the hydrogen storage alloy when the low set value is reached, thereby preventing the heat of the cooling water from being absorbed by the hydrogen storage alloy and delaying the warm-up of the engine.

[0005]

However, in the technique described in Japanese Patent Application Laid-Open No. 6-260202, the amount of heat required to release hydrogen from the hydrogen storage alloy is obtained from the cooling water. In addition, there is a problem that hydrogen cannot be extracted at the time of starting when the temperature of the cooling water is low.

Further, when the output of the fuel cell is low but the temperature of the cooling water is high (for example, during rapid deceleration from a high load operation), there is a problem that more hydrogen is supplied than necessary from the hydrogen storage alloy.

That is, there is a problem that both supply of hydrogen become unstable depending on the temperature of the cooling water.

In the technique described in Japanese Patent Application Laid-Open No. 8-144858, the supply of the cooling water to the hydrogen storage device is stopped so that the heat of the cooling water is not taken by the engine depending on the temperature of the cooling water. There is a problem that the cooling water temperature of the hydrogen storage device decreases (changes) and the amount of released hydrogen decreases (changes).

Here, when the pressure of the hydrogen storage device is reduced to prevent a decrease (change) in the amount of released hydrogen, rapid acceleration to a high load region where the operating pressure is high cannot be performed. That is, there is a problem that necessary hydrogen cannot be supplied according to the operating conditions.

That is, in these conventional techniques, there is a problem that the supply of hydrogen becomes unstable if the temperature of the cooling water fluctuates due to the operating load. There is a problem that varies.

Further, in these prior arts, the hydrogen required for the operation of the fuel cell or the hydrogen engine is configured to be supplied by the hydrogen from the hydrogen storage alloy under all the operating conditions. In order to maintain the temperature, it is necessary to select a hydrogen storage alloy having a property of releasing hydrogen even at a low temperature. The hydrogen storage alloy having such a property can be used at a high temperature, for example, at the operating temperature of a fuel cell (about 80 ° C.).
In order to occlude hydrogen, high pressure conditions (for example, 5 bar)
Above). At this time, the pressure of the air supplied to the fuel cell also needs to be high in accordance with the pressure of the hydrogen, and the operation load of a device for supplying the air, for example, a compressor, increases, thereby causing a decrease in operation efficiency. There is.

Further, when left under a low temperature condition,
There is a problem that the release of hydrogen from the hydrogen storage alloy continues, the pressure in the hydrogen supply path becomes high, hydrogen leaks, and hydrogen is wasted.

It is an object of the present invention to provide a fuel cell system which solves the above problems.

[0014]

According to a first aspect of the present invention, there is provided a fuel cell system including a hydrogen supply device, a hydrogen storage device having a hydrogen storage alloy, a fuel cell, and cooling water for cooling the fuel cell. The cooling water is configured to exchange heat with a hydrogen storage device, and the supply of hydrogen from the hydrogen supply device and the hydrogen storage device is controlled according to the temperature of the cooling water.

According to a second aspect, in the first aspect, a first flow path communicating the hydrogen supply device with the fuel cell and a second flow path branched from the first flow path and provided with the hydrogen storage device are provided. When,
A third flow path for circulating cooling water for the fuel cell, a radiator provided in the middle of the third flow path, and the hydrogen storage device stores and releases hydrogen when the fuel cell system is stopped before warming up. The hydrogen storage device is provided so as to exchange heat with cooling water downstream of the radiator of the third flow path, and the temperature of the cooling water is detected downstream of the radiator of the third flow path. Means for controlling the hydrogen storage device to release hydrogen from the hydrogen storage alloy to lower the temperature of the cooling water when the detected cooling water temperature reaches the operating upper limit temperature of the fuel cell. Have.

According to a third aspect, in the second aspect, a reforming reactor for producing a hydrogen-rich reformed gas is provided as a hydrogen supply device.

According to a fourth aspect of the present invention, in the second or third aspect, the control means controls the temperature of the cooling water which exchanges heat with the hydrogen storage device and the pressure acting on the hydrogen storage alloy to thereby control the hydrogen storage alloy. Control the absorption and release of hydrogen from

In a fifth aspect based on the fourth aspect, the control means includes a valve for adjusting a pressure and a flow rate of the hydrogen flowing through the first flow path. The hydrogen pressure acting on the hydrogen storage device and the hydrogen pressure during fuel cell operation are controlled independently.

In a sixth aspect based on the second aspect, the control means is configured to determine a radiator radiating amount and a fuel cell amount based on a cooling water temperature of the fuel cell, a vehicle speed, a temperature, and a required output value of the fuel cell. The amount of heat generated in the fuel cell is estimated, and the coolant temperature of the fuel cell is calculated based on the calorific value. The temperature of the water is lowered so that the temperature does not exceed the fuel cell operation upper limit temperature.

