JP6145683B2 - Fuel cell power generation system - Google Patents

Description

  The present invention relates to a fuel cell power generation system that uses generated power and exhaust heat of a fuel cell.

  Fuel cells are highly reactive because they produce electricity and heat by reacting a fuel gas containing at least hydrogen and an oxidant gas containing at least oxygen, and directly or indirectly convert the chemical energy of the fuel into electrical energy. Power generation efficiency can be obtained.

  In addition, the fuel cell power generation system is a system equipped with this fuel cell, which supplies electric power generated by the fuel cell, boils hot water by effectively using exhaust heat generated during power generation, and stores the boiled hot water in a hot water storage tank. The hot water can be supplied according to the user's demand for hot water supply.

  Here, the efficiency of the fuel cell power generation system is reduced when the generated heat cannot be stored as hot water. Therefore, if the hot water storage tank is full of hot water, it is necessary to stop power generation and maintain high efficiency. There is.

  However, if the hot water storage tank is simply filled and the power generation is stopped, the hot water storage tank will fill up quickly if the user's hot water consumption is low. However, the durability of the fuel cell power generation system may be adversely affected. On the other hand, if the user consumes a large amount of hot water, the user may run out of hot water when it is essential to use hot water. .

  Therefore, in order for the user to use the fuel cell power generation system comfortably and efficiently, it is essential to operate based on the user's power demand and hot water supply demand.

  Therefore, the conventional fuel cell power generation system predicts the user's power demand and / or hot water supply demand, and performs operation control based on the predicted demand.

  For example, Patent Literature 1 discloses a fuel cell power generation system that accurately predicts different power demands and / or hot water supply demands for individual users and improves operating efficiency.

  FIG. 9 shows a block diagram of a conventional fuel cell power generation system. The conventional fuel cell power generation system includes power demand and / or hot water supply demand prediction means 101, and various command input means 102 for selecting and inputting the start / stop of the fuel cell power generation system and the mode, and power demand data. Electric power demand measuring means 103 for measuring, hot water supply demand measuring means 104 for measuring hot water consumption, room temperature measuring means 105 for measuring room temperature data, calendar function 106 for inputting date and day of week, and time measurement A fuel processor that predicts electric power demand and / or hot water supply demand from the time keeping means 107, hot water storage amount measuring means 108 that measures the current hot water storage amount, and past case database 109, and the controller 110 generates hydrogen. And 111 and the fuel cell 112 are controlled to control the external load 113 such as electric power and hot water supply.

Japanese Patent No. 3897289

  However, since the conventional fuel cell power generation system performs start / stop based mainly on the user's power demand and / or demand predicted from the hot water supply demand, for example, depending on the stop time and the outside air temperature at the time of stop, In some cases, the fuel cell cannot be sufficiently cooled during stoppage or standby.

  During power generation, impurities may accumulate in the fuel cell. When impurities accumulate, performance degradation such as voltage drop may be caused, and durability of the fuel cell may be reduced.

  Here, the impurities that may accumulate during power generation are impurities contained in air in the atmosphere used for power generation and impurities generated from members used inside the fuel cell power generation system.

  Impurities contained in the atmosphere include sulfur dioxide and nitrogen oxides. In particular, sulfur dioxide is strongly adsorbed by catalysts made of noble metals used for fuel cell electrodes, causing catalyst poisoning, There exists an effect | action which reduces catalyst activity.

  In addition, impurities generated from members used in the fuel cell power generation system include organic impurities, which cover the catalyst surface in the same way, hindering the reaction, and preventing diffusion layers and flow paths. There is a possibility that the wettability is changed and gas diffusibility is hindered.

  On the other hand, among these impurities, for example, there are water-soluble impurities such as sulfur dioxide, and there is an impurity having a property of being well dissolved in the water produced by the fuel cell and condensed water condensed from the humidified water.

  Therefore, when the fuel cell is stopped, the temperature of the fuel cell is decreased, and water-soluble impurities are washed away to some extent by condensed water generated by condensation of generated water in the fuel cell or humidified water. Can do.

  However, the temperature of the fuel cell can be sufficiently cooled during the stop period, for example, when the stop time of the fuel cell is short, when the outside air temperature at the time of stop is high, or when the temperature decrease rate of the fuel cell is slow. Therefore, the amount of generated water in the fuel cell and the amount of humidified water to be condensed is reduced, and water-soluble impurities cannot be washed away sufficiently. Therefore, the accumulated impurities cause deterioration in fuel cell performance and durability. There was a problem to do.

  On the other hand, in order to determine whether or not the temperature of the fuel cell is sufficiently cooled during the stop or standby, a cooling medium for cooling the fuel cell is circulated during the stop or standby. It has been necessary to detect the temperature of the fuel cell that is stopped or waiting by detecting the temperature of the cooling medium.

