JP2008192393A - Fuel cell, fuel cell power generating system, and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the heat removing efficiency of a power conversion circuit to convert the electric output of a fuel cell to a prescribed form. <P>SOLUTION: In this fuel cell, unit cells each of which is equipped with an electrolyte and a pair of an oxidizer electrode and a fuel electrode disposed with the electrolyte held between them are laminated between a positive electrode current-collecting plate 4 and a negative electrode current-collecting plate 2, a cell laminated part 1 compressed and fastened by fastening plates 3, 5 from the outside of the positive electrode current-collecting plate 4 and the negative electrode current-collecting plate 2, and a heat transmitting plate 7 brought into contact with the positive electrode collecting plate 4 are provided, and the switching elements 81, 91 of the power conversion circuit to convert the electric output of the cell laminated part 1 to the prescribed form are brought into contact with the heat transmitting plate 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell, a fuel cell power generation system, and an operation method thereof.

  A fuel cell is an energy conversion device that generates electricity by electrochemically reacting fuel and an oxidant. The fuel is, for example, a mixed gas containing hydrogen, and the oxidant is, for example, air. This fuel cell is a high-efficiency and low environmental load power generation device, and research and development for performance improvement, cost reduction, and high durability are underway.

  There are many fields in which the application of fuel cells is being considered, but one of the fields that is being actively developed is home cogeneration systems. A household cogeneration system is composed of a power generation unit and a heat utilization unit, which are connected by a hot water circulation line to recover exhaust heat.

  The power generation unit is a unit in which a fuel cell stack which is a DC power generation device, a fuel processing system, an air supply system, a heat management system, a power converter, and the like are housed in a package. The fuel processing system reforms raw fuel gas such as city gas and propane gas to produce hydrogen rich gas and supplies it to the fuel electrode of the fuel cell main body. The air supply system supplies air to the oxidant electrode of the fuel cell main body. The thermal management system collects exhaust heat from the battery and the fuel processing system and inputs heat to the heat utilization unit. The power converter converts the direct current output of the fuel cell stack into alternating current that can be linked to the power system.

  The fuel cell stack is formed, for example, by stacking a plurality of unit cells in which a solid polymer film containing an electrolyte is sandwiched between an oxidant electrode (cathode) and a fuel electrode (anode). Energy conversion in a fuel cell is an electrochemical reaction in a unit cell represented by the following formula, taking a solid polymer form as an example.

Reaction at the fuel electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Reaction at the oxidant electrode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
Total reaction: 2H ₂ + O ₂ → 2H ₂ O (3)
The generated voltage of the unit cell is regulated by the Gibbs energy of the oxidation-reduction reaction at the electrode under operating conditions, and the theoretical upper limit is about 1.2V. Furthermore, due to the loss of activation polarization, concentration polarization, resistance, etc. accompanying the reaction, usually only a cell voltage of 1 V or less can be obtained. Therefore, normally, in order to obtain a required voltage, a large number of unit cells are stacked so as to be electrically connected in series and used as a stacked battery that is clamped from both ends. A stack battery with a reaction gas and cooling water, a power tap, an instrumentation line, etc., is called a fuel cell stack.

The unit cell is a conversion device that converts an energy drop (generated heat) associated with a chemical reaction into electric energy. The energy drop that has not been converted into electrical energy (bound energy, loss energy due to polarization) becomes heat. In order to prevent overheating of the cell and to recover the generated heat and use it effectively in the system, a cooling plate is inserted into the laminated battery, and the generated heat of the cell is transferred to the cooling water circulating in the fuel cell power generation system Let
JP 2005-349980 A JP 2002-8687 A

  Fuel cell power generation systems are required to reduce costs, improve durability, and improve reliability. In addition, when installed in a home, it is also required that the installation space is small, the energy use efficiency is high, and the merit of utility cost is obtained.

  A high cost device in the fuel cell power generation system is a cell stack. The cell laminate is a laminate of a large number of unit cells, separators, and cooling plates. Reducing the number of cell stacks to operate at a low voltage and high current reduces the amount of expensive stacked components used. Therefore, it is an effective method for cost reduction. Further, the reduction in the number of stacked layers is effective as a means for making the fuel cell stack compact.

  However, if the number of cells of the stacked battery is reduced and the battery is operated with a large current, the temperature gradient in the reaction surface of the unit cell increases, battery characteristics deteriorate, and the risk of cell damage increases. Such an adverse effect is particularly remarkable in the unit cell at the end where heat dissipation is large. In addition, the conversion efficiency of a power converter using an inverter or the like decreases as the main circuit current increases. For this reason, even if the direct current power (voltage × current) of the battery is the same, heat generation increases as the voltage becomes lower and the current becomes higher.

  For this reason, in order to reduce the large current and voltage of the stacked battery of the fuel cell power generation system, it is necessary to enhance the heat removal of the power converter.

  For example, Patent Document 1 discloses a method in which a switching element and a heat exchanger are integrated and heat generated from the switching element is used as a heat source for an air conditioner. Patent Document 2 discloses a method in which heat generated from a water-cooled large inverter is used for preheating process air by exchanging heat of warmed water with a radiator. However, it is difficult to apply the water cooling system to a small-scale system in terms of limitation of package size and increase of auxiliary power.

