JP5470542B2 - Solar cell evaluation method and solar cell evaluation system - Google Patents

Description

  The present invention relates to a solar cell evaluation method and an evaluation system.

  In solar cells, the conversion efficiency from light energy to electrical energy is one of the most important performances. The production scale of solar cells is often evaluated by the total amount of generated power, and in order to improve the production scale, it is indispensable to realize a solar cell with high conversion efficiency.

  One parameter that affects the conversion efficiency is a short-circuit photocurrent. This refers to the current generated when light is applied to a solar cell connected in a short-circuit state. Although it is desirable that all of the irradiated light is converted into an electric current, there are actually various loss processes, and not all of the irradiated light is converted into an electric current. Therefore, Patent Document 1 proposes a technique for evaluating the wavelength dependence of the conversion efficiency of a solar cell.

  A solar cell module generally has a structure in which a plurality of solar cells are connected in series on a single substrate. When light is irradiated on the surfaces of the plurality of solar cells, the irradiated light is converted into current, and current is generated in each solar cell. In such a solar cell module, the characteristics of each solar cell may vary due to various factors in the process. When there is a difference in the conversion efficiency of the plurality of solar cells, the current is limited to the solar cell having the lowest conversion efficiency.

  Therefore, Patent Document 2 proposes a technique that can measure the distribution of conversion efficiency at each position of the solar cell module. The solar cell evaluation apparatus described in Patent Document 2 includes a partial illumination light source that partially irradiates a solar cell module. The position of partial illumination on the solar cell module is scanned, and the conversion efficiency is measured for each partial illumination position.

  In a solar power generation system or solar power plant for home use, a solar cell unit that realizes a large area by connecting a plurality of solar cell modules having a plurality of solar cells in series in order to increase the generated power. Is used. Such a solar cell unit is installed on a roof or a rooftop.

  In the solar cell unit, the conversion efficiency may partially decrease due to a change with time. Therefore, it is desired to measure the conversion efficiency with the solar cell unit installed on the roof or the like. However, in the solar cell evaluation device described in Patent Document 2, it is necessary to illuminate the solar cell with partial illumination, and it is difficult to measure the conversion efficiency in a state where the solar cell is installed on a roof or the like. In particular, when evaluating a solar cell unit installed on a roof or the like, it is difficult to investigate safely.

Japanese Patent Laid-Open No. 60-83381 JP 2009-11115 A

  The present invention has been made in the background as described above, and the object of the present invention is to install the solar cell unit on a roof or the like without disconnecting a plurality of solar cell units to be connected. A solar cell evaluation method and a solar cell evaluation system that can accurately evaluate each position of a battery unit.

  The solar cell evaluation method according to the first aspect of the present invention is a solar cell evaluation method including a plurality of solar cells, wherein a part of the plurality of solar cells is shielded with a light shielding band, and the light shielding band The output from the solar cell is detected when light is applied to the entire surface of the solar cell shielded by the light shielding band while scanning in the first direction, and the direction of the light shielding band with respect to the solar cell is different. An output from the solar cell is detected when light is applied to the entire surface of the solar cell that is shielded by the light shielding band while changing in the second direction and scanning the light shielding band in the second direction. The conversion efficiency distribution of the solar cell is calculated based on the detected output from the solar cell. Thereby, it is possible to obtain a two-dimensional distribution of a decrease in conversion efficiency without disconnecting the connected solar battery cells, and it is possible to appropriately evaluate the solar battery.

In the solar cell evaluation method according to a second aspect of the present invention, in the above evaluation method, the light shielding band is formed of a light shielding film that transmits a part of light irradiated on the solar cell.
In the solar cell evaluation method according to a third aspect of the present invention, in the above evaluation method, the light shielding band is formed of a light shielding film that completely shields light applied to the solar cell, and the width of the light shielding band is The width of the solar battery cell is narrower. By using such a light shielding band, the solar cell can be more accurately evaluated.

  The solar cell evaluation method according to a fourth aspect of the present invention is characterized in that, in the above evaluation method, the conversion efficiency is calculated using the output from the detected solar cell as projection data of a back projection method. Thereby, the conversion efficiency distribution can be easily calculated, and the solar cell can be more accurately evaluated.