  The present invention solves the above-described conventional problem, and even when the outside air temperature at the time of stoppage is high, or without detecting the temperature of the fuel cell during stoppage or standby, a sufficient amount of condensed water can be obtained. It is an object of the present invention to provide a fuel cell power generation system that cools a fuel cell to an obtained temperature and suppresses performance degradation and durability degradation due to impurities.

In order to solve the above-described conventional problems, a fuel cell power generation system of the present invention includes a fuel cell that generates heat and electricity using a solid polymer electrolyte membrane, and a fuel cell temperature determination unit that determines the temperature of the fuel cell. The outside air temperature judging means for judging the outside air temperature, and when the fuel cell power generation is stopped, the temperature of the fuel cell immediately before the stop and the outside air temperature are used to determine whether the temperature of the fuel cell is stopped or in the standby state. Estimate the time when the temperature falls below the first temperature at which sufficient amount of condensed water is obtained to wash away impurities accumulated in the battery, and set the period up to the predicted time as the start prohibition period for prohibiting the next start of the fuel cell Starting a prohibition period setting means, the start-up of the fuel cell, power generation operation, a control unit for controlling the stop and wait, the controller is sometimes the fuel cell has stopped power generation, start prohibition period elapsed time after the stop Of setting means When the specified start-up prohibition period is exceeded, the next start-up of the fuel cell is permitted, and when the elapsed time after the stop of the fuel cell is less than the start-up prohibition period, the next start-up of the fuel cell is prohibited. is there.

  Thereby, even when the outside air temperature at the time of stoppage is high, or without detecting the temperature of the fuel cell at the time of stoppage or standby, the temperature of the fuel cell up to the first temperature at which a sufficient amount of condensed water can be obtained. Can be reduced.

  According to the fuel cell power generation system of the present invention, impurities accumulated in the fuel cell during power generation can be washed away with condensed water at the time of stoppage, and performance degradation and durability degradation due to impurities can be suppressed.

Block configuration diagram of a fuel cell power generation system according to Embodiment 1 (A) Explanatory drawing of example of power generation demand pattern of fuel cell power generation system (b) Explanatory drawing of example of hot water supply demand pattern of fuel cell power generation system The figure which shows the relationship between the temperature and time of the fuel cell at each outside temperature of the fuel cell power generation system The figure which shows the relationship between the starting prohibition period of the fuel cell of fuel cell power generation system, and outside temperature Diagram showing voltage behavior of impurity addition start / stop test of fuel cell power generation system Flowchart showing a control sequence of the fuel cell power generation system in the first embodiment. The figure which shows transition of the average temperature of the outside temperature of the day in each month A flowchart which shows the control sequence of the fuel cell power generation system in Embodiment 3. Block diagram of a conventional fuel cell power generation system

A first invention is a fuel cell that generates heat and electricity using a solid polymer electrolyte membrane;
Fuel cell temperature determining means for determining the temperature of the fuel cell;
Outside temperature judging means for judging outside temperature;
When power generation of the fuel cell is stopped, from the temperature of the fuel cell immediately before the stop determined by the fuel cell temperature determination unit and the outside air temperature determined by the outside air temperature determination unit, the stop of the fuel cell, or A time during which the standby temperature is equal to or lower than a first temperature at which a sufficient amount of condensed water is obtained to wash away impurities accumulated in the fuel cell during power generation is predicted, and a period until the predicted time is determined. Start prohibition period setting means for setting as a start prohibition period for prohibiting the next start,
A controller for controlling start-up, power generation operation, stop and standby of the fuel cell;
With
Wherein the controller, at the fuel cell has stopped power generation, in the case of more than start prohibition period the elapsed time after the stop of the fuel cell is set in the start prohibition period setting means, next startup of the fuel cell When the elapsed time after the stop of the fuel cell is less than the start prohibition period, control is performed to prohibit the next start of the fuel cell.

With this configuration, it is possible to predict the time during which the temperature of the fuel cell is equal to or lower than the first temperature from the temperature of the fuel cell at the time of stop and the outside air temperature without detecting the temperature of the fuel cell at the time of stop or standby. If the temperature of the fuel cell is reduced to the first temperature at which a sufficient amount of condensed water is obtained during stop or standby, the next power generation is not started. However, a sufficient amount of condensed water condensed in humidified water and generated water in the fuel cell is secured, and impurities accumulated during power generation can be washed away with condensed water at the time of power generation and removed. Decrease and durability can be suppressed.

  In addition, it is not necessary to detect the temperature of the fuel cell by circulating cooling water for cooling the fuel cell during stoppage or standby, and detecting the temperature of the cooling water. In addition, it is possible to reduce wasteful energy consumed during stoppage or standby, and maintain high efficiency of the fuel cell power generation system.

  According to a second invention, in the first invention, the fuel cell temperature determining means includes a fuel cell temperature detector for detecting a temperature of the fuel cell.

