JP4677023B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that can effectively use exhaust heat of a fuel cell while suppressing an increase in size.

With the recent increase in awareness of global environmental conservation, the spread of fuel cells that contribute to the prevention of global warming is expected. A fuel cell is a device that extracts electric power generated by an electrochemical reaction between hydrogen and oxygen, and generates heat when the electrochemical reaction is performed. In order to continue the power generation of the fuel cell, it is necessary to maintain the fuel cell at a predetermined temperature, so that the generated heat is taken away by supplying cooling water. In order to effectively use the heat generated in the fuel cell, it is common to build a cogeneration system that supplies the cooling water and stores the heat taken away in the hot water tank and supplies it to the heat demand as needed. (For example, refer to Patent Document 1). In many areas, heat demand tends to increase during the winter when temperatures are lower than those of other seasons. A conventional system equipped with a fuel cell increases the capacity of the hot water storage tank in accordance with the winter season when heat demand increases, or it can reduce the waste heat of the fuel cell that can be used by storing heat without increasing the capacity of the hot water storage tank. The amount of heat that could not be stored was discarded.
JP 2008-0666016 (FIG. 1 etc.)

  However, when the hot water storage tank is enlarged, the entire unit including the fuel cell becomes large, and the degree of freedom when installing in a general household has been reduced. On the other hand, when the hot water storage tank is not enlarged, the exhaust heat of the fuel cell cannot be used effectively.

  In view of the above-described problems, an object of the present invention is to provide a fuel cell system that can effectively use exhaust heat of a fuel cell while suppressing an increase in size.

In order to achieve the above object, a fuel cell system according to a first aspect of the present invention includes a fuel cell 20 that generates electricity and generates heat by an electrochemical reaction between hydrogen and oxygen, as shown in FIG. A heat storage tank 40 for storing heat generated in the battery 20; a cooling exhaust heat recovery system 23 for conveying the heat generated in the fuel cell 20 to the heat storage tank 40 through the media c and h and cooling the fuel cell 20. A cooling exhaust heat recovery system 23 having flow devices 22 and 32 for flowing the media c and h; and the temperature of the fuel cell 20 during power generation is higher in winter than in spring or autumn. And a control device 60 that adjusts the discharge flow rate of the flow devices 22 and 32 so as to increase the first predetermined temperature.

  With this configuration, the flow device is controlled such that the temperature of the fuel cell during power generation is higher than the temperature in spring or autumn by the first predetermined temperature in winter. The temperature of the medium in the tank can be increased, the available heat quantity (exergy) of the heat stored in the heat storage tank is increased, and the volume of the heat storage tank per unit heat quantity stored in the heat storage tank is reduced. Can do.

The fuel cell system according to a second aspect of the present invention, for example, as shown in FIG. 1, in the fuel cell system 1 according to the first aspect of the upper Symbol present invention, the control device 60, and the power temperature of the fuel cell 20 when there are, you adjust the discharge flow rate of the flow devices 22 and 32 as better temperature in summer than the temperature becomes lower second predetermined temperature in the spring or autumn.

  With this configuration, the flow device is controlled so that the temperature of the fuel cell during power generation is lower than the temperature in spring or autumn by a second predetermined temperature in summer. It can suppress that durability of the structural member of a battery falls, and can suppress the fall of the lifetime of a fuel cell.

  Further, the fuel cell system according to the third aspect of the present invention is stored in the heat storage tank 40 in the fuel cell system according to the first aspect or the second aspect of the present invention as shown in FIG. Heat consumption detecting means 65-68 for detecting the amount of consumed heat; the control device 60 is configured to distinguish seasons according to the heat consumption detected by the heat consumption detecting means 65-68. Has been.

  If comprised in this way, since a season is distinguished according to the consumption of the amount of heat detected by the heat consumption detection means, the amount of heat consumed can be made the operating temperature of the fuel cell that can store heat in the heat storage tank. The operating temperature of the fuel cell can be appropriately adjusted according to the required heat storage amount.

  Further, the fuel cell system according to the fourth aspect of the present invention detects the outside air temperature in the fuel cell system 1 according to the first aspect or the second aspect of the present invention as shown in FIG. An outside air temperature detecting means 81 is provided; the control device 60 is configured to distinguish seasons according to the outside air temperature detected by the outside air temperature detecting means 81.

  If comprised in this way, since a season is distinguished according to the outside temperature detected by the outside temperature detection means, the operation temperature of the fuel cell can be easily adjusted.

  Further, the fuel cell system according to the fifth aspect of the present invention is a calendar for recognizing a calendar in the fuel cell system 1 according to the first aspect or the second aspect of the present invention as shown in FIG. The controller 60 is configured to distinguish seasons according to a calendar based on the calendar 82.

