JP2023001986A - Fuel cell power generation device - Google Patents

Abstract

To provide a fuel cell power generation device capable of suppressing a cooling system from being excessively cool.SOLUTION: A fuel cell power generation device comprises: a fuel cell; a cooling system that supplies heating medium oil to the fuel cell; a pump provided on the cooling system to circulate the heating medium oil to the cooling system; a heater for heating the heating medium oil between an outlet of the fuel cell and a suction port of the pump; a temperature sensor that measures a temperature of the heating medium oil between the heater and the suction port; and a control device that increases or decreases a flow rate of the heating medium oil depending on the temperature measured by the temperature sensor.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to fuel cell power plants.

Conventionally, when the temperature of the fuel cell heat medium is lower than a predetermined temperature when the fuel cell system is started, there is a known technique for warming up the fuel cell early by raising the temperature of the fuel cell heat medium with an electric heater ( For example, see Patent Document 1).

Japanese Unexamined Patent Application Publication No. 2010-161080

Since thermal oil or water has insulating properties, it is sometimes used as a thermal medium for cooling fuel cells. In particular, thermal oil, which is more viscous than water, has lower heat transfer performance than water. Heat is easily accumulated in the heater. Therefore, a minimum flow rate of the heat transfer oil to be supplied to the cooling system is generally indicated so that the heater does not overheat or break.

However, if the flow rate of the heat medium oil flowing through the cooling system is too large when the temperature of the heat medium oil is relatively low, the temperature of the cooling system may become too cold. If the temperature of the cooling system becomes too cold, for example, the operating time of the heater for raising the temperature of the heat transfer oil becomes longer, resulting in increased energy loss.

The present disclosure provides a fuel cell power generator capable of suppressing overcooling of the cooling system.

In one aspect of the present disclosure,
a fuel cell;
a cooling system that supplies thermal oil to the fuel cell;
a pump provided in the cooling system for circulating the heat transfer oil in the cooling system;
a heater for heating the thermal oil between the outlet of the fuel cell and the suction port of the pump;
a temperature sensor that measures the temperature of the heat transfer oil between the heater and the suction port;
and a control device that increases or decreases the flow rate of the thermal oil according to the temperature measured by the temperature sensor.

According to one aspect of the present disclosure, overcooling of the cooling system can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structural example of the fuel cell power generator which concerns on one Embodiment. FIG. 3 is a diagram showing a first example of the relationship between the heater outlet temperature and the lower limit flow rate of heat medium oil; 4 is a flow chart showing an example of an operation control method for a fuel cell power generator according to one embodiment. FIG. 4 is a diagram showing each manipulated variable generated by the control device of the fuel cell power generator according to one embodiment; 4 is a flow chart showing an example of a method for setting a lower limit flow rate of heat transfer oil. FIG. 5 is a diagram showing a second example of the relationship between the heater outlet temperature and the lower limit flow rate of heat medium oil;

Embodiments will be described below.

FIG. 1 is a diagram showing a configuration example of a fuel cell power generator according to one embodiment. A fuel cell power generator 11 shown in FIG. 1 is a device that introduces fuel gas and oxidant gas and converts them into electrical energy. The fuel cell power plant 11 comprises, for example, a fuel cell 13, a DC-AC converter 12, a cooling system 27, a pump 28, a heater 19, a temperature sensor 17, an expansion tank 24 and a controller 20.

The fuel cell 13 is a device that electrochemically converts the chemical energy of a fuel such as hydrogen or methanol into electrical energy. The fuel cell 13 has a fuel electrode 14 , an air electrode 15 and a cooling plate 16 . The fuel cell 13 generates electricity through an electrochemical reaction between hydrogen or hydrogen-rich gas supplied to the fuel electrode 14 and oxygen contained in reaction air supplied to the air electrode 15 by the air blower 22 . Heat generated by the power generation of the fuel cell 13 is taken away by a cooling plate 16 incorporated in the cell stack, and the temperature of the fuel cell 13 is maintained at a predetermined operating temperature.