  Then, an object of this invention is to improve the heat removal efficiency of the power converter circuit which converts the electric output of a fuel cell into a predetermined form.

  In order to achieve the above-described object, the present invention provides a fuel cell in which a unit cell including an electrolyte and a pair of an oxidant electrode and a fuel electrode sandwiched between the electrolyte and the unit cell is disposed. A first separator having an oxidant flow path for supplying an oxidant gas to the oxidant electrode; a second separator having a fuel flow path for supplying a fuel gas to the fuel electrode; and A cooling plate formed with a cooling medium flow path through which the cooling medium flows in contact with the first and second separators is laminated between a pair of current collecting plates, and compressed and tightened from the outside of the current collecting plates with a clamping plate A cell stack unit, a heat transfer plate in contact with the current collector plate, and a heat-generating component that generates heat during operation provided in contact with the heat transfer plate, and the electrical output of the cell stack unit is in a predetermined form And a power conversion circuit for converting the power into the power.

  In the fuel cell power generation system, the present invention provides a unit cell including an electrolyte and a pair of oxidant electrode and fuel electrode disposed with the electrolyte interposed therebetween, and the oxidant electrode disposed with the unit cell interposed therebetween. A first separator having an oxidant channel for supplying an oxidant gas to the first separator, a second separator having a fuel channel for supplying a fuel gas to the fuel electrode, and the first and first separators. A cell stack formed by laminating a cooling plate formed with a cooling medium flow path through which a cooling medium flows in contact with two separators between a pair of current collecting plates, and compressed and clamped by a clamping plate from the outside of the current collecting plate Unit, a heat transfer plate in contact with the current collector plate, and a heat generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electric output of the cell stack portion into a predetermined form Surrounding the power conversion circuit together with the conversion circuit and the clamping plate A casing having an opening, an oxidant supply system for supplying an oxidant to the oxidant flow path, a fuel supply system for supplying fuel to the fuel flow path, and a cooling medium circulating in the cooling medium flow path And a system controller that controls the oxidant supply system, the fuel supply system, and the cooling system.

  The present invention also provides a unit cell having an electrolyte and a pair of an oxidant electrode and a fuel electrode arranged with the electrolyte in between, and an oxidant gas disposed between the unit cell and the oxidant electrode. A first separator having an oxidant channel to be supplied, a second separator having a fuel channel for supplying fuel gas to the fuel electrode, and the first and second separators in contact with each other A stack of cooling plates formed with a cooling medium flow path through which the cooling medium flows are stacked between a pair of current collecting plates, and the current collecting plate is compressed and clamped by a clamping plate from the outside of the current collecting plates; A heat transfer plate that contacts the plate, a power conversion circuit that includes a heat-generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electrical output of the cell stack portion into a predetermined form; A casing that surrounds the power conversion circuit together with a plate and has an opening An oxidant supply system for supplying an oxidant to the oxidant flow path, a fuel supply system for supplying fuel to the fuel flow path, a heat transfer plate temperature sensor for measuring a surface temperature of the heat transfer plate, and the cooling A cooling medium flow path comprising: a pump for driving the medium; a heat exchanger for removing heat from the cooling medium; and a cooling medium temperature sensor for detecting a temperature of the cooling medium at an outlet of the cooling medium flow path. And a cooling system that circulates the cooling medium, and a surface temperature of the heat transfer plate detected by the heat transfer plate temperature sensor and the cooling detected by the cooling medium temperature sensor. The number of revolutions of the pump is controlled based on the temperature of the medium.

  The present invention also provides a unit cell having an electrolyte and a pair of an oxidant electrode and a fuel electrode arranged with the electrolyte in between, and an oxidant gas disposed between the unit cell and the oxidant electrode. A first separator having an oxidant channel to be supplied, a second separator having a fuel channel for supplying fuel gas to the fuel electrode, and the first and second separators in contact with each other A stack of cooling plates formed with a cooling medium flow path through which the cooling medium flows are stacked between a pair of current collecting plates, and the current collecting plate is compressed and clamped by a clamping plate from the outside of the current collecting plates; A heat transfer plate that contacts the plate, a power conversion circuit that includes a heat-generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electrical output of the cell stack portion into a predetermined form; A casing that surrounds the power conversion circuit together with a plate and has an opening An oxidant supply system for supplying an oxidant to the oxidant flow path, a fuel supply system for supplying fuel to the fuel flow path, a heat transfer plate temperature sensor for measuring a surface temperature of the heat transfer plate, and the cooling A pump that drives the medium and a heat exchanger that removes heat from the cooling medium that flows on the primary side using the secondary cooling medium that flows on the secondary side, and a temperature of the cooling medium at the outlet of the cooling medium flow path are detected. A secondary cooling medium circulation in which the secondary cooling medium is cooled by a cooling medium temperature sensor and a radiator fan, and the secondary cooling medium is driven to circulate through the secondary side of the heat exchanger and the radiator. And a cooling system that circulates the cooling medium in the cooling medium flow path with a pump, and a surface temperature of the heat transfer plate detected by the heat transfer plate temperature sensor. The cooling medium Characterized in that the temperature sensor for controlling at least one rotational speed of the rotational speed and the radiator fan of the secondary cooling medium circulation pump based on the temperature of the cooling medium detected.