According to a seventh aspect of the present invention, in the third aspect, there is provided an oxygen monoxide removing device for removing carbon monoxide in the reformed gas and adjusting the concentration to a predetermined concentration, and discharged from the carbon monoxide removing device. The reformed gas flows into the hydrogen storage device.

In an eighth aspect based on the seventh aspect, a fourth flow path communicating the hydrogen storage device and the reforming reactor is provided,
The control means supplies the hydrogen released by the hydrogen storage alloy to the reforming reactor and controls the temperature of the reforming reactor to be maintained at the operating temperature by the reaction heat of the hydrogen.

According to a ninth aspect, in the fourth aspect, a fifth flow path bypassing the hydrogen storage device is provided in the third flow path, and a shutoff valve is provided in the second flow path. When shutting off and releasing hydrogen in the hydrogen storage alloy, the shut-off valve is opened. When the hydrogen storage alloy does not store and release hydrogen, the shut-off valve is closed to control the cooling water to flow into the fifth flow path.

[0023]

According to the first aspect of the present invention, the amount of hydrogen supplied to the fuel cell is increased from the amount of hydrogen supplied from the hydrogen storage alloy for cooling water temperature adjustment, and the amount of hydrogen supplied from the reformer is reduced. Therefore, hydrogen can be stably supplied to the fuel cell regardless of the cooling water temperature. Further, the temperature of the cooling water can be stabilized regardless of the operation load.

According to the second aspect of the present invention, the fuel cell uses the reformed gas from the reforming reactor below the upper limit operating temperature of the fuel cell and uses hydrogen released from the hydrogen storage alloy at the upper operating limit temperature. Since the power is controlled to generate power, the pressure of the air supplied to the fuel cell at low temperatures does not need to be high, and the hydrogen storage alloy does not release hydrogen when the fuel cell system is stopped. Is not reduced.

Since the cooling water of the fuel cell can be cooled by using the heat absorption when hydrogen is released from the hydrogen storage alloy, the cooling water of the fuel cell is combined with the cooling by the radiator for cooling the cooling water. It is possible to prevent the temperature from exceeding the operation upper limit temperature of the battery and becoming too high.

Further, since the cooling water is discharged from the fuel cell, cooled by the radiator, and then flows into the hydrogen storage device for storing the hydrogen storage alloy, high-temperature cooling water is supplied to the radiator. Inflow, the air-water temperature difference in the radiator can be increased, and the radiation efficiency in the radiator can be increased. Further, after cooling by the radiator, the cooling water is further cooled by the hydrogen storage alloy, so that the cooling water flowing into the fuel cell can be kept at a sufficiently low temperature.

During normal operation of the fuel cell system, the cooling performance of the radiator is set so that cooling is sufficient only with the radiator, and hydrogen is released from the hydrogen storage alloy only when the cooling water reaches the fuel cell operation upper limit temperature. Since the cooling water is cooled by absorbing the heat of the cooling water, the release of hydrogen from the hydrogen storage device can be suppressed, and the size of the hydrogen storage device can be reduced.

Except for high-load operation, the hydrogen absorbing alloy does not absorb heat from the cooling water and generates only the reaction heat of the fuel cell due to the reformed gas. Therefore, it is easy to maintain the fuel cell at an appropriate operating temperature. Can be.

According to the third aspect of the present invention, since the reforming reactor for generating the hydrogen-rich reformed gas is provided as the hydrogen supply device, the fuel cell system is operated by the hydrogen from the hydrogen storage device when the fuel cell system operates at a high load. Since hydrogen is provided, the amount of reformed gas generated in the reforming reactor can be reduced, and thus the capacity of the reforming reactor can be reduced.

The hydrogen concentration of the fuel gas supplied to the fuel cell by the hydrogen from the hydrogen storage device supplied at the time of high output is higher than that of the reformed gas during the normal operation. Power generation efficiency can be improved.

A fourth aspect of the present invention is to control the pressure acting on the hydrogen storage device with respect to the hydrogen equilibrium pressure determined by the temperature determined by the temperature of the cooling water that exchanges heat with the hydrogen storage device and the type of the hydrogen storage alloy. Controls the storage and release of hydrogen from the hydrogen storage alloy, so that the temperature of the cooling water can be appropriately controlled by the heat absorption and heat dissipation of the cooling water during the storage and release of hydrogen.

According to a fifth aspect of the present invention, a valve for adjusting the pressure of hydrogen flowing through the first flow path is provided, and the hydrogen pressure acting on the hydrogen supply device and the hydrogen storage device at a constant flow rate using the pressure adjustment valve. Since the hydrogen pressure during fuel cell operation is controlled independently, even when it is necessary to increase the hydrogen pressure acting on the hydrogen storage device, the operating pressure of the fuel cell is controlled independently to an appropriate pressure, and the fuel cell system is controlled independently. As a result, the efficiency can be maintained.