The fuel cell 13 has an inlet 13b through which thermal oil for cooling the fuel cell 13 is introduced, and an outlet 13a through which the thermal oil that has passed through the cooling plate 16 of the fuel cell 13 is discharged. The heat generated by the fuel cell 13 is released from the cooling plate 16 together with the heat transfer oil discharged to the outlet 13a.

The DC-AC converter 12 is a DC-AC converter that converts the DC power obtained by the power generation of the fuel cell 13 into AC power and supplies it to a load (not shown). The DC-AC converter 12 may be replaced with a DC-DC converter that converts the voltage of the DC power obtained by the power generation of the fuel cell 13 into DC power of a different voltage and supplies it to a load (not shown). .

The cooling system 27 is a cooling circuit that supplies heat medium oil such as insulating oil to the fuel cell 13 . The cooling system 27 includes, for example, a cooling plate 16 provided in the fuel cell 13 , an outlet path 27 a connecting the outlet 13 a of the fuel cell 13 and the suction port 28 a of the pump 28 , an outlet 28 b of the pump 28 and the fuel cell 13 . and an inlet path 27b connecting with the inlet 13b. The heat transfer oil discharged from the discharge port 28 b of the pump 28 to the inlet path 27 b circulates through the cooling system 27 .

The pump 28 is a circulation pump provided in the cooling system 27 and circulates the heat transfer oil in the cooling system 27 . The pump 28 has a suction port 28a, which is an inlet for the thermal oil, and a discharge port 28b, which is an outlet for the thermal oil. The pump 28 is operated by a motor (not shown) controlled by the controller 20 .

The heater 19 heats the thermal oil between the outlet 13 a of the fuel cell 13 and the suction port 28 a of the pump 28 . The heater 19 is, for example, a circulation heater provided in the outlet path 27a between the outlet 13a and the suction port 28a, and heats the thermal oil flowing through the outlet path 27a.

The temperature sensor 17 measures the temperature T of the heat medium oil between the heater 19 and the suction port 28a and outputs a sensor signal corresponding to the measured temperature T. The temperature sensor 17 is provided, for example, in the path portion between the outlet of the heater 19 and the suction port 28a of the pump 28 in the outlet path 27a, and measures the temperature T of the heat transfer oil that has passed through the outlet of the heater 19. In the example shown in FIG. 1, temperature sensor 17 measures temperature T between expansion tank 24 and heater 19 .

The expansion tank 24 branches from an outlet path 27 a of the cooling system 27 and is connected to the outlet path 27 a downstream of the heater 19 . The expansion tank 24 has, for example, a function of absorbing expansion or contraction of the thermal oil and a function of extracting gas generated in the thermal oil and releasing it into the atmosphere. The expansion tank 24 is provided at the top of the cooling system 27. For example, the expansion tank 24 is installed so that the liquid surface level of the heat transfer oil contained in the expansion tank 24 is higher than the uppermost cooling plate 16 (Fig. 1 indicates the position on the circuit, not the actual installation position).

The control device 20 is a controller that increases or decreases the flow rate of the heat medium oil flowing through the cooling system 27 according to the temperature measured by the temperature sensor 17 . Control device 20 is, for example, a programmable logic controller (PLC).

The controller 20 energizes the heater 19 to heat the heat medium oil by the heater 19 , and deenergizes the heater 19 to stop the heating of the heat medium oil by the heater 19 . The controller 20 controls the operation of the pump 28 , and more specifically controls the inverter that drives the motor that drives the pump 28 .

The functions of the control device 20 may be realized by causing a processor such as a CPU (Central Processing Unit) to operate according to a program stored in memory. The functions of the control device 20 may be realized by FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

When the fuel cell power generation device 11 is started or when the temperature of the heat medium flowing through the cooling system 27 is equal to or lower than a predetermined temperature threshold, the control device 20 heats the heat medium flowing through the cooling system 27 with the heater 19 so that the fuel cell Warm up 13 early. However, the heat transfer performance of the heat transfer oil is lower than that of water such as pure water. Therefore, it is required to flow the heat medium oil through the cooling system 27 at a certain flow rate or more so that the heater 19 does not burn out due to overheating.

