JP2001065975A - Cogeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cogeneration system which can supply hot water at a set temperature in a stable manner. SOLUTION: A heat exchanger 2 is provided for a hot water storage tank 1 to effect recovery of waste heat by effecting heat exchange with water in the tank 1, while hot water stored in the tank 1 is supplied through a temperature raising means 3 whose heating capacity is variable. A mixing means 4, wherein cooled water is fed and mixed into the hot water sent from the tank 1 to the temperature raising means 3, is provided. When the hot water of the tank 1 has a temperature higher than a set temperature, by mixing the cooled water to lower the temperature of the hot water so that water of the set temperature can be supplied. If the temperature of the hot water of the tank 1 is slightly lower than the set temperature, the mixing ratio of cooled water is raised to lower the temperature of the hot water, which water is fed to the temperature raising means 3 to heat it using a heating capacity of lower limit of the means 3, whereby the hot water can be heated to the set temperature and supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cogeneration system which generates electric power by using a generator such as a fuel cell or a gas engine, and obtains hot water and supplies hot water.

[0002]

2. Description of the Related Art A cogeneration system has been put into practical use in which a fuel cell or a gas engine is used to generate electric power, and water is heated by using waste heat generated during the electric power generation to supply hot water. ing. As a cogeneration system, there is a cogeneration system provided with a hot water tank for storing hot water, and provided with a heat exchanger for exchanging heat between water in the hot water tank and waste heat generated during power generation. In such a cogeneration system that supplies hot water, since the temperature of tap water or the like supplied to the hot water tank varies with the season, the temperature of the hot water in the hot water tank also varies with the season, and the amount of hot water and the amount of exhaust heat The temperature of the hot water in the hot water tank also fluctuates depending on the generation amount. For this reason, it is difficult to supply hot water at a constant hot water temperature set by the user.

Therefore, in Japanese Patent Application Laid-Open No. 8-28955, hot water in a hot water storage tank is heated to a predetermined constant temperature and supplied. FIG. 2 shows an example thereof.
1 is a hot water storage tank, 2 is a heat exchanger, 15 is a generator, 16 is a cooling tower, and 17 is an exhaust heat recovery line between the generator 15 and the heat exchanger 2. The hot water storage tank 1 is supplied with water from a water supply line 18, and the water supplied to the heat exchanger 2 exchanges heat with the waste heat from the generator 15 in the heat exchanger 2,
Heated. A hot water supply line 19 is connected to the hot water storage tank 1, and a hot water tap 20 is provided at a leading end of the hot water supply line 19. In the middle of the hot water supply line 19, a temperature raising means 3 formed by a boiler, a heat pump or the like is provided, and a bypass line 21 for short-circuiting and connecting the hot water storage tank 1 and the hot water tap 20 is connected. The hot water heated by the heat exchanger 2 and stored in the hot water storage tank 1 is supplied to a hot water tap 20 through a hot water supply line 19.
When the water temperature detected in step (1) is equal to or higher than the predetermined set temperature, the hot water in the hot water storage tank 1 is supplied to the hot water tap 20 through the bypass line 21 by switching the three-way valve 23.
When the water temperature detected by the water temperature detection sensor 22 is lower than a predetermined set temperature, the hot water in the hot water storage tank 1 is supplied to the temperature raising means 3 by switching the three-way valve 23, and the temperature is raised to the predetermined temperature by the temperature raising means 3. Then, the hot water is supplied to hot water tap 20. In this way, hot water having a temperature lower than the predetermined temperature is not supplied, and the usability is improved.

[0004]

However, in FIG. 2, when the temperature of the hot water stored in the hot water storage tank 1 is lower than a predetermined set temperature, the hot water is heated to the set temperature by the temperature raising means 3 to supply hot water. However, if the temperature of the hot water stored in the hot water storage tank 1 is higher than a predetermined set temperature, the hot water temperature cannot be adjusted, and the hot water is supplied at a high water temperature. Is not good.

A heating source having a variable heating capacity, such as a boiler or a heat pump, which is usually used as the temperature raising means 3, comprises:
There is a lower limit in the heating control range. For example, in the case of the hot water heater “RN-A524RFW” manufactured by Osaka Gas Co., Ltd., there is a control lower limit associated with the control of the gas burner. It is between issues. Therefore, when the temperature of the hot water in the hot water storage tank 1 is slightly lower than the set temperature,
, The temperature of the hot water may exceed the set temperature even if the heater is heated at the lower limit capacity. In this case, it is necessary to heat the hot water by the temperature raising means 3 and supply hot water exceeding the set temperature. ,
Either hot water with a temperature lower than the set temperature is supplied without operating the temperature raising means 3. That is, taking this water heater as an example, on / off control of whether to perform heating at the lower limit of No. 2.5 or no heating is performed, and there is a problem that the temperature of the hot water becomes unstable. .

