Air-cooled fuel cell system

Abstract

To provide an air-cooled fuel cell system excelling in drive performance of a fuel cell at low temperature while suppressing a case from increasing in size or becoming complicated.SOLUTION: A fuel cell system includes a fuel cell, a hydrogen system, a reactive air system, and a cooling air system. The fuel cell system has a case for housing the fuel cell. The case includes an upstream space and a downstream space in a flow direction of cooling air within the case, with the fuel cell as reference. The cooling air system has cooling-air blow means for generating a flow of the cooling air in the upstream space. The reactive air system includes a reactive air intake port and reactive air blow means in the upstream space. In a case where a predetermined switching condition arises, the fuel cell system stops driving the cooling air blow means and drives the reactive air blow means, thus reversing the flow of the cooling air within the case.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to air-cooled fuel cell systems. [Background technology]

[0002] Various technologies have been proposed regarding fuel cells (FCs), such as those disclosed in Patent Documents 1-5. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-185248 A [Patent Document 2] JP 2015-520500 A [Patent Document 3] JP 2001-015136 A [Patent Document 4] JP 2022-185251 A [Patent Document 5] JP 2022-185247 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, in order to circulate cooling air, it is necessary to enlarge the case, or to add a reversible cooling fan or mechanical structure.

[0005] The present disclosure has been made in consideration of the above-mentioned situation, and has as its main object to provide an air-cooled fuel cell system that has excellent operating performance of the fuel cell at low temperatures while suppressing the increase in size and complexity of the case. [Means for solving the problem]

[0006] The present disclosure provides an air-cooled fuel cell system, comprising: the fuel cell system includes a fuel cell, a hydrogen system that supplies hydrogen to the fuel cell, a reaction air system that supplies reaction air to the fuel cell, and a cooling air system that supplies cooling air to the fuel cell; the fuel cell has a reaction air flow path and a cooling air flow path having an independent flow path structure for the reaction air and the cooling air, The fuel cell system has a case, the case accommodates the fuel cell; the case has an upstream space and a downstream space in a flow direction of the cooling air inside the case based on the fuel cell, The cooling air system includes a cooling air blowing means for generating a flow of the cooling air in the downstream space, The reaction air system has a reaction air intake port and a reaction air blowing means in the upstream space, The fuel cell system is characterized in that, when a predetermined switching condition occurs, the fuel cell system stops driving the cooling air blowing means and drives the reaction air blowing means to reverse the flow of the cooling air in the case.

[0007] In the present disclosure, the specified switching condition may be at least one selected from the group consisting of when the outside air temperature is below a specified temperature, when the voltage amplitude value of the fuel cell is greater than or equal to a specified value, and when the temperature difference between the cooling air inlet temperature and the cooling air outlet temperature within the surface of the fuel cell is greater than or equal to a specified value. Effect of the Invention

[0008] The fuel cell system of the present disclosure provides excellent fuel cell operating performance at low temperatures while preventing the case from becoming large and complicated. [Brief description of the drawings]

[0009] [Figure 1] 1 is an exploded perspective view showing an example of a single cell of a fuel cell provided in a fuel cell system according to the present disclosure; [Diagram 2] FIG. 2 is a system configuration diagram showing an example of a fuel cell system according to the present disclosure during normal operation. [Diagram 3] FIG. 2 is a system configuration diagram showing an example of a fuel cell system according to the present disclosure during temperature equalization operation. [Figure 4] FIG. 4 is a schematic diagram showing an example of a temperature distribution in a cell during normal operation. [Diagram 5] FIG. 4 is a schematic diagram showing an example of temperature distribution within a cell during temperature equalization operation. [Figure 6] 4 is a flowchart showing an example of control of the fuel cell system of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of a fuel cell system that does not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. In the present disclosure, the gas supplied to the anode of the fuel cell is a fuel gas (anode gas), and the gas supplied to the cathode of the fuel cell is an oxidant gas (cathode gas). The fuel gas is a gas that mainly contains hydrogen and may be hydrogen. The oxidant gas is a gas that contains oxygen and may be oxygen, air, etc. In the present disclosure, air as the oxidant gas is referred to as reaction air, and air as the cooling gas is referred to as cooling air.