However, if the flow rate of the heat medium oil flowing through the cooling system 27 is too large when the temperature of the heat medium oil is relatively low, the temperature of the cooling system 27 may become too cold. If the temperature of the cooling system 27 is too low, for example, the energization time of the heater 19 for raising the temperature of the heat transfer oil will be longer, resulting in increased energy loss.

In this embodiment, an upper limit temperature T3 (see FIG. 2) is set in advance so that the temperature of the heater 19 does not exceed the maximum allowable use temperature of the heater 19 . The upper limit temperature T3 is the maximum temperature allowed for the temperature T of the heat transfer oil on the outlet side of the heater 19 (heater outlet temperature). There is a correlation between the heater outlet temperature of the heat medium oil and the circulation flow rate of the heat medium oil flowing through the cooling system 27. Specifically, the heater outlet temperature of the heat medium oil increases as the circulation flow rate of the heat medium oil increases. descend. Using such a correlation, the control device 20 determines the lower limit of the flow rate of the thermal oil flowing through the cooling system 27 (for example, the lower limit flow rate discharged from the pump 28) according to the temperature T measured by the temperature sensor 17. ) is increased or decreased (see FIG. 2). In the example shown in FIG. 2 , the control device 20 performs control to decrease the lower limit of the flow rate of the thermal oil flowing through the cooling system 27 as the temperature T measured by the temperature sensor 17 decreases.

By performing such control, the control device 20 can reduce the flow rate of the heat medium oil circulated through the cooling system 27 in a temperature range where the heater outlet temperature of the heat medium oil is lower than the upper limit temperature T3. As a result, overcooling of the cooling system 27 is suppressed, so that, for example, the energization time of the heater 19 for raising the temperature of the heat medium oil is shortened, and an effect of suppressing an increase in energy loss is obtained. Further, since the control device 20 measures the temperature T of the heat medium oil after being heated by the heater 19 with the temperature sensor 17, the flow rate of the heat medium oil passing through the heater 19 can be accurately adjusted so that the heater 19 does not overheat. can be increased or decreased.

For example, the control device 20 increases or decreases the flow rate of the heat medium oil discharged from the discharge port 28b of the pump 28 to the inlet path 27b of the cooling system 27 according to the temperature T measured by the temperature sensor 17. The flow rate of the heat transfer oil passing through the heater 19 in 27 can be increased or decreased.

In the example shown in FIG. 2, the controller 20 reduces the lower limit of the flow rate through the cooling system 27 as the temperature T measured by the temperature sensor 17 decreases. As a result, the controller 20 can reduce the flow rate flowing through the cooling system 27 to the lower limit flow rate that is set lower as the temperature T measured by the temperature sensor 17 is lower. Further, according to the example shown in FIG. 2, the control device 20 controls the flow rate of the cooling system 27 so that it does not fall below the lower limit flow rate that is set lower as the temperature T measured by the temperature sensor 17 decreases. The flow rate flowing through system 27 can be controlled.

Next, the form shown in FIG. 1 will be described in more detail.

The fuel cell power plant 11 may also include a temperature sensor 18 . Taking the temperature sensor 17 as an example of a first temperature sensor, the temperature sensor 18 is an example of a second temperature sensor.

The temperature sensor 18 measures the temperature t of the thermal oil between the outlet 28b of the pump 28 and the inlet 13b of the fuel cell 13, and outputs a sensor signal corresponding to the measured temperature t. The temperature sensor 18 is provided, for example, in a portion of the inlet path 27b between the discharge port 28b of the pump 28 and the inlet 13b of the fuel cell 13, and measures the temperature t of the thermal oil before entering the inlet 13b. .