  With this configuration, the fuel cell temperature detector accurately or directly or indirectly detects the temperature of the fuel cell immediately before stopping, and the amount of condensed water that is sufficiently washed out by the impurities set by the start prohibition period setting means. As a result, the accuracy of predicting the start-up prohibition period when the temperature is lower than the first temperature that can be ensured is improved, impurities can be more reliably removed, and performance degradation and durability degradation of the fuel cell can be suppressed.

In a third aspect based on the first aspect, the fuel cell temperature determination means includes a cooling unit that supplies a cooling medium to the fuel cell and cools it.
The temperature immediately before the stop of the fuel cell is estimated based on the relationship between the temperature of the cooling medium and the temperature of the fuel cell.

  With this configuration, the temperature of the fuel cell at the time of stopping can be estimated from the relationship between the temperature of the cooling medium that exchanges heat with the fuel cell at the time of power generation and the temperature of the fuel cell without detecting the temperature of the fuel cell at the time of stopping. Therefore, not only is the structure simple and economical, but the temperature data of the cooling medium at the inlet or outlet of the fuel cell at the time of stoppage can be used to obtain a more accurate fuel cell temperature. .

In a fourth aspect based on the first aspect, the outside air temperature determining means includes a calendar for managing the date and time.
The outside air temperature is determined based on the relationship between the date and the outside air temperature.

  With this configuration, using the annual outside temperature database of the place where the fuel cell power generation system is installed in advance, the vicinity of the place, or the place where the environment and season are similar, the outside temperature is calculated from the current date and time. Since the start prohibition period is obtained by predicting the time during which the temperature of the fuel cell is equal to or lower than the first temperature from the determined outside air temperature, the temperature of the fuel cell can be reduced with a simple configuration to generate power. Impurities accumulated therein can be washed away with condensed water at the time of stoppage, and can be removed, so that deterioration in fuel cell performance and durability can be suppressed.

In a fifth aspect based on any one of the first to fourth aspects, the outside air temperature determining means includes an outside air temperature detector for detecting the outside air temperature,
The start prohibition period setting means determines the temperature of the fuel cell from the outside temperature detected by the outside temperature detector when the elapsed time after the stop of the fuel cell is less than the start prohibition period predicted at the stop. A time when the temperature falls below the first temperature is predicted, and the start-up prohibition period is updated each time.

  With this configuration, even when the outside air temperature fluctuates after stopping or during standby, the start-up prohibition period can be corrected each time, and the temperature of the fuel cell is always made to reach the first temperature more accurately. Impurities can be washed away.

  In addition, if the outside air temperature decreases during stoppage or standby, the start-up prohibition period is shortened, so the stop time can be shortened, and if the start-up timing is earlier according to demand, the power generation time can be extended. Is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the same components as those of the above-described embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block configuration diagram of a fuel cell power generation system according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the fuel cell power generation system according to Embodiment 1 of the present invention includes a power supply unit that generates power by the fuel cell 1 and supplies power, and hot water generated by the heat generated when the fuel cell 1 generates power. And a hot water supply section for supplying hot water stored in the hot water storage tank 2.

  The power supply unit and the hot water supply unit are respectively provided with a power demand detection means 3 and a hot water supply demand detection means 4 to obtain supply power amount data information of the power supply unit and hot water consumption data information of the hot water supply unit. doing. The acquired data information is stored in the past case database 5.

  The fuel cell power generation system includes a demand prediction unit 6, and the demand prediction unit 6 includes a past case database 5, a power demand detection unit 3, and a power demand detection unit 3 so that a user can use electricity and hot water comfortably and efficiently. From the current power demand information and hot water demand information obtained from the hot water demand detecting means 4, a power demand and hot water demand suitable for each user are predicted, an operation plan is made based on the predicted value, and the controller 7 is configured to perform power control such as start of power generation, load control, and stop of power generation of the fuel cell 1 to efficiently supply power and hot water to the user.

  2A and 2B show examples of power generation demand and hot water supply demand of the fuel cell power generation system according to the embodiment of the present invention, respectively. The fuel cell power generation system according to the embodiment of the present invention has a rating of 750 W, but the rating range is not limited to this.

  The fuel cell power generation system according to the embodiment of the present invention, for example, as shown in FIG. 2 (a), starts power generation at 9:00 am when power demand increases, and power up to a maximum of 750W (hatched line) At the same time that the hot water is boiled with the heat generated during power generation, and the power generation of the fuel cell 1 is controlled so that the amount of hot water in the hot water storage tank 2 is almost full by 9 pm when the hot water supply demand reaches its peak. It is carried out.

  Then, power generation is stopped when the necessary amount of hot water is accumulated (around 10:00 pm) in accordance with the timing at which the peak of hot water demand is exceeded and the peak of power demand is also reduced.

  Next, the configuration of the fuel cell 1 and the mechanism of power generation will be described.