  If comprised in this way, since a season is distinguished according to the calendar based on a calendar, adjustment of the operating temperature of a fuel cell can be performed simply.

The fuel cell system according to the sixth aspect of the present invention is, for example, as shown in FIG. 1, in the fuel cell system 1 according to any one of the first to fifth aspects of the present invention. The cooling exhaust heat recovery system includes a cooling water system 21 that cools the fuel cell 20 when the medium c is introduced into the fuel cell 20, and exhaust heat that transports heat to the heat storage tank 40 when the medium h is introduced into the heat storage tank 40. And a heat exchanger 30 that performs heat exchange between the recovered water system 31, the medium c of the cooling water system 21, and the medium h of the exhaust heat recovery water system 31; the fluidizer is provided in the cooling water system 21. A cooling water pump 22 and an exhaust heat recovery water pump 32 provided in the exhaust heat recovery water system 31; a cooling water outlet temperature for detecting the temperature of the medium c derived from the fuel cell 20 of the cooling water system 21 The sensor 63 and the fuel cell of the cooling water system 21 Further comprising a cooling water inlet temperature sensor 64 for detecting the temperature of the medium c introduced into 20; adjust the discharge flow rate of the cooling water pump 22 based on the detected cooling water outlet temperature sensor 63 temperature, the cooling water by adjusting the discharge flow rate of the exhaust heat recovery water pump 32 based on the detected temperature at an inlet temperature sensor 64, it is configured to control the temperature of the fuel cell 20 when that power generation.

  With this configuration, the temperature of the coolant medium that affects the durability of the fuel cell can be controlled, and it is possible to directly perform control that suppresses a decrease in the life of the fuel cell. .

  According to the present invention, the temperature of the fuel cell during power generation is controlled such that the temperature in the winter is higher than the temperature in the spring or autumn by the first predetermined temperature. The temperature of the medium in the tank can be increased, the available heat quantity (exergy) of the heat stored in the heat storage tank is increased, and the volume of the heat storage tank per unit heat quantity stored in the heat storage tank is reduced. Can do.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or similar members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram of the fuel cell system 1. The fuel cell system 1 includes a fuel cell 20, a cooling water line 21 constituting a cooling water system, an exhaust heat recovery water line 31 constituting an exhaust heat recovery water system, a cooling water c flowing through the cooling water line 21, and an exhaust heat recovery. A heat exchanger 30 that performs heat exchange with the exhaust heat recovery water h flowing through the water line 31, a hot water storage tank 40 as a heat storage tank, and a control device 60 are provided. The cooling water c and the exhaust heat recovery water h function as a medium for conveying heat generated in the fuel cell 20 to the hot water storage tank 40. The cooling water system and the exhaust heat recovery water system constitute a cooling exhaust heat recovery system 23 together with the heat exchanger 30.

  The fuel cell 20 generates electricity and generates heat by an electrochemical reaction between hydrogen and oxygen, and is typically a solid polymer fuel cell. The fuel cell 20 takes away heat generated by an electrochemical reaction, a fuel electrode 20a for introducing a reformed gas g generated by a reformer (not shown), an air electrode 20c for introducing an oxidant gas t. The cooling unit 20r is included. The reformer (not shown) is a device that introduces raw material and process water and generates a reformed gas g rich in hydrogen by a steam reforming reaction. The raw materials are typically chain hydrocarbons (including natural gas) such as methane, ethane, and LPG, or mixtures mainly composed of hydrocarbons such as methanol and petroleum products (kerosene, gasoline, naphtha, etc.) This is a hydrocarbon-based raw material. The reformed gas g contains 40% or more of hydrogen, typically about 75%, and has a carbon monoxide concentration of about 10 ppm or less. The reason why the carbon monoxide concentration in the reformed gas g is reduced to such a value is to prevent the electrode catalyst of the fuel electrode 20a poisoned by carbon monoxide from being poisoned. The oxidant gas t is typically air. Although the fuel cell 20 is simply shown in the figure, in practice, a single cell is formed by sandwiching the solid polymer film between the fuel electrode 20a and the air electrode 20c, and this cell is formed in the cooling unit 20r. A plurality of layers are stacked via the.

  In the fuel cell 20, hydrogen in the reformed gas g supplied to the fuel electrode 20a is decomposed into hydrogen ions and electrons, and the hydrogen ions pass through the solid polymer film and move to the air electrode 20c. It moves to the air electrode 20c through the lead wire connecting the electrode 20a and the air electrode 20c, reacts with oxygen in the oxidant gas t supplied to the air electrode 20c to generate water, and generates heat during this reaction. To do. The heat generated by this reaction is removed by the cooling water c supplied to the cooling unit 20r. In other words, the fuel cell 20 is cooled by the cooling water c. Further, in this reaction, direct current power can be taken out when electrons pass through the conducting wire. The fuel cell 20 is electrically connected to a commercial power source 98 and a power load 99 via a power conditioner (not shown) that converts DC power to AC power.

