JP4523116B2 - Operation method of water electrolysis system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water electrolysis system, and more particularly to an operation method of a water electrolysis system including a water electrolysis apparatus having a cell group composed of a plurality of water electrolysis cells, and a solar battery as a power source of the cell group.
[0002]
[Prior art]
In order to operate the water electrolysis system efficiently, it is necessary to use the optimal operating point of the solar cell, that is, the operating current and operating voltage when the output is maximized. It varies depending on temperature, amount of solar radiation, etc. Therefore, conventionally, a DC-DC converter is connected in series between the solar cell and the water electrolysis device, and the DC-DC converter is controlled so as to obtain an output at the optimum operating point of the solar cell.
[0003]
[Problems to be solved by the invention]
However, according to the conventional method, since the DC-DC converter is used, there is a problem that the operation control of the system is complicated and the efficiency is 80 to 90% and further improvement is necessary. There was also a problem that the cost of the water electrolysis system increased with the adoption of the converter.
[0004]
[Means for Solving the Problems]
An object of the present invention is to provide the operation method in which the maximum output of the solar cell can be used for the operation of the water electrolysis system at an efficiency of 100% or close to it by adopting simple means. And
[0005]
In order to achieve the above object, according to the present invention, in operating a water electrolysis system comprising a water electrolysis apparatus having a cell group composed of a plurality of water electrolysis cells and a solar cell as a power source of the cell group, The solar battery and a plurality of water electrolysis cells in the cell group are electrically connected in series so that the number of use of the water electrolysis cells can be selected so that the output of the solar battery can be directly supplied to the cell group. and, the number of use of said water electrolysis cell, so as to utilize the maximum output of the solar cell, the current and voltage of the optimum operating point of the IV characteristics in accordance with the number of use of said water electrolysis cell the solar cell There is provided a method for operating a water electrolysis system, characterized in that it is selected to include or include current and voltage in the vicinity of the optimum operating point .
[0006]
The solar cell of IV (I: current, V: voltage) characteristic, for example, it varies depending on the temperature. On the other hand, in the cell group, a set of a water electrolysis cells connected in series is defined as (a) cell unit, and a set of a + 1 water electrolysis cells is defined as (a + 1) cell unit. If the set of electrolytic cells is an (a + n) cell unit, the IV characteristics are different for each cell unit.
[0007]
Therefore, taking the voltage on the x-axis and the current on the y-axis, draw the IV characteristics of the solar cell at a certain temperature, that is, a single curve, and (a) cell unit, (a + 1) cell unit ... a + n) When the IV characteristics of the cell unit, that is, a plurality of straight lines are drawn, some of the straight lines intersect with one curve, and each intersection becomes an operating point of the solar cell corresponding to each cell unit. In this case, it is possible to select and operate a cell unit having an intersection that meets or is close to the optimum operating point of the solar cell among a plurality of intersections, that is, the number of water electrolysis cells used. Depending on the cell unit, select a cell unit whose IV characteristic includes the current and voltage at the optimum operating point of the solar cell or the current and voltage near the optimum operating point. When operated, the maximum output of the solar cell at a certain temperature or at a temperature close to 100% can be used when operating the cell unit, and hence the water electrolysis system.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, a water electrolysis system 1 includes a water electrolysis device 3 having a cell group 2 and a solar cell 4 as a power source for the cell group 2. The cell group 2 includes a plurality of electrically connected cells in series, in the embodiment, first to eighth water electrolysis cells C1 to C8. Between the (−) and (+) terminals of the first and second water electrolysis cells C1 and C2, between the (−) and (+) terminals of the second and third water electrolysis cells C2 and C3. Between the (−) and (+) terminals of the seventh water electrolysis cells C6 and C7 and between the (−) and (+) terminals of the seventh and eighth water electrolysis cells C7 and C8, respectively, via the connection line 5. Connected. Between the adjacent water electrolysis cells C1 and C2..., One lead wire 6 of the first to seventh switches S1 to S7 is connected to the connection line 5 between C7 and C8, and (−) of the eighth water electrolysis cell C8. One lead wire 6 of the eighth switch S8 is connected to the terminal. The other lead wire 7 of the first and eighth switches S1 and S8 is connected to both ends of the connection line 8, and the other lead wire 7 of the second to seventh switches S2 to S7 is connected to an intermediate portion of the connection line 8, respectively. Connected.
[0009]
The (+) terminal of the first water electrolysis cell C1 is connected to the (+) terminal of the solar cell 4 via the connection line 9, while the other end of the connection line 8 on the eighth switch S8 side is connected to the connection line 10. To the (−) terminal of the solar cell 4. Thus, the output of the solar battery 4 is directly supplied to the cell group 2 by closing the eighth switch S8 and opening other switches.
[0010]