[0011] The present disclosure provides an air-cooled fuel cell system, comprising: the fuel cell system includes a fuel cell, a hydrogen system that supplies hydrogen to the fuel cell, a reaction air system that supplies reaction air to the fuel cell, and a cooling air system that supplies cooling air to the fuel cell; the fuel cell has a reaction air flow path and a cooling air flow path having an independent flow path structure for the reaction air and the cooling air, The fuel cell system has a case, the case accommodates the fuel cell; the case has an upstream space and a downstream space in a flow direction of the cooling air inside the case based on the fuel cell, The cooling air system includes a cooling air blowing means for generating a flow of the cooling air in the downstream space, The reaction air system has a reaction air intake port and a reaction air blowing means in the upstream space, The fuel cell system is characterized in that, when a predetermined switching condition occurs, the fuel cell system stops driving the cooling air blowing means and drives the reaction air blowing means to reverse the flow of the cooling air in the case.

[0012] In the conventional technology, in order to circulate the cooling air, it is necessary to provide a special fan that can rotate in a reverse direction, which has problems such as the need to enlarge the case, increasing the cost of the device, and the problem of the special fan that can rotate in a reverse direction reducing the efficiency of the cooling fan during normal operation. Providing a mechanism to reverse the fan or installing an additional fan for reverse flow has problems such as the need to enlarge the case and increasing the cost of the device. Furthermore, in the conventional technology, the temperature adjustment of the fuel cell using cooling air and the supply of reaction air to the fuel cell are controlled by the same fan, so that it is not possible to control each independently, for example, when it is desired to supply a large amount of reaction air to the fuel cell while keeping the cooling air at a very small flow rate. The present disclosure relates to an effective method for equalizing temperature during low-temperature operation of an air-cooled fuel cell, which draws in reaction air from the intake compartment, reverses the flow of the cooling air flow path, and equalizes the temperature within the cell surface; this eliminates the need to provide a special fan that can rotate in reverse, prevents the case from becoming larger and more complicated, and improves the operating performance of the fuel cell at low temperatures.

[0013] The fuel cell system includes a fuel cell that generates electricity by reacting hydrogen with air, a hydrogen system that supplies the hydrogen needed to generate electricity to the fuel cell, a reaction air system that supplies reaction air to the fuel cell, and a cooling air system that supplies cooling air to the fuel cell to cool the heat generated by power generation.

[0014] The fuel cell may have only one unit cell (cell) of the fuel cell, or may be a fuel cell stack (stack) which is a laminate of a plurality of cells. In this disclosure, both cells and fuel cell stacks may be referred to as fuel cells. The number of cells stacked in the fuel cell stack is not particularly limited, and may be, for example, from 2 to several hundred. The fuel cell stack may have wavy cooling fins on each cell to provide cooling air flow paths. The fuel cell stack may have current collector plates, pressure plates, etc. at the ends in the stacking direction.

[0015] A fuel cell has a reactant air flow path (oxidant gas flow path) and a cooling air flow path (cooling gas flow path) with independent flow path structures for the reactant air and the cooling air, and may further have a hydrogen gas flow path (fuel gas flow path). A flow path structure in which the reaction air and the cooling air are separate means that there is no sharing of air between the flow paths from the supply of air to the fuel cell to the exhaust of air from the fuel cell. Note that the flow path for exhausting the air exhausted from the fuel cell to the outside of the fuel cell system may or may not be separate.