  In general, the polymer electrolyte fuel cell 20 has a lower temperature (operating temperature) during power generation, and the lowering of the durability of the solid polymer membrane and the cell sealing material is suppressed (for example, (Based on life prediction by Arrhenius plot). The temperature of the fuel cell 20 during power generation typically depends on the amount of heat exchanged with the cooling water c.

  The heat exchanger 30 is a device that performs heat exchange between the cooling water c that cools the fuel cell 20 and the exhaust heat recovery water h that is a medium that stores heat generated in the fuel cell 20 in the hot water storage tank 40. Typically, a plate heat exchanger is used. The heat exchanger 30 is configured so that the cooling water c and the exhaust heat recovery water h are not mixed. The heat exchanger 30 receives heat from the fuel cell 20 and exchanges heat between the cooling water c whose temperature has risen and the exhaust heat recovery water h whose temperature is lower than that of the cooling water c by the counter flow, and the heat generated in the fuel cell 20. Is transmitted from the cooling water c to the exhaust heat recovery water h. By making the cooling water c and the exhaust heat recovery water h into separate flows using the heat exchanger 30, the water quality of the cooling water c and the exhaust heat recovery water h can be individually managed.

  The hot water tank 40 is a device that stores heat generated during an electrochemical reaction in the fuel cell 20 using the exhaust heat recovery water h as a medium. The hot water tank 40 is typically formed of a container that is long in the vertical direction and rich in corrosion resistance. By being formed long in the vertical direction, it is easy to form a temperature stratification in which the temperature of the exhaust heat recovery water h stored inside decreases from the upper part toward the lower part. The heat stored in the hot water storage tank 40 using the exhaust heat recovery water h as a medium is used at any time for heat demand (not shown) such as hot water supply and heating equipment (floor heating, fan coil unit, etc.). . In the hot water storage tank 40, a hot water outlet pipe 42 for supplying the stored exhaust heat recovery water h as supply hot water Wp to heat demand such as hot water supply or heating equipment is provided at the top, and heat is used by the heating equipment or the like. A hot water return pipe 43 for introducing the return warm water Wq whose temperature has decreased is provided at the lower part, and a supply water pipe 48 for introducing make-up water Ws (for example, city water) for replenishing hot water consumed by hot water supply or the like is provided at the lower part. Are connected to each other. The supply hot water Wp, the return hot water Wq, and the exhaust heat recovery water h have different names depending on their uses, and are the same when viewed as substances, and are mixed in the hot water tank 40.

  Typically, the warm water forward pipe 42 is provided with a heater (not shown) (not shown) that heats and raises the supply warm water Wp supplied to the heat demand. The hot water outgoing pipe 42 is provided with a flow meter 65 that detects the flow rate of the supplied hot water Wp supplied to meet the heat demand. Further, a hot water outgoing pipe temperature sensor 66 that detects the temperature of the supplied hot water Wp supplied toward the heat demand is provided in the hot water outgoing pipe 42 on the downstream side of the heater (not shown). The hot water return pipe 43 is provided with a hot water return pipe temperature sensor 67 for detecting the temperature of the return hot water Wq returned to the hot water storage tank 40 due to the use of heat in heat demand. The makeup water pipe 48 is provided with a water meter 68 as a water amount detection means for measuring the amount of makeup water Ws supplemented to the hot water tank 40. When the supply hot water Wp led out from the warm water forward pipe 42 and the amount of makeup water Ws introduced from the makeup water pipe 48 are the same, the makeup water pipe 48 and the water meter 68 need not be provided.