The control device 20 controls the flow rate of the heat transfer oil flowing through the cooling system 27 according to the temperature t measured by the temperature sensor 18, and the temperature T measured by the temperature sensor 17. Increase or decrease the lower limit of the flow rate of the heat transfer oil. As a result, the flow rate of the heat medium oil flowing through the cooling system 27 can be adjusted according to the temperature t on the inlet 13b side of the fuel cell 13, and the lower limit of the flow rate of the heat medium oil flowing through the cooling system 27 can be set to the temperature at the outlet side of the heater 19. It can be adjusted according to T.

The fuel cell power plant 11 may comprise a bypass line 26 connected in parallel with the pump 28 . The bypass path 26 is a circulation path whose inlet side is connected to the discharge port 28b and whose outlet side is connected to the suction port 28a. A control valve 25 and a heat exchanger 31 are provided in the bypass path 26 . In the cooling system 27, part of the heat medium oil discharged from the pump 28 is sent to the cooling plate 16 of the fuel cell 13, and the remaining heat medium oil is sent to the heat exchanger 31 and the control valve 25 on the bypass path 26. is formed to be returned to the suction port 28a side of the pump 28 via the .

The control device 20 adjusts the temperature of the heat medium oil flowing through the cooling system 27 by controlling the degree of opening of the control valve 25 according to the temperature t of the heat medium oil measured by the temperature sensor 18 . The control device 20 can control the temperature t of the thermal oil measured by the temperature sensor 18 to a predetermined target temperature, for example, by controlling the degree of opening of the control valve 25 . Thereby, the control device 20 can adjust the temperature of the fuel cell 13 to a target temperature corresponding to the current generated by the fuel cell 13 .

The heat exchanger 31 is supplied with an external heat medium such as external cooling water and exchanges heat with the heat medium oil flowing through the bypass passage 26 . The external heat medium is heat-exchanged by passing through the heat exchange device 36 and supplied to the radiator 38 . The radiator 38 is, for example, a cooler that air-cools the external heat medium using a fan or the like. The external heat medium whose temperature has been lowered by the radiator 38 is supplied to the heat exchanger 31 .

FIG. 3 is a flow chart showing an example of an operation control method for a fuel cell power generator according to one embodiment. FIG. 4 is a diagram showing each manipulated variable generated by the controller of the fuel cell power generator according to one embodiment. Note that the magnitude of each manipulated variable shown on the vertical axis in FIG. 4 is appropriately scale-converted. Next, FIGS. 3 and 4 will be described.

When the control device 20 is activated by turning on the main power supply of the fuel cell power generation device 11 , the control device 20 starts operating the pump 28 so that the heat medium oil circulates in the cooling system 27 . In step S10, the controller 20 determines that the temperature t on the side of the inlet 13b detected by the temperature sensor 18 during operation of the pump 28 at the time of starting or after starting is higher than a predetermined first threshold temperature t1 (see FIG. 4). Determine whether it is low. When the temperature t is equal to or lower than the first threshold temperature t1, the controller 20 energizes the heater 19 in order to raise the temperature of the thermal oil to a temperature suitable for cooling the fuel cell 13 (step S20). On the other hand, when the temperature t is higher than the first threshold temperature t1, the controller 20 deenergizes the heater 19 (step S40).

In step S20, the controller 20 increases the output of the heater 19 as the temperature t on the inlet 13b side detected by the temperature sensor 18 decreases (see FIG. 4). Thereby, when the temperature t is equal to or lower than the first threshold temperature t1, the thermal oil can be heated early when the temperature t of the thermal oil is relatively low. In step S20, the controller 20 gradually lowers the output of the heater 19 as the temperature t on the side of the inlet 13b detected by the temperature sensor 18 rises (see FIG. 4).

In step S30, the control device 20 determines whether or not the temperature t on the side of the inlet 13b detected by the temperature sensor 18 is equal to or lower than the first temperature threshold value t1. When the temperature t is equal to or lower than the first temperature threshold t1, the controller 20 continues heating by the heater 19 (step S20). On the other hand, when the temperature t is higher than the first temperature threshold value t1, the control device 20 determines that the temperature rise of the thermal oil is completed, and stops the heating by the heater 19 (step S40). Thus, the control device 20 stops heating the thermal oil by the heater 19 after the temperature t measured by the temperature sensor 18 exceeds the first threshold temperature t1 (see FIG. 4).