[0016] The cell may have a flow path structure for passing the reaction air and the cooling air such that the flow of the cooling air and the flow of the reaction air cross each other in a plan view. The flow of the cooling air and the flow of the reaction air may cross each other or be perpendicular to each other. The cell may have a power generation portion. The power generating section may have a rectangular shape in a plan view. The power generating section may be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes. The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include a fluorine-based electrolyte membrane such as a thin film of perfluorosulfonic acid containing water, and a hydrocarbon-based electrolyte membrane. The electrolyte membrane may be, for example, a Nafion membrane (manufactured by DuPont). The two electrodes are the anode (fuel electrode or hydrogen electrode) and the cathode (oxygen electrode or air electrode). The electrodes include a catalyst layer and may include a gas diffusion layer as necessary, and the power generating portion may be a membrane electrode gas diffusion layer assembly (MEGA). The catalyst layer includes a catalyst, and the catalyst may include a catalytic metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity. Examples of the catalytic metal that can be used include platinum (Pt) and alloys of Pt with other metals (e.g., Pt alloys mixed with cobalt and nickel, etc.) The catalytic metal used as the cathode catalyst and the catalytic metal used as the anode catalyst may be the same or different. The electrolyte may be a fluorine-based resin, etc. As the fluorine-based resin, for example, a Nafion solution, etc. may be used. The catalytic metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalytic metal (catalyst-supporting carrier) and the electrolyte may be mixed. The support for supporting the catalytic metal may be, for example, a carbon material such as carbon that is generally available commercially. The gas diffusion layer may be a conductive member having air holes. Examples of the conductive member include porous carbon materials such as carbon cloth and carbon paper, and porous metal members such as metal mesh and foamed metal. The fuel cell may include a separator. The separators collect the electric current generated by power generation and function as partition walls. In a fuel cell, the separators are usually arranged on both sides of the power generation section in the stacking direction so that the power generation section is sandwiched between a pair of separators. One of the pair of separators is an anode separator and the other is a cathode separator. The anode separator may have grooves that serve as hydrogen gas flow paths on the surface facing the power generation section. The cathode separator may have grooves that serve as reaction air channels on the surface facing the power generation section. The separator may have holes forming manifolds such as supply holes and discharge holes for circulating a fluid in the stacking direction of the cells. The separator may be made of, for example, dense carbon obtained by compressing carbon to make it gas impermeable, or a press-molded metal (for example, iron, titanium, stainless steel, etc.). The cell may include an insulating resin frame disposed on the outer side (periphery) of the membrane electrode assembly in the planar direction between the anode separator and the cathode separator. The resin frame is molded into a plate-like and frame-like shape using a thermoplastic resin, and seals the gap between the anode separator and the cathode separator while holding the membrane electrode assembly in its central region. For the resin frame, for example, a resin such as PE, PP, PET, or PEN can be used. The resin frame may be a three-layer sheet composed of three layers with an adhesive layer disposed on the surface layer.

[0017] The fuel cell system may include a control device. The control device may control the reaction air system, the hydrogen system, the cooling air system, etc., and may control the entire fuel cell system. The control device physically has, for example, a processing device such as a CPU (central processing unit), a ROM (read-only memory) that stores control programs and control data processed by the CPU, a storage device such as a RAM (random access memory) that is mainly used as various working areas for control processing, and an input / output interface, and may be an ECU (electronic control unit), etc.

[0018] The fuel cell system has a case. The case houses a fuel cell. The case has an upstream space on the intake side and a downstream space on the exhaust side in the direction of cooling air flow within the case relative to the fuel cell. The case has an intake port and an exhaust port for a cooling air system. The upstream space is a partitioned space from the air intake port to the fuel cell, and the downstream space is a partitioned space from the fuel cell to the cooling air blowing means.

[0019] The reaction air system supplies reaction air to the fuel cell as an oxidant gas, and adjusts the flow rate of the reaction air. The reaction air system has a reaction air intake port and a reaction air blowing means in the upstream space in the case. A pressure loss body (air filter) may be installed in the reaction air intake port. The reaction air blowing means may be an air compressor, an air pump, an air blower, an air fan, or the like. The reaction air system may have an inlet sealing valve at the inlet of the reaction air of the fuel cell and an outlet sealing valve at the outlet of the reaction air of the fuel cell. The inlet sealing valve and the outlet sealing valve may be disposed in an upstream space in the case or in a downstream space in the case. In the present disclosure, the fuel cell has an independent flow path structure for the reaction air and the cooling air, and valves (an inlet side sealing valve and an outlet side sealing valve) are installed at the inlet and outlet of the reaction air of the fuel cell in the reaction air system, making it possible to seal the cathode of the fuel cell with a smaller volume than when the fuel cell has a flow path structure in which the reaction air and the cooling air are common.

[0020] The cooling air system supplies cooling air as a cooling gas to the fuel cell, and adjusts the flow rate of the cooling air. The cooling air system has a cooling air blowing means for generating a flow of cooling air in the downstream space in the case. The cooling air system has an intake port for drawing in air from the outside. A pressure loss body (air filter) may be installed in the intake port. The cooling air blowing means may be an air compressor, an air pump, an air blower, an air fan, or the like.

[0021] The hydrogen system supplies hydrogen as a fuel gas to the fuel cell and adjusts the flow rate of the hydrogen, and may include a hydrogen tank, a hydrogen inlet valve, an injector, a hydrogen purge valve, a gas-liquid separator, a hydrogen pump for hydrogen circulation, an ejector for hydrogen circulation, and hydrogen piping.