  The cooling unit 20r of the fuel cell 20 and the heat exchanger 30 are connected by a cooling water line 21 through which the cooling water c flows. By connecting the fuel cell 20 and the heat exchanger 30 with the cooling water line 21, a circulation flow path in which the cooling water c circulates between them is formed. The cooling water line 21 includes a first cooling water line 21 </ b> A for flowing the cooling water c from the fuel cell 20 to the heat exchanger 30, and a second cooling water line 21 </ b> B for flowing the cooling water c from the heat exchanger 30 to the fuel cell 20. And have. Hereinafter, when it is not necessary to distinguish between the first cooling water line 21A and the second cooling water line 21B, these are collectively referred to simply as “cooling water line 21”. The first cooling water line 21A is provided with a cooling water outlet temperature sensor 63 as cooling water temperature detecting means for detecting the temperature of the cooling water c derived from the cooling unit 20r. The cooling water outlet temperature sensor 63 is preferably provided in the first cooling water line 21A in the vicinity of the cooling unit 20r. Or the cooling water exit temperature sensor 63 may be provided in the cooling part 20r of the exit part of the cooling water c. A cooling water pump 22 as a flow device for circulating the cooling water c is inserted and disposed in the second cooling water line 21B. Although the cooling water pump 22 may be inserted and arranged in the first cooling water line 21A, in order to avoid the cooling part 20r from becoming negative pressure from the viewpoint of protecting the fuel cell 20, the second cooling water line 21B is provided. It is preferably inserted and arranged. The second cooling water line 21B is provided with a cooling water inlet temperature sensor 64 that detects the temperature of the cooling water c introduced into the cooling unit 20r. In the present embodiment, the cooling water inlet temperature sensor 64 is provided in the second cooling water line 21B between the cooling water pump 22 and the heat exchanger 30, but the second cooling water line in the vicinity of the cooling unit 20r. It may be provided in 21B, and may be provided in the cooling part 20r of the inlet part of the cooling water c.

  The heat exchanger 30 and the hot water storage tank 40 are connected by an exhaust heat recovery water line 31 through which the exhaust heat recovery water h flows. When the heat exchanger 30 and the hot water storage tank 40 are connected by the exhaust heat recovery water line 31, a circulation passage through which the exhaust heat recovery water h circulates is formed. The exhaust heat recovery water line 31 includes a first exhaust heat recovery water line 31A for flowing the exhaust heat recovery water h from the heat exchanger 30 to the hot water storage tank 40, and an exhaust heat recovery water h from the hot water storage tank 40 to the heat exchanger 30. And a second exhaust heat recovery water line 31B. Hereinafter, when it is not necessary to particularly distinguish the first exhaust heat recovery water line 31A and the second exhaust heat recovery water line 31B, these are collectively referred to simply as “exhaust heat recovery water line 31”. The first exhaust heat recovery water line 31A is preferably connected to the hot water storage tank 40 at the top of the hot water storage tank 40, more preferably at the top of the hot water storage tank 40, and the second exhaust heat recovery water line 31B is preferably hot water storage. It is connected to the hot water storage tank 40 at the bottom of the hot water tank 40, more preferably at the bottom of the hot water storage tank 40. By being connected in this way, it becomes easy to form a temperature stratification of the exhaust heat recovery water h stored in the hot water tank 40. An exhaust heat recovery water pump 32 as a flow device for circulating the exhaust heat recovery water h is inserted and disposed in the second exhaust heat recovery water line 31B. The exhaust heat recovery water pump 32 may be inserted into the first exhaust heat recovery water line 31A.

  The first exhaust heat recovery water line 31 </ b> A and the second exhaust heat recovery water line 31 </ b> B upstream of the exhaust heat recovery water pump 32 are connected by a bypass line 35. The bypass line 35 flows the exhaust heat recovery water h flowing through the first exhaust heat recovery water line 31A to the second exhaust heat recovery water line 31B without flowing into the hot water storage tank 40 (bypassing the hot water storage tank 40). Road. At the connecting portion between the first exhaust heat recovery water line 31A and the bypass line 35, the exhaust heat recovery water h flowing through the first exhaust heat recovery water line 31A is allowed to flow into the hot water storage tank 40, and the hot water storage tank 40 is bypassed. A three-way valve 62 is provided as switching means for switching between flowing into the second exhaust heat recovery water line 31B. The three-way valve 62 is preferably disposed so that the distance between the three-way valve 62 and the hot water tank 40 is as short as possible. The three-way valve 62 is configured to receive a signal from the control device 60 and switch the flow path electrically. The first exhaust heat recovery water line 31 </ b> A is provided with a bypass temperature sensor 61 as a temperature detector that detects the temperature of the exhaust heat recovery water h immediately upstream of the three-way valve 62.

  The control device 60 controls the operation of the fuel cell system 1. The control device 60 is connected to the cooling water pump 22 and the exhaust heat recovery water pump 32 through signal cables, respectively, so that the start and stop and the rotation speed of the cooling water pump 22 and the exhaust heat recovery water pump 32 can be controlled. It is configured. The control device 60 is connected to the three-way valve 62 via a signal cable, and is configured to be able to switch the flow path of the three-way valve 62 by transmitting a signal. The control device 60 is connected to the bypass temperature sensor 61, the cooling water outlet temperature sensor 63, the cooling water inlet temperature sensor 64, the hot water outgoing pipe temperature sensor 66, and the hot water return pipe temperature sensor 67 through signal cables. The temperature signals are received from the sensors 61, 63, 64, 66, and 67, respectively. The control device 60 is connected to the flow meter 65 and the water meter 68 through signal cables, respectively, and is configured to receive the flow signal from the flow meter 65 and the water meter 68, respectively. The fuel cell system 1 includes an outside air temperature sensor 81 as outside air temperature detecting means for detecting outside air temperature. The control device 60 is connected to the outside air temperature sensor 81 through a signal cable, and is configured to receive a temperature signal from the outside air temperature sensor 81. The fuel cell system 1 also includes a calendar 82 that recognizes the calendar. The calendar 82 is typically built in a computer and configured to keep time as data. The control device 60 is configured to exchange data with the calendar 82. The control device 60 and the calendar 82 may be configured integrally.

