JPH08130837A - Solar power supply - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a solar cell power supply device that can flexibly cope with high load voltage. [Solution] A solar cell power supply device comprising solar cells 1 and 2 and a chemical cell 5 connected in series, one output terminal connected to the solar cell, and the other output terminal connected to the chemical cell. Therefore, the solar cell and the chemical cell are connected in series so that the voltage of the chemical cell biases the semiconductor junction of the solar cell in the reverse direction when a load is connected between the output terminals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar battery power supply device in which a required DC output voltage can be easily set and solar power can be taken out to the maximum.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 10, a backflow prevention diode 53, 5 is provided in each of a solar cell group 51, 52 in which a plurality of cells (solar cell elements) are connected in series.
4 is connected in series, and the solar cell groups 51 and 52 are connected in parallel so that the output can be taken out from the output terminals 55 and 56, or the solar cell group 51 as shown in FIG. , 52, and a secondary battery 57 are connected in parallel.

Here, a load is connected between the output terminals 55 and 56, but the voltage required for this load varies and often changes. Therefore, simply output terminal 5
When a load is directly connected between 5 and 56, the operating voltage of the solar cell may deviate from the operating voltage Vm that gives the maximum output point Pm, and it is often impossible to effectively take out the photovoltaic power generated originally. .

Therefore, normally, between the output terminals 55 and 56,
By connecting a DC-DC converter, a DC-AC inverter, etc. to separate the load voltage from the solar cell operating voltage and keeping the solar cell operating voltage always near Vm, efforts are made to maximize the photovoltaic power generation. Done.

However, DC-DC converters and DC-
In order to operate an AC inverter, it consumes power itself, and its power consumption generally tends to increase as the conversion ratio between the output voltage and the input voltage increases. Therefore, when the voltage required for the load increases and the output voltage of the DC-DC converter or DC-AC inverter increases, the input voltage to them, that is, the operating voltage of the solar cell also increases, so that the number of cells in series is increased. Will need to be increased.

The voltage required for the load is, for example, 5 to 1
There are relatively small ones such as 2V, but usually 100
Generally, about 200 V is used, and a load that consumes a large amount of power tends to improve energy efficiency by using a higher voltage and reducing a current.

On the other hand, the output voltage of one cell is small. For example, in the case of a Si crystal solar cell, the output voltage of one solar cell that gives the maximum output even under sunlight of 100 mW / cm ² is about 0.5V. is there. Therefore, in order to obtain a voltage of 100 to 200 V that is usually required for a load, 200 to 400 cells of Si crystal solar cells must be connected in series. This is 2 to 4 to install the minimum unit of the solar battery power source when using a 10 cm square cell.
This means that it requires a footprint of m ² .

Recently, in order to reduce the manufacturing cost of solar cells, there is a tendency to increase the area of cells from 10 cm square to 15 cm square or more. If the area of one cell increases 2.25 times from 10 cm square to 15 cm square, the minimum unit installation area of the solar cell power source will increase in proportion to it. Conventionally, if such a large installation area cannot be taken, a 10 cm square cell is cut into ½, ⅓, ¼, etc. to make a small area cell, By connecting them in series, we have made it possible to obtain the required voltage even with a small installation area.

However, such a measure causes a high cost of the manufacturing process for modularization, has a low degree of freedom in cell cutting, etc., and is a restrictive method for coping. Also, the operating voltage Vm at which the solar cell gives the maximum output
Changes depending on the temperature of the solar cell and the amount of solar radiation,
In order to always maintain the operating voltage of the solar cell near Vm, it is necessary to measure the temperature of the solar cell, measure the amount of solar radiation and / or an electrical control system. These eventually lead to structural complication of the solar cell power supply device, which is one of the causes of the high cost.

Therefore, the present invention solves the conventional problems,
It is an object of the present invention to provide a solar cell power supply device that can flexibly cope with a high load voltage.

[0011]

In order to solve the above-mentioned problems, a solar cell power supply device of the present invention comprises a solar cell and a chemical cell, wherein the voltage of the chemical cell reverses the semiconductor junction of the solar cell. It is characterized in that they are connected in series so as to be biased. Here, the solar cell refers to one or more connected cells.

Further, for example, a chemical battery is used as a secondary battery, bias detecting means for detecting application of a reverse bias voltage or a forward bias voltage to the solar cell, and a solar cell power source by an output signal from the bias detecting means. The output circuit of the device may be provided with a switch that opens and closes (opens with a reverse bias and closes with a forward bias), and a bypass diode connected to each cell constituting the solar cell.

