JP2005267944A - Fuel cell system, and stop control method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system by collecting heat for effective operation of the same, and to provide a stop control method of the same. <P>SOLUTION: The fuel cell body 3 generates electric power by using a fuel and an oxidant gas, and the heat generated at the power generation is transferred to a heat exchanger 4, by circulating cooling water, and the water supplied to the heat exchanger is turned into hot water, and the heat is collected in a hot water tank 5. A controller 10 calculates an estimated volume of the water which may be used until next start of the system by the user and compares it with present volume of hot water in the hot water tank 5, when the system is stopped. When the present volume is smaller than the estimated volume, the heat generated at the fuel cell body 3 is turned into hot water via the heat exchanging device 4 and collected in the hot water tank 5, by driving a cooling water pump 8 and a heat collection pump 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a hot water storage tank and capable of recovering heat generated in the fuel cell main body to the hot water storage tank via a battery cooling water system, and controlling the implementation of heat recovery when the fuel cell is stopped. The present invention relates to a system and its stop control method.

In a fuel cell system, high-temperature exhaust heat is generated by a chemical reaction during power generation, and thus thermal energy is recovered in the form of hot water or steam. As a fuel cell system for performing such heat recovery, for example, the one disclosed in Patent Document 1 below can be cited. FIG. 3 is a block diagram showing the fuel cell system described in the document.
In the fuel cell main body 100, power generation is performed using the hydrogen-rich reformed gas generated by the fuel reformer 120 and the air (oxidant gas) sent from the blower 130. The heat generated in the fuel cell main body 100 during power generation is conveyed to the outside by the cooling water flowing through the cooling pipe 101, and the heat obtained from the cooling water flows through the pipe 103 via the heat exchanger 102. To be stored in the hot water storage tank 104 as hot water.

  When the power generation of the fuel cell main body 100 is terminated, the fuel cell main body 100 does not generate heat at the same time as the power generation is stopped. Therefore, until now, the cooling water pump 105 and the city water pump 106 have also stopped carrying operations, City water circulation was also stopped. However, in this fuel cell system, since the fuel cell main body 100 itself that has stopped generating power remains at a high temperature for a while, it is provided in the cooling pipe 101 in order to recover the heat held by the fuel cell main body 100. The heat generated by the fuel cell is efficiently recovered by operating the pumps 105 and 106 until the temperature detector 111 falls below a predetermined threshold value.

By the way, a fuel cell installed in a general household does not require electric energy or heat energy for 24 hours. Therefore, it is appropriate to stop the operation of the fuel cell system when the resident goes out or goes to bed. On the other hand, the required amount of electricity or heat may rise sharply, but if the fuel cell system is started suddenly, hydrogen generation by the reformer cannot catch up, resulting in the need for residents. However, it is not possible to supply a sufficient amount of electric power or heat, and it is necessary to purchase insufficient electric power from an electric power company. In addition, an auxiliary hot water heater must be separately prepared. Therefore, in the following Patent Document 2, a system for controlling the operation of the fuel cell system based on the consumer's behavior pattern is proposed.
JP 2002-367646 A (page 3-5, FIG. 3) JP 2002-190309 A (page 4-7, FIG. 1)

  However, when the operation of the fuel cell system is stopped, it is not always a preferable control method to always recover heat as in Patent Document 1. For example, a large amount of hot water is used even in general households in winter, so it is sufficient to recover heat when the system is stopped and store hot water in hot water storage tank 104. However, in summer, heat consumption is reduced because the amount of hot water used is reduced. Will store extra hot water. On the other hand, when heat recovery is performed when the system is stopped, the temperature of each part of the fuel cell main body 100 is lowered. Therefore, when starting the next time, the recovered heat in the hot water storage tank 104 is used to prevent flooding. Or the temperature of the fuel cell main body 100 must be increased with a heater or the like, which is inefficient.