  With continued reference to FIG. 1, the operation of the fuel cell system 1 will be described. First, the operation of the fuel cell system 1 in the middle season (spring or autumn) will be described. When power demand occurs in the power load 99, the control device 60 controls the fuel cell system 1 so that the fuel cell 20 generates power. At this time, in the fuel cell 20, the reformed gas g is introduced into the fuel electrode 20a, and the oxidant gas t is introduced into the air electrode 20c. In the fuel cell 20, hydrogen in the reformed gas g and the oxidant gas t Electricity is generated by an electrochemical reaction with oxygen. Since the power generated by the fuel cell 20 is DC power, it is supplied to the power demand 99 after being converted to AC power by a power conditioner (not shown). The control device 60 typically includes the reformed gas g and the oxidant introduced into the fuel cell 20 so that the fuel cell 20 generates electric power that is smaller than the power consumption in the electric power demand 99 by a predetermined capacity (for example, 100 w). The flow rate of the gas t is controlled. The power that is still insufficient when the power demand 99 is supplied with power from the fuel cell 20 is compensated by being supplied with the commercial power source 98. Since the fuel cell 20 is difficult to follow a steep fluctuation in power demand due to its nature, the fuel cell 20 generates power by generating power that is smaller than the power consumption in the power demand 99 by a predetermined capacity. This prevents the generated power from flowing back into the commercial power system. In addition, in order to cope with the case where the generated power in the fuel cell 20 exceeds the power consumption of the power demand 99, the surplus power is consumed without causing reverse power flow by converting the surplus power (surplus power) into heat. An electric heater (not shown) may be provided.

  The fuel cell 20 generates heat as power is generated. The control device 60 activates the cooling water pump 22 and the exhaust heat recovery water pump 32 when the reformed gas g and the oxidant gas t are introduced into the fuel cell 20. The control device 60 transmits a signal to the three-way valve 62 and initially sets the water flow direction of the three-way valve 62 so that the exhaust heat recovery water h flows through the bypass line 35, and is detected by the bypass temperature sensor 61. The water flow direction of the three-way valve 62 is switched so as to flow into the hot water tank 40 when the temperature is equal to or higher than the temperature that can be used for heat demand (for example, an arbitrary temperature of 45 to 50 ° C.). When the cooling water pump 22 is activated, the cooling water c circulates through the cooling water line 21. Thereby, the cooling water c introduced into the cooling unit 20r of the fuel cell 20 takes heat from the fuel cell 20 and rises in temperature, while the fuel cell 20 is cooled. The fuel cell 20 is maintained at a temperature suitable for power generation by being cooled with the cooling water c. The cooling water c whose temperature has been increased due to the removal of heat from the fuel cell 20 is reduced in temperature to such an extent that the heat exchanger 30 can cool the fuel cell 20 by exchanging heat with the exhaust heat recovery water h. The temperature of the recovered water h rises. The cooling water c whose temperature has decreased circulates in the cooling water line 21 so as to be re-introduced into the cooling unit 20r and take away the heat generated in the fuel cell 20. At this time, the control device 60 adjusts the discharge flow rate of the cooling water pump 22 so that the temperature detected by the cooling water outlet temperature sensor 63 becomes a predetermined temperature (for example, 75 ° C.) in the intermediate season, and the cooling water inlet temperature. The discharge flow rate of the exhaust heat recovery water pump 32 is adjusted so that the temperature detected by the sensor 64 becomes a predetermined temperature (for example, 65 ° C.) in the middle season. By adjusting in this way, the temperature of the fuel cell 20 can be stabilized, and the fuel cell 20 can be operated stably.

