Hydrogen production system, hydrogen production method, and program

Abstract

A hydrogen production system, a hydrogen production method, and a program are provided that are capable of stably extracting current from solar panels and producing hydrogen. The system includes an estimation unit (21) that estimates the maximum power point in the output characteristics of a solar panel (1), a setting unit (22) that sets the operating range of MPPT control based on the maximum power point, a DC / DC converter (24) that acquires the output power of the solar panel (1) and outputs a voltage, an electrolytic cell (3) that electrolyzes water using the output voltage of the DC / DC converter, and a control unit (23) that controls the output voltage of the DC / DC converter (24) so ​​that the operating point of the solar panel (1) approaches the maximum power point. When the operating point is within the operating range, the control unit (23) controls the output voltage of the DC / DC converter (24) with a first variable voltage ΔV, and when the operating point is outside the operating range, it controls the output voltage of the DC / DC converter (24) with a second variable voltage ΔV / n.

Description

[Technical Field]

[0001] The present disclosure relates to a hydrogen production system, a hydrogen production method, and a program for producing hydrogen using power output from solar panels. [Background technology]

[0002] A system that uses surplus electricity generated by solar panels to electrolyze water and produce hydrogen has been put into practical use.

[0003] Patent Document 1 discloses a method for producing hydrogen by extracting a current at the operating point where the power output from a solar panel is maximized and supplying this current to an electrolysis cell. For example, for a solar panel output characteristic curve with voltage on the horizontal axis and power generation on the vertical axis, the open-circuit voltage of the solar panel is used as the starting point, and a maximum power point (MPP) is searched for using an MPPT (Maximum Power Point Tracking) method such as the hill-climbing method. It discloses that efficient water electrolysis can be achieved by extracting a current within a voltage range around this maximum power point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-85602 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the curve showing the relationship between the output power and voltage of a solar panel changes in a mountain-like shape, with the output power increasing as the voltage changes. When searching for the MPP while varying the operating point using the MPPT method described above, the operating point may not remain near the MPP (the peak of the mountain) but may move away from it. This instability is particularly pronounced during times of low solar radiation, such as in the morning and evening.

[0006] In such cases, it is necessary to reset the MPPT control unit and restart the MPPT from the open circuit voltage. When the control unit is reset, current cannot be supplied to the electrolysis cell until the operating point again reaches the vicinity of the MPP, which causes the problem of reduced hydrogen production efficiency.

[0007] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a hydrogen production system, a hydrogen production method, and a program that are capable of stably producing hydrogen even during times of low solar radiation. [Means for solving the problem]

[0008] A hydrogen production system according to one embodiment of the present disclosure includes an estimation unit that estimates a maximum power point in the output characteristics of a solar panel; a setting unit that sets an operating range for MPPT control based on the maximum power point; a voltage conversion unit that acquires the output power of the solar panel and outputs a voltage; an electrolysis cell that electrolyzes water using the output voltage of the voltage conversion unit; and a control unit that controls the output voltage of the voltage conversion unit so that the operating point of the solar panel approaches the maximum power point, wherein the control unit controls the output voltage of the voltage conversion unit with a first variable voltage when the operating point is within the operating range, and controls the output voltage of the voltage conversion unit with a second variable voltage that is smaller than the first variable voltage when the operating point is outside the operating range.

[0009] In one embodiment of the hydrogen production method of the present disclosure, an estimation unit estimates a maximum power point in the output characteristics of a solar panel, a setting unit sets an operating range of MPPT control based on the maximum power point, a voltage conversion unit acquires the output power of the solar panel and outputs a voltage, a control unit controls the output voltage of the voltage conversion unit so that the operating point of the solar panel approaches the maximum power point and supplies it to an electrolysis cell, and the control unit controls the output voltage of the voltage conversion unit with a first variable voltage when the operating point is within the operating range, and controls the output voltage of the voltage conversion unit with a second variable voltage smaller than the first variable voltage when the operating point is outside the operating range.