According to a sixth aspect of the present invention, there is provided a cooling water temperature of a fuel cell,
From the vehicle speed, the air temperature, and the required output value of the fuel cell, the radiator heat release amount and the heat generation amount of the fuel cell are estimated, and the cooling water temperature of the fuel cell is calculated based on these. When it is estimated that the temperature exceeds the upper limit temperature of the battery operation, hydrogen is released from the hydrogen storage alloy to lower the temperature of the cooling water, and the temperature is controlled so as not to exceed the upper limit temperature of the fuel cell operation. Before the temperature actually exceeds the operation upper limit temperature, it is possible to release hydrogen in consideration of the response delay of the temperature detection means and the heating response delay of the hydrogen storage alloy. It is possible to prevent the temperature from exceeding the operation upper limit temperature and becoming too high.

According to a seventh aspect of the present invention, there is provided an oxygen monoxide removing device for removing carbon monoxide in the reformed gas and adjusting the concentration to a predetermined concentration. Since the gas flows into a storage device (hereinafter referred to as CO) and the concentration of carbon monoxide in the reformed gas flowing into the hydrogen storage device is reduced, poisoning of the hydrogen storage alloy by CO can be suppressed.

According to an eighth aspect of the present invention, there is provided a fourth flow path communicating the hydrogen storage device and the reforming reactor, supplying the hydrogen released by the hydrogen storage alloy to the reforming reactor, and controlling the temperature of the reforming reactor. Since the control is performed so as to maintain the operating temperature, the temperature of the reforming reactor can be maintained at the operating temperature during the standby operation of the fuel cell.

According to a ninth aspect of the present invention, a fifth flow path bypassing the hydrogen storage device is provided in the third flow path, and a shutoff valve is provided in the second flow path to shut off when hydrogen is stored or released in the hydrogen storage alloy. When the valve is opened and the hydrogen storage alloy does not store and release hydrogen, the shutoff valve is closed to control the cooling water to flow into the fifth flow path, so that the hydrogen storage alloy does not release and store hydrogen. In this case, the temperature of the hydrogen storage alloy decreases, the hydrogen dissociation pressure decreases, and the shutoff valve is closed, so that unnecessary release of hydrogen from the hydrogen storage alloy is suppressed, and the efficiency of the fuel cell system can be improved.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a fuel cell system when the present invention is applied to a fuel cell vehicle will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. The fuel cell 1 is provided with a fuel electrode and an air electrode, and a hydrogen-rich reformed gas and air are supplied to each electrode to generate power.

The air is supplied from the air supply device 2 to the air electrode, while the reformed gas supplied to the fuel electrode is supplied to the reforming reactor 3.
Generated by For this reason, the reforming reactor 3 has a fuel tank 4
Is vaporized in the evaporator 6 and the water in the water tank 5 is supplied with vaporized fuel and water vapor.

Reforming reactor 3 supplied with fuel and steam
Then, a reforming reaction occurs to generate a hydrogen-rich reformed gas, and this reformed gas is adjusted to a predetermined CO concentration by a carbon monoxide (hereinafter, referred to as CO) remover 7 provided downstream thereof. The pressure is supplied to the fuel electrode of the fuel cell 1 via the pressure regulating valve 13.

Exhaust air discharged from the air electrode after power generation in the fuel cell 1 is supplied to the combustor 8, and excess waste hydrogen discharged from the fuel electrode is similarly supplied to the combustor 8, The exhaust hydrogen and exhaust air are combusted. This combustion gas is supplied to the evaporator 6, and the heat of the combustion gas causes the tanks 4, 5,
The fuel and water supplied from are vaporized. The combustion gas is exhausted after being used for vaporizing fuel and water.

In the middle of the fuel cell 1 and the combustor 8, condensers 9 and 10 for condensing moisture are respectively installed in a flow path through which exhaust hydrogen flows and a flow path through which exhaust air flows. Further, pressure control valves 11 and 12 are provided between each of the condensers 9 and 10 and the combustor 8. The water condensed in the condensers 9 and 10 is stored in the water tank 5.

The capacitors 9 and 10 are provided for improving the efficiency of the fuel cell system, and the system can function without using any capacitors.

In this embodiment, the reforming reactor 3 is used as a means for supplying hydrogen to the fuel cell 1. However, the hydrogen is directly supplied to the fuel cell 1 using a hydrogen high-pressure tank or the like. You can also.

Further, in the present system, a hydrogen storage tank (hydrogen storage device) 14 containing a hydrogen storage alloy branches off from a flow path 20 (first flow path) connecting the CO remover 7 and the pressure regulating valve 13. It is installed on the road 21 (second flow path). Cooling water for cooling the fuel cell 1 is supplied to the hydrogen storage tank 14, and the hydrogen storage alloy in the hydrogen storage tank 14 releases or stores hydrogen by using the heat of the cooling water. The cooling water discharged from the hydrogen storage tank 14 is sent to the fuel cell 1 again for cooling the fuel cell 1.