  The exhaust heat recovery water h whose temperature has been increased by exchanging heat with the cooling water c in the heat exchanger 30 then flows into the upper part of the hot water tank 40. On the other hand, exhaust heat recovery water h having a temperature lower than that of the cooling water c introduced into the heat exchanger 30 is derived from the lower part of the hot water tank 40. The exhaust heat recovery water h derived from the lower part of the hot water storage tank 40 is introduced into the heat exchanger 30 and heat exchange with the cooling water c is performed to increase the temperature. A temperature stratification is formed in the hot water storage tank 40 by introducing exhaust heat recovery water h having a high temperature from above. From the viewpoint of preventing the formed temperature stratification from being disturbed as much as possible, the dynamic pressure of the exhaust heat recovery water h introduced into the hot water tank 40 should be as small as possible.

  The exhaust heat recovery water h having a high temperature stored in the hot water storage tank 40 is supplied as hot water Wp to the heat demand (not shown) such as hot water supply and heating equipment (floor heating, fan coil unit, etc.) via the hot water outgoing pipe 42. Supplied. When the temperature of the supply hot water Wp supplied to the heat demand is lower than the temperature used in the heat demand, it is heated by a heater (not shown). For example, when the hot water Wp supplied to the heat demand is supplied to a place where water as a substance is not consumed using the heat of the heating equipment or the like, the temperature is lowered due to the use of heat in the heating equipment or the like. It returns to the lower part of the hot water tank 40 through the hot water return pipe 43 as return hot water Wq later. When supplied to a place with water consumption as a substance such as hot water supply, the water consumed for hot water supply or the like is replenished to the lower part of the hot water tank 40 through the replenishment water pipe 48 as make-up water Ws. The As a result, the temperature of the exhaust heat recovery water h flowing out from the lower part of the hot water tank 40 is lower than that of the cooling water c introduced into the heat exchanger 30. Information on the amount of water supplied to the hot water tank 40 is transmitted to the control device 60 as a signal.

  Here, the exhaust heat recovery water h stored in the hot water storage tank 40 has a higher utility value as the temperature is higher from the viewpoint of heat utilization. When the temperature of the exhaust heat recovery water h flowing into the hot water storage tank 40 rises, the amount of heat stored in the hot water storage tank 40 can be increased, or the hot water storage tank 40 can be made smaller without changing the amount of stored heat, and can be used. This is because the amount of heat (exergy) increases. The temperature of the exhaust heat recovery water h flowing into the hot water storage tank 40 can be increased by increasing the operating temperature of the fuel cell 20. However, as described above, the lower the operating temperature of the fuel cell 20 is, the lower the durability of the solid polymer membrane and the cell sealing material is suppressed. For example, the fuel cell system for general households preferably has a durability of at least 10 years, and from the viewpoint of extending the life, it is preferable to perform an operation that suppresses a decrease in the durability of the fuel cell. In the fuel cell system 1, the following control is performed in order to make the most of the conflicting advantages.

  FIG. 2 is a flowchart for explaining the control of the fuel cell system 1. The fuel cell system 1 generally increases the operating temperature of the fuel cell 20 in the winter when the heat demand is increased to a first predetermined temperature higher than the temperature in the intermediate season (spring and autumn). In summer when the temperature decreases, the operating temperature of the fuel cell 20 is set to be a second predetermined temperature lower than the temperature in the intermediate season. When the fluctuation range of the operating temperature of the fuel cell 20 and the fluctuation range of the temperature of the exhaust heat recovery water h flowing into the hot water storage tank 40 are the same, the temperature of the exhaust heat recovery water h flowing into the hot water storage tank 40 is also the fuel. It rises or falls according to the operating temperature of the battery 20. Further, the “first predetermined temperature” can be an arbitrary value, but within the upper limit operating temperature of the fuel cell 20, the maximum amount of the exhaust heat recovery water h that has a heat storage amount within a range that can be consumed by heat demand. While making it as close as possible to the temperature, the temperature of the cooling water c introduced into the fuel cell 20 is set to a temperature at which the fuel cell 20 can be continuously cooled without excessively affecting the durability of the fuel cell 20. It is preferable to determine within a range where The “second predetermined temperature” can be an arbitrary value, but the amount of heat consumed by the heat demand can be covered by the exhaust heat of the fuel cell 20 as much as possible (in the direction of increasing the operating temperature of the fuel cell 20). In consideration of the balance between reducing the durability of the solid polymer membrane and the cell sealing material as much as possible (working to lower the operating temperature of the fuel cell 20). Is preferably determined. By increasing the operating temperature of the fuel cell 20 in the winter, and lowering it below the operating temperature in the intermediate season except during the winter, the exhaust heat of the fuel cell 20 can be effectively used while suppressing an increase in the size of the fuel cell system 1. The lifetime of the fuel cell 20 can be extended rather than increasing the operating temperature of the fuel cell 20 throughout the year. In addition, by lowering the operating temperature of the fuel cell 20 in the summer and setting it to be higher than the operating temperature in the intermediate season except in the summer, the life of the fuel cell 20 can be extended.