  ADVANTAGE OF THE INVENTION According to this invention, the heat removal efficiency of the power converter circuit which converts the electric output of a fuel cell into a predetermined form can be improved.

  An embodiment of a fuel cell power generation system according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a longitudinal sectional view of a cell stack in a first embodiment of a fuel cell power generation system according to the present invention. FIG. 2 is a cross-sectional view of the unit cell in the present embodiment.

  The battery stack 50 has a cell stack portion 1 in which a plurality of unit cells 70 are stacked.

  The unit cell 70 has an electrolyte 71 and a pair of oxidant electrode (cathode) 73 and fuel electrode (anode) 74 sandwiching the electrolyte 71. The electrolyte 71 is held, for example, in a solid polymer film. For each of the oxidant electrode 73 and the fuel electrode 74, a conductive porous material that transmits gas is used.

  A solid polymer fuel cell operates at, for example, 100 ° C. or lower. For this reason, in order to promote the reaction, a thin layer of the catalyst 72 is formed between the oxidant electrode 73 and the electrolyte 71 and between the fuel electrode 74 and the electrolyte 71. As the catalyst, a platinum catalyst or an alloy catalyst mainly composed of platinum can be used. Further, a binder resin, a hydrophilic material, or a water repellent material is mixed with a catalyst as necessary.

  The unit cell 70 includes a pair of separators (separators) 75 and 76 that sandwich the oxidant electrode 73 and the fuel electrode 74. Separating plates 75 and 76 are made of a material that does not transmit gas such as fuel gas and oxidant gas, or a method of isolating gas by impregnating water into a porous plate, for example, by its bubble pressure. May be used. In the separator plate 75 in contact with the oxidant electrode 73, an oxidant channel 77 through which an oxidant gas such as air flows is formed. A separator 76 in contact with the fuel electrode 74 is formed with a fuel flow path 78 through which a fuel gas such as hydrogen flows.

  The unit cell 70 further includes a cooling plate 6 in contact with the separator plates 75 and 76. A coolant channel 79 is formed in the cooling plate 6. The heat generated in the cell stack 1 is discharged to the outside of the fuel cell by the cooling medium flowing through the coolant channel 79. The cooling medium is water, for example.

  The cell stack portion 1 is sandwiched between the negative electrode current collector plate 2 and the positive electrode current collector plate 4 at both ends in the stacking direction. The negative electrode current collector plate 2 is grounded. The cell stack portion 1 sandwiched between the negative electrode current collector plate 2 and the positive electrode current collector plate 4 is sandwiched between the negative electrode clamp plate 3 and the positive electrode clamp plate 5. A rod 51 passes through the negative electrode clamping plate 3 and the positive electrode clamping plate 5. The cell stack portion 1 is clamped by the negative electrode clamping plate 3 and the positive electrode clamping plate 5 whose movement is restricted by the nut 52 attached to the rod 51. Of the cooling plates 6 of the cell stack portion 1, those in contact with the positive electrode current collector plate 4 are called end cooling plates 66.

  Around the cell stack portion 1, a coupling portion 32 that distributes fuel and oxidant gas and cooling water to a predetermined flow path is provided.

  Further, a part of the positive electrode clamping plate 5 has a through portion, and a heat transfer plate 7 attached to the positive electrode current collector plate 4 is disposed in the through portion. The heat transfer plate 7 is arranged close to the low temperature portion in the reaction surface in consideration of the temperature distribution in the reaction surface of the cell stack 1.

  A casing 13 is provided on the opposite side of the cell stack 1 with the positive electrode clamping plate 5 interposed therebetween. A sound absorbing material 15 is disposed on the inner surface of the casing 13. The sound absorbing material 15 also has a heat insulating function. The casing 13 is provided with an exhaust port 61 and an air supply port 62.

  A chopper circuit 43 and an inverter circuit 42 are housed inside the casing 13. The chopper circuit 43 and the inverter circuit 42 are fixed to the heat transfer plate 7.

  The chopper circuit 43 includes a switching element 81, a ripple absorbing capacitor 11, and other components 82. The ripple absorbing capacitor 11 is connected to the bus bar 10 extending from the negative electrode current collector plate 2 and the conductor 9 extending from the positive electrode current collector plate 4. The switching element 81 is fixed so as to be in thermal contact with the surface of the heat transfer plate 7. The ripple absorbing capacitor 11 and other components 82 of the chopper circuit 43 other than the switching element 81 are installed separately from the switching element 81.

  The inverter circuit 42 includes a switching element 91 and other components 92. The switching element 91 is fixed so as to be in thermal contact with the surface of the heat transfer plate 7. The parts 92 of the inverter circuit 42 other than the switching element 91 are installed separately from the switching element 91.