In step S<b>50 , the controller 20 controls the flow rate of the cooling system 27 by PI adjustment according to the temperature t measured by the temperature sensor 18 . P in PI represents proportional control, and I represents integral control. For example, when the temperature t measured by the temperature sensor 18 is higher than the first threshold temperature t1, the controller 20 controls the temperature t measured by the temperature sensor 18 to reach a predetermined target temperature. The flow rate of the heat medium oil discharged to the system 27 is increased or decreased by PI adjustment. For example, the controller 20 performs PI adjustment such that the larger the deviation ΔT obtained by subtracting the target temperature from the temperature t measured by the temperature sensor 18, the greater the flow rate of the thermal oil discharged from the pump 28 to the cooling system 27. . As a result, the temperature of the heat medium oil circulating in the cooling system 27 is accelerated, so that the temperature t (equivalent to the temperature of the fuel cell 13) measured by the temperature sensor 18 can be quickly brought close to the target temperature.

In step S50, when the temperature t measured by the temperature sensor 18 is higher than the first threshold temperature t1, the control device 20 increases the temperature t of the thermal oil measured by the temperature sensor 18. Control to increase the degree of opening may be performed (see FIG. 4). As the opening degree of the control valve 25 increases, the flow rate of the heat medium oil passing through the heat exchanger 31 on the bypass path 26 increases. As a result, the temperature of the heat medium oil circulating in the cooling system 27 is accelerated, so that the temperature t (equivalent to the temperature of the fuel cell 13) measured by the temperature sensor 18 can be quickly brought close to the target temperature. When the temperature t measured by the temperature sensor 18 exceeds the second threshold temperature t2, the control device 20 stops increasing the opening of the control valve 25 and maintains the opening of the control valve 25 at the maximum opening. do. The second threshold temperature t2 is set higher than the first threshold temperature t1.

FIG. 5 is a flow chart showing an example of a method for setting the lower limit flow rate of heat transfer oil. FIG. 6 is a diagram showing the relationship between the heater outlet temperature and the lower limit flow rate of the heat medium oil in the setting method of FIG. When the control device 20 increases or decreases the flow rate of the thermal oil flowing through the cooling system 27 (for example, when increasing or decreasing the flow rate of the thermal oil by PI adjustment in step 50 of FIG. 3 described above), for example, FIGS. 6, the lower limit flow rate of the heat transfer oil flowing through the cooling system 27 is set. Note that F1<F2<F3 and T1<T2<T3<T4.

In step S60, the control device 20 determines whether or not the heater outlet temperature measured by the temperature sensor 17 is equal to or lower than the upper limit temperature T3. The upper limit temperature T3 is the maximum temperature allowed for the heater outlet temperature. When the heater outlet temperature is not equal to or lower than the upper limit temperature T3, the controller 20 sets the lower limit flow rate of the heat medium oil to F3 (step S65). On the other hand, when the heater outlet temperature is lower than the upper limit temperature T3, the controller 20 determines whether the heater outlet temperature measured by the temperature sensor 17 is lower than the upper limit temperature T2 (step S70). When the heater outlet temperature is not equal to or lower than the upper limit temperature T2, the controller 20 sets the lower limit flow rate of the heat medium oil to F3 (step S75). On the other hand, when the heater outlet temperature is lower than the upper limit temperature T2, the controller 20 determines whether the heater outlet temperature measured by the temperature sensor 17 is lower than the upper limit temperature T1 (step S80). When the heater outlet temperature is not equal to or lower than the upper limit temperature T1, the controller 20 sets the lower limit flow rate of the heat medium oil to F2 (step S85). On the other hand, when the heater outlet temperature is equal to or lower than the upper limit temperature T1, the controller 20 sets the lower limit flow rate of the heat medium oil to F1 (step S90).