  The fuel cell 1 includes a membrane electrode assembly (MEA) in which an anode and a cathode are formed on both surfaces of an electrolyte membrane having hydrogen ion conductivity, and a fuel gas and an oxidant gas on the anode and the cathode, respectively. It is comprised with the stack which laminated | stacked the single cell module which consists of a separator in which the flow path which supplies and discharges was formed.

Here, the electrolyte membrane is composed of, for example, a solid polymer electrolyte made of perfluorocarbon sulfonic acid polymer, and the anode and the cathode are a catalyst in which a noble metal such as platinum is supported on porous carbon having high oxidation resistance, hydrogen The catalyst layer is composed of a mixture of an ionomer of a polymer electrolyte having ion conductivity, and a gas diffusion layer having air permeability and electron conductivity laminated on the catalyst layer.

  At this time, an alloy catalyst such as platinum-ruthenium is generally used as the anode catalyst so as to suppress poisoning due to impurities contained in the fuel gas, particularly carbon monoxide.

  The gas diffusion layer is made of carbon paper, carbon cloth, carbon non-woven fabric or the like that has been subjected to water repellent treatment in order to promote drainage of the generated water.

  The separators disposed on the anode and the cathode are made of a conductive material such as carbon or metal, and the fuel gas or the oxidizing agent is respectively provided on the side facing the electrode surface of the anode or the cathode. For example, a serpentine-like flow path for supplying or discharging gas is formed.

  Further, a cooling medium flow path for supplying and discharging a cooling medium for cooling the fuel cell 1 is formed on the side of the anode or cathode separator that does not directly face the anode or the cathode, respectively.

  A fuel cell 1 is configured by fastening and integrating a stack in which single cells are stacked, a current collector for taking out current from both ends of the stack, and a pair of end plates. A heat insulating material is disposed to prevent heat radiation to the exhaust and to improve exhaust heat recovery efficiency.

  Then, as shown in FIG. 1, an oxidant gas (air) containing at least oxygen is supplied to the cathode passage (C) of the fuel cell 1, a fuel gas containing at least hydrogen is supplied to the anode passage (A), and The cooling medium can be supplied to the cooling medium path (W).

  Here, the air supplied to the cathode is supplied using an oxidant gas supply means such as a blower, and if necessary, an impurity removing means for removing impurities in the air and a humidifying means for humidifying the air are provided. .

  Further, the hydrogen supplied to the anode is generated by the fuel processor 8.

  Here, the configuration of the fuel processor 8 and the mechanism of hydrogen generation will be described. The fuel processor 8 includes a desulfurization unit that removes a sulfur compound that becomes a catalyst poison contained as an odorant from a source gas such as a city gas, a source gas supply unit that adjusts and supplies a flow rate of the desulfurized source gas, A reforming unit that generates hydrogen-containing fuel gas by steam reforming the desulfurized raw material gas; a CO conversion unit that converts the carbon monoxide generated in the reforming unit to reduce the concentration of carbon monoxide; Furthermore, it is comprised with the CO removal part which selectively oxidizes and removes the carbon monoxide contained in fuel gas. Air in the atmosphere is supplied to the CO removal unit.

  Here, for example, when methane is used as the raw material gas, the reaction shown in (Chemical Formula 1) and (Chemical Formula 2) occurs in the reforming unit with water vapor to generate hydrogen.

  In addition, the reaction shown in (Chemical Formula 3) is performed by summing up all reactions occurring in the reforming section.

  However, the reformed gas generated in the reforming section contains about 10% carbon monoxide in addition to hydrogen. Carbon monoxide poisons the catalyst contained in the anode in the operating temperature range of the fuel cell and reduces its catalytic activity. Therefore, as shown in the reaction formula of (Chemical Formula 2), carbon monoxide generated in the reforming unit is converted into carbon dioxide in the CO conversion unit. This reduces the concentration of carbon monoxide to about 5000 ppm.

  Further, the carbon monoxide having a reduced concentration is selectively oxidized with oxygen taken from the atmosphere by the reaction represented by (Chemical Formula 4) in the CO removal section. As a result, the concentration of carbon monoxide can be reduced to about 10 ppm or less, which can suppress a decrease in the catalytic activity of the anode catalyst.

  Further, during power generation, air taken from the atmosphere is supplied to the anode, and about 1 to 2% of air is mixed with the hydrogen gas generated by the fuel processor 8 (air bleed), thereby slightly remaining carbon monoxide. The impact can be further reduced.

  Next, the cooling unit will be described. The cooling unit includes a cooling medium tank 9 a that stores a cooling medium that cools the fuel cell 1, a cooling medium pump 9 b that supplies the cooling medium, and the heat generated in the fuel cell 1 through the cooling medium flow path (W). The heat exchanger 10 is configured by a heat exchanger 10 that heat-exchanges and further heat-exchanges to produce hot water. Low temperature water or hot water at the lower part of the hot water storage tank 2 is supplied to the heat exchanger 10 by the hot water circulation pump 2a, exchanges heat with a high temperature cooling medium, becomes hot hot water, and is returned to the upper part of the hot water storage tank 2. It is configured to be stored.