  The chopper circuit 43 and the inverter circuit 42 are controlled by the switching control circuit 14 provided outside the casing 13.

  An AC output terminal 12 is provided outside the casing 13. A temperature sensor 17 is disposed on the surface of the heat transfer plate 7.

  FIG. 3 is a circuit diagram of the power conversion circuit in the present embodiment.

  The cell stacking unit 1 is a DC output device. However, the fuel cell power generation system of the present embodiment is used in conjunction with an electric power system, for example, while operating an AC device generally used in a home. Therefore, it is necessary to convert the DC power generated in the cell stack unit 1 into AC in the system and adjust the voltage, frequency, and phase to enable connection to the power system. The power conversion circuit bears all such adjustment functions.

  The power conversion circuit controls the operation of these booster circuits and orthogonal conversion circuits that perform power conversion, adjusts voltage, frequency, and phase, and controls the detection of abnormalities and communication with system control devices. It consists of a circuit.

  Although there are several methods for boosting and orthogonal transformation, in this embodiment, the chopper circuit 43 and the inverter circuit 42 are combined.

  The chopper circuit 43 obtains a voltage higher than the applied voltage by turning on / off the generated voltage of the cell stack 1 at a high frequency by the switching element and accumulating the inductance generated in the reactors L1, L2 in the capacitors C1, C2. The voltage increase ratio is controlled by the ON / OFF time ratio. The boosted voltage is applied to the inverter circuit 42.

  In the inverter circuit 42, the switching elements S3, S4, S5, and S6 generate a polarity reversal of polarity at an AC frequency and a control waveform by a PWM (Pulse Width Modulation) system that is high frequency ON / OFF time control. An AC waveform with suppressed harmonics is obtained by superimposing.

  In addition to a transistor (bipolar transistor), a semiconductor element such as a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) may be used as the switching element. Further, a high-frequency inverter circuit including a rectifier circuit and a high-frequency transformer may be used for the power conversion circuit.

  FIG. 4 is a cross-sectional view showing the inside of the electric chamber compartment in the present embodiment together with the battery stack. In FIG. 4, the air flow is also shown by the dashed arrows.

  The electrical room compartment 18 houses the switching control circuit 14, the system controller 19, and the switchboard 20, and an electrical room ventilation fan 21 is attached. The electric chamber section 18 communicates with the casing 13. The outside air sucked by the electric room ventilation fan 21 is introduced into the casing 13 through the air supply port 62 and is discharged from the exhaust port 61.

  FIG. 5 is a block diagram of the cooling system in the present embodiment.

  The cooling system for cooling the cell stack portion 1 has a primary side pipe 44 and a secondary side pipe 45. The coolant flowing through the primary side pipe 44 and the coolant flowing through the secondary side pipe 45 exchange heat through the heat exchanger 23.

  The coolant 28 flowing through the primary side pipe 44 is driven by the primary coolant pump 22 inserted in the middle of the primary side pipe 44, and is supplied to the coolant channel 79 of the cell stacking section 1 through the coupling part 32. Then, it is discharged to the outside of the cell stack portion 1 through the coupling portion 32. The coolant 28 discharged outside the cell stack 1 passes through the heat exchanger 23 and is then stored in the coolant tank 24. A battery outlet temperature sensor 25 is attached in the middle of the primary side pipe 44, and the temperature of the coolant 28 discharged to the outside of the cell stack portion 1 is measured.

  The coolant driven by the secondary coolant pump 26 inserted in the middle of the secondary side pipe 45 is cooled by the radiator 27 inserted in the middle of the secondary side pipe 45.

  In the fuel cell power generation system of the present embodiment, in addition to the battery stack including the above-described power conversion circuit and the cooling system, the fuel electrode 74 is manufactured by reforming raw fuel gas such as city gas and propane gas to produce hydrogen rich gas. A fuel supply system for supplying gas to the oxidant electrode 73, an oxidant supply system for supplying air as an oxidant to the oxidant electrode 73, and the like.

  Next, the operation of this fuel cell power generation system will be described.

  In this fuel cell power generation system, the system controller 19 monitors the surface temperature of the heat transfer plate 7 with the temperature sensor 17, while the cooling amount of the radiator 27, the rotational speed of the secondary coolant pump 26 and the primary coolant pump 22. Control etc.

  Further, the system controller 19 determines an abnormality by comparing the surface temperature of the heat transfer plate 7 measured by the temperature sensor 17 with a predetermined threshold value. Further, the system controller 19 determines an abnormality by comparing the temperature of the primary coolant discharged from the cell stack unit 1 measured by the battery outlet temperature sensor 25 with a predetermined threshold value. In addition, by measuring the number of rotations of the primary coolant pump 22 or directly measuring the flow rate of the coolant flowing through the primary pipe 44, it is checked whether the coolant on the primary side is flowing properly. May be determined. The system controller 19 determines whether or not the fuel cell power generation system can be operated based on whether or not these abnormalities exist. Thereby, it is suppressed that the temperature of elements, such as the cell lamination | stacking part 1 and the switching elements 81 and 91 of a power converter circuit, rises excessively.