The control device 20 increases or decreases the flow rate of the thermal oil flowing through the cooling system 27 so that the flow rate of the thermal oil flowing through the cooling system 27 does not fall below the lower limit flow rate set according to FIGS. As a result, the lower the heater outlet temperature, the more the flow rate of the heat transfer oil flowing through the cooling system 27 can be reduced. Therefore, in a temperature range where the heater outlet temperature is relatively low, it is possible to suppress excessive cooling of the cooling system 27 due to excessive heat transfer oil flowing through the cooling system 27 .

When increasing or decreasing the flow rate of the heat medium oil flowing through the cooling system 27 (for example, when increasing or decreasing the flow rate of the heat medium oil by PI adjustment in step 50 of FIG. 3 described above), the control device 20 2, the lower limit flow rate of the heat transfer oil flowing through the cooling system 27 may be set.

Further, when the heater outlet temperature measured by the temperature sensor 17 rises to the heater protection temperature T4, the control device 20 stops the power generation of the fuel cell 13 to prevent the heater 19 from burning out and the fuel cell power generator 11 to operate. may be stopped.

Although the embodiments have been described above, the technology of the present disclosure is not limited to the above embodiments. Various modifications and improvements such as combination or replacement with part or all of other embodiments are possible.

REFERENCE SIGNS LIST 11 fuel cell generator 12 DC-AC converter 13 fuel cell 13a outlet 13b inlet 14 fuel electrode 15 air electrode 16 cooling plate 17 temperature sensor 18 temperature sensor 19 heater 20 controller 22 air blower 24 expansion tank 25 control valve 26 bypass path 27 cooling system 27a outlet path 27b inlet path 28 pump 28a suction port 28b discharge port 31 heat exchanger 36 heat exchange device 38 radiator

Claims (10)

a fuel cell;
a cooling system that supplies thermal oil to the fuel cell;
a pump provided in the cooling system for circulating the heat transfer oil in the cooling system;
a heater for heating the thermal oil between the outlet of the fuel cell and the suction port of the pump;
a temperature sensor that measures the temperature of the heat transfer oil between the heater and the suction port;
and a control device that increases or decreases the flow rate of the thermal oil according to the temperature measured by the temperature sensor. a second temperature sensor that measures the temperature of the thermal oil between the outlet of the pump and the inlet of the fuel cell;
2. The controller controls the flow rate according to the temperature measured by the second temperature sensor, and increases or decreases the lower limit of the flow rate according to the temperature measured by the temperature sensor. The fuel cell power generator according to . 3. The fuel cell power generator according to claim 2, wherein said controller stops heating said thermal oil by said heater after said temperature measured by said second temperature sensor exceeds a predetermined threshold temperature. a bypass path provided with a control valve and a heat exchanger and connected in parallel to the pump;
When the temperature measured by the second temperature sensor is higher than the threshold temperature, the control device increases the degree of opening of the control valve as the temperature measured by the second temperature sensor increases. The fuel cell power generator according to claim 3. 5. The fuel cell power generator according to any one of claims 2 to 4, wherein said control device controls said temperature measured by said second temperature sensor to reach a predetermined target temperature. 2. The fuel cell power generator according to claim 1, wherein said controller increases or decreases said lower limit of said flow rate according to said temperature measured by said temperature sensor. 7. The fuel cell power generator according to claim 6, wherein said controller controls said flow rate so that said flow rate does not fall below said lower limit. The fuel cell power generator according to any one of claims 1 to 7, wherein the controller reduces the flow rate as the temperature measured by the temperature sensor decreases. 9. The fuel according to any one of claims 1 to 8, wherein the control device increases or decreases the flow rate discharged from the discharge port of the pump to the cooling system according to the temperature measured by the temperature sensor. Battery generator. 10. The fuel cell power generator according to any one of claims 1 to 9, wherein said control device increases or decreases said flow rate passing through said heater according to said temperature measured by said temperature sensor.

Images