[0013]

The operating current Im that gives the maximum output of the solar cell is
It is determined almost in proportion to the amount of solar radiation on the solar cell, and the relationship between the operating current Im and the operating voltage Vm shows a characteristic having a positive slope. On the other hand, the relationship between the operating current Im and the operating voltage Eb of the chemical battery shows a characteristic having a negative slope because of the internal resistance of the chemical battery.

The relationship between the operating voltage Vm and the operating temperature shows a characteristic having a negative slope, and the relationship between the operating voltage Eb and the operating temperature shows a characteristic having a positive slope.

Therefore, if the output voltage Es of the solar cell power supply device is set to Es = Eb + Vm, the Es becomes almost constant regardless of the value of the operating current Im (ie, the amount of solar radiation) and the fluctuation of the operating temperature. By keeping it, the operation near the maximum output point of the solar cell becomes possible.

As a result, it is not necessary to measure the temperature of the solar cell or measure the amount of solar radiation, which has been conventionally required to keep the operating voltage of the solar cell near the operating voltage Vm that gives the maximum output of the solar cell. By simply performing a simple control of keeping Es (= Eb + Vm) substantially constant, it is possible to maximize the solar power generated by the solar battery power supply device.

[0017]

EXAMPLE An example according to the present invention will be described in detail. First, as shown in FIG. 1, solar cell groups 1 and 2 in which a plurality of cells are connected in series are connected in parallel via backflow prevention diodes 3 and 4, and a chemical battery (here, a lead storage battery) 5 is connected. Connected in series to these solar cells PV,
A description will be given of the solar cell power supply device S1 that can output a desired output from the output terminals 6 and 7.

Voltage Es applied between output terminals 6 and 7
Is the operating voltage Vm of the solar cell PV plus the operating voltage Eb of the chemical cell 5. That is, the solar cell PV
If the number of series connections is small and the voltage required for the load is not reached, by connecting the number of the chemical cells 5 in series in the direction in which the p / n junction of the solar cell PV can be reverse biased,
The required output voltage of the solar cell power supply device can be easily set.

Further, in this way, the operating current of the chemical cell 5 becomes the same as the operating current of the solar cell PV. The operating current Im that gives the maximum output Pm of the solar cell PV is determined almost in proportion to the amount of solar radiation to the solar cell PV, and the operating current I
The relationship between m and the operating voltage Vm shows a characteristic having a positive slope as schematically shown in FIG.

On the other hand, the relationship between the operating current Im and the operating voltage Eb of the chemical battery 5 is shown in FIG.
The characteristic has a negative slope as shown in. Therefore, the output voltage of the solar battery power supply S1 is Es = Eb + V
When set to m, as shown in FIG. 4, regardless of the value of the operating current Im (that is, the amount of solar radiation), it can be maintained at a substantially constant Es, and the operation near the maximum output point of the solar cell PV can be performed. It will be possible.

Similarly, the dependence of the operating voltage (Vm) and the operating voltage (Eb) on the operating temperature (T) also has the characteristic shown in FIG. 5, so if these are connected in series, Es (= Eb + Vm).
By keeping the above substantially constant, it is possible to operate near the maximum output point of the solar cell PV regardless of the operating temperature.

That is, the output voltage Es (=) is eliminated by omitting the solar cell temperature measurement and solar radiation amount measurement, which are conventionally required to keep the operating voltage of the solar cell near the operating voltage Vm that gives the maximum output of the solar cell. By simply performing a simple control of keeping Eb + Vm) almost constant, it is possible to maximize the solar power generated by the solar battery power supply device.

Next, another embodiment of the present invention, which is a solar cell power supply device S2 of FIG. 6, will be described. The solar cell power supply device S2 is provided with a bias detecting means 9 in parallel with the solar cell PV in FIG. 1, the output circuit is opened by the reverse bias detection signal from the bias detecting means 9, and is output by the forward bias detection signal. A switch 8 for closing the circuit is provided between the chemical cell 5 and the solar cell PV.

This is to prevent the solar cell power source device S2 from operating only by the electromotive force of the chemical battery 5 when the electromotive force of the solar cell PV is exhausted at night or the like. That is, if the switch 8 and the bias detection means 9 are not provided, when the electromotive force of the solar cell PV is exhausted, the bypass diode 13 is forward biased by the electromotive force of the chemical cell 5, so that the solar cell power source device S2 is not provided. The current passing through the bypass diode 13 continues to flow, and the chemical battery 5 continues to be discharged. Therefore, when the bypass diode 13 is provided, the switch 8 and the bias detection means 9 are provided so that the solar cell power supply device S2 does not operate only by discharging the secondary battery. It should be noted that the bypass diode 13 is usually used in the solar cell in order to reduce a decrease in output when some cells are shaded and to prevent a large reverse bias from being applied to the shaded cells. It is provided.