  A solar cell system according to a fifth aspect of the present invention is a solar cell evaluation system including a plurality of solar cells, and includes a light shielding band that shields a part of the plurality of solar cells, and the light shielding band. Change means for changing the direction with respect to the solar cell, a detector for detecting an output from the solar cell when light is irradiated on the entire surface of the solar cell shielded by the light shielding band, and detected by the detector And a processing unit that calculates the conversion efficiency distribution of the solar cell based on the output from the solar cell. The conversion efficiency distribution can be calculated by detecting the output of the solar cell shielded by the light shielding band. Thereby, it is possible to obtain a two-dimensional distribution of a decrease in conversion efficiency without disconnecting the connected solar battery cells, and it is possible to appropriately evaluate the solar battery.

In the solar cell system according to a sixth aspect of the present invention, in the above system, the light shielding band is formed of a light shielding film that transmits a part of light irradiated on the solar cell.
In the solar cell system according to a seventh aspect of the present invention, in the above system, the light shielding band is composed of a light shielding film that completely shields light irradiated on the solar cell, and the width of the light shielding band is It is narrower than the width of the solar battery cell. By using such a light shielding band, the solar cell can be more accurately evaluated.

A solar cell system according to an eighth aspect of the present invention is characterized in that, in the above-described system, the conversion efficiency is calculated using the output from the detected solar cell as projection data of a back projection method. . Thereby, the conversion efficiency distribution can be easily calculated, and the solar cell can be more accurately evaluated.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell evaluation method and solar cell evaluation system which can evaluate a solar cell appropriately can be provided, without isolate | separating the photovoltaic cell connected.

It is a figure which shows a part of structure of the solar cell evaluation system which concerns on embodiment. It is a figure which shows the state which installed the solar cell evaluation system which concerns on embodiment on the roof. It is a figure which shows the structure of the detector used in the solar cell system which concerns on embodiment. It is a figure which shows an example of the light quantity fall distribution of a solar cell unit, and the positional relationship of the light-shielding zone on a solar cell unit.

  Embodiments of the present invention will be described below with reference to the drawings. The following description shows preferred examples of the present invention, and the scope of the present invention is not limited to the following examples. In the following description, the same reference numerals denote the same contents.

  The configuration of the solar cell evaluation system according to the present embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing a part of the configuration of a solar cell evaluation system 10 according to the present embodiment. As shown in FIG. 1, the solar cell evaluation system 10 includes a rail 11, a traveling unit 12, and a light shielding band 13. The solar cell evaluation system 10 according to the present invention uses the solar cell unit 20 as an evaluation target.

  Here, the configuration of the solar cell unit 20 will be described. The solar cell unit 20 has a plurality of solar cell modules 21 connected in series. In the example shown in FIG. 1, nine solar cell modules 21 are arranged in a matrix. Each solar cell module 21 includes a plurality of solar cells 22 connected in series. In the example shown in FIG. 1, 6 × 4 solar cells 22 are arranged in a matrix. Therefore, all the solar cells 22 provided in the solar cell unit 20 are connected in series.

  The solar cell unit 20 is installed on a roof, for example. The solar cell evaluation system 10 evaluates the solar cell unit 20 in a state where it is installed on a roof or the like without disconnecting the solar cells 22 connected in series. In the solar cell evaluation system 10, a part of the light irradiated to the solar cell unit 20 is blocked by the light shielding band 13, and a decrease in output is measured by a shadow formed by the light shielding band 13. Then, the conversion efficiency distribution is calculated by scanning the shading band 13 and using the lowered output from the solar cell as projection data of the back projection method.

  The rail 11 is disposed so as to surround the periphery of the solar cell unit 20. As the rail 11, for example, an assembly-type one that can connect a plurality of rail components to a desired length can be used. Thereby, regardless of the size of the solar cell unit 20, a rail having an appropriate length can be installed. In addition, in the example shown in FIG. 1, although the rail 11 is arrange | positioned at rectangular shape, it is not limited to this. The shape of the rail 11 can be changed according to the shape of the solar cell unit 20.