[0010] One aspect of the present disclosure is a program for causing a computer to function as the hydrogen production system. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to stably extract current from solar panels and produce hydrogen. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing the configuration of a hydrogen production system according to the first embodiment. [Figure 2] FIG. 2 is a graph showing the relationship between the voltage of the solar panel and the generated power, and the relationship between the voltage of the solar panel and the current supplied from the solar panel to the electrolytic cell. [Figure 3A] FIG. 3A is a circuit diagram showing a configuration of a DC / DC converter. [Figure 3B] FIG. 3B is a block diagram showing a specific configuration of the control circuit shown in FIG. 3A. [Figure 4] FIG. 4 is a graph showing the current-voltage characteristics of the electrolytic cell. [Figure 5] FIG. 5 is a flowchart showing the voltage setting procedure in the hydrogen production system according to the first embodiment. [Figure 6]FIG. 6 is an enlarged view of a main portion of the curve s11 shown in FIG. [Figure 7] FIG. 7 is a block diagram showing the configuration of a hydrogen production system according to the second embodiment. [Figure 8] FIG. 8 is a graph showing the relationship between the amount of solar radiation and the output voltage of a solar panel. [Figure 9] FIG. 9 is a block diagram showing the configuration of a hydrogen production system according to the third embodiment. [Figure 10] FIG. 10 is a graph showing the relationship between the output voltage and the output power of a solar panel. [Figure 11] FIG. 11 is a graph showing the relationship between the input voltage and current of the electrolytic cell. [Figure 12] FIG. 12 is a graph showing the relationship between the output voltage and the efficiency of the DC / DC converter. [Figure 13] FIG. 13 is a block diagram showing the configuration of a hydrogen production system according to the fourth embodiment. [Figure 14] FIG. 14 is a hardware configuration diagram of the hydrogen production system according to the embodiment. [Figure 15] FIG. 15 is a graph showing the relationship between time and the amount of solar radiation. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Description of the First Embodiment] Hereinafter, embodiments will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a hydrogen production system 101 according to a first embodiment. As shown in Fig. 1, the hydrogen production system 101 includes a solar panel 1, a voltage control device 2, an electrolysis cell 3, a water tank 4, and a hydrogen cylinder 5. Note that the solar panel may be abbreviated as "PV."

[0014] The solar panel 1 is installed outdoors, converts solar energy into electricity, and outputs the electricity to the voltage control device 2.

[0015] The voltage control device 2 includes an estimation unit 21, a setting unit 22, a control unit 23, and a DC / DC converter 24 (voltage converter).

[0016] The estimation unit 21 estimates the maximum power point (hereinafter referred to as "MPP") on a curve that shows the relationship between the output voltage and power generation of the solar panel 1. That is, the estimation unit 21 estimates the MPP (maximum power point) in the output characteristics of the solar panel 1. FIG. 2 is a graph showing the relationship between the voltage and power generation of the solar panel 1, and the relationship between the voltage of the solar panel 1 and the current supplied from the solar panel 1 to the electrolytic cell 3. Four curves s1 to s4 show the relationship between the voltage and power generation of the solar panel 1, with curve s1 showing the case when the amount of solar radiation is high and curve s4 showing the case when the amount of solar radiation is low. Curve s11 shows the relationship between the output voltage of the solar panel 1 and the current supplied from the solar panel 1 to the electrolytic cell 3.

[0017] Each of the curves s1 to s4 changes so as to be convex upward. In other words, it has a peak. The estimation unit 21 estimates the MPP for each of the curves s1 to s4 based on the specifications of the solar panel 1 (denoted as "PV specifications" in the figure). The MPP is the point at which each of the curves s1 to s4 peaks, and by bringing the output voltage of the solar panel 1 closer to the MPP, it is possible to output power with higher efficiency. Hereinafter, the output voltage when the solar panel 1 outputs power will be referred to as the "operating point."

[0018] The setting unit 22 sets the operating range of the MPPT control based on the MPP estimated by the estimation unit 21. That is, the setting unit 22 sets the operating range of the MPPT control based on the MPP. "Maximum power point tracking (MPPT) control" refers to control that brings the operating point closer to the peak value (MPP), such as a hill-climbing method. "Operating range of MPPT control" refers to a range close to the MPP in which the MPPT method can stably bring the operating point closer to the MPP. As an example, the operating range of the MPPT control can be set to a voltage range of 150V to 250V shown on the horizontal axis of FIG. 2. Hereinafter, the "operating range of MPPT control" will be simply abbreviated as "operating range." The operating range is not limited to the range of 150V to 250V, as long as it includes the MPP.

[0019] The control unit 23 controls the output voltage of the DC / DC converter 24 so that the operating point of the solar panel 1 approaches the MPP shown in Fig. 2. The output voltage of the DC / DC converter 24 is the input voltage of the electrolytic cell 3, which will be described later. When the input voltage of the electrolytic cell 3 increases, the current that the DC / DC converter 24 extracts from the solar panel 1 increases, and as a result, the operating point shifts to the left in Fig. 2.

