JP2001068125A - Fuel cell power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reverse power follow to commercial power line when consumption power is smaller than the generated power and to suppress increase in facility cost by installing an electric heater to which the generated power is supplied in a hot water tank to which waste heat is supplied. SOLUTION: A fuel cell main body 15 generates power by bonding hydrogen supplied from a CO gas removing device 14 with oxygen in compressed air supplied from an air compressor 16, and converting ions produced into charges of an anode and a cathode. The generated power is converted into AC 100 V through a DC/DC converter 3 and an inverter 4, and supplied to a house through a line breaker 5 and consumed there. Water in a storage tank 2 is heated by waste heat of a fuel cell 1 with a heating part 18a during circulation within heating pipe 18. When the consumption power in the house exceeds the generated power, power shortage is supplemented with commercial power, and when it is opposite, reverse power flow is prevented with the line breaker 5, excess power is supplied to an electric heater 21 for the storage tank 2 to heat water or hot water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell power generation system, and more particularly to an operation control technique.

[0002]

2. Description of the Related Art In general, household energy demand consists of electricity demand for electric appliances, heat demand for hot water supply and kitchens, and heat demand for heating equipment. Regarding the power of these demands, thermal power plants that use the thermal energy generated when burning fuels such as oil, natural gas, coal,
At the time of power generation, almost the same amount of heat as the amount of electricity is emitted, and no effective use of heat is attempted.

On the other hand, in facilities such as hospitals, schools, and buildings,
The use of a power generation system by a fuel cell is being promoted (for example, see Japanese Patent Application Laid-Open No. H10-311564). Fuel cells convert the energy of hydrogen and oxygen into water when converted into electricity.The fuel cell can generate electricity as long as it continues to supply hydrogen as a fuel, and has the advantage of high conversion efficiency from fuel to electricity. There is. In the future, it is expected that this fuel cell power generation system will be widely used for home use and that the generated heat will be used effectively for hot water supply while generating power in individual houses.

[0004] The fuel cell power generation system is configured so that the power generated by the fuel cell can be used alone or together with commercial power. Considering the use of this system for home use, the power consumption of individual general homes will vary greatly depending on whether or not they are at home. If the power consumption in the home exceeds the power generation, the power generated by the fuel cell power generation system is supplemented with commercial power if the power consumption in the home exceeds the power generation. On the other hand, when the power consumption becomes smaller than the power generation amount, the power generated by the home system flows to the power transmission side of the commercial power (reverse power flow).

It is preferable to prevent reverse power flow. The reason is that, for example, when the power supply from the power company is stopped due to a power outage or the like, the restoration work is performed. If this occurs, the work will be hindered.

[0006]

However, if an attempt is made to prevent reverse power flow in this type of system, the cost may increase for the following two reasons.

One of the reasons is that the configuration and control of the fuel cell become complicated when the power generation amount is adjusted to the power consumption in order to prevent reverse power flow.

[0008] This point will be described more specifically.
Fuel cells are devices that generate electricity by directly reacting hydrogen produced by reforming city gas and the like with oxygen in the air.
Generally, unreacted hydrogen that has passed through the fuel cell body is used as a heating source for a reforming process of city gas or the like. When the power load suddenly changes, the output can be adjusted to the load by controlling the current value of the fuel cell body.However, the reaction rate of hydrogen and oxygen changes according to the amount of power generation, and The amount of heating in the quality process varies.

For example, when the load suddenly decreases, the power generation amount of the fuel cell body decreases in accordance with the load, and the reaction rate (fuel utilization rate) of hydrogen decreases, while it is a heat source of the reforming process. Since the amount of unreacted hydrogen increases, the temperature of the reformer and the like rises sharply, and hot spots and the like occur on the heating surface of the reformer. On the other hand, when the load increases sharply, the reaction rate of hydrogen in the fuel cell body increases, resulting in insufficient heating of the reforming process and an incomplete reforming reaction.

In order to stabilize the fuel cell body and the reforming process when the electric power load fluctuates, the amount of reformed gas fuel such as city gas, the amount of air, and the amount of water for reforming must be adjusted in accordance with the electric power load. Since control is required, a plurality of valves and the like are required. Further, control of the pressure and flow rate of the reforming process is more likely to cause a time lag than control of the electric power, so that it is necessary to increase the number of detection points (sensors and the like) to shorten the time lag. As described above, since it is necessary to use various sensors, valves, and the like to make the generated power correspond to the power consumption, the equipment cost increases, and the cost also increases in terms of control.