  On the other hand, in Patent Document 2, since the operation of the fuel cell system is controlled based on the consumer's behavior pattern, the power shortage that occurs when the power or heat output amount cannot catch up with the power consumption or heat consumption by the consumer, Problems such as running out of hot water are eliminated. And since it is controlled based on an action pattern, it is thought that extra hot water is not stored. However, in Patent Document 2, since control is performed so as not to cause power shortage and hot water shortage, when the temperature of each part of the fuel cell main body 100 is lowered due to recovery at the time of system stoppage, startup when the operation is restarted next time Energy is not considered.

  Therefore, an object of the present invention is to provide a fuel cell system that performs heat recovery for efficiently operating the fuel cell system, and a stop control method thereof.

  The fuel cell system of the present invention is connected to a fuel cell main body that generates power using hydrogen-rich fuel and oxidant gas, and the fuel cell main body and a cooling pipe that circulates cooling water using a cooling water pump. Past usage conditions such as heat exchangers, hot water storage tanks connected via heat recovery pipes that feed water and hot water with the heat exchangers and heat recovery pumps, and power consumption and hot water usage by users by time A controller for storing the usage data to be shown and controlling the driving of the cooling water pump and the heat recovery pump, and a first sensor for measuring the amount of hot water stored in the hot water storage tank, Based on the measurement result from the first sensor and the use data, when the system is stopped, the current hot water storage amount in the hot water tank and the user's hot water use estimation until the next system startup When the amount of stored hot water is less than the estimated amount of user hot water used, the cooling water pump and the heat recovery pump are driven to generate heat generated in the fuel cell main body. In this case, the hot water storage tank is used to change the water into hot water.

Further, in the fuel cell system of the present invention, the hot water storage tank is provided with a second sensor for measuring the hot water temperature, and the controller is configured to perform the second operation even when the current hot water storage amount is larger than the estimated user hot water usage amount. When the lower temperature of the hot water stored in the hot water tank measured from the sensor is lower than a predetermined temperature, the cooling water pump and the heat recovery pump are driven to heat the fuel cell main body with the heat exchanger. Instead of this, the hot water storage tank is used for collection.
The fuel cell system of the present invention is characterized in that the first sensor and the second sensor have a plurality of thermocouples arranged in the height direction of the hot water tank.
Furthermore, the fuel cell system of the present invention has an outside air temperature sensor for measuring the outside air temperature, and the controller increases the heat recovery energy that can be recovered from the fuel cell body when the system is stopped and the temperature of the fuel cell body at the next start-up. Compared with the reduction amount of the startup energy required to make the heat recovery, the heat recovery is not performed when the heat recovery energy is smaller.

  On the other hand, the fuel cell system stop control method according to the present invention generates power using fuel and oxidant gas in the fuel cell main body, and circulates cooling water through the heat generated during power generation in the fuel cell main body. This is a fuel cell system in which the water sent to the heat exchanger is converted into hot water and heat is recovered in the hot water storage tank. When the system is stopped, the amount of hot water currently stored in the hot water storage tank And the estimated amount of hot water used by the user until the next system start-up, and if the amount of hot water stored is less than the estimated amount of hot water used by the user, the heat generated in the fuel cell body is heated via the heat exchanger. It is characterized in that it is collected in a hot water tank instead of.

In addition, the fuel cell system stop control method according to the present invention holds usage data indicating past usage conditions such as hourly power consumption and hot water usage by the user, and starts the next system based on the usage data. It is characterized in that the estimated amount of hot water used by the user is obtained and compared with the current amount of hot water stored in the hot water tank.
Further, the fuel cell system stop control method according to the present invention provides a hot water storage tank even when the current hot water storage amount in the hot water storage tank is larger than the estimated amount of hot water usage of the user required until the next system activation. When the temperature of the hot water stored in the battery is lower than a predetermined temperature, the heat of the fuel cell main body is changed to hot water through a heat exchanger and recovered in the hot water storage tank when the system is stopped.
Furthermore, the fuel cell system stop control method according to the present invention includes a heat recovery energy that can be recovered from the fuel cell main body when the system is stopped, and a startup energy reduction amount that is required to raise the temperature of the fuel cell main body at the next start-up. Is compared, and when the heat recovery energy is smaller, heat recovery is not performed.

