JPS60107270A - Multivariable operation and control of fuel cell - Google Patents

Abstract

PURPOSE:To enable electric energy to be efficiently produced by maximizing total thermal efficiency which is the product of fuel utilization efficiency, current efficiency and voltage efficiency through multivariable control. CONSTITUTION:The relationship between load current and total thermal efficiency is obtained from both the relationship between the load current of a fuel cell 1 and its voltage and the relationship between the load current and fuel utilization efficiency by using the temperature of the fuel cell 1 as a variable. These data are used as the inputs to a control device 9 so as to control the temperature of the fuel cell 1 so that its thermal efficiency beomes maximum for each load current. The temperature of the fuel cell 1 is detected by a temperature sensing element 8. When a fuel contained in anolyte is consumed, the consumption is detected by a concentration sensor 7 and then a fuel supply valve 10 is opened by the control device 9 to supply the fuel from a fuel tank 11 into an anolyte tank 2.

Description

[Detailed Description of the Invention] A fuel cell is a direct current power generation device that electrochemically converts the chemical energy of fuel directly into electrical energy, and has advantages such as high efficiency over a wide load range and long environmental protection. . In order to efficiently extract electrical energy from a fuel cell, a method has been adopted in which fuel and oxidizer are supplied according to the load and the cell temperature is primarily controlled. In addition, there is a control method that detects the battery voltage and supplies fuel to maintain a predetermined voltage.

However, since such a method is a method in which the set value is uniquely determined and controlled, it cannot be said that the fuel cell is necessarily operated under conditions that maximize the overall thermal efficiency of the fuel cell. For example, in the fuel pressure control method for gaseous fuel cells and the concentration control method for liquid fuel cells, even if the optimal pressure and concentration are set for a certain load current, if the load changes, the settings are no longer optimal ( Become.

The present invention solves these shortcomings and provides a fuel cell reversal control method with large remaining number control in order to extract electrical energy from the fuel cell with maximum overall thermal efficiency.

Next, details of the present invention will be explained using examples.

This embodiment relates to a liquid fuel cell, in which hydrazine is used as the fuel, and when the load current is set, the hydrazine concentration and cell temperature are controlled so that the thermal efficiency is maximized. In general, the thermal efficiency of a fuel cell can be expressed as the product of cell efficiency and mainstream efficiency, or in the case of liquid fuel cells, this must be multiplied by fuel utilization efficiency. Here, the current efficiency represents the ratio of how much chemical energy of the fuel supplied to the electrode is converted into electric energy, which is approximately 10
It is close to 0%, and the thermal efficiency of a liquid fuel cell is approximated by the product of voltage efficiency and fuel utilization efficiency.

FIG. 1 shows a hydrazine-fueled circulating fuel cell to which the present invention is applied; l is the cell body, in which 20 unit cells with an effective area of 150 cni are stacked, and the electrical Connected in series. The anolyte is stored in an anolyte tank 2 and supplied to the battery body 1 by an anolyte pump 3. A starting heater 4 and a radiator 5 are built in between the anolite pump 3 of the anolite circulation system and the battery main body l. used for adjustment. Reference numeral 6 denotes a cooling fan for dissipating heat generated in the battery body 1 from the surface of the radiator 5 by circulating the anolyte. 7 is a concentration sensor for detecting the fuel concentration in amerite. The anolyte containing unreacted fuel discharged from the battery body 1 is directly collected into the anolyte tank 2. 8 is a temperature sensing element that detects battery temperature.

When the fuel in the anorite is consumed, it is detected by the concentration sensor 7, and the control device 9 opens and closes the fuel supply valve IO to supply fuel from the fuel tank 11 to the anorite tank 2.

If not shown in FIG. 1, the control device 9 can automatically operate and stop the liquid fuel cell shown in FIG. Efficiency F:! from liquid fuel cells, such as control to constantly monitor the fuel a content in the anorite and maintain it within a predetermined concentration range, control to maintain the concentration of electrolyte within a predetermined range, etc.
<Includes all controls for extracting electrical energy, and also determines whether the voltage of the cell body 1 and the pressure of each unit cell 7B drops abnormally or the liquid level in the anorite tank 2 drops below a predetermined position. Alternatively, control is included to safely shut down the liquid fuel cell when the temperature of the 71i pond rises abnormally.

The control range and the li+11 rotation and stop sequence can be freely set using the command display device fiτ12. Air is supplied to the riLFl main body 1 by an air blower 13tζ, and unreacted air is discharged from each battery 1 as it is.

FIG. 2 is a load current-cell voltage curve of the battery main body 1 shown in the first [¥1], and the fuel concentration is 25%.

FIG. 3 shows negative current-fuel utilization efficiency curves, both of which take battery temperature as a parameter. The relationship between load current and total thermal efficiency calculated from FIGS. 2 and 3 is shown in FIG. 4+C.

FIG. 5 shows the results when these data are input to the control device 9 and the battery temperature is controlled so that the thermal efficiency is maximized for each load current. As you can see from this result9
The battery temperature when the thermal efficiency at A is maximum 1 is 55℃, 1
The temperature was 65°C for 5A and 75°C for 21A, indicating that the battery temperature was controlled so that the maximum overall thermal efficiency was maintained for any group 7u current. Also, as shown in Table 1? A comparison of the present results with the results obtained using the jL voltage control method shows that the multi-frequency control method is superior.

Although we have explained the case where the fuel concentration is constant at 25%, the data when the fuel concentration is used as a control component is the control bag bl:t.
By inputting to 9, even more efficient operation is possible. Although the explanation has been given with a focus on liquid fuel cells, it is clear that the invention can be applied not only to stationary liquid fuel cells but also to fuel cells using hydrocarbon fuels.

As described above, when operating using the fuel cell operation control method using the multivariable control method according to the present invention, the operating conditions are automatically set so that the overall thermal efficiency is maximized, so electrical work can be carried out efficiently. It is of great industrial value, as it allows the extraction of orchie.

4 Simple explanation of the drawings Fig. 1 is a diagram of a liquid fuel cell using hydrazine as fuel to which the present invention is applied, and Fig. 2 is a diagram of the load current of the cell main body of the liquid fuel cell - electric/I! ! Voltage curve diagram, Figure 3 is load current-fuel utilization efficiency curve diagram, Figure 4 is liquid fuel turtle? 1 μm load current -
The comprehensive thermal efficiency curve diagram, Figure 5, shows the operational results of the liquid fuel IT pond.

I is the battery body, 7 is the concentration sensor, 9 is a control device, 11 is a fuel tank patent applicant representative Negative current (A) Tribute current! A)

Claims (1)

[Scope of Claims] 1. In a fuel cell consisting of a fuel electrode, an oxidizer electrode, an electrolyte, a fuel chamber that supplies fuel to the fuel electrode, and an oxidizer chamber that supplies oxidizer to the oxidizer electrode, fuel utilization is achieved through multivariable control. A fuel cell multivariable operation control method characterized by maximizing overall thermal efficiency, which is the product of efficiency, current efficiency, and voltage efficiency. 2. A fuel cell multivariable operation control method, characterized in that the control verification elements as claimed in the claims are fuel supply amount, battery temperature, discharge current, and battery 7n pressure. 3. A multivariable feed battery multivariable operation control method as set forth in claim 2. 4. In claim 2, the fuel supply amount, which is a control element of multivariable control, is determined by gas twisting.