[0020] In this embodiment, an MPPT method such as hill climbing is employed to set the input voltage of the electrolytic cell 3 (the output voltage of the DC / DC converter 24). Specifically, the input voltage of the electrolytic cell 3 is initially set to voltage Vec. Furthermore, a fluctuating voltage "ΔV" is added or subtracted from voltage Vec at a predetermined control period to change the current extracted from the solar panel 1, thereby controlling the output voltage of the DC / DC converter 24 so that the operating point of the solar panel 1 approaches the MPP. That is, when the input voltage of the electrolytic cell 3 changes, the current extracted from the solar panel 1 by the DC / DC converter 24 also changes, ultimately displacing the operating point of the solar panel 1. The control unit 23 performs hill climbing processing by adding or subtracting a fluctuating voltage ΔV to or from voltage Vec at a predetermined control period to control the operating point to approach the MPP.

[0021] Specifically, in curve s1 shown in Fig. 2, when the output voltage of the solar panel 1 when open is around 250 V, the control unit 23 increases the input voltage Vec of the electrolytic cell 3 by a voltage ΔV. That is, ΔV is added to the voltage Vec, increasing the current extracted from the solar panel 1 and shifting the operating point leftward in Fig. 2 to approach the MPP. Furthermore, if the operating point becomes lower than the MPP, ΔV is subtracted from the voltage Vec, shifting the operating point rightward in Fig. 2 to approach the MPP.

[0022] The control unit 23 performs a process (hill climbing method) in which, when the operating point of the solar panel 1 is to the right of the MPP (right side of the hill) on the curve s1 in Figure 2, it adds ΔV to the voltage Vec, and when it is to the left of the MPP (left side of the hill), it subtracts ΔV from the voltage Vec, thereby controlling the operating point of the solar panel 1 to approach the MPP and improving the power efficiency when hydrogen is produced by the electrolysis cell 3.

[0023] Furthermore, when the operating point of the solar panel 1 is outside the operating range set by the setting unit 22, the control unit 23 changes the above-mentioned fluctuation voltage ΔV to a smaller value. Specifically, the control unit 23 changes the fluctuation voltage "ΔV (first fluctuation voltage)" to "ΔV / n (n>1; second fluctuation voltage)." "n" is a value greater than 1, for example, n=2, 3, etc.

[0024] Therefore, when the operating point of the solar panel 1 is within the operating range, the control unit 23 adds or subtracts ΔV to or from the voltage Vec for each control cycle. When the operating point of the solar panel 1 is outside the operating range, the control unit 23 adds or subtracts ΔV / n to or from the voltage Vec for each control cycle. In other words, the control unit 23 changes the voltage Vec in small increments. When the operating point of the solar panel 1 is outside the operating range, the control unit 23 reduces the fluctuating voltage to prevent the operating point of the solar panel 1 from shifting suddenly and avoid the control unit 23 being reset.

[0025] That is, when the operating point is within the operating range, the control unit 23 controls the output voltage of the DC / DC converter 24 with a first variable voltage (ΔV), and when the operating point is outside the operating range, the control unit 23 controls the output voltage of the DC / DC converter 24 with a second variable voltage (ΔV / n) that is smaller than the first variable voltage (ΔV).

[0026] The DC / DC converter 24 receives the DC voltage output from the solar panel 1, converts it into a DC voltage of a predetermined level, and supplies it to the electrolytic cell 3. The DC / DC converter 24 is an example of a voltage conversion unit that acquires the output power of the solar panel 1 and outputs a voltage. FIG. 3A is a circuit diagram showing an example of the DC / DC converter 24. As shown in FIG. 3A, the DC / DC converter 24 includes a switching circuit 51 and a control circuit 60. The switching circuit 51 includes two switches SW1 and SW2, each configured, for example, by FETs, a coil L1, capacitors C1 and CL, and a load RL. The load RL shown in FIG. 3A corresponds to the electrolytic cell 3, and the supply power corresponds to the output voltage of the solar panel 1.

[0027] Fig. 3B is a block diagram showing a specific configuration of the control circuit 60. As shown in Fig. 3B, the control circuit 60 includes a PI controller 61, a PWM module 62, and A / D converters 63 and 64. The PI controller 61 includes an integrator and a proportional multiplier. The PI controller 61 can change the response speed of the control circuit 60 by changing the gain Kp of the proportional multiplier. That is, the control unit 23 adjusts the gain of the DC / DC converter 24 to set the first fluctuation amount and the second fluctuation voltage.