  A transistor that is switched at high speed generates heat due to a collector loss at an intermediate state between On (saturated state) and On / Off. When the junction temperature of the semiconductor element rises due to heat generation, the operation becomes unstable, and thermal runaway may occur, leading to damage. Generally, the upper limit of the junction temperature is said to be about 150 ° C. to 175 ° C. for silicon elements and the like. In practice, the operating temperature can be lowered to about 120 ° C. in order to ensure reliability during long-term use. preferable.

  In the fuel cell power generation system of the present embodiment, the heat generated in the switching element 81 of the chopper circuit 43 and the switching element 91 of the inverter circuit 42 during operation passes through the positive current collector plate 4 from the heat transfer plate 7 along the temperature gradient. Then, the heat is transmitted to the end cooling plate 66, and the switching elements 81 and 91 are removed of heat. Further, in the unit cell 70 in contact with the positive electrode current collector plate 4, heat radiation is compensated by heat generated from the switching elements 81 and 91.

  Since the switching control circuit 14 is installed in the electric chamber section 18 away from the switching elements 81 and 91, it is thermally disconnected from the switching elements 81 and 91. Further, the influence of electromagnetic noise from the switching elements 81 and 91 received by the switching control circuit 14 can be remarkably reduced. Further, the inside of the casing 13 and the electric room compartment 18 is ventilated while being kept at a higher pressure than the surroundings by the outside air introduced from the electric room ventilation fan 21. Further, by introducing an air flow into the casing 13, heat radiation from components constituting other power conversion circuits such as a reactor and a capacitor that are not in contact with the heat transfer plate 7 is promoted.

  Thus, in the fuel cell power generation system of the present embodiment, the heat removal efficiency of the power conversion circuit can be increased.

  Furthermore, oscillation noise such as switching noise from the switching elements 81 and 91 and other power conversion circuit components such as a reactor is shielded by the casing 13, and transmission to the outside is suppressed. In addition, the inside of the casing 13 is maintained and ventilated throughout the operation, so that inflammable gas can be prevented from entering. Furthermore, since the bus bar 10 is grounded and the positive terminal is housed inside the casing, the charging part is not exposed and safety is high.

  In the battery stack 50, the temperature of the switching elements 81 and 92 and the end cooling plate 66 is monitored by the temperature sensor 17 provided on the heat transfer plate 7, and overheating of both the power conversion circuit and the cell stack unit 1 is detected. Can be monitored.

  FIG. 6 is a graph showing an example of temperature distribution during operation of the fuel cell power generation system according to the present embodiment.

  This temperature distribution is an example in the following fuel cell power generation system.

The end cooling plate 66 is configured such that the flow passage area of the coolant flow passage 79 is larger than that of the central cooling plate so that about twice as much cooling water can flow. As switching elements, a total of eight silicon power transistors were used for each of the chopper and the inverter, and all the switching elements were fixed to the heat transfer plate 7 having an area of 50 cm ² . As the heat transfer plate 7, an austenitic stainless steel plate (thermal conductivity: 16 W / mK) subjected to gold plating is used. An industrial grade aluminum alloy (thermal conductivity: 190 W / mK) is used as the heat transfer plate. The element internal thermal resistance is 3.5 K / W, the collector loss is 7.5 W per element, and the contact thermal resistance / insulating plate thermal resistance is about 0.8 K / W.

  At this time, the temperature of the end of the cell stack 1, that is, the end cooling plate 66 is expected to be 65 ° C., and the temperature of the switching element junction is expected to be about 103 ° C. it can.

  FIG. 7 is a graph showing the relationship between the current density of the unit cell (end cell) in contact with the positive electrode current collector plate and the cell voltage in the present embodiment. In FIG. 7, for comparison, the relationship between the current density and the end cell voltage in a general fuel cell is shown by a broken line.

  As described above, in the fuel cell power generation system of the present embodiment, as a result of suppressing the heat radiation at the air outlet portion, the flooding of the end cells is eliminated and the characteristics at a high current density are improved.

[Second Embodiment]
FIG. 8 is a longitudinal sectional view of a cell stack in the second embodiment of the fuel cell power generation system according to the present invention.

  In the battery stack 50 of the present embodiment, the radiation fins 68 are attached to the switching elements 81 and 91.

  FIG. 9 is a block diagram of the oxidant supply system in the present embodiment.

  The oxidant supply system supplies oxidant gas to the oxidant flow path 77 (see FIG. 2) via the coupling portion 32. The oxidant gas discharged from the cell stacking unit 1 is discharged to the exhaust pipe 35 through the coupling unit 32. An exhaust temperature sensor 34 is attached to the exhaust pipe 35.

  Air as the oxidant gas is sucked by the process air blower 29 and introduced into the casing 13 from the air supply port 62 via the first air supply pipe 36. The air introduced into the casing 13 is discharged from the exhaust port 61 and supplied to the coupling portion 32 via the second air supply conduit 37. A flow control valve 30 is inserted between the process air blower 29 and the supply port 62. A shutoff valve 31 is inserted between the exhaust port 61 and the coupling portion 32. Further, a bypass pipe 33 extending from the process air blower 29 to the coupling portion 32 without passing through the casing 13 is also provided. A humidifier may be introduced downstream of the shut-off valve 31.