The present invention has been made in view of the above points, and has as its object to provide a cogeneration system capable of stably supplying hot water at a set temperature.

[0007]

According to a first aspect of the present invention, there is provided a cogeneration system comprising: a hot water tank;
Cogeneration system in which a heat exchanger 2 for exchanging heat with water in the tank and recovering waste heat is provided, and hot water stored in a hot water storage tank 1 is supplied through a heating means 3 having a variable heating capacity. , Characterized in that mixing means 4 is provided between the hot water tank 1 and the temperature raising means 3, which is capable of supplying cold water to hot water sent from the hot water tank 1 to the temperature raising means 3 and mixing the same. is there.

According to a second aspect of the present invention, in the first aspect, a first measuring means 5 for measuring a flowing water amount and a water temperature is provided between the mixing means 4 and the temperature raising means 3, and the first measuring means is provided. The ratio of hot water to cold water mixed by the mixing means 4 is controlled based on the amount of flowing water and the water temperature measured in 5.

According to a third aspect of the present invention, in the first or second aspect, a second measuring means 6 for measuring a flowing water amount and a water temperature is provided between the hot water tank 1 and the mixing means 4,
A third measuring means 7 for measuring a flowing water amount and a water temperature of the cold water supplied to the mixing means 4 is provided, and based on the flowing water amounts and the water temperatures measured by the second and third measuring means 6 and 7, the mixing means 4 is provided. And controlling the ratio of hot water and cold water to be mixed.

According to a fourth aspect of the present invention, in the third aspect, there is provided a fourth measuring means for measuring the temperature of the hot water stored in the hot water storage tank, and the water temperature measured by the fourth measuring means is provided. , The ratio of hot water and cold water mixed by the mixing means 4 at the start of hot water supply is controlled.

[0011]

Embodiments of the present invention will be described below.

FIG. 1 shows an example of an embodiment of the present invention, and the embodiment of FIG. 1 shows a cogeneration system for supplying hot water using a fuel cell 10 as a generator. The fuel cell 10 has a reformer 26 that generates a hydrogen-rich reformed gas from the raw fuel.
The reformer 26 is supplied with a raw fuel such as a hydrocarbon-based gas, liquid, or solid, or an alcohol fuel such as a methanol-based fuel through a raw fuel introduction passage 27, and converts the raw fuel and steam into steam. It is formed so as to generate a hydrogen-rich reformed gas by a hydrogen reaction. Examples of the hydrocarbon-based gas include methane gas, propane gas, butane gas, and liquefied petroleum gas. Examples of the hydrocarbon-based liquid include kerosene, light oil, and gasoline. Examples of the alcohol fuel include methanol and ethanol. For home use, a gas or kerosene containing propane gas, butane gas, or methane gas as a main component is preferable in terms of availability and handleability. A reaction in which a natural gas (mainly methane gas) is used as a raw fuel to generate a hydrogen-rich reformed gas by a steam reforming reaction in the reformer 26 will be described below.

CH ₄ + 2H ₂ O → 4H ₂ + CO _{2 The} above-mentioned steam reforming reaction requires a catalytic reaction at a high temperature. Therefore, the inside of the reformer 26 is heated to a predetermined temperature (600 to 7).
(00 ° C.). The heating method is not particularly limited, but heating can be performed by burning natural gas or the like as a raw fuel. The exhaust gas generated by this combustion is exhausted from an exhaust path 28, and the hydrogen-rich reformed gas generated in the reformer 26 is sent out from a gas supply pipe 29.

The reformed gas generated by the reformer 26 as described above is supplied from the gas supply pipe 29 to the anodes of a plurality of cells 30 constituting the fuel cell 10, and the cathode contains air containing oxygen. By supplying, power is generated from hydrogen in the reformed gas and oxygen in the air. As the fuel cell 10, there are various types such as a phosphoric acid type, a molten carbonate type, and a solid polymer type. However, in a cogeneration system using only hot water supply and power generation without using steam, a solid high-temperature system operating at a relatively low temperature is used. Molecular form is preferred. The electricity generated in this way is transmitted to various external electric devices via the transmission line 31. The power transmission may not be performed directly to the electric equipment, but may be performed by combining an inverter and the like.