[0028] Reducing the gain Kp can slow down the response of the DC / DC converter 24. Conversely, increasing the gain Kp can speed up the response of the DC / DC converter 24. Slowing down the response of the DC / DC converter 24 has the same effect as lowering the above-mentioned voltage fluctuation ΔV.

[0029] That is, when the operating point of the solar panel 1 falls outside the operating range, the control unit 23 can obtain the same effect as changing the fluctuating voltage ΔV to ΔV / n by reducing the gain Kp and delaying the response of the DC / DC converter 24. This makes it possible to prevent the operating point of the solar panel 1 from being suddenly displaced, and to avoid the control unit 23 being reset.

[0030] The electrolytic cell 3 shown in FIG. 1 electrolyzes water into oxygen O2 and hydrogen H2 using the DC voltage output from the DC / DC converter 24. That is, the electrolytic cell 3 electrolyzes water using the output voltage of the voltage conversion unit (DC / DC converter 24). When the input voltage reaches a certain level, the electrolytic cell 3 passes a current to electrolyze water. FIG. 4 is a graph showing the current-voltage characteristics of the electrolytic cell 3, with the horizontal axis representing the input voltage and the vertical axis representing the current. FIG. 4 shows the characteristics when the number of stack cells in the electrolytic cell 3 is "3." As shown in FIG. 4, when the input voltage of the electrolytic cell 3 is gradually increased, the current increases sharply when the input voltage reaches approximately 4.3 V, and water is electrolyzed to produce hydrogen.

[0031] The water tank 4 stores water and supplies it to the electrolytic cell 3 .

[0032] The hydrogen cylinder 5 stores the hydrogen H2 produced in the electrolysis cell 3.

[0033] Fig. 5 is a flowchart showing the procedure for voltage setting processing in the hydrogen production system 101 according to the first embodiment. Fig. 6 is an enlarged view of a main portion of the curve s11 shown in Fig. 2. Hereinafter, the procedure for setting the output voltage of the DC / DC converter 24 in the hydrogen production system 101 according to the first embodiment will be described with reference to Figs. 5 and 6. The processing shown in Fig. 5 is executed by the voltage control device 2 shown in Fig. 1.

[0034] The specifications of the solar panel 1 are input to the estimation unit 21. Based on the specifications of the solar panel 1, the estimation unit 21 estimates the MPP (maximum power point) on a voltage-power curve (curves s1 to s4 shown in FIG. 2) that indicates the relationship between voltage and power generation. Furthermore, the setting unit 22 sets an operating range (operating range of MPPT control) for each of the curves s1 to s4. For example, the range (150V to 250V) indicated by reference symbol R1 in FIG. 6 is set as the operating range.

[0035] In step S11 of FIG. 5, the hydrogen production system 101 is started up. When the hydrogen production system 101 is started up, the solar panel 1 starts generating power and outputs it. The power generated by the solar panel 1 changes in an upwardly convex, mountain-like shape according to the output voltage, as shown by curve s1 in FIG. 2, for example. The control unit 23 also sets the output voltage of the DC / DC converter 24 to 0 V. That is, the input voltage Vec of the electrolytic cell 3 is initially set to 0 V.

[0036] In step S12, the control unit 23 sets the output voltage of the DC / DC converter 24 (the input voltage of the electrolytic cell 3) to (Vec+ΔV). As a result, the current extracted by the DC / DC converter 24 from the solar panel 1 increases, and the operating point of the solar panel 1 shifts to the left from 250 V shown in FIG. 2.

[0037] In step S13, the control unit 23 collects the output voltage and current values ​​output from the solar panel 1, and calculates the current power generation PVcp (voltage x current).

[0038] In step S14, the control unit 23 determines whether the operating point of the power PVcp calculated this time is within the operating range set by the setting unit 22. The operating range is, for example, the area indicated by the reference R1 in FIG. 6, and the output voltage of the solar panel 1 is in the range of 150V to 250V. When the operating point is within the operating range (S14; YES), the control unit 23 proceeds to step S15, and when it is outside the operating range (S14; NO), the control unit 23 proceeds to step S18. For example, in the example of the curve s1 shown in FIG. 2, the control unit 23 is initially at the open-circuit voltage (near 250V) of the solar panel 1 and is within the operating range. Therefore, a YES determination is made in step S14, and the process proceeds to step S15.

[0039] In step S15, the control unit 23 compares the current power generation power PVcp with the previous power generation power PVbp. When "PVbp < PVcp", the process proceeds to step S16, and when "PVbp > PVcp", the process proceeds to step S17. Here, when "PVbp < PVcp", it is the area on the right side of the MPP shown by the curve s1 in FIG. 2, and when "PVbp > PVcp", it is the area on the left side of the MPP shown by the curve s1.