  In such a fuel cell power generation system, the shut-off valve 31 is opened during operation, the flow rate adjusting valve 30 is operated to adjust the introduction ratio of process air into the casing 13, and the switching elements 81 and 91 are air-cooled. To do. The switching elements 81 and 91 are cooled from both the air flowing inside the casing 13 and the end cooling plate 66 of the cell stack 1. The air introduced into the casing 13 is preheated by exchanging heat with the switching elements 81 and 91.

  Further, by closing the shut-off valve 31 during the stop, moisture is prevented from flowing back from the cell stack portion 1. The diversion ratio to the casing 13 can be adjusted while monitoring the measured value of the temperature sensor 17 on the heat transfer plate and the output of the exhaust temperature sensor 34. Alternatively, the shunt ratio may be adjusted according to the battery current.

  FIG. 10 is a graph showing an example of the schedule of the diversion ratio of the battery current and the process air to the casing in the present embodiment.

  Further, similarly to the first embodiment, the system controller 19 determines an abnormality from the surface temperature of the heat transfer plate 7 or the temperature of the coolant on the primary side discharged from the cell stack portion 1, An abnormality is determined by comparing the temperature of the air exhausted from the cell stack 1 measured by the exhaust temperature sensor 34 with a predetermined threshold value. The system controller 19 determines whether or not the fuel cell power generation system can be operated based on whether or not these abnormalities exist. Thereby, it is suppressed that the temperature of elements, such as the cell lamination | stacking part 1 and the switching elements 81 and 91 of a power converter circuit, rises excessively.

  Thus, in the fuel cell power generation system of the present embodiment, the heat generated by the switching element during operation can be used for preheating oxidant such as air supplied to the cell stack 1. In addition, it is possible to change the ratio of the amount used for preheating the oxidizing agent and the amount used for keeping the unit cell 70 in contact with the positive electrode current collector plate 4 of the cell stack 1 out of the heat generated by the switching element. For this reason, it becomes possible to control the temperature distribution inside the unit cell 70 more finely.

  FIG. 11 is a graph showing the relationship between the location of the unit cell in contact with the positive electrode current collector plate in this embodiment and the temperature. In FIG. 11, for comparison, an example of a temperature in a general fuel cell is shown by a broken line.

  As shown in FIG. 11, the temperature distribution inside the unit cell 70 can be made more uniform, and the characteristics can be stabilized.

  As described above, in the fuel cell power generation systems according to the first and second embodiments of the present invention, a special cooling loop is configured even when the number of unit cells is reduced and heat generation is increased. Without excessively rising the temperature of the power conversion circuit. Moreover, the characteristic fall of the unit cell of the fuel cell located in an edge part can be suppressed. Furthermore, switching noise can be reduced. As described above, the fuel cell power generation system can be reduced in cost, made compact, highly efficient and quiet, which greatly contributes to the improvement of commercial value.

  The above description is merely an example, and the present invention is not limited to the above-described embodiments, and can be implemented in various forms. Moreover, it can also implement combining the characteristic of each embodiment.

It is a longitudinal cross-sectional view of the battery stack in 1st Embodiment of the fuel cell power generation system which concerns on this invention. It is sectional drawing of the unit cell in 1st Embodiment of the fuel cell power generation system which concerns on this invention. 1 is a circuit diagram of a power conversion circuit in a first embodiment of a fuel cell power generation system according to the present invention. It is sectional drawing which shows the inside of the electric chamber division in 1st Embodiment of the fuel cell power generation system which concerns on this invention with a battery stack. 1 is a block diagram of a cooling system in a first embodiment of a fuel cell power generation system according to the present invention. It is a graph which shows the example of the temperature distribution during driving | operation of the fuel cell power generation system in 1st Embodiment of the fuel cell power generation system which concerns on this invention. It is a graph which shows the relationship between the current density of the unit cell which contacts the positive electrode current collecting plate in 1st Embodiment of the fuel cell power generation system which concerns on this invention, and cell voltage. It is a longitudinal cross-sectional view of the battery stack in 2nd Embodiment of the fuel cell power generation system which concerns on this invention. It is a block diagram of the oxidizing agent supply system in 2nd Embodiment of the fuel cell power generation system which concerns on this invention. It is a graph which shows the example of the schedule of the shunt ratio of the battery current and process air to the casing in 2nd Embodiment of the fuel cell power generation system which concerns on this invention. It is a graph which shows the relationship between the location of the unit cell which contacts the positive electrode current collecting plate in 2nd Embodiment of the fuel cell power generation system which concerns on this invention, and temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cell laminated part, 2 ... Negative electrode current collecting plate, 3 ... Negative electrode clamping plate, 4 ... Positive electrode current collecting plate, 5 ... Positive electrode clamping plate, 6 ... Cooling plate, 7 ... Heat-transfer plate, 9 ... Conductor, DESCRIPTION OF SYMBOLS 10 ... Bus bar, 11 ... Ripple absorption capacitor, 12 ... AC output terminal, 13 ... Casing, 14 ... Switching control circuit, 15 ... Sound absorbing material, 17 ... Temperature sensor, 18 ... Electric compartment, 19 ... System controller, 20 DESCRIPTION OF SYMBOLS ... Distribution board, 21 ... Electric room ventilation fan, 22 ... Primary coolant pump, 23 ... Heat exchanger, 24 ... Coolant tank, 25 ... Battery outlet temperature sensor, 26 ... Secondary coolant pump, 27 ... Radiator, 28 ... Coolant, 29 ... Process air blower, 30 ... Flow control valve, 31 ... Shut-off valve, 32 ... Joint section, 33 ... Bypass pipe, 34 ... Exhaust temperature sensor, 35 ... Exhaust pipe, 36, 37 ... Air supply pipe Road, 42 ... Inverter circuit, 43 ... Cho Par circuit 44 ... Primary side piping 45 ... Secondary side piping 50 ... Battery stack 51 ... Rod 52 ... Nut 61 ... Exhaust port 62 ... Air supply port 66 ... End cooling plate 68 ... Heat radiation Fins 70 ... Unit cells 71 ... Electrolytes 72 ... Catalysts 73 ... Oxidant electrodes (cathodes) 74 ... Fuel electrodes (anodes) 75, 76 ... Separators 77 ... Oxidant channels 78 ... Fuel flows Path 79: coolant channel 81, 91 ... switching element