  During operation of the fuel cell system 1, the control device 99 detects the difference between the temperature detected by the hot water outgoing pipe temperature sensor 66 and the temperature detected by the hot water return pipe temperature sensor 67, and the supply hot water detected by the flow meter 65. The amount of heat consumed in the heat demand is calculated from the flow rate of Wp, the flow rate of the makeup water Ws detected by the water meter 68, and the temperature of the makeup water Ws for each season stored in the control device 99 in advance. The value of the amount of heat is compared with the amount of heat consumed for each season stored in advance in the control device 99 to determine whether or not it is the winter season (ST1). In the winter season, the cooling water pump 22 and the exhaust water are discharged so that the temperature of the cooling water c detected by the cooling water outlet temperature sensor 63 is higher than the intermediate temperature by a first predetermined temperature (10 ° C. in the present embodiment). The discharge flow rate of the heat recovery water pump 32 is adjusted (ST2). In the present embodiment, the discharge flow rate of the cooling water pump 22 is adjusted so that the temperature detected by the cooling water outlet temperature sensor 63 becomes 85 ° C., and the temperature detected by the cooling water inlet temperature sensor 64 becomes 75 ° C. Thus, the discharge flow rate of the exhaust heat recovery water pump 32 is adjusted. In this way, the amount of heat stored in the hot water storage tank 40 can be increased, or the hot water storage tank 40 can be made smaller without changing the amount of stored heat, and the temperature of the exhaust heat recovery water h in the hot water storage tank 40 increases, so that supply is possible. The temperature of the hot water Wp can be increased, and the amount of available heat can be increased.

  If it is determined that it is not winter in the step (ST1) for determining whether or not it is the winter season, the amount of heat consumed in the heat demand is calculated in the manner described above, and the calculated amount of heat is stored in the control device 99 in advance. Whether it is summer or not is determined by comparing with the heat consumption for each season (ST3). In the summer season, the cooling water pump 22 and the exhaust water are discharged so that the temperature of the cooling water c detected by the cooling water outlet temperature sensor 63 is lower than the intermediate season by a second predetermined temperature (10 ° C. in the present embodiment). The discharge flow rate of the heat recovery water pump 32 is adjusted (ST4). In the present embodiment, the discharge flow rate of the cooling water pump 22 is adjusted so that the temperature detected by the cooling water outlet temperature sensor 63 becomes 65 ° C., and the temperature detected by the cooling water inlet temperature sensor 64 becomes 55 ° C. Thus, the discharge flow rate of the exhaust heat recovery water pump 32 is adjusted. If it does in this way, the fall of durability of the solid polymer membrane of fuel cell 20 and the sealing material of a cell can be controlled, and the life of fuel cell system 1 can be extended.

  If it is determined that it is not summer in the step of determining whether it is summer (ST3), the set temperature is not changed, and the temperature of the cooling water c detected by the cooling water outlet temperature sensor 63 is maintained at the set temperature in the intermediate season. (ST5). In the present embodiment, the discharge flow rate of the cooling water pump 22 is adjusted so that the temperature detected by the cooling water outlet temperature sensor 63 becomes 75 ° C., and the temperature detected by the cooling water inlet temperature sensor 64 becomes 65 ° C. Thus, the discharge flow rate of the exhaust heat recovery water pump 32 is adjusted. Adjusting the temperature of the cooling water c by adjusting the temperature of the cooling water c to make the temperature of the exhaust heat recovery water h flowing into the hot water storage tank 40 a first predetermined temperature higher than the intermediate season (ST2); After the step of lowering the temperature of the exhaust heat recovery water h flowing into the hot water storage tank 40 by the second predetermined temperature from the intermediate season (ST4), or the step of maintaining the set temperature in the intermediate season (ST5), respectively. The process returns to the step of determining whether or not it is winter (ST1).

  In the above description, the amount of heat consumed by the heat demand is calculated, and the season is determined by comparing the calculated amount of heat with the amount of heat consumed for each season stored in the control device 99 in advance. Instead of determining the season based on the amount of heat consumed for heat demand, the season is determined by comparing the temperature detected by the outside air temperature sensor 81 with the outside air temperature for each season stored in the control device 99 in advance. Alternatively, the season may be determined by comparing the calendar grasped by the calendar 82 with the correspondence between the season and the calendar stored in the control device 99 in advance. If the season is determined based on the heat consumption of heat demand, the fuel cell 20 can be operated at a temperature balanced with the heat consumption. In this case, the outside air temperature sensor 81 and the calendar 82 may be omitted ( It is not necessary to provide it). When judging the season based on the outside air temperature, the flow meter 65, the hot water outgoing pipe temperature sensor 66, the hot water return pipe temperature sensor 67, and the calendar 82 can be omitted, and the configuration necessary for judging the season Becomes simple. When judging the season based on the calendar 82, the flow meter 65, the hot water outgoing pipe temperature sensor 66, the hot water return pipe temperature sensor 67, and the outside air temperature sensor 81 can be omitted, and are necessary for judging the season. A simple configuration.