  The traveling unit 12 is a moving body that moves on the rail 11. In this example, two traveling units 12 are provided. In addition, as the traveling unit 12, it is preferable to use a self-propelled unit that moves using a rechargeable battery or the like as a power source. As a result, the traveling unit 12 can easily move the entire circumference of the rail 11. Although not shown here, the traveling unit 12 includes an antenna for performing wireless communication with a processing unit 17 (described later) that controls the position of the traveling unit 12 on the rail 11, an encoder that measures the current position, and the like. ing.

  A light shielding band 13 is installed between the two traveling units 12. The light shielding band 13 shields at least a part of each of the solar cells 22. As shown in FIG. 1, the light shielding band 13 has a thin band shape, and forms a band-shaped shadow on the solar cell unit 20.

  As the light shielding zone 13, for example, a semi-transmissive film that transmits a part of the light irradiated to the solar battery cell 22 can be used. When a semi-transmissive film is used as the light shielding band 13, the width of the light shielding band 13 may be a width that covers all of the single solar battery cell 22 or may be narrower than the width of the solar battery cell 22. Further, the transmittance of the semi-transmissive film can be appropriately changed depending on the amount of light irradiated to the solar battery cell 22 or the like. The transmittance of the semipermeable membrane can be set to 50%, for example.

  Moreover, it is also possible to use a light shielding band 13 that completely shields the light applied to the solar battery cell 22. When a light-shielding film that completely shields light is used as the light-shielding band 13, the width of the light-shielding band 13 cannot be a width that covers all the solar cells 22. As described above, since the solar cells 22 are connected in series, the output from the solar cell cannot be obtained if any of the solar cells 22 is completely shielded from light.

  In this case, the width of the light shielding band 13 is narrower than the width of one solar battery cell 22. For example, the width can be set such that about 20% of the area of one solar battery cell 22 is shielded from light. Of course, the width of the light-shielding band 13 is not limited to this example, and can be changed as appropriate. The width of the light shielding band 13 can be set to 10 mm, for example. Of course, the width of the light shielding band 13 is not particularly limited, and may be determined according to the width of the solar battery cell 22 or the necessary resolution.

  The shading band 13 is a winding type and can be expanded and contracted. As the distance between the two traveling units 12 increases, the length of the light shielding band 13 increases, and as the distance between the two traveling units 12 decreases, the length of the light shielding band 13 decreases. That is, the shading band 13 is arranged in a state where it is stretched between the two traveling units 12 without any slack, regardless of the position where the two traveling units 12 move on the rail 11.

  When the traveling unit 12 moves on the rail 11 at a predetermined speed, the solar cell unit 20 can be scanned by the shading band 13. Moreover, the direction with respect to the solar cell unit 20 of the light-shielding zone 13 can be changed by changing the speed of each of the two traveling units 12. That is, an arbitrary position on the solar cell unit 20 can be scanned at an arbitrary angle with a linear shadow formed by the light shielding band 13. The position of the traveling unit 12 and the speed of movement on the rail 11 are controlled by a processing unit 17 described later.

  In FIG. 2, the state which installed the solar cell evaluation system 10 and the solar cell unit 20 on the roof is shown. The rail 11, the traveling unit 12, and the light-shielding band 13 which are a part of the solar cell evaluation system 10 are made lightweight, and can be safely lifted on the roof by a lift 14, as shown in FIG. Thus, the solar cell evaluation system 10 of the present invention can perform the evaluation while the solar cell unit 20 is installed on the roof.

  In the present embodiment, sunlight is used as a light source for irradiating light on the entire surface of the solar cell unit 20. For this reason, a large light source such as a solar simulator is not required. However, a solar simulator that emits light having the same spectrum as sunlight may be used as the light source.

  In the present embodiment, all the solar battery cells 22 are connected in series in the solar battery unit 20. When a shadow is partially created by the light shielding band 13, the current value taken out from the solar battery unit 20 is limited by the solar battery cell 22 where the maximum shadow is formed. For this reason, when the output taken out from the solar cell unit 20 is simply converted into current and voltage, the current from the solar cell 22 in which the maximum shadow is formed is merely read out, and the conversion efficiency is calculated by a computer tomograph (CT). It is not possible to obtain a two-dimensional distribution of the decrease in.