As shown in FIGS. 7 and 8, the chemical cells 5a and 5b may be connected in series to the solar cells 1 and 2, respectively.

Further, FIG. 9 shows an example in which the solar cell power supply device S7 is applied to a residential solar power generation system in which the system is linked. Here, 10 is a timer, 11 is a switch,
Reference numeral 12 is a secondary battery charger. In order to cover the power consumption of an average Japanese house consisting only of conventional solar cells, it is necessary to install a solar cell module of about 3 kWp (kilowatt peak). Assuming 12%, installation of a solar cell module of 3 kWp requires a 25 m ² installation area such as a roof.

However, in the conventional Japanese house roof,
In many cases, a single roof surface cannot occupy a 25m ² solar cell module installation area, and the sunshine conditions are significantly different, such as the south-facing inclined surface, which is convenient for solar power generation, and the east- and west-facing roof surfaces and balconies The current situation is that the installation area can be finally secured together with the required installation area.

As described above, assuming that the outputs of the solar cell modules installed in places where the sunshine conditions are significantly different are combined into one DC-AC inverter input, each solar cell module outputs the maximum output point at each illuminance. It will operate at a deviated operating point, resulting in a loss of a substantial portion of the photovoltaic power that would otherwise be obtained.

When the solar battery power supply device of the present invention is applied to such a conventional Japanese house, the installed amount of solar battery modules required to cover the average amount of power used in a Japanese house is 2 It can be reduced to about 1 to 2 kWp depending on the amount of secondary battery. Therefore, as shown in FIG. 9, the solar cell module installation roof surface can be covered by only two or south facing roof surfaces.

By doing so, not only the above-described effects can be sufficiently obtained, but also the use of the solar cell installation place where the sunshine conditions are different can be minimized. In addition, it is connected to the secondary battery charger through the secondary battery charging circuit switch that closes only the late-night power hours of the secondary battery and opens it at other times. Is automatically charged during the midnight power hours.

[0031]

As described above, according to the present invention, the required operating voltage of the solar battery power supply device can be obtained by adjusting the operating voltage of the chemical battery. The degree of freedom in setting the number is greatly increased. Further, the solar battery power supply device can be installed by using a solar battery module of a fixed standard even in a small installation area. Here, if the installation area is the same, a solar cell power supply device having a larger output can be installed. Further, by using a secondary battery as the chemical battery and charging the secondary battery with midnight power, it is possible to provide a solar battery power supply device that contributes highly to leveling (peak cut) of power demand. Furthermore, not only is it possible to maximize the amount of photovoltaic power generated by a simple control that keeps the output terminal voltage almost constant, but it is also possible to control the output terminal voltage in detail even with changes in operating temperature and illuminance as in the past. No need for control.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment according to the present invention.

FIG. 2 is a relationship diagram between operating current and operating voltage of a solar cell.

FIG. 3 is a relationship diagram between an operating current and an operating voltage of a chemical battery.

FIG. 4 is a relationship diagram between an operating current and an output voltage of a solar cell power supply device.

FIG. 5 is a relational diagram of operating temperature, operating voltage of solar cell, operating voltage of chemical cell, and output voltage of solar cell power supply device.

FIG. 6 is a schematic configuration diagram showing another embodiment according to the present invention.

FIG. 7 is a schematic configuration diagram showing another embodiment according to the present invention.

FIG. 8 is a schematic configuration diagram showing another embodiment according to the present invention.

FIG. 9 is a schematic configuration diagram showing another embodiment according to the present invention.

FIG. 10 is a schematic configuration diagram showing a conventional solar cell power supply device.

FIG. 11 is a schematic configuration diagram showing a conventional solar cell power supply device.

[Explanation of symbols]

 PV (1, 2) ... Solar cell 5 ... Chemical cell 9 ... Bias detecting means S1, S2, S7 to S11 ... Solar cell power supply device

Claims (1)

[Claims] 1. A solar cell power supply device comprising a solar cell and a chemical cell connected in series so that the voltage of the chemical cell biases the semiconductor junction of the solar cell in the reverse direction.