On the other hand, when the power generation amount is kept constant irrespective of the fluctuation of the power consumption, the surplus power is generated if the power consumption is small. For this reason, at the time of isolated operation, it is necessary to detect whether or not the reverse power flow due to the surplus power is generated, and if the reverse power flow is generated, it is necessary to cut off the current corresponding to the surplus power. The provision of such a detection mechanism and a cutoff function increases costs.

[0012] From the above, in a fuel cell power generation system used in a home or the like where power load fluctuation is relatively large,
It is desired that the reverse power flow does not occur and that the cost be reduced. The present invention has been made in view of such a problem, and an object of the present invention is to provide a fuel cell power generation system with a reverse power flow to commercial power when power consumption is less than power generation. And to prevent the cost from rising.

[0013]

According to the present invention, water in a hot water storage tank generally used for hot water supply or the like in this type of system can be heated by using electric power generated by a fuel cell. .

Specifically, a solution taken by the present invention is to provide a fuel cell (1) and a hot water storage tank (2) to which the exhaust heat of the fuel cell (1) is given. It is assumed that the fuel cell power generation system is configured to be able to use the generated power alone or together with commercial power. The hot water storage tank (2) is provided with an electric heater (21) to which electric power generated by the fuel cell (1) is supplied.

In the above configuration, the electric heater (21) is
When the power consumption is smaller than the power generation amount of the fuel cell (1), it is preferable to drive with surplus power.

In the above configuration, the fuel cell (1)
Is preferably controlled such that the amount of power generation has a constant capacity.

In the above configuration, the electric heater (2
It is preferable that the direct current generated by the fuel cell (1) be supplied to (1).

Further, in the above configuration, the electric heater
(21) is preferably constituted by a freezing prevention heater provided in the hot water storage tank (2).

In the above-mentioned solution, in a home or the like provided with a fuel cell power generation system, when the power consumption is larger than the power generation of the fuel cell (1), commercial power can be used in combination. On the other hand, if the power consumption is smaller than the power generated by the fuel cell (1), the surplus power is used for the hot water storage tank (2) while using only the power generated by the fuel cell (1) at home, etc. The electric power is supplied to the electric heater (21), and the surplus power is used together with the exhaust heat of the fuel cell (1) to store the hot water
(2) Heat or keep the water or hot water inside.

When the amount of power generated by the fuel cell (1) is made constant, surplus electric power that varies according to power consumption is supplied to the electric heater (21), and the water in the hot water storage tank (2) is heated. You.

When a DC current is supplied to the electric heater (21), DC power generated by the fuel cell (1) is supplied to the electric heater (21) before being converted into AC. .

[0022]

According to the above means, when the power consumption in the system is smaller than the power generation amount of the fuel cell (1), the surplus power is supplied to the electric heater (21) for the hot water storage tank (2). Since the power can be supplied, the reverse power flow to the commercial power does not occur, and the surplus power can be used effectively. Further, since it is not necessary to provide various control devices for preventing reverse power flow even when the amount of generated power is constant, it is possible to prevent an increase in system cost.

Also, since no reverse power flow occurs without changing the amount of power generated by the fuel cell (1), the amount of power generated by the fuel cell (1) can be kept at a constant capacity. Not only can be used for heating the water in the hot water storage tank (2), but also the control of the fuel cell (1) becomes easy.

When a direct current is supplied to the electric heater (21), the electric heater (21) differs from the case where an alternating current is supplied.
Since the inverter is not required before the operation, a decrease in efficiency due to the inverter can be prevented.

Further, when the electric heater (21) is also used as an anti-freezing heater provided in the hot water storage tank (2) in a cold region or the like, the cost can be reduced since the dedicated electric heater (21) becomes unnecessary. .

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a device configuration of the fuel cell power generation system according to this embodiment. This fuel cell power generation system is a household system using city gas, as shown in the figure, a fuel cell (1), a hot water storage tank (2), a DC / DC converter (3), and an inverter (4).
, And a system breaker (5), and is connected to a service line (7) for power from a commercial power supply (6).