The characteristics of the hydrogen storage alloy contained in the hydrogen storage tank 14 are such that the hydrogen storage alloy has the characteristic of releasing hydrogen at the optimum operating temperature of the fuel cell, and that the fuel cell system is stopped. At low temperatures, it absorbs hydrogen,
An alloy having characteristics of not releasing (low hydrogen dissociation pressure) is selected. As an alloy having such properties, for example, a _{Ti 0.5 Zr 0.5 Mn 1.7 Cu 0.3} .

The cooling water discharged from the fuel cell 1 has a high temperature and is cooled by a radiator 15 installed upstream of the hydrogen storage tank 14.

A temperature sensor 16 for detecting the temperature of the cooling water discharged from the radiator 15 is provided by the radiator 1.
5 and a pressure sensor 17 for detecting the hydrogen pressure applied to the hydrogen storage tank 14
It is installed downstream of the remover 7.

The cooling water cooled by the radiator 15 is sent for heat exchange with the hydrogen storage tank 14, and thereafter returns to the fuel cell 1. Reference numeral 24 denotes a flow path (third flow path) through which the cooling water of the fuel cell 1 circulates.

Further, the temperature sensor 16 or the pressure sensor 1
A controller (control means) 18 for controlling the release or storage of hydrogen from the hydrogen storage tank 14 based on the output of the hydrogen storage tank 14 by the pressure of the hydrogen storage tank 14 is provided. The controller 18 can control the pressure of the hydrogen storage tank 14 by controlling the pressure regulating valve 13. By using a pressure control valve 13 that can adjust the pressure at a constant flow rate, this control can be performed independently of the operation pressure control of the fuel cell 1. The controller 18 can control the supply amounts of fuel and water by the fuel injection valve 32 and the water injection valve 31. The controller 18 is configured as described above.
When the temperature of the cooling water detected by the fuel cell reaches the operation upper limit temperature of the fuel cell 1 (for example, during high-speed running or high-load operation), hydrogen is released from the hydrogen storage tank 14 and heat of the cooling water is absorbed. Thus, the pressure applied to the hydrogen storage tank 14 is controlled by controlling the opening of the pressure regulating valve 13 so as to lower the cooling water temperature. At the same time, the amount of fuel and water supplied to the reforming reactor 3 is controlled so that the total amount of hydrogen supplied to the fuel cell 1 is controlled to be constant.

The amount of hydrogen supplied to the fuel cell can be kept constant by reducing the amount of hydrogen supplied from the reformer by increasing the amount of hydrogen supplied from the hydrogen storage alloy for cooling water temperature adjustment. Hydrogen can be stably supplied to the fuel cell regardless of the water temperature. Further, the temperature of the cooling water can be stabilized regardless of the operation load.

On the other hand, during low-temperature operation such as idling operation,
The fuel cell 1 is operated by the reformed gas from the reforming reactor 3, and the hydrogen storage alloy has a characteristic of only storing hydrogen and not releasing hydrogen at a low temperature. Is not supplied to the fuel cell 1.

The relationship between the equilibrium hydrogen pressure and the hydrogen composition showing the characteristics of the hydrogen storage alloy is generally shown in FIG. The higher the temperature of the hydrogen storage alloy, the higher the equilibrium dissociation pressure, and the release of hydrogen under high pressure conditions becomes possible.

The relationship between hydrogen storage and release of hydrogen in the hydrogen storage alloy is expressed by the following equation.

Hydrogen storage: (2 / n) M + H ₂ → (2 / n) MH _n + ΔH (heat): Exothermic reaction Hydrogen release: (2 / n) M + H ₂ ← (2 / n) MH _n −ΔH (heat) ): Endothermic reaction (Reference: Hydrogen storage alloys-From basic to advanced technology-Supervisor: Hideo Tamura, Published by: NTN Corporation) where n is the number of moles and M is the alloy Is a symbol representing the molecular formula of

In a normal fuel cell system, the characteristics as a hydrogen storage alloy are required to store a large amount of hydrogen with little heat in order to effectively cool the cooling water of the fuel cell. As for the characteristics of the hydrogen storage alloy, a material having a large endothermic amount per weight and a large endothermic amount-ΔH per hydrogen generation amount is selected.

As shown in FIGS. 2 and 3, when the fuel cell system is stopped, the temperature rises, but the hydrogen storage alloy is maintained at the system cold state point in the figure to prevent the release of hydrogen, and the hydrogen storage rate is reduced. Held high.

When the fuel cell system is in a normal operation state, the pressure applied to the hydrogen storage alloy is controlled so that the hydrogen storage alloy reaches an operation point A in the figure, and the hydrogen composition is maintained at a high level.