[0040] In step S16, the control unit 23 adds ΔV to the output voltage of the DC / DC converter 24 (the input voltage Vec of the electrolytic cell 3). Therefore, the current taken out by the DC / DC converter 24 from the solar panel 1 increases, and the operating point on the curve s1 in FIG. 2 is displaced to the left (i.e., climbing the hill), approaching the MPP.

[0041] In step S17, the control unit 23 subtracts ΔV from the output voltage of the DC / DC converter 24 (the input voltage Vec of the electrolytic cell 3). Therefore, the current value taken out by the DC / DC converter 24 from the solar panel 1 is reduced, and the operating point on the curve s1 in FIG. 2 is displaced to the right (i.e., climbing the hill), approaching the MPP. That is, by the hill-climbing method, the power is controlled to be supplied from the solar panel 1 to the DC / DC converter 24 at an operating point near the MPP.

[0042] On the other hand, if it is determined in the process of step S14 that the currently collected power PVcp is outside the operating range (S14; NO), the process proceeds to step S18. Since the power PVcp is outside the operating range, it is the region on the left side of the operating range R1 shown in FIG. 6, that is, the region where the output voltage is lower than the MPP shown in FIG. 2 (the region on the left side of the MPP).

[0043] In step S18, the control unit 23 compares the current generated power PVcp with the previous generated power PVbp. If "PVbp < PVcp", the process proceeds to step S19. If "PVbp > PVcp", the process proceeds to step S20.

[0044] In step S19, the control unit 23 subtracts ΔV / n from the output voltage of the DC / DC converter 24 (the input voltage Vec of the electrolytic cell 3). Therefore, the current value taken out by the DC / DC converter 24 from the solar panel 1 is reduced, and the operating point on the curve s1 in FIG. 2 is displaced to the right (i.e., climbing the hill) and approaches the MPP. The amount of displacement at this time is smaller than the amount of displacement by the process of step S16 described above.

[0045] In step S20, the control unit 23 adds ΔV / n to the output voltage of the DC / DC converter 24 (the input voltage Vec of the electrolytic cell 3). Therefore, the current value taken out by the DC / DC converter 24 from the solar panel 1 increases, and the operating point on the curve s1 in FIG. 2 is displaced to the left. The amount of displacement at this time is smaller than the amount of displacement by the process of step S17 described above. That is, the control unit 23 controls the operating point to approach the MPP with the voltage change amount of ΔV / n per time by the hill climbing method.

[0046] As shown in Fig. 4, when the input voltage of the electrolytic cell 3 increases and reaches a certain voltage (e.g., 4.3 V), the current value increases abruptly. Therefore, when the output voltage of the DC / DC converter 24 is increased, the current extracted from the solar panel 1 by the DC / DC converter 24 increases abruptly. On the curve s11 (voltage-current characteristic curve) shown in Fig. 6, the operating point p1 is abruptly displaced to the left in the direction of the arrow Y1, and deviates from the operating range R1. In this embodiment, outside the operating range of MPPT control, the fluctuating voltage is changed from ΔV to a smaller ΔV / n, thereby preventing the operating point from rapidly deviating from the operating range R1.

[0047] 5, if "PVcp=0", the process proceeds to step S21. In step S21, the control unit 23 determines that there is no solar radiation, and returns the process to step S11.

[0048] As described above, the hydrogen production system 101 according to this embodiment includes an estimation unit 21 that estimates the maximum power point (MPP) in the output characteristics of the solar panel 1, a setting unit 22 that sets the operating range of MPPT control based on the maximum power point, a DC / DC converter 24 (voltage conversion unit) that acquires the output power of the solar panel 1 and outputs a voltage, an electrolytic cell 3 that electrolyzes water using the output voltage of the DC / DC converter 24, and a control unit 23 that controls the output voltage of the DC / DC converter 24 so that the operating point of the solar panel 1 approaches the MPP. When the operating point is within the operating range, the control unit 23 controls the output voltage of the DC / DC converter 24 with a first variable voltage, and when the operating point is outside the operating range, the control unit 23 controls the output voltage of the DC / DC converter 24 with a second variable voltage that is smaller than the first variable voltage.

[0049] In the hydrogen production system 101 according to the first embodiment, when the operating point of the solar panel 1 is within the operating range, the single fluctuation voltage in the output voltage of the DC / DC converter 24 (the input voltage of the electrolytic cell 3) is set to ΔV, so that the operating point can be brought immediately closer to the MPP (see FIG. 2). This makes it possible to produce hydrogen with high efficiency.