  Therefore, in the present invention, a detector having the following configuration is used in order to read out the decrease in power generation capacity integrated along the linear shadow formed by the light shielding band 13. In FIG. 3, an example of a structure of the detector of the solar cell evaluation system 10 which concerns on this Embodiment is shown. As shown in FIG. 3, the detector includes a current detection unit 15, a voltage detection unit 16, and load resistors 1 to 4. When the solar cell evaluation system 10 evaluates the solar cell unit 20, the power that is the product of the current and voltage is read instead of mere current / voltage conversion.

  The current detection unit 15 is connected to the output line of the solar cell unit 20. The current detection unit 15 is a current detection element and detects an output current from the solar cell unit 20. From the detection value by the current detection unit 15, it can be seen that the output current is reduced due to the shadow formed by the light shielding band 13. The output current from the current detection unit 15 is converted into a digital signal and input to the processing unit 17. The processing unit 17 may convert the detection signal from the current detection unit 15 into a digital signal.

  One end of the changeover switch 18 is connected to the output line of the solar cell unit 20. The changeover switch 18 is connected to one of short circuit (grounding), load resistors 1 to 4 and open. The voltage detection unit 16 detects the voltage applied to the connected load resistance or the like while switching the load condition with the changeover switch 18. The voltage detected by the voltage detection unit 16 is input to the processing unit 17 converted into a digital signal.

  The processing unit 17 is an information processing apparatus such as a personal computer, and performs predetermined arithmetic processing on the detection signal. The processing unit 17 includes, for example, a CPU (Central Processing Unit) that is an arithmetic processing unit, a ROM (Read Only Memory) or RAM (Random Access Memory) that is a storage area, a communication interface, and the like, and a conversion efficiency distribution. A process necessary for calculation is executed.

  For example, the ROM stores an arithmetic processing program for performing arithmetic processing, various setting data, and the like. Then, the CPU reads out the arithmetic processing program stored in the ROM and develops it in the RAM. Then, the program is executed according to the setting data and the output from the current detection unit 15, the voltage detection unit 16, and the like. Furthermore, the processing unit 17 includes a monitor for displaying the calculation processing result.

  Further, the processing unit 17 controls driving of the traveling unit 12. That is, the processing unit 17 controls the angle of the light shielding band 13 with respect to the solar cell unit 20 and the scanning direction. Accordingly, the processing unit 17 recognizes the position of the shadow by the light shielding band 13 with respect to the solar cell unit 20. For this reason, the processing unit 17 can recognize how much output is present when the line-shaped light is incident on which position of the solar cell unit 20.

  From the solar cell unit 20 when there is a defect and there is a shadow due to the light shielding band 13 at a place where the conversion efficiency is relatively high, and when the light shielding band 13 is present at a place where there is a defect and the conversion efficiency is relatively low The amount of decrease in output changes. In the places where there are no defects, the output is greatly reduced compared to the places where there are defects. Therefore, by monitoring the position of the light shielding band 13 and the decrease in the output of the solar cell unit 20, it is possible to identify a defective portion.

  The current detection unit 15 and the voltage detection unit 16 detect the output from the solar cell unit 20 when the light shielding band 13 is scanned in one direction as needed. Thereby, the fall of the output in the different position of the solar cell unit 20 can be measured.

  Further, the scanning direction of the light shielding band 13 is changed by a predetermined angle under the control of the traveling unit 12, and the output from the solar cell unit 20 when scanning in the direction is detected as needed. By repeating this, the shading band 13 is scanned from various angles, and these detection results are stored in the processing unit 17. That is, the projection data when the shadow is formed in two or more directions by changing the angle of the shadow by the light shielding band 13 with respect to the solar cell unit 20 is collected. That is, it is possible to read the decrease in power generation capacity that is line-integrated along the shadow of the light shielding band 13.

  The processing unit 17 calculates the spatial distribution of the decrease in conversion efficiency of the solar cell 12 using the stored detection data. For example, a two-dimensional image with a reduced conversion efficiency distribution spread in two dimensions can be obtained by computed tomography (CT). That is, one-dimensional detection data can be converted into a two-dimensional conversion efficiency distribution and imaged.