When power is generated in the fuel cell 10 as described above, waste heat is generated from the reformer 26 and the cells 30 of the fuel cell 10, and a heat exchange means for recovering the waste heat is provided. There are various heat exchange means. For example, a heat exchanger 32 attached to each cell 30 of the fuel cell 10 and a heat exchanger 33 attached to the exhaust path 28 of the reformer 26 are used. A heat medium circulating path 34 is connected between the heat exchangers 32 and 33, and a heat medium circulating pump 35 circulates the heat medium.

On the other hand, the hot water tank 1 is provided with a hot water circulation path 36 connected to the upper end and the lower end thereof.
The hot water in the hot water storage tank 1 is circulated. The heat exchanger 2 is formed by disposing the meandering heat exchange part 36a of the hot water circulation path 36 and the meandering heat exchange part 34a of the heat medium circulation path 34 in the casing. The heat exchangers 2, 32, and 33 are not particularly limited as long as they perform heat exchange between fluids.

The hot water storage tank 1 is further provided with a water supply port 40 at a lower end thereof, and the water supply port 40 is provided with a water supply passage 4 such as a water supply pipe.
1 is connected so that cold water such as tap water is supplied into the hot water storage tank 1. A hot water supply port 42 is provided at the upper end of the hot water storage tank 1, and a hot water supply path 43 is connected to the hot water supply path 43. The hot water supply path 43 is connected to the temperature raising means 3. The temperature raising means 3 serves as an auxiliary heating source of hot water in the hot water storage tank 1 and has a variable heating capacity such as a boiler using gas or kerosene, an electric heater, or a heat pump. It is formed of a material that can be heated to heat the hot water so as to change the temperature to a predetermined set temperature.

In the cogeneration system formed as described above, when the heat medium circulating pump 35 is operated to pass the heat medium in the heat medium circulation path 34 through the heat exchangers 32 and 33, the heat medium is The heat is exchanged with the exhaust heat of the exhaust cell 28 of the cell 30 and the reformer 26 and heated. On the other hand, when the hot water circulation pump 37 is operated to circulate the hot water (water) in the hot water storage tank 1 through the hot water circulation path 36, the hot water is exchanged with the exhaust heat as described above, and the heated heat medium circulates. The heat is exchanged with the heat medium in the passage 34 in the heat exchanger 2 to increase the temperature. In this way, the hot water in the hot water storage tank 1 recovers waste heat when the fuel cell 10 generates electric power, exchanges heat and raises the temperature, and is stored in the hot water storage tank 1 as high-temperature hot water. The hot water stored in the hot water storage tank 1 is supplied by supplying cold water from the water supply port 40 into the hot water storage tank 1 to be pushed out of the hot water supply port 42 into the hot water supply path 43 and supplied with hot water. When the temperature is lower than the predetermined temperature, the temperature is raised to a predetermined set temperature by the temperature raising means 3 and then supplied to a faucet or the like.

Here, a hot water supply path 44 such as a water supply pipe is connected to a hot water supply path 43 between the hot water storage tank 1 and the temperature raising means 3.
The hot water supplied from the hot water storage tank 1 to the hot water supply channel 43 is supplied to the hot water supply channel 44.
And cold water such as tap water supplied from the company to mix hot and cold water. The mixing means 4 may be formed by providing a valve capable of controlling the amount of flowing water in each of the hot water supply path 43 and the water supply path 44. However, in order to be able to freely set the hot water supply amount with a faucet or the like, the mixing means 4 is required.
It is preferable to form a mixing means 4 by providing a mixing valve at the connection between the water supply path 44 and the water supply passage 44.

The mixing means 4 controls the mixing ratio of hot water and cold water by mixing the mixing means 4 with the heating means 3.
This can be performed by the first measuring means 5 including the water temperature sensor 5a and the flow rate sensor 5b provided in the hot water supply passage 43. That is, the temperature of the hot water mixed with the cold water by the mixing means 4 is measured by the water temperature sensor 5a and the flow rate of the hot water is measured by the flow rate sensor 5b. For example, when the measured temperature of the hot water is higher than the set temperature, the temperature is measured. By increasing the supply amount of cold water from the water supply passage 44 or decreasing the supply amount of hot water from the hot water supply port 42 according to the flow rate, the mixing ratio of the cold water is increased, and the measured temperature of the hot water is set. When the temperature is lower than the temperature, the mixing ratio of the hot water is increased by decreasing the supply amount of the cold water from the water supply passage 44 or increasing the supply amount of the hot water from the hot water supply port 42 according to the temperature and the flow rate. Things.