  The fuel cell 1 is provided with fuel cell temperature detectors 11a and 11b as fuel cell temperature determination means at the inlet and outlet of the fuel cell 1 and circulates through the coolant flow path (W) by the coolant pump 9b. The temperature at the inlet and / or the outlet of the fuel cell 1 is detected, and the temperature of the fuel cell 1 at the time of power generation and at the time of stoppage can be determined from the detected temperature of the cooling medium.

  In addition, an outside air temperature judging means 12 for judging the outside air temperature is provided, and the outside air temperature where the fuel cell power generation system is placed at the time of stop or standby can be judged.

  In the fuel cell power generation system configured as described above, when the fuel gas containing at least hydrogen is supplied to the anode and the oxidizing gas containing at least oxygen is supplied to the cathode and an external load is connected to the fuel cell 1, the hydrogen in the fuel gas reacts. As shown in the formula (Chemical Formula 5), electrons are released at the interface between the anode catalyst and the electrolyte to form hydrogen ions.

  The released hydrogen ions move to the cathode through the electrolyte membrane, and receive electrons at the cathode catalyst-electrolyte interface. At this time, it reacts with oxygen supplied to the cathode, and water is generated as shown in the reaction formula (Formula 6).

  When the above reactions are combined, the reaction shown in (Chemical Formula 7) is performed.

  By the way, various impurities are contained in the atmosphere. For example, sulfur dioxide and nitrogen oxides can be raised. In particular, sulfur dioxide is used as a catalyst made of noble metals used for electrodes of fuel cells. Adsorbs strongly, causes catalyst poisoning, and has an effect of reducing catalyst activity.

  In addition, some members used in the fuel cell power generation system generate impurities, for example, there are members that generate impurities such as organic matter, and these impurities also cover the catalyst surface. Thus, there is an effect of inhibiting the reaction or changing the wettability of the diffusion layer and the flow path to inhibit the gas diffusibility.

  When these impurities enter and accumulate in the fuel cell 1 during power generation, there may be a case where performance decreases such as a voltage drop or the durability of the fuel cell 1 decreases.

  On the other hand, among these impurities, for example, there are water-soluble impurities such as sulfur dioxide, and there are also impurities that dissolve well in the generated water of the fuel cell 1 and condensed water condensed from humidified water.

  Therefore, if the temperature of the fuel cell 1 is sufficiently lowered when the fuel cell 1 is stopped, the produced water in the fuel cell 1 or the humidified water is condensed to produce condensed water, and if it is a water-soluble impurity, After stopping, it can be dissolved in the condensed water during standby, and the condensed water in which impurities are dissolved together with the fuel gas or oxidant gas supplied next time is discharged out of the system of the fuel cell 1, It can be washed away to some extent.

  The temperature of the fuel cell 1 at the time of stopping, which does not affect the durability of the fuel cell 1 and can sufficiently wash out impurities, is defined as a first temperature.

  In the fuel cell power generation system according to Embodiment 1 of the present invention, the fuel cell 1 is stopped from the temperature of the fuel cell 1 determined by the fuel cell temperature determining means 11a and 11b and the outside air temperature determined by the outside air temperature determining means 12. Alternatively, it includes a start prohibition period setting means 13 that predicts a time during which the temperature during standby is equal to or lower than the first temperature and sets a period until the predicted time as a start prohibition period for prohibiting the next start of the fuel cell 1. When the elapsed time after the stop of the fuel cell 1 is equal to or longer than the start prohibition period set when the fuel cell is stopped, the device 7 permits the next start of the fuel cell 1 and the elapsed time after the stop of the fuel cell 1 starts. When the prohibition period is not reached, the fuel cell 1 is controlled to be prohibited from starting next time.

  With this configuration, the fuel cell temperature detectors 11a and 11b can directly or indirectly detect the temperature of the fuel cell 1 at the time of stop with high accuracy and secure a sufficient amount of condensed water to wash away impurities sufficiently. Since the prediction accuracy of the start-up prohibition period when the temperature is lower than the temperature is improved, impurities can be more reliably removed, and the fuel cell performance deterioration and durability deterioration can be suppressed.

Here, in order to experimentally investigate the relationship between the temperature of the fuel cell 1 and the elapsed time after the stop, the temperature near the center of the fuel cell 1 is directly detected using a thermocouple, and power generation, stop, and standby The temperature change of the fuel cell 1 was measured. The temperature of the fuel cell 1 immediately before the stop was about 64 ° C.

  Moreover, in order to investigate the dependence with respect to external temperature, the temperature of the fuel cell 1 in each external temperature when the temperature of the constant temperature chamber was changed with 10-35 degreeC was arrange | positioned in a constant temperature room, and the temperature of the constant temperature room was measured. .