Further, the fuel cell system has a high output,
When the amount of heat exceeds the amount of heat radiation in the radiator 15 and the cooling water is not sufficiently cooled, the temperature of the cooling water increases,
The temperature of the hydrogen storage alloy in the hydrogen storage tank 14 into which the cooling water flows also rises, and the hydrogen storage alloy releases hydrogen to lower the cooling water temperature. The pressure applied to the hydrogen storage alloy is controlled so that hydrogen is not released until the pressure becomes. The state in which the pressure is maintained so as to reach the operating upper limit temperature of the fuel cell corresponds to the operating point B in FIG. 3, and the temperature exceeding the operating upper limit temperature of the fuel cell is detected from the temperature of the cooling water detected by the temperature sensor 16. In this case, the pressure regulating valve 13 is adjusted, the load pressure on the hydrogen storage alloy is reduced to the operating point C to release hydrogen from the hydrogen storage alloy, and the heat of the cooling water is absorbed by the hydrogen storage alloy. Decrease the temperature of

Next, the operating state of the fuel cell system and the supply of hydrogen to the fuel cell will be described.

First, in a warm-up state in which the fuel cell system is started from a stopped state, the hydrogen storage alloy has a characteristic of absorbing hydrogen but not releasing hydrogen. Is supplied with the hydrogen-rich reformed gas generated in the reforming reactor 3.

When the fuel cell system shifts to the normal operation state, by setting the cooling capacity of the radiator 15 to the necessary capacity during the normal operation of the fuel cell 1, the supply of hydrogen from the hydrogen storage alloy is avoided as much as possible. Reforming reactor 3
It is covered by the reformed gas generated in the above. Note that even during normal operation, the temperature of the cooling water of the fuel cell 1 is detected using the temperature sensor 16, and when the temperature reaches the operation upper limit temperature, hydrogen is supplied from the hydrogen storage alloy to the fuel cell, while heat absorption by the hydrogen storage alloy is performed. Thereby, the cooling water temperature can be lowered. At this time, the amount of hydrogen supplied to the fuel cell 1 is controlled such that the amount of reformed gas from the reforming reactor 3 and the amount of hydrogen from the hydrogen storage tank 14 are constant.

When the fuel cell system performs high-temperature, high-load operation, the cooling water becomes high in temperature due to the amount of heat exceeding the cooling capacity of the radiator 15, but the cooling water due to the heat absorption of the hydrogen storage alloy is taken into consideration. Thus, the coolant temperature can be maintained at the fuel cell operating temperature. At this time, if the amount of hydrogen released from the hydrogen storage alloy is set to an amount that can cover most of the amount of hydrogen required in the fuel cell 1, the reforming reactor 3 can be downsized.

When the fuel cell system is stopped, control is performed so that hydrogen (reformed gas) generated due to a delay with respect to the stop command to the reforming reactor 3 is stored in the hydrogen storage tank 14. Even when the stop state continues, the hydrogen is not released because the hydrogen storage alloy is in a low temperature state, and the pressure of the hydrogen storage tank 14 does not increase.

In this system, the hydrogen storage tank 14
Pressure is detected by a pressure sensor 17, and the pressure regulating valve 13 is used based on the detected pressure and the temperature of the cooling water flowing into the hydrogen storage tank 14 and a hydrogen equilibrium pressure determined by characteristics specific to the type of the hydrogen storage alloy. Thus, the pressure acting on the hydrogen storage tank 14 can be controlled. Therefore, the storage and release of hydrogen from the hydrogen storage tank 14 can be controlled based on this pressure control. At this time, the pressure control for storing and releasing hydrogen is performed independently of the pressure control of the fuel cell 1.

Therefore, in the present invention, the fuel cell 1 uses the heat absorption when hydrogen is released from the hydrogen storage alloy.
The cooling water of the fuel cell 1 can be cooled in combination with the cooling by the radiator 15 for cooling the cooling water to prevent the cooling water of the fuel cell 1 from exceeding the operation upper limit temperature of the fuel cell 1 and becoming over-temperature. Can be.

The cooling water is discharged from the fuel cell 1 and cooled by the radiator 15, and then flows into the hydrogen storage tank 14 for storing the hydrogen storage alloy. Cooling water flows in, and the difference in air-water temperature in the radiator 15 can be increased.
Heat dissipation efficiency can be increased. Furthermore, since the cooling water is further cooled by the hydrogen storage alloy after cooling by the radiator 15, the cooling water flowing into the fuel cell 1 can be kept at a sufficiently low temperature.

During high load operation of the fuel cell system, the amount of reformed gas generated in the reforming reactor 3 may be reduced because the hydrogen from the hydrogen storage tank 14 supplies hydrogen to the fuel cell 1. And therefore the reforming reactor 3
Capacity can be reduced.

The hydrogen concentration of the fuel gas supplied to the fuel cell 1 by the hydrogen from the hydrogen storage tank 14 supplied at the time of high output is higher than that of the reformed gas during normal operation. Power generation efficiency can be improved.

Further, when the temperature of the cooling water of the fuel cell becomes high, hydrogen is released from the hydrogen storage alloy and the heat of the cooling water is absorbed, thereby lowering the temperature of the cooling water and obtaining condensed water from the exhaust air. It is possible. Also, the cooling water becomes hot,
For example, when the load is high, hydrogen from the hydrogen storage alloy is supplied to the fuel cell, so that the ratio of the amount of water required in the reforming reactor to the amount of water obtained by condensing from the exhaust gas is reduced, and the Water balance can be balanced.