  Therefore, according to the fuel cell system of the present invention, usage data indicating past usage conditions such as hourly power usage and hot water usage by the user is stored, and the driving of the cooling water pump and the heat recovery pump is controlled. It has a controller to calculate and compare the amount of hot water stored in the hot water tank when the system is shut down and the estimated amount of hot water used by the user until the next system startup. When the amount is small, the cooling water pump and the heat recovery pump are driven to convert the heat generated in the fuel cell main body into hot water via the heat exchanger and recovered in the hot water storage tank. Since heat is recovered when the amount of hot water stored in the tank is less than the estimated amount of user hot water used, it is possible to prevent hot water from running out, and when the amount of hot water stored in the hot water tank is sufficient at the time of stoppage, heat recovery is possible. Not because it has become possible to operate the next startup efficiently the fuel cell system by reducing the starting energy during.

  Further, in the fuel cell system stop control method according to the present invention, when the system is stopped, the current hot water storage amount in the hot water storage tank is compared with the estimated hot water usage amount of the user until the next system start-up, and the current hot water storage amount Is less than the estimated amount of user hot water used, the heat generated in the fuel cell body is converted into hot water via a heat exchanger and recovered in the hot water storage tank. Since heat is recovered when the amount is less than the estimated usage, it is possible to prevent running out of hot water, and heat recovery is not performed when the amount of hot water stored in the hot water tank is sufficient at the time of stoppage. As a result, the fuel cell system can be operated efficiently.

Next, a fuel cell system and a stop control method thereof according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the fuel cell system of the present embodiment.
The fuel cell system of the present embodiment has a fuel reformer 1 that generates hydrogen by a reforming reaction from city gas mixed with steam, and the hydrogen-rich reformed gas generated by the fuel reformer 1 And a fuel cell main body 3 that generates power using air (oxidant gas) fed from a blower (not shown). In addition to the reformed gas, the fuel sent to the fuel electrode of the fuel cell main body 3 includes pure hydrogen and a hydrogen-containing gas other than the reformed gas. In the direct methanol type, methanol may be supplied in liquid form. .

A condenser 2 is connected between the fuel reformer 1 and the fuel cell body 3 for recovering excess moisture in the reformed gas. Further, the fuel cell system is connected to a heat exchanger 4 for recovering heat generated in the fuel cell main body 3. That is, a cooling pipe 6 for flowing cooling water is connected between the fuel cell body 3 and the heat exchanger 4, and the cooling water is circulated between the fuel cell body 3 and the heat exchanger 4 in the cooling pipe 6. A cooling water pump 8 is provided.
Further, the fuel cell system is provided with a hot water storage tank 5 for storing hot water heated by heat recovered from the fuel cell main body 3, and a heat recovery pipe 7 is provided between the hot water storage tank 5 and the heat exchanger 4. Is connected. The heat recovery pipe 7 is also provided with a heat recovery pump 9 for circulating the water in the hot water tank 5.

  The fuel cell main body 3 obtains electric power from the reformed gas rich in hydrogen generated by the fuel reformer 1 and air supplied from a blower (not shown), and heat is also generated at that time. On the other hand, the reformed gas generated in the fuel reformer 1 is a gas rich in hydrogen by adding water to a power generation raw material such as city gas, and is heated by a burner and thus becomes hot and humid. Yes. Therefore, when the reformed gas from the fuel reformer 1 is sent to the fuel cell body 3 as it is, the temperature of the fuel cell body 3 is low, so that the saturated water vapor condenses and wets the electrolyte membrane excessively, causing flooding. Cause. For this reason, the reformer gas from the fuel reformer 1 is dropped by the condenser 2 and the temperature is lowered and supplied to the fuel cell main body 3.

  On the other hand, the operating fuel cell body 3 generates heat and the temperature rises, but at the time of startup, the temperature of the fuel cell body 3 itself is low. Therefore, in order to avoid flooding, the moisture in the reformed gas is dropped through the condenser 2 as described above. However, this is not sufficient, and the fuel cell body 3 must be warmed with a heater and requires energy. Therefore, in the fuel cell system of the present embodiment including the hot water tank 5, when hot water necessary for raising the temperature of the fuel cell main body 3 is in the hot water tank 5, without using a heater (not shown), Hot water is sent from the hot water tank 5 to the heat exchanger 4, and the heat is transmitted to the cooling water so that the temperature of the fuel cell body 3 is raised.