  The measurement results are shown in FIG. As shown in FIG. 3, the temperature of the fuel cell 1 decreases with the elapsed time after power generation stop at any outside air temperature. The lower the outside air temperature, the faster the temperature of the fuel cell 1 decreases. It was found that the higher the temperature, the slower the temperature of the fuel cell 1 decreases. For example, when the outside air temperature is 20 ° C., by detecting the temperature (T) of the fuel cell 1, the time to reach the first temperature (T 1) is approximately 4 from the relationship between the measured temperature of the fuel cell 1 and time. It turns out that it is time later.

  Therefore, according to the fuel cell power generation system of Embodiment 1 of the present invention, the relationship between the temperature of the fuel cell 1 at the time of stoppage, the outside air temperature, and the elapsed time after the stop is obtained in advance, and the relational expression or database is stored. Prepare and predict the temperature of the fuel cell 1 at the time of stop or standby from the outside air temperature, and the temperature of the fuel cell 1 will not affect the durability of the fuel cell 1 and thoroughly wash out impurities. It has been found that the time to reach the first temperature (T1) can be predicted.

  Here, the temperature of the fuel cell 1 has been described in advance by experimentally measuring at each outside air temperature in advance. However, the heat capacity of the material constituting the fuel cell 1 and the physical properties such as thermal resistance are determined. The temperature change of the fuel cell after stopping at each outside air temperature may be calculated and obtained in advance.

  Further, if the period up to the time to reach the first temperature (T1) at which sufficient amount of condensed water is obtained to wash away impurities accumulated in the fuel cell 1 during power generation is defined as the start-up prohibition period, the start-up prohibition period It was found that the outside air temperature has a relationship as shown in FIG.

  Next, in order to confirm the performance of the fuel cell 1 with respect to the impurities of the fuel cell power generation system configured as described above, the fuel cell 1 was generated and stopped by adding impurities to the air supplied to the cathode in a simulated manner. The voltage behavior was investigated.

  Sulfur dioxide was used as an impurity, an oxidant gas mixed to a concentration of about 5 ppb was supplied, a start / stop test was repeated for power generation and stop, and the amount of voltage decrease after a certain time after start was measured. . In addition, in order to compare the voltage behavior due to the difference in temperature of the fuel cell 1 at the time of stop or standby, the temperature of the fuel cell 1 at the time of standby is the first temperature at which impurities accumulated in the fuel cell 1 can be washed away ( T1) When the power generation is resumed after reaching (for example, 45 ° C.) and when the temperature of the fuel cell 1 during standby is, for example, the outside air temperature is high, the first temperature of the fuel cell 1 The start / stop test was repeatedly performed for the case where power generation was resumed at a temperature (for example, 55 ° C.) higher than the temperature (T1).

  The measurement results are shown in FIG. From FIG. 5, when the start and stop are performed so that the temperature of the fuel cell 1 during standby reaches the first temperature (T1) (for example, 45 ° C.) at which impurities accumulated in the fuel cell 1 can be washed away. Since there was almost no voltage drop and it was the same as the voltage level during normal power generation when no impurities were added, the impurities were washed away by condensed water during stop or standby, and the influence of impurities was eliminated. understood.

On the other hand, when starting and stopping at a temperature higher than the first temperature (for example, 55 ° C.), there is a tendency that the voltage gradually decreases, and the impurities cannot be completely washed out by one start and stop. It was found that the voltage drop tends to increase due to the accumulated impurities.

  Here, the first temperature (T1) at which the impurities accumulated in the fuel cell 1 can be washed away is not limited to 45 ° C. or the like, but depends on the concentration of impurities and the amount of accumulated impurities. If the temperature is lower than the temperature of the fuel cell 1 at the time, condensed water is produced by condensation, and the same cleaning effect can be obtained. Preferably, it is set at least 10 ° C. lower than the temperature of the fuel cell 1 at the time of power generation, and from the relationship between the amount of voltage drop allowable in the fuel cell power generation system and the stop time required for the fuel cell power generation system, It is desirable to set a temperature at which impurities can be effectively washed away.

  In addition, the amount of impurities accumulated in the fuel cell 1 during power generation and the amount of impurities that can be washed away at one start / stop are correlated, and the amount of impurities that may be accumulated in advance within the power generation time, or It is preferable to experimentally obtain a first temperature (T1) at which impurities can be washed out according to the concentration, and to lower the set value of the first temperature (T1) as the amount of impurities increases.

  Further, the first temperature (T1) for washing out the impurities does not have to be the same set value every time, and may be changed periodically. By periodically changing, it is possible to remove the impurities when they are accumulated within the allowable range. If they are removed together, the normal stop time can be shortened and efficient operation is possible. It becomes.