  In the above description, the set temperature is set to the second predetermined temperature lower than the intermediate season in the summer, but if the heat demand does not decrease even in the summer, for example, in the flowchart of FIG. The step (ST3) for determining whether or not and the step (ST4) for lowering the set temperature to the second predetermined temperature from the intermediate season are omitted, and it is determined that it is not winter in the step (ST1) for determining whether or not it is winter. In such a case, the process may proceed to a step (ST5) of maintaining the set temperature in the middle season. In other words, the operating temperature of the fuel cell 20 in the summer may be the same as that in the intermediate season without lowering the second predetermined temperature.

  In the case where it is not necessary to increase the amount of heat that can be used, for example, the heat demand does not increase even in the winter season, the step (ST1) for determining whether or not it is the winter season in the flowchart in FIG. The first predetermined temperature higher step (ST2) is omitted, and control is started from the step (ST3) for determining whether or not the summer season, and the set temperature is lowered to the second predetermined temperature from the intermediate season. After the step (ST4) or the step of maintaining the set temperature in the intermediate season (ST5), it may be configured to return to the step of determining whether or not it is summer (ST3). That is, the operating temperature of the fuel cell 20 in winter may be the same as that in the middle season without increasing the first predetermined temperature. In this case, since the operating temperature of the fuel cell 20 is lowered to the second predetermined temperature in summer, the life of the fuel cell 20 can be extended.

1 is a schematic system diagram of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining the effect | action of the fuel cell system which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 20 Fuel cell 22 Cooling water pump 23 Cooling exhaust heat recovery system 30 Heat exchanger 32 Exhaust heat recovery water pump 40 Heat storage tank 60 Control device 63 Cooling water outlet temperature sensor 65 Flow meter 66 Hot water outgoing pipe temperature sensor 67 Hot water Return pipe temperature sensor 68 Water meter 81 Outside air temperature sensor 82 Calendar c Cooling water h Waste heat recovery water

Claims (6)

A fuel cell that generates electricity and generates heat by an electrochemical reaction between hydrogen and oxygen;
A heat storage tank for storing heat generated in the fuel cell;
A cooling exhaust heat recovery system for transporting heat generated in the fuel cell to the heat storage tank via a medium and cooling the fuel cell, the cooling exhaust heat recovery system having a fluid device for flowing the medium;
A control device that adjusts the discharge flow rate of the fluidizing device so that the temperature of the fuel cell during power generation is higher than the temperature in spring or autumn by a first predetermined temperature in winter. Prepare;
Fuel cell system. The control device adjusts the discharge flow rate of the fluidizing device so that the temperature of the fuel cell when generating power is a second predetermined temperature lower in summer than in spring or autumn. to that;
The fuel cell system according to claim 1 . Heat consumption detecting means for detecting consumption of heat stored in the heat storage tank;
The control device is configured to distinguish seasons according to the heat consumption detected by the heat consumption detection means;
The fuel cell system according to claim 1 or 2. An outside air temperature detecting means for detecting the outside air temperature;
The controller is configured to distinguish seasons according to the outside air temperature detected by the outside air temperature detecting means;
The fuel cell system according to claim 1 or 2. Provide a calendar that recognizes the calendar;
The controller is configured to distinguish seasons according to a calendar based on the calendar;
The fuel cell system according to claim 1 or 2. The cooling exhaust heat recovery system includes a cooling water system that cools the fuel cell when the medium is introduced into the fuel cell, and an exhaust heat recovery water system that transports heat to the heat storage tank when the medium is introduced into the heat storage tank. And a heat exchanger that exchanges heat between the cooling water medium and the exhaust heat recovery water medium;
The flow device includes a cooling water pump provided in the cooling water system and an exhaust heat recovery water pump provided in the exhaust heat recovery water system;
A cooling water outlet temperature sensor for detecting a temperature of a medium derived from the fuel cell of the cooling water system; and a cooling water inlet temperature sensor for detecting a temperature of a medium introduced into the fuel cell of the cooling water system. ;
The discharge flow rate of the cooling water pump is adjusted based on the temperature detected by the cooling water outlet temperature sensor , and the discharge flow rate of the exhaust heat recovery water pump is adjusted based on the temperature detected by the cooling water inlet temperature sensor. Configured to control the temperature of the fuel cell when generating electricity;
The fuel cell system according to any one of claims 1 to 5.

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