  During operation of the fuel cell system, heat generated in the fuel cell main body 3 is conveyed to the outside by cooling water flowing through the cooling pipe 6. That is, the heat generated in the fuel cell main body 3 is circulated between the fuel cell main body 3 and the heat exchanger 4 by driving the cooling water pump 8. At this time, the cooling water takes heat of the fuel cell main body 3 and transfers it to the heat exchanger 4 side. On the other hand, when the heat recovery pump 9 is driven to flow the heat recovery pipe 7 and water is sent to the heat exchanger 4, the heat exchanger 4 performs heat exchange and changes to hot water. Therefore, the heat generated in the fuel cell main body 3 is thus recovered as hot water and collected in the hot water storage tank 5. The hot water is used as it is at home, and is used as a heat source for raising the temperature of the fuel cell body 3 when starting the fuel cell system as described above.

  By the way, the fuel cell system of this embodiment has a controller 10 that controls the entire system, and the storage device stores a stop control program that controls heat recovery when the system is stopped. Further, a hot water storage tank sensor 11 is installed in the hot water storage tank 5, and the controller 10 can detect the hot water temperature together with the amount of hot water from this measurement signal. That is, as the hot water storage tank sensor 11 of the present embodiment, for example, a plurality of thermocouples arranged in the height direction of the hot water storage tank 5 can be considered. Thereby, the height of a molten metal surface can be measured with the measurement temperature of the thermocouple of each height with temperature measurement. In addition, an outside air temperature sensor 12 is installed in the system and is connected to the controller 11. The controller 11 is connected so as to be able to drive and control the cooling water pump 8 and the heat recovery pump 9 that circulate the cooling water in the cooling pipe 6 and flow the water to the heat recovery pipe 7 as described above. Yes.

In this fuel cell system, past usage conditions such as power consumption and hot water usage by the user are stored as usage data, and start / stop is automatically performed based on this usage data. It has become. The usage data is sequentially updated by the learning function of the controller 10 based on the usage status of the fuel cell system.
The stop control program, which is a feature of the present embodiment, also uses this use data to control driving of the cooling water pump 8 and the heat recovery pump 9 while referring to measurement signals from the hot water tank sensor 11 and the outside air temperature sensor 12. Is configured to do. Here, FIG. 2 is a diagram showing a flowchart of a stop control method executed by the stop control program.

The controller 10 predicts the current power demand and hot water demand from the usage data related to the hourly power usage and hot water usage (demand prediction), and automatically controls the start / stop of the fuel cell system.
Therefore, when a system stop command is issued from the demand prediction (S101), the supply of the reformed gas from the fuel reformer 1 to the fuel cell main body 3 is stopped and the power generation is stopped. At this time, a measurement signal is sent from the hot water storage tank sensor 11 of the hot water storage tank 5 to the controller 10, and the hot water storage amount at the time of stoppage is confirmed. On the other hand, the controller 10 obtains the amount of hot water in the hot water storage tank 5 used by the user from the stored use data until the next system startup.

  Therefore, when there is a system stop command, the current hot water storage amount in the hot water storage tank 5 is compared with the estimated user hot water usage amount until the next system activation (S102). If the current hot water storage amount is smaller than the user hot water usage estimated amount by this comparison (S102: NO), a drive signal is sent from the controller 10 to the cooling water pump 8 and the heat recovery pump 9 to recover heat. . That is, heat from the fuel cell main body 3 is taken by the cooling water flowing through the cooling pipe 6, and the water flowing through the heat recovery pipe 7 is changed into hot water by the heat exchanger 4 and sent to the hot water storage tank 5, thereby Is recovered (S111).