  FIG. 6 is a flowchart showing the operation of the fuel cell power generation system according to Embodiment 1 of the present invention. As shown in FIG. 6, in the fuel cell power generation system according to Embodiment 1 of the present invention, when power generation is stopped (STEP 101), the start prohibition period setting unit 13 sets the temperature of the fuel cell 1 at the time of stop, From the outside air temperature, a start-up prohibition period in which the temperature of the fuel cell 1 at the time of stop or standby is equal to or lower than the first temperature (T1) is predicted (STEP 102). When the controller 7 determines that the elapsed time after the stop is equal to or longer than the activation prohibition period (STEP 103), the controller 7 performs control so as to permit the next activation (STEP 104).

  According to this configuration, since the next power generation is not started until the temperature of the fuel cell 1 is sufficiently lowered, even when the cooling rate of the fuel cell 1 is slow, such as when the outside air temperature at the time of stop is high, A sufficient amount of condensed water condensed from humidified water or humidified water can be secured, and impurities accumulated during power generation can be stopped, standby, or washed away with condensed water during startup, and removed. 1 and the durability can be suppressed.

  Further, it is not necessary to detect the temperature of the fuel cell 1 by circulating a cooling medium that cools the fuel cell 1 during stoppage or standby, and detecting the temperature of the cooling medium. In addition to being economical, it is possible to reduce wasteful energy consumed during stoppage or standby, and maintain high efficiency of the fuel cell power generation system.

(Embodiment 2)
In the fuel cell power generation system according to Embodiment 2 of the present invention, in Embodiment 1, the fuel cell temperature determination unit includes a cooling unit that supplies a cooling medium to the fuel cell 1 for cooling, and is obtained in advance. Embodiment 1 in that the temperature when the fuel cell is stopped is not detected but is estimated using a relational expression or a database based on the relationship between the temperature of the cooling medium and the temperature of the fuel cell 1. However, the rest of the configuration is the same, and the description is omitted.

According to this configuration, the temperature of the coolant that exchanges heat with the fuel cell 1 and the temperature of the fuel cell 1 under each power generation condition of the fuel cell 1 can be detected without detecting the temperature of the fuel cell 1 at the time of stopping. By measuring the relationship in advance and creating a database, it is possible to estimate the temperature of the fuel cell 1 at the time of stopping, which not only simplifies the configuration and is economical, but also immediately after stopping power generation. By using the temperature data of the cooling medium at one inlet or outlet, a more accurate temperature of the fuel cell 1 can be obtained.

  Therefore, according to the fuel cell power generation system of the second embodiment of the present invention, as in the first embodiment, impurities accumulated during power generation are stopped, washed away, or washed away with condensed water during start-up and removed. It is possible to suppress the performance degradation and durability degradation of the fuel cell 1.

(Embodiment 3)
In the fuel cell power generation system according to Embodiment 3 of the present invention, in Embodiment 1, the outside air temperature determination means 12 includes a calendar for managing the date and time, predicts the outside air temperature based on the relationship between the date and the outside air temperature, Although it differs from Embodiment 1 by the point which estimates a starting prohibition period from the said estimated outside temperature, it is the same structure other than that, and abbreviate | omits description.

  FIG. 7 shows the transition of the average temperature of the outside air temperature during the day of a typical month in each season of the year at a certain point. If the location, season, date and time of the outside air temperature are determined, the outside air temperature changes almost on average every year, and even if the outside air temperature cannot be detected in real time, the outside air temperature is judged from the date and time. can do.

  Therefore, if the current date and time is known by preparing in advance an annual outside temperature database of the place where the fuel cell power generation system is installed, the vicinity thereof, or the place where the environment and season are similar, From the detected outside air temperature, the temperature of the fuel cell 1 can be predicted from the relational expression between the outside air temperature measured in advance and the temperature of the fuel cell 1 as shown in FIG.

  Accordingly, the configuration of the third embodiment of the present invention estimates the outside air temperature from the date and time at the time of stopping without directly detecting the outside air temperature at the time of stopping, so that the start prohibition period can be predicted with a simple structure. Similarly, impurities accumulated during power generation can be stopped, waited, or washed away with condensed water during start-up, and can be removed, thereby suppressing deterioration in performance and durability of the fuel cell 1. it can.

(Embodiment 4)
The fuel cell power generation system according to Embodiment 4 of the present invention is the fuel cell power generation system according to any one of Embodiments 1 to 4, wherein the outside air temperature determination means 12 includes an outside air temperature detector that detects the outside air temperature, and the start prohibition period setting is performed. When the elapsed time after the stop of the fuel cell 1 is less than the start prohibition period predicted when the fuel cell 1 is stopped, the outside air temperature is detected by the outside air temperature detector, and the temperature of the fuel cell 1 is determined from the detected outside air temperature. Although it is different from Embodiments 1 to 3 in that the time when the temperature falls below the first temperature is predicted and the activation prohibition period is updated each time, the configuration is the same as in the first to third embodiments, and the description is omitted.