The mixing ratio of the hot water and the cold water by the mixing means 4 is controlled in addition to the hot water tank 1 and the mixing means 4.
A second measuring means 6 including a water temperature sensor 6a and a flow rate sensor 6b provided in the hot water supply passage 43;
4 can be performed by the third measuring means 7 including the water temperature sensor 7a and the flow rate sensor 7b. That is, the temperature of the hot water supplied from the hot water storage tank 1 is measured by the water temperature sensor 6a, the flow rate of the hot water is measured by the flow rate sensor 6b, and the temperature of the cold water supplied from the water supply passage 44 is measured by the water temperature sensor 7a. At the same time, the flow rate of the hot water is measured by the flow rate sensor 7b, and the temperature of the hot water mixed by the mixing means 4 is calculated from the temperature and the flow rate of the hot water and the temperature and the flow rate of the cold water, so that the mixing ratio of the hot water and the cold water is calculated. It can be sought and controlled. In this case, when the flow sensor 5b is used together, one of the flow sensors 6b and 7b can be omitted. This is because the flow rate of the hot water from the hot water storage tank 1 can be obtained without the flow rate sensor 6b by subtracting the measurement value of the flow rate sensor 7b from the measurement value of the flow rate sensor 5b. This is because the flow rate of the chilled water from the water supply passage 44 can be obtained without the flow rate sensor 7b by subtracting the measurement value of the sensor 6b. Conversely, if the flow sensors 6b and 7b are provided, the flow rate supplied to the temperature raising means 3 can be obtained without the flow sensor 5b.

A fourth measuring means 8 comprising a temperature sensor 8a is provided near the hot water supply port 42 in the hot water storage tank 1 so as to measure the temperature of the hot water near the hot water supply port 42.
At the start of hot water supply, the mixing ratio of the hot water and the cold water to be mixed by the mixing means 4 is controlled based on the temperature of the hot water measured by the temperature sensor 8a, and after the hot water supply is started, the hot water storage tank 1 and the mixing means The mixing ratio between the hot water and the cold water to be mixed by the mixing means 4 is controlled based on the temperature of the hot water measured by the water temperature sensor 6a provided in the hot water supply passage 43 between the hot water supply channels 43 at the start of hot water supply. It is possible to accurately control the mixing ratio of hot water and cold water. That is, at the time of starting hot water supply, the temperature of the hot water in hot water supply path 43 is lower than the temperature of the hot water stored in hot water storage tank 1.
If the mixing ratio of hot water and cold water is controlled based on the temperature of hot water in the hot water supply, control cannot be performed with an accurate mixing ratio. By controlling the mixing ratio of the cold water, the control can be performed with an accurate mixing ratio.

As described above, in controlling the mixing ratio of the hot water and the cold water to be mixed by the mixing means 4 based on the measurement results by the measuring means 5 to 8, the temperature of the hot water mixed with the cold water is set by the user. The mixing ratio is controlled so as to approach the temperature. However, as described above, the heating means 3 having a variable heating capacity has a lower limit in the heating control range. For example, Osaka Gas Co., Ltd.
In the case of the hot water heater "RN-A524RFW", the control range is between 2.5 and 24, and when the hot water in the hot water storage tank 1 is slightly lower than the set temperature, heating is performed at the lower limit capacity of 2.5. Even if it is performed, the temperature of the heated hot water may exceed the set temperature. Therefore, in this case, the amount of cold water supplied from the water supply passage 44 to the hot water supply passage 43 is controlled to increase the mixing ratio of the cold water, and the temperature of the hot water supplied to the temperature raising means 3 is reduced. By heating this hot water with the lower limit heating capacity of the temperature raising means 3, the temperature of the heated hot water becomes the set temperature. For example, when the set temperature of the hot water to be supplied is 42 ° C., the temperature of the hot water supplied to the temperature raising means 3 is 40 ° C., and the amount of flowing water is 5 liter / min.
, The heating amount required in the temperature raising means 3 is 0.7 k
W. On the other hand, if the lower limit heating capacity of the temperature raising means 3 is No. 2.5, the heating amount is 4.4 kW.
The temperature of the hot water heated by the temperature raising means 3 exceeds 42 ° C. Therefore, in this case, if the ratio of the cold water mixed by the mixing means 4 is increased to control the temperature of the hot water supplied to the temperature increasing means 3 to 29.5 ° C., the lower limit of the temperature increasing means 3 4 set the temperature of the hot water heated by the ability
It can be 2 ° C. In this manner, hot water can be supplied stably at the set temperature.