[0022] When a predetermined switching condition occurs, the fuel cell system performs cell temperature equalization operation by stopping the operation of the cooling air blowing means and operating the reaction air blowing means to reverse the flow of cooling air inside the case. Because the cooling air flows in the opposite direction to normal operation inside the fuel cell, the temperature inside the cell can be equalized. The specified switching condition may be at least one selected from the group consisting of when the outside air temperature is below a specified temperature, when the voltage amplitude value of the fuel cell is greater than or equal to a specified value, and when the temperature difference between the cooling air inlet temperature and the cooling air outlet temperature within the surface of the fuel cell is greater than or equal to a specified value.

[0023] FIG. 1 is an exploded perspective view showing an example of a single cell of a fuel cell provided in a fuel cell system of the present disclosure. 1 includes cooling fins (cooling air flow paths) 2 that serve as flow paths for cooling air (cooling gas) 7, a reaction air inlet 3, a reaction air outlet 4, a hydrogen gas inlet 5, a hydrogen gas outlet 6, two separators 11, and an MEA and a resin frame 12 sandwiched between the two separators 11. As shown in FIG. 1, the fuel cell 1 has a flow path structure in which the reaction air 9 and the cooling air 7 are independent of each other.

[0024] FIG. 2 is a system configuration diagram showing an example of the fuel cell system of the present disclosure during normal operation. FIG. 3 is a system configuration diagram showing an example of the fuel cell system of the present disclosure during temperature equalization operation. FIG. 4 is a schematic diagram showing an example of the temperature distribution in the cell during normal operation. FIG. 5 is a schematic diagram showing an example of temperature distribution within the cell during temperature equalization operation. The fuel cell system shown in Figs. 2 and 3 includes a case 50, a fuel cell stack 10, a reaction air system 20, a cooling air system 30, and a hydrogen system. In Figs. 2 and 3, the hydrogen system is omitted for convenience. The reaction air system 20 includes a reaction air intake port 21, an air blower 22, an inlet side sealing valve 23, and an outlet side sealing valve 24. The cooling air system 30 includes a cooling fan 31 and an intake port 32. The intake port 32 may include an intake filter. The fuel cell system shown in Figs. 2 and 3 includes sealing valves 23 and 24 at the inlet and outlet of the reaction air system 20, and includes independent blowing means 22 and 31 for the reaction air system 20 and the cooling air system 30. The reaction air intake port 21 may include an air filter. The fuel cell stack 10 has a flow path structure in which reaction air and cooling air have independent flow paths. Case 50 has an upstream space 52 and a downstream space 53 separated by a partition wall 51 in the flow direction of cooling air 7 inside case 50 with respect to fuel cell stack 10. The upstream space 52 is a separated space from the air intake port 32 to the fuel cell stack 10, and the downstream space 53 is a separated space from the fuel cell stack 10 to the cooling fan 31. 2 and 3, the reaction air intake port 21, air blower 22, inlet side sealing valve 23, and outlet side sealing valve 24 of the reaction air system 20 are accommodated in the cooling air upstream space 52. By providing the reaction air intake port 21 in the upstream space 52 on the cooling air intake side, the cooling fan 31 can be stopped and the air blower 22 can be driven to reverse the flow of cooling air inside the case as shown in FIG.

[0025] In an air-cooled fuel cell stack, outside air is taken in directly into the fuel cell stack, so the side where the outside air is taken in has a temperature close to the outside air temperature T1 (Figs. 2 and 4). The cooling air is warmed by heat generated by the cells, and the temperature at the outlet side of the cells becomes T2, which is higher than T1. For example, when operating at T1 = -5°C and T2 = 50°C, the low-temperature part 61 of the cells is cooled, and the amount of liquid water increases excessively, causing flooding and a decrease in power generation performance, or freezing and clogging, making it impossible to generate power. At this time, temperature equalization operation reverses the cooling air flow within the cell and transfers heat from the high temperature part 60 to the low temperature part 61, making it possible to equalize the cell temperature and prevent a decrease in fuel cell performance (Figs. 3 and 5). Because the reaction air is exhausted to the outside as in normal operation, moist exhaust gas does not flow back. In cases where the reaction air intake port is not provided in the upstream space on the cooling air intake side, or where there is no pressure loss body at the intake port, backflow of cooling air does not occur. If the reaction air flow path and cooling air flow path of the fuel cell are not configured as independent flow path structures, reverse flow of moist common cooling reaction air may cause condensation inside the case, resulting in malfunctions of electronic devices, etc.; however, by having independent flow path structures for the reaction air flow path and cooling air flow path of the fuel cell, the above-mentioned malfunctions can be avoided.