[0050] Furthermore, when the operating point of the solar panel 1 is outside the operating range, the single voltage fluctuation voltage in the output voltage of the DC / DC converter 24 is set to ΔV / n, which is smaller than ΔV. This reduces the amount of displacement of the operating point due to a single control, and prevents the operating point from deviating significantly from the MPP, even if, for example, the current flowing through the electrolytic cell 3 suddenly increases. This prevents the control unit 23 from being reset, and allows hydrogen production to continue without shutting down the electrolytic cell 3.

[0051] Furthermore, in this embodiment, an example has been described in which the voltage ΔV is changed to ΔV / n to suppress a sudden shift in the operating point due to a single control operation. However, the gain of the DC / DC converter 24 may be reduced to slow the response. Specifically, when the operating point is outside the operating range, the gain Kp of the PI controller 61 mounted in the control circuit 60 shown in FIG. 3B may be reduced. By reducing the gain Kp, the response of the DC / DC converter 24 can be slowed, and the operating point can be prevented from deviating significantly from the MPP. This prevents the control unit 23 from being reset frequently, allowing hydrogen production to continue without stopping the electrolytic cell 3.

[0052] [Description of the Second Embodiment] Next, a second embodiment will be described. FIG. 7 is a block diagram showing the configuration of a hydrogen production system 102 according to the second embodiment. The hydrogen production system 101 according to the second embodiment differs from the first embodiment described above in that it includes a pyranometer 6. Since the other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are used and a description of the configuration will be omitted. In the second embodiment, an estimation unit 21 is connected to the pyranometer 6, and a power curve and MPP are estimated based on the amount of solar radiation measured by the pyranometer 6 and the IV characteristics of the solar panel 1. A setting unit 22 sets an operating range (operating range of MPPT control) based on the amount of solar radiation measured by the pyranometer 6. This will be described in detail below.

[0053] The estimation unit 21 collects data on the amount of solar radiation and the MPP voltage over a certain period (for example, two weeks) while the control unit 23 is performing normal MPPT operation. As a result, five characteristic curves corresponding to the amount of solar radiation are collected, for example, as shown in FIG. 8. The circles in FIG. 8 indicate MPPs. The maximum MPP voltage among the collected characteristic curves is found and designated as voltage Vpm.

[0054] The setting unit 22 sets the lower limit voltage Vll of the operating range according to the following equation (1).

[0055] Vll=Vpm-2*(Voc-Vpm)=3Vpm-2Voc…(1) Here, Voc is the open circuit voltage of the solar panel 1.

[0056] As a result, the region indicated by symbol R2 in Fig. 8 is set as the operating range. In the hydrogen production system 102 according to the second embodiment, the same processing as in the first embodiment is executed based on the operating range set by equation (1), and the operating point of the solar panel 1 is controlled to approach the MPP.

[0057] Therefore, as in the first embodiment, when the operating point of the solar panel 1 is within the operating range, the single fluctuation voltage in the output voltage of the DC / DC converter 24 (the input voltage of the electrolytic cell 3) is set to ΔV, so the operating point can be brought immediately closer to the MPP (see FIG. 2 ), making it possible to produce hydrogen with high efficiency.

[0058] Furthermore, when the operating point of the solar panel 1 is outside the operating range, the single fluctuation voltage in the output voltage of the DC / DC converter 24 is set to ΔV / n, which is smaller than ΔV. This reduces the amount of displacement of the operating point, and prevents the operating point from deviating significantly from the MPP, even if, for example, the current flowing through the electrolytic cell 3 suddenly increases. This prevents the control unit 23 from being reset frequently, and allows hydrogen production to continue without shutting down the electrolytic cell 3.

[0059] Furthermore, since the operating range of the MPPT control is set based on the data measured by the pyranometer 6, it is possible to control the operating point to approach the MPP with higher precision. Also, even if there are no specifications for the solar panel 1, it is possible to set an appropriate operating range.

[0060] [Description of the Third Embodiment] Next, a third embodiment will be described. Fig. 9 is a block diagram showing the configuration of a hydrogen production system 103 according to the third embodiment. The hydrogen production system 103 according to the third embodiment differs from the first embodiment described above in that the startup power of the electrolytic cell 3 (indicated as "EC startup power" in the figure) is input to the estimation unit 21. The other configuration is the same as that of the first embodiment shown in Fig. 1, so the same reference numerals are used and a description of the configuration will be omitted. That is, the estimation unit 21 sets the MPP point and operating range based on the specifications at the time of startup of the electrolytic cell.