In the case of switching from high-load running to low-load running, for example, the cooling water at the outlet of the radiator 15 maintained at a temperature equal to or higher than the fuel cell operation upper limit temperature such as running on a steep uphill road and then running on a downhill road. When the temperature can be predicted to decrease, the pressure acting on the hydrogen storage tank 14 is set to be equal to or higher than the hydrogen equilibrium pressure, and excess hydrogen generated due to a delay in response to a decrease in the output of the reforming reactor 3 can be stored to improve the efficiency. .
Such control can be performed when the system is stopped.

The cooling water temperature of the fuel cell 1 is controlled by the radiator 15.
It has a configuration for detecting downstream (temperature sensor 16),
Only when the cooling capacity of the cooling water in the radiator 15 is exceeded (for example, during high-load operation), hydrogen is released from the hydrogen storage tank 14 and heat of the cooling water is absorbed to cool the cooling water. During normal operation of the fuel cell system,
By setting the cooling performance of the radiator 15 so that cooling is sufficient only by the cooling capacity of the radiator 15, the number of times of releasing hydrogen from the hydrogen storage tank 14 can be suppressed, and the hydrogen storage tank 14 can be downsized.

In an operation that does not require a high load, no hydrogen is released from the hydrogen storage tank 14, so no heat is absorbed from the cooling water, and only the reaction heat of the fuel cell 1 by the reformed gas is generated. The fuel cell 1 can be easily maintained at an appropriate temperature.

After the operation of the fuel cell system is stopped, the release of hydrogen stops as the temperature of the hydrogen storage alloy decreases, and the pressure in the hydrogen storage tank 14 does not increase. Therefore, it is possible to prevent the pressure of the hydrogen storage tank 14 from increasing during the operation stop of the system, and to prevent hydrogen from leaking.

On the other hand, the characteristics of the hydrogen storage alloy used in the present embodiment depend on the operating temperature of the fuel cell 1 (for example, about 80 ° C.).
° C), and has a characteristic of absorbing hydrogen below this temperature, so that hydrogen can be easily absorbed at low temperatures such as when the system is stopped.

The release of hydrogen from the hydrogen storage alloy is applied to the hydrogen storage tank 14 in accordance with the characteristics of the hydrogen storage alloy so that the hydrogen is released at the upper limit operating temperature of the fuel cell 1 while maintaining the predetermined operating pressure of the fuel cell 1. The controllable pressure can be controlled, so that the selection range of the hydrogen storage alloy can be widened.

In a fuel cell system provided with a normal hydrogen storage alloy, it is necessary to increase the pressure applied to the hydrogen storage alloy during hydrogen storage, and the pressure acting on the fuel electrode of the fuel cell is high. . Therefore, the Membrane Electrode Assese constituting the fuel cell
When the pressure acting on mbly (hereinafter, referred to as MEA) is largely different between the fuel electrode and the air electrode, it is necessary to increase the thickness in order to prevent the deterioration, which leads to a decrease in power generation efficiency. become. In order to prevent this pressure difference, it is conceivable to increase the pressure acting on the air electrode.However, at this time, it is necessary to increase the load on a device for supplying air, for example, a compressor, and the operating efficiency of the system decreases. There's a problem. In the present invention, since the pressure applied to the hydrogen storage tank 14 and the operating pressure of the fuel cell 1 are controlled independently, even when it is necessary to increase the hydrogen pressure acting on the hydrogen storage tank, the operation of the fuel cell can be performed independently. By controlling the pressure to an appropriate pressure, the efficiency of the fuel cell system can be maintained.

In a fuel cell system provided with a reforming reactor, water required for a reforming reaction and a CO reduction reaction (shift reaction) in a CO remover is discharged, and exhaust air discharged from the fuel cell is cooled by the fuel cell. It is common to use water after cooling with water and condensing. However, when the temperature of the cooling water of the fuel cell becomes high, it becomes difficult to obtain the condensed water required in the reforming reactor. However, in the present invention, when the cooling water of the fuel cell has a high temperature, hydrogen is released from the hydrogen storage alloy, and the heat of the cooling water is absorbed, thereby lowering the temperature of the cooling water,
It is possible to obtain condensed water from the exhaust air. In addition, when the cooling water is at a high temperature, for example, when the load is high, hydrogen from the hydrogen storage alloy is supplied to the fuel cell, so that the reformed gas generating capacity of the reforming reactor can be reduced. It is possible to balance the water balance of the fuel cell system by reducing the required amount of water and reducing the ratio to the amount of water obtained by condensing from the exhaust gas. Further, the capacity of the reforming reactor 3 can be reduced.