If the temperature of the hot water supplied to the temperature raising means 3 is low enough not to exceed the set temperature even if it is heated within the heating control range of the temperature raising means 3, the same control as described above is not performed. Alternatively, heating by the temperature raising means 3 may be performed.

[0025]

As described above, according to the first aspect of the present invention, a hot water tank is provided with a heat exchanger for exchanging heat with water in the hot water tank to recover exhaust heat, and the hot water stored in the hot water tank is provided. In a cogeneration system in which hot water is supplied via a heating means having a variable heating capacity, between the hot water tank and the heating means, cold water can be supplied to hot water sent from the hot water tank to the heating means and mixed. Since the mixing means is provided, if the hot water in the hot water tank is higher than the set temperature, the temperature can be lowered by mixing cold water to supply hot water at the set temperature. When the temperature is slightly lower than the set temperature, the mixing ratio of the cold water is increased and the temperature is lowered and supplied to the temperature raising means, and the hot water is heated at the lower limit heating capacity of the temperature raising means to reach the set temperature. Warm up hot water and supply hot water It is intended that becomes possible, as it can be stably hot water hot water set temperature.

According to a second aspect of the present invention, there is provided a first measuring means for measuring a flowing water amount and a water temperature between the mixing means and the temperature increasing means, wherein the flowing water amount and the water temperature measured by the first measuring means are provided. , The ratio of hot water and cold water mixed by the mixing means is controlled, so that the ratio of hot water to cold water can be accurately controlled according to the measured flowing water amount and water temperature.

According to a third aspect of the present invention, there is provided a second measuring means for measuring the amount of flowing water and the temperature of the water between the hot water tank and the mixing means, and measuring the amount of flowing water and the temperature of the cold water supplied to the mixing means. The third measuring means is provided, and the ratio of hot water and cold water mixed by the mixing means is controlled based on the amount of flowing water and the water temperature measured by the second and third measuring means. The ratio of hot water to cold water can be accurately controlled according to the amount of flowing water and the water temperature.

According to a fourth aspect of the present invention, there is provided a fourth measuring means for measuring the temperature of the hot water stored in the hot water tank, and mixing at the start of hot water supply based on the water temperature measured by the fourth measuring means. Since the ratio of hot water and cold water to be mixed is controlled by the means, it is possible to accurately control the mixing ratio of hot water and cold water at the start of hot water supply according to the temperature of the hot water in the hot water storage tank. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot water storage tank 2 Heat exchanger 3 Heating means 4 Mixing means 5 First measuring means 6 Second measuring means 7 Third measuring means 8 Fourth measuring means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuichiro Yasuda 1048 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd. F-term (reference) 3L025 AC01

Claims (4)

[Claims] 1. A hot water tank is provided with a heat exchanger for exchanging heat with hot water in the hot water tank to recover exhaust heat, and hot water stored in the hot water tank is supplied to the hot water tank via a heating means having a variable heating capacity. In the cogeneration system, the mixing means is provided between the hot water tank and the temperature raising means, the mixing means being capable of supplying cold water to hot water sent from the hot water tank to the temperature raising means and mixing. Cogeneration system. 2. A method according to claim 1, further comprising: first measuring means for measuring a flowing water amount and a water temperature between the mixing means and the temperature increasing means, and the mixing means based on the flowing water amount and the water temperature measured by the first measuring means. The cogeneration system according to claim 1, wherein a ratio of hot water and cold water to be mixed is controlled. And a second measuring means for measuring a flowing water amount and a water temperature between the hot water storage tank and the mixing means,
A third measuring means for measuring a flowing water amount and a water temperature of the cold water supplied to the mixing means, and based on the flowing water amount and the water temperature measured by the second and third measuring means, hot water and cold water mixed by the mixing means. The cogeneration system according to claim 1, wherein the ratio is controlled. And a fourth measuring means for measuring a temperature of the hot water stored in the hot water storage tank, wherein the hot water is mixed with mixing water at the start of hot water supply by mixing means based on the water temperature measured by the fourth measuring means. The cogeneration system according to claim 3, wherein the ratio of the chilled water is controlled.