[0061] In the third embodiment, the starting power of the electrolytic cell 3 is input to the estimation unit 21 to estimate the power curve and MPP. For example, the curve shown in FIG. 10 is obtained. Furthermore, the setting unit 22 sets the operating range based on the starting power of the electrolytic cell 3. This will be explained in detail below.

[0062] The estimation unit 21 acquires the startup voltage Vth and startup current Ith of the electrolytic cell 3 based on the specifications of the electrolytic cell 3. As shown in Fig. 11, the startup voltage Vth is the voltage when the current of the electrolytic cell 3 starts to increase, and the startup current Ith is the current at that time. The estimation unit 21 calculates the power Pec when the electrolytic cell 3 starts up using the following equation (2):

[0063] Pec=Vth*Ith …(2) The input power Ppv of the DC / DC converter 24 required at this time is calculated using the conversion efficiency η of the DC / DC converter 24 according to the following equation (3).

[0064] Ppv=Vth*Ith / η …(3) Fig. 12 is a diagram showing the conversion efficiency curve of the DC / DC converter 24. As shown in Fig. 12, the conversion efficiency η varies depending on the output voltage. The conversion efficiency η can be read based on the conversion efficiency curve shown in Fig. 12. For example, η = 0.7.

[0065] When the system starts up (the amount of solar radiation increases from zero) and the output power of the solar panel 1 increases while performing MPPT operation, the output voltage of the solar panel 1 when the input power of the DC / DC converter 24 reaches Ppv is defined as Vpm. Then, as in the second embodiment described above, the lower limit voltage Vll of the operating range is calculated using the following equation (4).

[0066] Vll=3Vpm-2Voc …(4) As a result, the region indicated by symbol R3 in Fig. 10 is set as the operating range. In the hydrogen production system 103 according to the third embodiment, the same processing as in the first embodiment is executed based on the operating range set by equation (4), and the operating point of the solar panel 1 is controlled to approach the MPP.

[0067] Therefore, as in the first embodiment, when the operating point of the solar panel 1 is within the operating range, the single fluctuation voltage in the output voltage of the DC / DC converter 24 (the input voltage of the electrolytic cell 3) is set to ΔV, so the operating point can be brought immediately closer to the MPP (see FIG. 2 ), making it possible to produce hydrogen with high efficiency.

[0068] Furthermore, when the operating point of the solar panel 1 is outside the operating range, the single fluctuation voltage in the output voltage of the DC / DC converter 24 is set to ΔV / n, which is smaller than ΔV. This reduces the amount of displacement of the operating point, and prevents the operating point from deviating significantly from the MPP, even if, for example, the current flowing through the electrolytic cell 3 suddenly increases. This prevents the control unit 23 from being reset frequently, and allows hydrogen production to continue without shutting down the electrolytic cell 3.

[0069] Furthermore, since the operating range of the MPPT control is set based on the startup power of the electrolytic cell 3, it is possible to control the operating point to approach the MPP with higher accuracy. Also, even if there are no specifications for the solar panel 1, it is possible to set an appropriate operating range.

[0070] [Description of the Fourth Embodiment] Next, a fourth embodiment will be described. Fig. 13 is a block diagram showing the configuration of a hydrogen production system 104 according to the fourth embodiment. The fourth embodiment differs from the first embodiment in that it includes a plurality of electrolytic cells 3-1 to 3-n and a plurality of DC / DC converters 24-1 to 24-n. That is, the voltage control device 2 includes a plurality of DC / DC converters 24-1 to 24-n (voltage conversion units). The voltage control device 2 also includes a plurality of electrolytic cells 3-1 to 3-n connected to the respective DC / DC converters 24-1 to 24-n. In Fig. 13, "electrolytic cell" is abbreviated as "EC."

[0071] In FIG. 13, the voltage control device 2 may have the configurations shown in the second and third embodiments described above.

[0072] In the hydrogen production system 104 according to the fourth embodiment, the plurality of electrolytic cells 3-1 to 3-n are activated to electrolyze water, so that hydrogen can be produced with higher efficiency.

[0073] The hydrogen production systems 101 to 104 according to the first to fourth embodiments described above can be configured with the hardware shown in Fig. 14. That is, the hydrogen production systems 101 to 104 can be configured with a CPU 201, a memory 202, a key input device 203, a display device 204, an I / F 205, and a data storage device 206.