A temperature sensor 11 for detecting the temperature is attached to the solar cell 4, and temperature information from the temperature sensor 11 is transmitted to a switch controller 12 that controls opening and closing of the switches S <b> 1 to S <b> 8. Thereby, based on the temperature information of the solar cell 4, the switch controller 12 selects the number of water electrolysis cells C1 to C8 to be used so that the maximum output of the solar cell 4 can be used. In this case, the temperature of the solar cell 4 is approximately proportional to the amount of solar radiation to the solar cell 4, and the amount of solar radiation (W / m ^2).
) Is x, and temperature (° C.) is y, the temperature y is expressed as y≈35.489x + 1.9118 as an example.
[0011]
For example, when the first to sixth water electrolysis cells C1 to C6 are used as a 6-cell unit, the 6-cell unit appears by closing the sixth switch 6 and opening the remaining switches. Similarly, the 7-cell unit appears when the seventh switch S7 is closed and the remaining switches are opened, and the 8-cell unit appears when the eighth switch S8 is closed and the remaining switches are opened.
[0012]
In FIG. 2, one curve L1 indicates the IV characteristics of the solar cell 4 at 25 ° C. (the amount of solar radiation: 0.65 W / m ² ), and the other curve L2 indicates the output characteristics of the solar cell 4. Indicates. In this case, the optimum operating point P of the solar cell 4 is a point of the operating voltage 16.7 V and the operating current 90 A at which the relative output is maximized.
[0013]
On the other hand, in FIG. 2, the straight line L3 passing through the point P1 of the operating voltage 11.6V and the operating current 0A indicates the IV characteristic of the 6-cell unit, and the straight line L4 passing through the point P2 of the operating voltage 14.3V and the operating current 0A is 7 The straight line L5 passing through the point P3 of the cell unit IV characteristics and further the operating voltage 17.2V and the operating current 0A indicates the IV characteristics of the 8-cell unit.
[0014]
In this case, the curve L1 indicating the IV characteristics of the solar cell 4 intersects with the three straight lines L3 to L5 indicating the IV characteristics of the 6 to 8 cell units, and the intersection of the curve L1 and the straight line L4 regarding the 7 cell units is the sun. This is the optimum operating point P of the battery 4.
[0015]
Under such circumstances, the thermometer 11 detects the temperature of the solar cell 4 at 25 ° C., and the temperature information from the thermometer 11 is transmitted to the switch controller 12. Thereby, based on the temperature information of the solar cell 4, the switch controller 12 selects the number of water electrolysis cells C1 to C8 to be used so that the maximum output of the solar cell 4 can be used. That is, the 7-cell unit appears by closing the seventh switch S7 and opening the remaining switches.
[0016]
FIG. 3 shows the relationship between the IV characteristics when the temperature of the solar cell 4 is 80 ° C. (the amount of solar radiation: 2.20 W / m ² ) and the IV characteristics of 6 to 8 cell units.
[0017]
In this case, the optimum operating point P of the solar cell 4 is a point of operating voltage 13.5V and operating current 90A, and at this point P, a straight line L3 indicating the IV characteristics of the 6-cell unit intersects the curve L1.
[0018]
Under such a situation, the six-cell unit appears by closing the sixth switch S6 and opening the remaining switches in cooperation with the temperature sensor 11 and the switch controller 12.
[0019]
【The invention's effect】
According to the present invention , a solar battery and a plurality of water electrolysis cells of the cell group are electrically connected in series so that the number of use of these water electrolysis cells can be selected so that the output of the solar battery can be directly supplied to the cell group. The IV characteristics according to the number of water electrolysis cells used include the current and voltage at the optimum operating point of the solar cell, or include the current and voltage in the vicinity of the optimum operating point. By selecting in this way, it is possible to provide an operation method capable of utilizing the maximum output of the solar cell for the operation of the water electrolysis system with an efficiency of 100% or close thereto. In addition, since the output of the solar cell can be directly supplied to a plurality of water electrolysis cells in the cell group , the operation control of the system is simple because the conventionally required DC-DC converter is not necessary. Electrolysis systems are also inexpensive.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a water electrolysis system.
FIG. 2 is a graph showing an example of IV characteristics related to a solar cell and 6 to 8 cell units.
FIG. 3 is a graph showing another example of IV characteristics related to a solar cell and 6 to 8 cell units.
[Explanation of symbols]
1 ………… Water electrolysis system 2 ……………… Cell group 3 ……………… Water electrolysis device 4 ……………… Solar cells C1 to C8 …… First to eighth water electrolysis cell

Claims (1)

A water electrolysis system comprising a water electrolysis device (3) having a cell group (2) comprising a plurality of water electrolysis cells (C1 to C8) and a solar cell (4) as a power source for the cell group (2). In driving,
The solar cell (4) and a plurality of water electrolysis cells (C1 to C8) of the cell group (2) so that the output of the solar cell (4) can be directly supplied to the cell group (2) . The number of water electrolysis cells (C1 to C8) used can be selected and electrically connected in series ,
The number of used the water electrolysis cell (C1 to C8), so as to utilize the maximum output of the solar cell (4), IV characteristics according to the number of use of said water electrolysis cell (C1 to C8) is the A method for operating a water electrolysis system, comprising selecting or including a current and voltage at or near an optimum operating point of a solar cell .

Images