[0026] FIG. 6 is a flowchart showing an example of control of the fuel cell system of the present disclosure. First, the temperature is determined. For example, it is determined whether the outside air temperature or the temperature T1 in the fuel cell system is lower than a predetermined temperature T0. The predetermined temperature T0 can be set to any value as appropriate, and may be set to the outside air temperature of 0°C, for example. If T1 is equal to or higher than the predetermined temperature T0, the normal mode is executed and the control is terminated. On the other hand, if T1 is lower than the predetermined temperature T0, the low temperature mode is executed. In the low temperature mode, the presence or absence of puddles or icing is determined. The presence or absence of puddles or icing may be determined, for example, when a drop in cell voltage or voltage fluctuation is confirmed by a cell voltage monitor. In addition, since puddles increase when power generation is performed for a certain period of time or more in a low temperature state, the presence of puddles may be determined in this case. Furthermore, a temperature sensor may be installed in the low temperature section of the fuel cell to directly measure the temperature of the fuel cell, and if the temperature of the fuel cell is below a predetermined temperature, the presence of icing may be determined. If there is no puddle or ice, the normal mode is executed and the control is terminated. On the other hand, if there is puddle or ice, the operation of the cooling air blowing means is stopped and the reaction air blowing means is driven to perform the cell temperature equalization operation. After the temperature equalization operation, a recovery judgment is performed. The recovery judgment may be made when the dropped cell voltage, as measured by a cell voltage monitor, rises to a normal voltage. Alternatively, the recovery may be judged as being made as a result of completion of warm-up when the temperature equalization operation has been performed continuously for a certain period of time or more. Furthermore, a temperature sensor may be installed in the low-temperature portion of the fuel cell to directly measure the temperature of the fuel cell, and if the temperature of the fuel cell is equal to or higher than a predetermined temperature, the recovery may be judged as being made. If the recovery judgment determines that the temperature has recovered, normal operation is performed and the control is terminated. On the other hand, if the recovery judgment determines that the temperature has not recovered, the temperature equalization operation is continued and a judgment is made to interrupt the operation. The decision to interrupt may be made, for example, when the outside air temperature T1 rises to or exceeds a predetermined temperature T0. Also, the decision to interrupt may be made when the load required for the fuel cell system changes. Furthermore, the decision to interrupt may be made when an interruption from another mode occurs. When the interruption determination determines that the operation should be interrupted, normal operation is performed and the control is terminated. On the other hand, when the interruption determination determines that the operation should not be interrupted, the temperature equalization operation is continued. [Explanation of symbols]

[0027] 1. Cell 2. Cooling fins (cooling air flow path) 3.Reaction air inlet 4.Reaction air outlet 5. Hydrogen gas inlet 6. Hydrogen gas outlet 7. Cooling air (cooling gas) 8. Hydrogen gas 9.Reaction air 10. Fuel Cell Stack 11. Separator 12.MEA, resin frame 20.Reaction air system 21.Reaction air intake 22. Air Blower 23. Inlet side sealing valve 24.Outlet side sealing valve 30. Cooling air system 31. Cooling fan 32. Air intake 50. Case 51. Bulkhead 52. Upstream space 53. Downstream space 60. High temperature section 61. Low temperature section

Claims

1. An air-cooled fuel cell system, the fuel cell system includes a fuel cell, a hydrogen system that supplies hydrogen to the fuel cell, a reaction air system that supplies reaction air to the fuel cell, and a cooling air system that supplies cooling air to the fuel cell; the fuel cell has a reaction air flow path and a cooling air flow path having an independent flow path structure for the reaction air and the cooling air, The fuel cell system has a case, the case accommodates the fuel cell; the case has an upstream space and a downstream space in a flow direction of the cooling air inside the case based on the fuel cell, The cooling air system includes a cooling air blowing means for generating a flow of the cooling air in the downstream space, The reaction air system has a reaction air intake port and a reaction air blowing means in the upstream space, When a predetermined switching condition occurs, the fuel cell system stops driving the cooling air blowing means and drives the reaction air blowing means to reverse the flow of the cooling air in the case.

2. 2. The fuel cell system according to claim 1, wherein the specified switching condition is at least one selected from the group consisting of when the outside air temperature is below a specified temperature, when the voltage amplitude value of the fuel cell is equal to or greater than a specified value, and when the temperature difference between the cooling air inlet temperature and the cooling air outlet temperature within the surface of the fuel cell is equal to or greater than a specified value.

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