[0074] The I / F 205 connects to external devices via a Universal Serial Bus (USB), an Inter-Integrated Circuit (I2C), etc. The key input device 203 inputs data such as the specifications of the solar panel 1 and the startup power of the electrolytic cell 3 from outside. The CPU 201 executes an application that runs on the memory 202 and controls the output voltage of the DC / DC converter 24.

[0075] FIG. 15 is a graph showing the relationship between the time of day and the amount of solar radiation in May in Japan. The amount of solar radiation is shown on a horizontal surface. In the example shown in FIG. 15, sunrise is at 4:30 and sunset is at 7:00 p.m. The solar radiation angle at which good power can be generated from the solar panel 1 is 40 degrees or more, which is the time period from 8:00 to 4:00 p.m. in the example shown in FIG. 15.

[0076] The time period during which the reset operation of the control unit 23 shown in the first to fourth embodiments frequently occurs is approximately from 5:00 to 8:00. Since the amount of hydrogen generated is proportional to the amount of solar radiation, when compared using the integrated value of the amount of solar radiation, the time period from 8:00 to 16:00 is "(2.0 + 3.7) * 4h = 22.8", and the time period from 5:00 to 8:00 is "(2.0 * 3h) / 2 = 3.0". The amount that can be contributed to an increase in the amount of hydrogen produced by avoiding the reset of the control unit 23 is "(3.0 / 22.8) * 100 = 13%". From the above, it can be seen that the amount of hydrogen produced can be increased by approximately 10% at most.

[0077] It can be seen that the hydrogen production systems 101 to 104 according to the first to fourth embodiments described above can produce hydrogen with high efficiency by suppressing power loss due to reset operations during times of low solar radiation.

[0078] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist thereof. [Explanation of symbols]

[0079] 1. Solar panels 2. Voltage control device 3. Electrolysis Cell 4 water tank 5 Hydrogen Cylinders 6 Pyranometer 21 Estimation part 22 Setting section 23 Control Unit 24 DC / DC converter (voltage conversion section) 51 Switching Circuit 60 Control circuit 101, 102, 103, 104 Hydrogen production system R1, R2, R3 MPPT operating range

Claims

1. an estimation unit that estimates a maximum power point in the output characteristics of the solar panel; a setting unit that sets an operating range of MPPT control based on the maximum power point; a voltage conversion unit that acquires the output power of the solar panel and outputs a voltage; an electrolytic cell that electrolyzes water using the output voltage of the voltage conversion unit; a control unit that controls the output voltage of the voltage conversion unit so that the operating point of the solar panel approaches the maximum power point; Equipped with the control unit controls the output voltage of the voltage conversion unit with a first variable voltage when the operating point is within the operating range; When the operating point is outside the operating range, the output voltage of the voltage conversion unit is controlled by a second variable voltage that is smaller than the first variable voltage. Hydrogen production system.

2. The estimation unit estimates the maximum power point based on specifications of the solar panel, and the setting unit sets the operating range based on the specifications of the solar panel. The hydrogen production system according to claim 1 .

3. Further provided is a pyranometer for measuring the amount of solar radiation; The estimation unit estimates the maximum power point based on the amount of solar radiation measured by the pyranometer, and the setting unit sets the operating range based on the amount of solar radiation. The hydrogen production system according to claim 1 .

4. The estimation unit estimates the maximum power point based on specifications at the time of startup of the electrolytic cell, and the setting unit sets the operating range based on the specifications at the time of startup of the electrolytic cell. The hydrogen production system according to claim 1 .

5. The voltage conversion unit and the electrolytic cell are provided in plural. The hydrogen production system according to any one of claims 1 to 4.

6. The control unit adjusts a gain of the voltage conversion unit to set the first variable voltage and the second variable voltage. The hydrogen production system according to claim 1 .

7. The estimation unit estimates a maximum power point in the output characteristics of the solar panel, a setting unit that sets an operation range of MPPT control based on the maximum power point; a voltage conversion unit that acquires the output power of the solar panel and outputs a voltage; a control unit that controls the output voltage of the voltage conversion unit so that the operating point of the solar panel approaches the maximum power point and supplies the output voltage to the electrolytic cell; The control unit controls the output voltage of the voltage conversion unit with a first variable voltage when the operating point is within the operating range, and controls the output voltage of the voltage conversion unit with a second variable voltage that is smaller than the first variable voltage when the operating point is outside the operating range. Hydrogen production methods.

8. A program that causes a computer to function as the estimation unit, the setting unit, and the control unit that are installed in the hydrogen production system according to claim 1.

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