  If the current hot water storage amount is larger than the user hot water usage estimation amount (S102: YES), the lower temperature of the hot water stored in the hot water storage tank 5 is confirmed by the hot water storage tank sensor 11 (S103). When the comparison temperature is 50 ° C. and the hot water storage lower temperature is 50 ° C. or more (S103: NO), no drive signal is sent from the controller 10 to the cooling water pump 8 or the heat recovery pump 9, and the heat recovery is performed. Not performed (S112). This is because the temperature of the hot water stored in the hot water tank 5 is sufficient. That is, in this embodiment, when the hot water storage lower temperature is less than 50 ° C. (S103: YES), heat recovery for increasing the temperature of the hot water stored in the hot water storage tank 5 is performed under a certain condition (S104). To do.

Therefore, when the temperature of the hot water storage is lower than 50 ° C., the heat recovery energy (fixed value for each system) that can be recovered from the fuel cell body 3 by driving the heat recovery pump 9 or the like when the system is stopped, and the next activation The start-up energy reduction amount required to raise the temperature of the fuel cell main body 3 is sometimes compared (S104).
If the heat recovery is performed when the system is stopped, the remaining exhaust heat can be recovered. However, since the temperature of each part of the fuel cell main body 3 is lowered, the fuel cell main body 3 must be heated up at the next start-up, so the startup energy is increased. A lot is needed. On the other hand, if heat recovery is not performed when the system is stopped, the exhaust heat remains and the temperature of each part of the fuel cell main body 3 is prevented from decreasing. However, in the state where the time until the next start-up is long or the outside air temperature is low, the temperature of each part of the fuel cell body 3 is lowered even if heat recovery is not performed, and the start-up energy is required in the same way as when heat recovery is performed. Become.

Therefore, the controller 10 first creates a map based on the calculation from the heat capacity and the experimental data in addition to the outside air temperature measured by the outside air temperature sensor 12, and from the time until the next system start-up confirmed by the usage data. Natural heat dissipation is required. Even if the amount of heat remains in the fuel cell main body 3 without being recovered, it is reduced by natural heat dissipation. Therefore, the amount of startup energy reduction that is required for starting the system next time is obtained from the obtained amount of natural heat dissipation.
Therefore, when the hot water storage lower temperature is less than 50 ° C., the next startup energy reduction amount is compared with the heat recovery energy (S104), and if the heat recovery energy is smaller (S104: NO), the controller 10 No drive signal is sent to the cooling water pump 8 or the heat recovery pump 9 and heat recovery is not performed (S113). In this case, rather than heating the fuel cell body 3 using the heat recovery energy recovered at the time of starting the system, it is better to maintain the temperature of the fuel cell body 3 by the amount of exhaust heat left without being recovered, This is because the required starting energy can be suppressed.

  On the other hand, if the heat recovery energy is larger (S104: YES), a drive signal is sent from the controller 10 to the cooling water pump 8 and the heat recovery pump 9 to perform heat recovery (S114). In this case, since the time until the next system start-up is long or the outside air temperature is low, the fuel cell body 3 does not have enough heat to suppress the start-up energy when the system is next started by natural heat dissipation. This is because the waste heat of the fuel cell main body 3 can be effectively utilized if the heat is recovered and changed into hot water. That is, the temperature of the hot water in the hot water storage tank 5 whose bottom temperature is less than 50 ° C. can be raised, and the startup energy for raising the temperature of the fuel cell body 3 at the time of the next startup can be stored. is there.

Therefore, according to the fuel cell system and its stop control method described above, since the heat is recovered when the current hot water storage amount in the hot water storage tank 5 is smaller than the user hot water usage estimated amount, it is possible to prevent hot water shortage, Since heat recovery is not performed when the amount of hot water stored in the hot water storage tank 5 is sufficient at the time of stoppage, the fuel cell system can be operated efficiently by reducing the startup energy at the next startup.
Moreover, even when the amount of hot water stored in the hot water tank 5 is sufficient, the temperature of the hot water can be set to an appropriate value by measuring the lower temperature of the hot water and recovering heat. In particular, at that time, it is judged whether heat recovery should be performed by comparing the amount of reduction of heat recovery energy and start-up energy. In this respect also, the start-up energy is reduced and the fuel cell system is operated efficiently. Can now.

  The fuel cell system and the stop control method thereof according to the present invention are not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the fuel cell system.