Claims (17)

A unit cell having an electrolyte and a pair of oxidant electrode and fuel electrode disposed with the electrolyte interposed therebetween, and an oxidant flow path disposed with the unit cell interposed therebetween to supply an oxidant gas to the oxidant electrode The cooling medium flows in contact with the first separator plate formed with the second separator plate formed with the fuel flow path for supplying fuel gas to the fuel electrode and the first and second separator plates. A stack of cooling plates formed with a cooling medium flow path between a pair of current collector plates, and a cell laminate portion compressed and clamped with a clamping plate from the outside of the current collector plates;
A heat transfer plate in contact with the current collector plate;
A power conversion circuit that includes a heat generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electrical output of the cell stack to a predetermined form;
A fuel cell comprising:   The fuel cell according to claim 1, further comprising a casing surrounding the power conversion circuit together with the fastening plate.   The fuel cell according to claim 1, further comprising a member having at least one of a sound absorbing function and a heat insulating function provided on an inner surface of the casing.   The fuel cell according to claim 2, wherein an opening is formed in the casing.   5. The power conversion circuit includes at least one of a chopper circuit, an inverter circuit, and a high-frequency inverter circuit including a rectifier circuit and a high-frequency transformer. The fuel cell as described.   The fuel cell according to claim 5, wherein the heat generating component is a semiconductor switching element.   The fuel cell according to any one of claims 1 to 6, wherein the heat generating component is fixed to a surface of the heat transfer plate.   8. The fuel cell according to claim 1, further comprising air-cooling type cooling fins attached to the heat generating component.   The fuel cell according to any one of claims 1 to 8, wherein the unit cell is a polymer electrolyte fuel cell. A unit cell having an electrolyte and a pair of oxidant electrode and fuel electrode disposed with the electrolyte interposed therebetween, and an oxidant flow path disposed with the unit cell interposed therebetween to supply an oxidant gas to the oxidant electrode The cooling medium flows in contact with the first separator plate formed with the second separator plate formed with the fuel flow path for supplying fuel gas to the fuel electrode and the first and second separator plates. A stack of cooling plates formed with a cooling medium flow path between a pair of current collector plates, and a cell laminate portion compressed and clamped with a clamping plate from the outside of the current collector plates;
A heat transfer plate in contact with the current collector plate;
A power conversion circuit that includes a heat generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electrical output of the cell stack to a predetermined form;
A casing that surrounds the power conversion circuit together with the fastening plate and has an opening formed therein;
An oxidant supply system for supplying an oxidant to the oxidant flow path;
A fuel supply system for supplying fuel to the fuel flow path;
A cooling system for circulating a cooling medium in the cooling medium flow path;
A system controller for controlling the oxidant supply system, the fuel supply system and the cooling system;
A fuel cell power generation system comprising: A switchboard for branching the electrical output of the power conversion circuit into a supplementary power supply in the system and a system output to the outside;
An electrical compartment that houses the switchboard;
A fan that ventilates the electrical compartment and sends a portion of the exhaust through the opening to the casing;
The fuel cell power generation system according to claim 10, comprising:   The oxidant supply system includes a blower, a first oxidant supply pipe extending from the blower to the casing, a second oxidant supply pipe extending from the casing to the oxidant flow path, The fuel cell power generation system according to claim 10 or 11, further comprising: a shutoff valve inserted in the middle of the second oxidant supply conduit.   The cooling system includes a heat transfer plate temperature sensor that measures a surface temperature of the heat transfer plate, a pump that drives the cooling medium, a heat exchanger that removes heat from the cooling medium, and an outlet of the cooling medium flow path. A cooling medium temperature sensor for detecting a temperature of the cooling medium at the system controller, wherein the system controller detects the surface temperature of the heat transfer plate detected by the heat transfer plate temperature sensor and the cooling medium temperature sensor The fuel cell power generation system according to any one of claims 10 to 12, wherein the number of revolutions of the circulation pump is controlled based on a temperature of a cooling medium.   The cooling system includes an oxidant outlet temperature sensor that measures the temperature of the gas at the outlet of the oxidant channel, and the system controller further includes the gas controller based on the temperature of the gas detected by the oxidant outlet temperature sensor. The fuel cell power generation system according to claim 13, wherein the number of revolutions of the pump is controlled.   