The fuel cell (1) includes a desulfurizer (11) and a reformer (1).
2), transformer (13), CO gas remover (14), battery body (15),
An air compressor (16) and a burner (17) are provided. Then, a desulfurizer (11) and a reformer (1)
2), transformer (13), CO gas remover (14), and battery body (1
5) are connected in order. The air compressor (16) is connected to the reformer (12) from the burner (17) side, and is also connected to the battery body (15), and the reformer (12) and the battery body (15) Supply compressed air to The battery body (15) is connected to the burner (17) side of the reformer (12), and sends exhaust gas to the reformer (12).

The desulfurizer (11) is configured to remove a sulfur component in the city gas supplied from the city gas supply source (8).

The reformer (12) reacts the desulfurized city gas with water supplied from a tank (not shown) while heating it with a burner (17) to form a reformer mainly containing carbon dioxide and hydrogen. Generate gas. More specifically, the battery body (15)
Exhaust gas (anode exhaust gas containing hydrogen gas and cathode exhaust gas containing water vapor and air) and air compressor (16)
While heating the compressed air from the burner (17) and heating the city gas and water in the presence of a not-shown reforming catalyst provided in the reformer (12), a reformed gas is generated. .

The reformed gas also contains carbon monoxide,
The transformer (13) transforms the carbon monoxide into carbon dioxide. Further, the CO gas remover (14) further oxidizes and removes the carbon monoxide since the efficiency is reduced if carbon monoxide remains in the reformed gas.

The battery body (15) has a cathode and an anode, and combines a mixed gas of carbon dioxide and hydrogen sent from a CO gas remover with oxygen in air sent from an air compressor (16). Thus, an electrode reaction for exchanging electrons between the anode and the cathode is performed. Then, electric power is obtained by converting ions generated when hydrogen and oxygen are combined into electric charges of the cathode and the anode.

Although the figure shows that water generated by this reaction is discarded, this water is collected and reformed.
It may be supplied to (12).

The hot water storage tank (2) is provided with a heating pipe (18) for heating water in the tank (2) using waste heat of the fuel cell (1). ) Are arranged in the fuel cell (1). The heating pipe (18) includes a heating section (18a) to which the exhaust heat of the fuel cell (1) is given, and a heating pipe (18).
A pump (18b) for circulating water or hot water therein is provided. When the water circulates through the heating pipe (18),
By passing through (18a), heat is given to water from the fuel cell (1).

The battery body (15) is connected to an output voltage (for example, DC1).
For example, 140 V with direct current from 5 V to DC 60 V)
Through a DC / DC converter (3) that boosts the voltage to about a level, an inverter (4) that converts 140 V DC to 100 V AC, and a system breaker (5) that has a function to detect reverse power flow. 6) is connected to the service line (7) for power to the home. The system circuit breaker (5) is configured to prevent reverse power flow and, if reverse power flow occurs, to detect reverse power flow and cut off current.

DC / DC converter (3) and inverter
A direct-current electric heater (21) is connected between the heater and (4). The electric heater (21) is provided in the hot water storage tank (2), and is configured to heat water or hot water in the tank (2).

This fuel cell power generation system always has a constant power (for example, 1K
w). When the power consumption in the home exceeds the power generation, the shortage is supplemented by the commercial power, while when the power consumption is less than the power generation, the electric heater (21) is driven by the surplus power. It is configured to be.

-Operation- Next, the operation of the fuel cell power generation system during power generation will be described.

First, the sulfur component of the city gas is removed in the desulfurizer (11), and the gas is sent to the reformer (12). In the reformer, the cathode exhaust gas and the anode exhaust gas from the battery body (15) and the compressed air from the air compressor (16) are mixed, heated by the burner (17) and burned. Then, the city gas and water are heated and reacted in the presence of a catalyst (not shown) provided in the reformer (12), and a reformed gas mainly containing carbon dioxide and hydrogen is generated.

Although the reformed gas contains carbon monoxide as described above, the carbon monoxide component is reduced in the shift converter (13). Further, after oxidizing and removing carbon monoxide in the CO gas remover (14), a mixed gas of carbon dioxide and hydrogen is supplied to the battery body (15). In the battery body (15), hydrogen sent from the CO gas remover (14) and oxygen in the compressed air sent from the air compressor (17) are combined, and ions generated at that time are combined. Electric power is obtained by being converted into the electric charges of the cathode and the anode.

The water in the hot water storage tank (2) is
When circulating in (18), it is heated by the exhaust heat of the fuel cell (1) in the heating section (18a).

On the other hand, the electric power generated by the battery body (15)
The DC / DC converter (3) boosts the voltage to 140 V DC and the inverter (4) converts it to AC 100 V, and then supplies it to the home via a system breaker (5) for consumption.