In the second embodiment shown in FIG. 4, the configuration of the first embodiment is provided with a calculating means 19 storing a performance map of the radiator 15, and the calculating means includes a cooling water temperature of the fuel cell 1, a vehicle speed, and the like. The vehicle information, such as the temperature and the required output of the fuel cell, is input, and the calculating means 19 calculates the heat radiation amount of the radiator from the radiator performance map, and calculates the calorific value of the fuel cell 1.

The calculating means 19 estimates whether the cooling water temperature of the fuel cell 1 exceeds the operation upper limit temperature from the heat radiation amount of the radiator 15 and the calorific value of the fuel cell 1. The opening degree of the pressure control valve 13 is adjusted to control the pressure of the hydrogen storage tank 14 to be small, and hydrogen is released from the hydrogen storage tank 14 in consideration of the delay of the control system and the like, and the heat of the cooling water is reduced to hydrogen. The heat absorption of the storage alloy lowers the temperature of the cooling water.

Therefore, it is estimated whether or not the temperature of the cooling water of the fuel cell 1 exceeds the operation upper limit temperature. Since it is possible to set the time at which the temperature of the cooling water is reduced by the heat absorption by the storage alloy, it is possible to prevent the fuel cell 1 from temporarily exceeding the operation upper limit temperature and becoming excessively high.

In the third embodiment shown in FIG. 5, the hydrogen in the reformed gas is stored in the hydrogen storage alloy, and the hydrogen released from the hydrogen storage alloy is supplied to the reforming reactor 3. It is. The configuration is different from that of the second embodiment in that CO 2
A flow path (first flow path) 2 that connects the remover 4 and the fuel cell 1
A one-way valve 22 that allows the flow of hydrogen only in the direction of the hydrogen storage tank 14 is provided in the middle of a flow path (second flow path) 21 that communicates with the hydrogen storage tank branched from 0, and hydrogen from the hydrogen storage tank 14 is provided. (Fourth flow path) 23 for supplying the water upstream of the reforming reactor 3. In addition, a flow path 30 is configured to supply air to the reforming reactor 3. Note that the fuel cell 1 may be configured so that part of the hydrogen from the hydrogen storage tank 14 can be supplied to the fuel cell 1 as in the other embodiments.

Here, during standby operation or the like in which power generation in the fuel cell 1 is not required, hydrogen and air from the air supply device 25 are supplied to the reforming reactor 3 from the hydrogen storage tank 14, and the reforming reactor 3 And an oxidation reaction is caused in the CO remover 5,
The operating temperature of the reforming reactor 3 (here, the operating temperature is within the active temperature range of the catalyst and is a temperature capable of generating a reformed gas suitable for operating the fuel cell). That is, when power generation by the fuel cell 1 is not required,
The reforming reactor 3 stops generating reformed gas, and the reforming reactor 3
The temperature of the fuel cell 1 decreases, and it is necessary to perform the warm-up operation again at the next operation, and the power cannot be generated until the warm-up is completed. In the present embodiment, the power generation of the fuel cell 1 is stopped. By supplying hydrogen to the reforming reactor 3 even in the state, the temperature of the reforming reactor 3 can be maintained at the operating temperature, and the power generation of the fuel cell 1 can be started immediately at the next operation.

Further, by supplying hydrogen to the reforming reactor 3, the CO concentration in the reformed gas can be reduced, the poisoning of the fuel cell by CO can be suppressed, and the life can be extended.

When hydrogen from the hydrogen storage tank is supplied to the reforming reactor 3 and the fuel cell 1 during the normal operation, the amount of hydrogen used is increased as compared with the other embodiments. The accompanying heat absorption increases, and the cooling performance of the cooling water of the fuel cell 1 can be further improved. As a result, the radiator can be reduced, and the mountability on the vehicle can be improved.

In the fourth embodiment shown in FIG. 6, the cooling water of the fuel cell 1 is supplied to the hydrogen storage tank 14 through the cooling water flow path (third flow path) 24 only when hydrogen is absorbed or released by the hydrogen storage alloy. To transfer the heat of the cooling water of the fuel cell 1 to the hydrogen storage tank 14, and otherwise, the cooling water bypasses the hydrogen storage tank 14. The configuration is different from that of the second embodiment in that a one-way valve 22 is provided instead of a one-way valve 22, a flow path (fifth flow path) 26 that bypasses the hydrogen storage tank 14, a flow path 24 and a flow path 26 is provided with a three-way valve 27 installed at a branch. Further, the air from the air supply unit 2 is connected to the reforming reactor 3 and C
A flow path 28 is provided so as to be supplied to the O remover 7.

To store hydrogen in the hydrogen storage alloy, the three-way valve 27 is switched so that the cooling water flows through the hydrogen storage tank, the shut-off valve 25 is opened, and at the same time, the pressure regulating valve 1 is opened.
13 is controlled to control the hydrogen pressure in the hydrogen storage tank 14 and the reforming reactor 3. When there is no storage and release of hydrogen in the hydrogen storage alloy, the shutoff valve 25 is closed and the three-way valve 27 is closed.
Is switched so that the cooling water bypasses the hydrogen storage tank 14.