  The outside air temperature determining means 12 can detect an outside air temperature and use, for example, a temperature sensor that monitors the outside air temperature to prevent freezing. Alternatively, even if the outside air temperature is not directly detected, another temperature sensor may be substituted if there is a correlation with the outside air temperature and the outside air temperature can be estimated.

  FIG. 8 is a flowchart showing the operation of the fuel cell power generation system according to Embodiment 3 of the present invention. As shown in FIG. 8, in the fuel cell power generation system according to the fourth embodiment of the present invention, when power generation is stopped (STEP 201), the start prohibition period setting means 13 is stopped as in the first embodiment. Sometimes, the start-up prohibition period is determined from the temperature of the fuel cell 1 and the outside air temperature (T21) (STEP 202).

Then, at an arbitrary time until the start prohibition period is reached when the elapsed time after the stop is less than the set start prohibition period (STEP 203), the outside air temperature detector (T22) at that time is detected by the outside air temperature detector, The start prohibition period setting means 13 predicts and updates the start prohibition period in which the temperature of the fuel cell 1 is equal to or lower than the first temperature from the detected outside air temperature (T22) (STEP 204).

  Then, the controller 7 performs control so as to permit the next activation (STEP 205) when the elapsed time after the stop is predicted and the latest activation prohibition period has elapsed.

  For example, in FIG. 3, when the outside air temperature at the time of stoppage is 20 ° C., even if the start prohibition period is once predicted to be about 4 hours, the outside air temperature is detected again before 4 hours elapses. For example, if it is determined that the outside air temperature has decreased to 10 ° C., for example, the start prohibition period can be updated by correcting the start prohibition period from 4 hours to 3 hours.

  Alternatively, if it can be determined that the detected outside air temperature has increased to 30 ° C. before the lapse of 4 hours, the start prohibition period can be extended from 4 hours to 8 hours for correction.

  Therefore, according to the fuel cell power generation system of Embodiment 4 of the present invention, even when the outside air temperature fluctuates during stoppage or standby, the start-up prohibition period can be corrected and updated each time. Thus, the temperature can be made to reach the first temperature more accurately, so that impurities can be reliably washed away.

  In addition, if the outside air temperature decreases during shutdown or standby, the start-up prohibition period can be shortened, so the stop time can also be shortened, the start-up timing can be shortened, and the power generation time can be extended. can do.

  As described above, the fuel cell power generation system of the present invention can be used in an environment containing impurities, or can be applied to a fuel cell using a member containing impurities, and is a mobile fuel cell, an automobile fuel cell, and a stationary device. It can be applied to uses such as fuel cells.

DESCRIPTION OF SYMBOLS 1 Fuel cell 7 Controller 11a, 11b Fuel cell temperature judgment means 12 Outside air temperature judgment means 13 Startup prohibition period setting means

Claims (5)

A fuel cell that generates heat and electricity using a solid polymer electrolyte membrane; and
Fuel cell temperature determining means for determining the temperature of the fuel cell;
Outside temperature judging means for judging outside temperature;
When power generation of the fuel cell is stopped, from the temperature of the fuel cell immediately before the stop determined by the fuel cell temperature determination unit and the outside air temperature determined by the outside air temperature determination unit, the stop of the fuel cell, or A time during which the standby temperature is equal to or lower than a first temperature at which a sufficient amount of condensed water is obtained to wash away impurities accumulated in the fuel cell during power generation is predicted, and a period until the predicted time is determined. Start prohibition period setting means for setting as a start prohibition period for prohibiting the next start,
A controller for controlling start-up, power generation operation, stop and standby of the fuel cell;
With
Wherein the controller, at the fuel cell has stopped power generation, in the case of more than start prohibition period the elapsed time after the stop of the fuel cell is set in the start prohibition period setting means, next startup of the fuel cell And when the elapsed time after the stop of the fuel cell is less than the start prohibition period, control to prohibit the next start of the fuel cell,
Fuel cell power generation system.   The fuel cell power generation system according to claim 1, wherein the fuel cell temperature determination unit includes a fuel cell temperature detector that detects a temperature of the fuel cell. The fuel cell temperature determination means includes a cooling unit that supplies a cooling medium to the fuel cell and cools it.
The fuel cell power generation system according to claim 1, wherein the temperature of the fuel cell is determined based on a relationship between a temperature of the cooling medium and a temperature of the fuel cell. The outside temperature determining means includes a calendar for managing the date and time,
The fuel cell power generation system according to claim 1, wherein the outside air temperature is determined based on a relationship between a date and an outside air temperature. The outside air temperature judging means includes an outside air temperature detector for detecting outside air temperature,
The start prohibition period setting means determines the temperature of the fuel cell from the outside temperature detected by the outside temperature detector when the elapsed time after the stop of the fuel cell is less than the start prohibition period predicted at the stop. The fuel cell power generation system according to any one of claims 1 to 4, wherein a time when the temperature falls below the first temperature is predicted, and the start-up prohibition period is updated each time.

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