The power consumption in the home is
When the amount of power generation in (1) is exceeded, the shortfall is supplemented by commercial power. On the other hand, when the power consumption is smaller than the power generation amount, the surplus power is supplied to the electric heater (21) for the hot water storage tank (2) because the reverse power flow is prevented by the system breaker (5). Therefore, when the power consumption is smaller than the amount of power generation, the water or hot water in the hot water storage tank (2) is heated by using the electric heater (21) together with the exhaust heat of the fuel cell (1).

-Effects of Embodiment- In a home provided with the fuel cell power generation system of this embodiment,
Commercial power can be used in combination if the power consumption is higher than the power generated by the fuel cell (1), while if the power consumption is lower than the power generated by the fuel cell (1), the fuel can be used. While the water in the hot water storage tank (2) is heated by the exhaust heat of the battery (1), the water in the hot water storage tank (2) can be heated and kept warm using the surplus power. For this reason, surplus power can be used effectively and reverse power flow to the transmission line of commercial power can be prevented.

Further, since the reverse power flow can be prevented without changing the power generation amount of the fuel cell (1), the control is easy because the power generation amount of the fuel cell (1) is fixed. . Further, it is not necessary to provide control devices such as various valves and temperature sensors in order to change the amount of power generation by reducing the amount of gas or the amount of water, thereby preventing an increase in system cost. .

A DC electric heater is provided in the hot water storage tank (2).
Using (21), DC power generated by the fuel cell (1) is supplied to the electric heater (21) before it is converted to AC.
It is possible to prevent a decrease in efficiency due to conversion from DC to AC.

[0047]

Other Embodiments of the Invention The present invention may be configured as follows with respect to the above embodiment.

For example, the electric heater (21) can also be used as an anti-freezing heater provided in the hot water storage tank (2) in a cold region or the like. By doing so, an electric heater (21) dedicated to heating the hot water storage tank (2) becomes unnecessary, and the cost can be reduced.

Further, in the above embodiment, the system breaker (5) having the function of detecting the reverse power flow and the function of interrupting the current when the reverse power flow occurs is used. A reverse power flow prevention device that only prevents power flow may be used. In other words, if even the reverse power flow is always prevented, the surplus power is consumed by the electric heater, so that a reverse power flow prevention device having a simpler structure than the system circuit breaker can be used. In the above embodiment, a system breaker is used as a more reliable safety device.

In the above embodiment, an example in which the power generation system of the present invention is applied to a home has been described.
Of course, it can be applied to places other than the home.

The fuel cell (1) may use a fuel other than hydrogen, such as alcohol, phosphoric acid, carbon monoxide, etc., and supply only oxygen instead of air as an oxidant. You may do so.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a device configuration of a fuel cell power generation system according to an embodiment of the present invention.

[Explanation of symbols]

 (1) Fuel cell (2) Hot water storage tank (3) DC / DC converter (4) Inverter (5) System breaker (6) Commercial power supply (7) Power service line (8) City gas supply source (11) Desulfurizer (12) Reformer (13) Transformer (14) CO gas remover (15) Battery (16) Air compressor (17) Burner (18) Heating pipe (18a) Heating section (18b) Pump (21) Electric heater

Continued on the front page (72) Inventor Shuji Ikegami 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries, Ltd. Sakai Seisakusho Kanaoka Factory F-term (reference) 5H027 AA02 BA01 BA16 BA19 DD06 KK52 MM21 MM26

Claims (5)

[Claims] A fuel cell (1) and a hot water storage tank (2) to which exhaust heat of the fuel cell (1) is given, wherein electric power generated by the fuel cell (1) is used alone or together with commercial electric power. A fuel cell power generation system configured to be usable, wherein a hot water storage tank (2) is provided with an electric heater (21) supplied with electric power generated by the fuel cell (1). . 2. The fuel cell power generation system according to claim 1, wherein the electric heater is driven by supplying surplus power when the power consumption is smaller than the power generation of the fuel cell. 3. The fuel cell power generation system according to claim 1, wherein the fuel cell (1) is controlled so that the amount of power generation is constant. 4. The fuel cell power generation system according to claim 1, wherein a direct current generated by the fuel cell is supplied to the electric heater. 5. The electric heater (21) is constituted by an anti-freezing heater provided in the hot water storage tank (2).
5. The fuel cell power generation system according to any one of items 4 to 4.