The cooling system uses a heat transfer plate temperature sensor that measures the surface temperature of the heat transfer plate, a pump that drives the cooling medium, and a secondary cooling medium that flows on the secondary side of the cooling medium that flows on the primary side. A heat exchanger that removes heat, a cooling medium temperature sensor that detects a temperature of the cooling medium at an outlet of the cooling medium flow path, a radiator that cools the secondary cooling medium using a radiator fan, and the secondary side A secondary cooling medium circulation pump that drives the cooling medium to circulate through the secondary side of the heat exchanger and the radiator, and the system controller detects the heat transfer detected by the heat transfer plate temperature sensor. Controlling at least one of the rotational speed of the secondary coolant circulating pump and the rotational speed of the radiator fan based on the surface temperature of the hot plate and the temperature of the coolant detected by the coolant temperature sensor. The fuel cell power generation system according to any one of claims 10 to 12, characterized. A unit cell having an electrolyte and a pair of oxidant electrode and fuel electrode disposed with the electrolyte interposed therebetween, and an oxidant flow path disposed with the unit cell interposed therebetween to supply an oxidant gas to the oxidant electrode The cooling medium flows in contact with the first separator plate formed with the second separator plate formed with the fuel flow path for supplying fuel gas to the fuel electrode and the first and second separator plates. A cooling plate in which a cooling medium flow path is formed is laminated between a pair of current collector plates, and a cell stack portion compressed and clamped by a clamping plate from the outside of the current collector plate, and heat transfer in contact with the current collector plate A power conversion circuit that includes a plate, a heat-generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electrical output of the cell stack portion into a predetermined form; and the power conversion together with the clamping plate A casing surrounding the circuit and having an opening formed therein; An oxidant supply system that supplies oxidant to the fuel flow path, a fuel supply system that supplies fuel to the fuel flow path, a heat transfer plate temperature sensor that measures the surface temperature of the heat transfer plate, and a pump that drives the cooling medium; A heat exchanger for heat removal that removes heat from the cooling medium and a cooling medium temperature sensor that detects the temperature of the cooling medium at the outlet of the cooling medium flow path, and circulates the cooling medium in the cooling medium flow path A cooling system, and a method for operating a fuel cell power generation system comprising:
A fuel cell power generation system that controls the rotational speed of the pump based on the surface temperature of the heat transfer plate detected by the heat transfer plate temperature sensor and the temperature of the cooling medium detected by the cooling medium temperature sensor. Driving method. A unit cell having an electrolyte and a pair of oxidant electrode and fuel electrode disposed with the electrolyte interposed therebetween, and an oxidant flow path disposed with the unit cell interposed therebetween to supply an oxidant gas to the oxidant electrode The cooling medium flows in contact with the first separator plate formed with the second separator plate formed with the fuel flow path for supplying fuel gas to the fuel electrode and the first and second separator plates. A cooling plate in which a cooling medium flow path is formed is laminated between a pair of current collector plates, and a cell stack portion compressed and clamped by a clamping plate from the outside of the current collector plate, and heat transfer in contact with the current collector plate A power conversion circuit that includes a plate, a heat-generating component that generates heat during operation provided in contact with the heat transfer plate, and converts the electrical output of the cell stack portion into a predetermined form; and the power conversion together with the clamping plate A casing surrounding the circuit and having an opening formed therein; An oxidant supply system that supplies oxidant to the fuel flow path, a fuel supply system that supplies fuel to the fuel flow path, a heat transfer plate temperature sensor that measures the surface temperature of the heat transfer plate, and a pump that drives the cooling medium; A heat exchanger for removing heat from the cooling medium flowing on the primary side using the secondary cooling medium flowing on the secondary side, a cooling medium temperature sensor for detecting the temperature of the cooling medium at the outlet of the cooling medium flow path, and a radiator A radiator for cooling the secondary cooling medium by a fan, and a secondary cooling medium circulation pump for driving the secondary cooling medium to circulate through the secondary side of the heat exchanger and the radiator; A cooling system for circulating the cooling medium in the cooling medium flow path, and an operating method of the fuel cell power generation system comprising:
Based on the surface temperature of the heat transfer plate detected by the heat transfer plate temperature sensor and the temperature of the cooling medium detected by the cooling medium temperature sensor, the rotational speed of the secondary cooling medium circulation pump and the rotational speed of the radiator fan A method for operating a fuel cell power generation system, wherein at least one of the above is controlled.

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