Therefore, when the hydrogen storage alloy does not release and store hydrogen, the temperature of the hydrogen storage alloy decreases, the hydrogen dissociation pressure decreases, and the shut-off valve 24 is closed. Release of hydrogen from the fuel cell can be suppressed, and the efficiency of the fuel cell system can be improved.

When the reforming reactor 3 is provided as a hydrogen supply device as in the present embodiment, the pressure of the reformed gas may be increased only when the hydrogen storage alloy stores hydrogen. The operation efficiency of the vessel 2 can be improved.

The present invention is not limited to the above-described embodiment, and it is apparent that various modifications can be made within the scope of the technical idea of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fuel cell system illustrating a first embodiment of the present invention.

FIG. 2 is a diagram illustrating characteristics of the hydrogen storage alloy.

FIG. 3 is a characteristic diagram of the hydrogen storage alloy showing operating points of the fuel cell.

FIG. 4 is a schematic diagram illustrating a fuel cell system according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating a fuel cell system according to a third embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a fuel cell system according to a fourth embodiment of the present invention. .

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fuel cell 2 air supply device 3 reforming reactor 4 fuel tank 5 water tank 6 evaporator 7 CO remover 8 combustor 13 pressure regulating valve 14 hydrogen storage tank 15 radiator 16 temperature sensor 17 pressure sensor

Claims (9)

[Claims] 1. A fuel cell system comprising a hydrogen supply device, a hydrogen storage device having a hydrogen storage alloy, a fuel cell, and cooling water for cooling the fuel cell, wherein the cooling water exchanges heat with the hydrogen storage device. A fuel cell system configured to control supply of hydrogen from a hydrogen supply device and a hydrogen storage device according to a temperature of the cooling water. 2. A first flow path communicating the hydrogen supply device with the fuel cell, a second flow path branched from the first flow path and provided with the hydrogen storage device, and circulating cooling water for the fuel cell. A third flow path; a radiator provided in the middle of the third flow path; and the hydrogen storage device includes a hydrogen storage alloy having a characteristic of absorbing and not releasing hydrogen when the fuel cell system is stopped before warming up. Installing the hydrogen storage device so as to exchange heat with cooling water downstream of the radiator of the third flow path, and providing means for detecting the temperature of cooling water downstream of the radiator of the third flow path; Means for controlling the hydrogen storage device so as to release hydrogen from the hydrogen storage alloy to lower the temperature of the cooling water when the cooling water temperature reaches the operating upper limit temperature of the fuel cell. The fuel cell system described in 1 Temu. 3. The fuel cell system according to claim 2, wherein a reforming reactor for generating a hydrogen-rich reformed gas is provided as the hydrogen supply device. 4. The method according to claim 1, wherein the control means controls the storage and release of hydrogen from the hydrogen storage alloy by controlling the temperature of the cooling water that exchanges heat with the hydrogen storage device and the pressure acting on the hydrogen storage alloy. 4. The fuel cell system according to claim 2, wherein: 5. The control means includes a valve for adjusting a pressure and a flow rate of hydrogen flowing through the first flow path, and using the pressure adjusting valve to control a hydrogen pressure and a fuel acting on a hydrogen supply device and a hydrogen storage device. The fuel cell system according to claim 4, wherein the hydrogen pressure during battery operation is controlled independently. 6. The control means estimates a radiator heat release amount and a fuel cell heat generation amount from a cooling water temperature of the fuel cell, a vehicle speed, an air temperature, and a required output value of the fuel cell. The fuel cell cooling water temperature is calculated, and when the calculated cooling water temperature is estimated to exceed the fuel cell operation upper limit temperature, hydrogen is released from the hydrogen storage alloy to lower the cooling water temperature, and the fuel cell operation is performed. 3. The fuel cell system according to claim 2, wherein control is performed so as not to exceed an upper limit temperature. 7. An apparatus for removing carbon monoxide in a reformed gas and adjusting the concentration thereof to a predetermined concentration, wherein the reformed gas discharged from the apparatus for removing carbon monoxide flows into the hydrogen storage device. The fuel cell system according to claim 3, wherein: 8. A fourth flow path communicating the hydrogen storage device and the reforming reactor is provided, wherein the control means supplies the hydrogen released by the hydrogen storage alloy to the reforming reactor, The fuel cell system according to claim 7, wherein the temperature of the reforming reactor is controlled so as to maintain the operating temperature by the operation. 9. A fifth flow path bypassing a hydrogen storage device in the third flow path, and a shutoff valve in the second flow path, wherein the control device stores and releases hydrogen in a hydrogen storage alloy. 5. The method according to claim 4, wherein the shut-off valve is opened, and when the hydrogen storage alloy does not store and release hydrogen, the shut-off valve is closed to control the cooling water to flow into the fifth flow path.
3. The fuel cell system according to item 1.