It is the block diagram which showed the fuel cell system which performs the stop control method of this invention. It is the figure which showed the flowchart of the stop control method performed by a stop control program. It is a block diagram which shows the conventional fuel cell system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel reformer 2 Condenser 3 Fuel cell main body 4 Heat exchanger 5 Hot water storage tank 6 Cooling piping 7 Heat recovery piping 8 Cooling water pump 9 Heat recovery pump 10 Controller 11 Hot water storage tank sensor 12 Outside temperature sensor

Claims (8)

A fuel cell body that generates power using hydrogen-rich fuel and oxidant gas;
A heat exchanger connected to the fuel cell body and a cooling pipe for circulating cooling water by a cooling water pump;
A hot water tank connected through a heat recovery pipe that feeds water and hot water by the heat exchanger and a heat recovery pump;
A controller that stores usage data indicating past usage conditions such as power consumption and hot water usage by the user every hour, and controls the driving of the cooling water pump and the heat recovery pump;
A first sensor for measuring the amount of hot water stored in the hot water tank,
The controller calculates a current hot water storage amount in the hot water storage tank and an estimated hot water usage amount of the user until the next system start-up when the system is stopped based on the measurement result from the first sensor and the use data. If the current hot water storage amount is less than the estimated user hot water use amount, the heat generated by the fuel cell body is driven via the heat exchanger by driving the cooling water pump and the heat recovery pump. A fuel cell system, wherein the fuel cell system is adapted to be collected in the hot water tank instead of hot water. The fuel cell system according to claim 1, wherein
The hot water storage tank is provided with a second sensor for measuring the hot water temperature, and the controller is stored in the hot water storage tank measured from the second sensor even when the current hot water storage amount is larger than the estimated amount of user hot water usage. When the lower temperature of the hot water is lower than a predetermined temperature, the cooling water pump and the heat recovery pump are driven so that the heat of the fuel cell main body is changed to hot water by the heat exchanger and recovered in the hot water storage tank. A fuel cell system characterized by being made. In the fuel cell system according to claim 1 or 2,
The fuel cell system, wherein the first sensor and the second sensor are a plurality of thermocouples arranged in a height direction of the hot water storage tank. In the fuel cell system according to claim 2 or 3,
The controller has an outside air temperature sensor that measures outside air temperature, and the controller recovers heat recovery energy that can be recovered from the fuel cell main body when the system is stopped, and the startup energy reduction required to raise the temperature of the fuel cell main body at the next start-up. A fuel cell system characterized in that heat recovery is not performed when the amount of heat recovery energy is smaller than the amount of heat recovery energy. The fuel cell body uses the fuel and oxidant gas to generate power. The heat generated in the fuel cell body during power generation is circulated through the cooling water, transferred to the heat exchanger, and further sent to the heat exchanger. A fuel cell system in which water is converted into hot water and heat is collected in a hot water tank,
When the system is shut down, the current hot water storage in the hot water tank is compared with the user's estimated hot water usage until the next system startup. The fuel cell system stop control method is characterized in that the heat generated in is converted into hot water through a heat exchanger and recovered in a hot water storage tank. In the fuel cell system stop control method according to claim 5,
Stores usage data indicating past usage conditions, such as the amount of power used and the amount of hot water used by the user, and calculates the estimated amount of hot water usage for the user until the next system startup based on the usage data. A stop control method for a fuel cell system, characterized in that comparison is made with the current hot water storage amount. In the fuel cell system stop control method according to claim 5 or 6,
Even if the amount of hot water stored in the hot water tank is larger than the estimated amount of hot water used by the user until the next system start-up, if the temperature of the hot water stored in the hot water tank is lower than the specified temperature, A fuel cell system stop control method characterized in that when the system is stopped, the heat of the fuel cell main body is changed to hot water via a heat exchanger and recovered in a hot water storage tank. In the fuel cell system stop control method according to claim 7,
If the heat recovery energy that can be recovered from the fuel cell body at the time of system shutdown is compared with the amount of startup energy reduction required to raise the temperature of the fuel cell body at the next startup, and the heat recovery energy is smaller A stop control method for a fuel cell system, wherein heat recovery is not performed.

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