  That is, the processing unit 17 converts the conversion efficiency of the solar cell unit 20 based on the detection results detected by the current detection unit 15 and the voltage detection unit 16 when the direction of the light shielding band 13 with respect to the solar cell unit 20 is changed and scanned. Calculate the two-dimensional distribution of the decrease in. Of the two-dimensional distribution obtained in this way, a portion with higher conversion efficiency than the surrounding can be evaluated as a defective portion.

For example, assuming that the conversion efficiency distribution of the solar cell unit 20 is E (x, y), when the width of the light shielding band 13 is sufficiently small, the decrease in the output generated in the shadow portion is as shown in the following formula (1). Become.

  Here, I (x, y) is a light amount reduction distribution of a shadow portion formed by the light shielding band 13. When the light amount distribution of the shadow portion formed by the light shielding band 13 is constant, it can be made constant by I (x, y) = C. Ds is a minute length along the light shielding band 13. The line integration along the light shielding band 13 corresponds to a decrease in output.

  If the integrated value along the shading band 13 is developed on the computer memory (back projection) and the inverse transformation of the point spread function (PSF) is applied, a two-dimensional conversion efficiency distribution can be obtained. Can do. For example, a filtered back projection (FBP) method can be used.

  At this time, the transmission intensity of the X-ray in the X-ray CT corresponds to the output of the detector. That is, the linear absorption coefficient of the measurement target in X-ray CT corresponds to a decrease in output due to a strip-shaped shadow. The integrated value of power for one shadow line of the light shielding band 13 becomes projection data. The two-dimensional spatial distribution of the absorption coefficient in the X-ray CT corresponds to the two-dimensional spatial distribution having a reduced conversion efficiency.

  As described above, by performing the same process as the process of obtaining the tomographic image from the projection data in the X-ray CT with respect to the detection data of the output of the solar cell unit 20, it is possible to calculate the spatial distribution of the conversion efficiency decrease. . That is, a two-dimensional distribution of a reduction in conversion efficiency can be calculated by the same process as the X-ray CT that irradiates collimated X-rays. In addition, you may attach a linear encoder to the solar cell evaluation system 10 as needed. Thereby, the irradiation position on the solar cell unit 20 can be grasped more accurately.

この場合、処理部１７に遮光帯１３の光量分布の関数を記憶させ、変換効率の低下の二次元分布を得ることができる。 In the above example, the decrease in the power generation capacity that is line-integrated along the shadow by the light shielding band 13 is read out, but the present invention is not limited to this. For example, when the light shielding band 13 is wide, a two-dimensional distribution of a decrease in conversion efficiency may be calculated using a function in the width direction of the light shielding band 13.
FIG. 4 shows an example of the light amount reduction distribution of the solar cell unit 20 and the positional relationship of the shadow by the light shielding band 13 on the solar cell unit 20. As shown in FIG. 4, the conversion efficiency distribution of the solar cell unit 20 is E (x, y), the width direction of the shadow portion of the light shielding band 13 is u, the length direction is v, and the light quantity reduction distribution is I ( u, v). The decrease in output generated in the shaded area of the light shielding band 13 is as shown in the following equation (2).

In this case, the processing unit 17 can store a function of the light amount distribution of the light shielding band 13 to obtain a two-dimensional distribution with a reduced conversion efficiency.

  As described above, in the present invention, the solar cell unit 20 can be safely evaluated in a state where the solar cell unit 20 is installed on a roof, a solar power plant, or the like. Moreover, even if it is the photovoltaic cell 22 connected in series, the output from the solar cell unit 20 is detected, changing the scanning direction of the strip | belt-shaped shadow formed with the light shielding band 13 as mentioned above, and predetermined. By performing the arithmetic processing, it is possible to obtain a two-dimensional distribution of a decrease in conversion efficiency.

  The function of measuring the efficiency distribution with CT has high positional accuracy of the measurement result. For this reason, it is possible to accurately identify the defective module and the defective portion of the solar cell unit 20 without disconnecting the series-connected solar cells 22 using the result obtained by using the CT. When a defective part where the power generation efficiency is partially reduced is identified, the conversion efficiency of the entire solar cell unit 20 is improved at low cost by replacing only the solar cell module 21 including the defective part. Is possible.

  As shown in this embodiment mode, measurement can be performed in a short time by scanning a band-like shadow. In the above description, the output from the solar cell unit 20 is measured when scanning in one direction, but the output from the solar cell unit 20 may be measured when scanning in both directions.

  The solar cell unit 20 has a kw class output. Therefore, if a load resistance as shown in FIG. 3 is connected continuously, it may overheat and ignite. Therefore, for example, when the read cycle is 10 msec, the load is connected to one of the loads 1 to 4 for 100 μsec. Moreover, a heat radiator may be provided or water cooling may be performed to prevent overheating. The present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Solar cell evaluation system 11 Rail 12 Traveling unit 13 Shading zone 14 Lift 15 Current detection unit 16 Voltage detection unit 17 Processing part 18 Changeover switch 20 Solar cell unit 21 Solar cell module 22 Solar cell

Claims (14)

A solar cell evaluation method comprising a plurality of solar cells,
Shielding a part of the plurality of solar cells with a strip-shaped shading band;
While scanning said light-shielding zone, detects the output from the solar cell when irradiated with light on the entire surface of the solar cell is shielded by the shielding band,
To change the angle with respect to the solar cell of the light-shielding band,
After changing the angle while scanning the light-shielding band, detects the output from the solar cell on the entire surface of the solar cell is shielded by the light-shielding band when irradiated with light,
Based on the detected output from the solar cell, to calculate the conversion efficiency distribution of the solar cell,
Solar cell evaluation method. The shading band is constructed between two traveling units that move on the outer periphery of the solar cell,
By changing the positional relationship between the two traveling units, the angle of the shading band with respect to the solar cell is changed.
The solar cell evaluation method according to claim 1. The shading band is
It expands and contracts according to the change in the distance between the two traveling units.
The solar cell evaluation method according to claim 2. The shading band is of a winding type
The solar cell evaluation method according to claim 2 or 3, wherein The solar cell evaluation method according to any one of claims 1 to 4, wherein the light-shielding band is formed of a light-shielding film that transmits a part of light applied to the solar cell. The light-shielding band is composed of a light-shielding film that completely shields light applied to the solar cell,
Wherein the width of the light blocking zone, a solar cell evaluation method according to any one of claims 1-4, characterized in that narrower than the width of the solar cell. The solar cell evaluation method according to any one of claims 1 to 6 , wherein the conversion efficiency is calculated using the detected output from the solar cell as projection data of a back projection method. A solar cell evaluation system comprising a plurality of solar cells,
A strip-shaped shading band that shields part of the plurality of solar cells; and
Changing means for changing an angle of the light shielding band with respect to the solar cell;
A detector for detecting an output from the solar cell when the entire surface of the solar cell shielded by the light-shielding band is irradiated with light;
Before and after changing the angle , based on the output from the solar cell detected by the detector, a processing unit that calculates the conversion efficiency distribution of the solar cell;
A solar cell evaluation system comprising: Comprising two traveling units that move around the outer periphery of the solar cell;
The shading band is constructed between the two traveling units,
By changing the positional relationship of the plurality of traveling units, the angle of the light shielding band with respect to the solar cell is changed.
The solar cell evaluation system according to claim 8. The shading band is
It expands and contracts according to the change in the distance between the two traveling units.
The solar cell evaluation system according to claim 9. The shading band is of a winding type
The solar cell evaluation system according to claim 9 or 10, wherein: The solar cell evaluation system according to any one of claims 8 to 11, wherein the light-shielding band is formed of a light-shielding film that transmits a part of light applied to the solar cell. The light-shielding band is composed of a light-shielding film that completely shields light applied to the solar cell,
The width of the light-shielding band solar cell evaluation system according to any one of claims 8 to 11, characterized in that narrower than the width of the solar cell. The solar cell evaluation system according to any one of claims 8 to 13 , wherein the conversion efficiency is calculated by using the detected output from the solar cell as projection data of a back projection method.

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