WO2012168250A1

WO2012168250A1 - Method for assessing potential induced degradation of solar cells and photovoltaic panels

Info

Publication number: WO2012168250A1
Application number: PCT/EP2012/060615
Authority: WO
Inventors: Henning Nagel
Original assignee: Schott Solar Ag
Priority date: 2011-06-05
Filing date: 2012-06-05
Publication date: 2012-12-13
Also published as: DE102011051091B4; DE102011051091A1; WO2012168250A4

Abstract

The invention relates to a method for assessing potential induced degradation of solar cells and photovoltaic panels. In a first method step of said method, a first electric current is applied to a solar cell or to a photovoltaic panel, and, after the elapse of a first time interval, an electric characteristic of the solar cell or of the photovoltaic panel is measured. If the change in the electric characteristic or in the potential induced degradation derived therefrom exceeds a pre-defined first threshold value, the solar cell or the photovoltaic panel undergoes a second method step, in which the solar cell or the photovoltaic panel are subjected to different environmental conditions than during the first method step, preferably to simulated realistic operating conditions, and an electric characteristic of the solar cell or of the photovoltaic panel is measured, said electric characteristic being used to assess the potential induced degradation of the solar cell or of the photovoltaic panel.

Description

METHOD FOR EVALUATING THE HIGH VOLTAGE DEGRADATION OF SOLAR CELLS AND PHOTOVOLTAIC MODULES

The present application claims the priorities of the German patent applications

DE 10 2011 104 692.9 "METHOD OF EVALUATING THE HIGH VOLTAGE DEGRADATION OF PHOTOVOLTAIC MODULES" filed on Jun. 5, 2011 and DE 10 2011 051 091.5 "METHOD OF EVALUATING THE HIGH VOLTAGE DEGRADATION OF PHOTOVOLTAIC MODULES" filed on Jun. 15, 2011, the entire content of which is hereby expressly incorporated by reference.

FIELD OF THE INVENTION The present invention generally relates to the evaluation of solar cells and

Photovoltaic modules, for example, in the context of their production, and in particular relates to a method for evaluating the high voltage degradation (HVS) or potential induced degradation (PID) of solar cells and photovoltaic modules. Another aspect of the present invention relates to the use of such a method in the manufacture of solar cells or photovoltaic modules.

Background of the invention

A typical photovoltaic module comprises a plurality of solar cells, which are connected in series by means of metallic connectors. The solar cells are in one

Embedding material laminated, which is insulating and should protect them from the weather. Today, the series connection of the solar cells in a photovoltaic module and the series connection of several such photovoltaic modules to a system regularly generates system voltages of several 100 volts, so that there are very high electric fields between the solar cell and ground potential, which lead to undesirable displacement and leakage currents. As a result, in particular charges can be permanently deposited on the surface of the solar cells, which can significantly reduce their parallel resistance and thus their efficiency. In

Photovoltaic modules, this process is especially made possible and kept going, because the solar cells in the module but not as hermetically encapsulated and isolated, as the material properties should give. The encapsulation material in which the solar cells are embedded, the module frame and even the front cover glass allow the formation of leakage currents. This affects not only crystalline silicon solar cells, but also thin-film solar cells.

At high system voltages, a reduction of the parallel resistance of crystalline solar cells and thus performance degradation can occur. This can abruptly start after a relatively long time, namely when the surface charge density on the solar cells has exceeded a certain threshold. Until this time, however, it is impossible to estimate whether the respective photovoltaic module will degrade or not. This makes it impossible to make an early prediction about a module lifetime of at least 25 years.

J. Berghold, O. Frank et al., "Potential Induced Degradation of Solar Cells and Panels", 5 ^th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain, pp. 3753-3759 and S. Pingel , O. Frank et al., "potential Induced degradation of solar cells and panels", proceedings of the 35 ^th IEEE PVSC, 2010, discloses a module test process in which the front glass is a constant and continuous

Water film is applied by spraying and a high voltage between the cell matrix and the module frame is applied to determine the degradation of electrical characteristics, in particular current-voltage characteristics or the parallel resistance. By increasing the temperature, voltage and humidity or by occupying the

Modules with a water film can accelerate the potential-induced degradation. Modules that are sufficiently stable for a sufficiently long time in these accelerated tests are considered stable for the entire module lifetime. For modules that are in these However, this does not necessarily mean that accelerated tests will prove to be unstable under real-world conditions because the conditions during the accelerated tests do not match the actual real conditions of use. Consequently, these instable modules would actually have to be tested under realistic climatic conditions with full simulation of actual operating conditions, but this would result in a very long test time due to the abrupt onset of degradation behavior described above. Summary of the invention

The object of the present invention is to provide an accelerated method for the realistic evaluation of the degradation of solar cells and photovoltaic modules under the influence of a high electrical voltage, the so-called potential-induced degradation (PID). Further aspects of the present invention relate to the use of such a method in the manufacture of solar cells or photovoltaic modules.

A method according to the present invention essentially uses a two-step test. In a first method step, a first electrical voltage, very particularly preferably a direct electrical voltage, is applied to a solar cell or a photovoltaic module, and an electrical parameter of the solar cell or of the photovoltaic module is measured after a first predetermined time interval. In particular, an accelerated test can be carried out in this first method step, as explained in more detail below. Following the first method step, the solar cell or the photovoltaic module is transferred to a second method step only if the change in the electrical parameter or the high-voltage degradation derived therefrom exceeds a predetermined threshold value. This predetermined first threshold value can be comparatively low or can also correspond to the natural operating fluctuations of a solar cell that is considered to be stable or a photovoltaic module that is considered to be stable, that is to say essentially vanishing. If this first predetermined threshold is not exceeded, the solar cell or the Photovoltaic module rated as stable and the test procedure aborted. If, however, the first predetermined threshold value is exceeded, the solar cell or the photovoltaic module is subjected to a different process in a second process step than during the first process step, as explained below, and at least once an electrical characteristic of

Measured solar cell or the photovoltaic module, based on the high voltage degradation of the solar cell or the photovoltaic module can be assessed. In particular, these conditions prevailing during the second process step can simulate realistic operating conditions, as explained in more detail below.

Thus, not all solar cells or photovoltaic modules are subjected to both process steps, but only the solar cells or photovoltaic modules that are assessed as potentially unstable after the first process step. Although this may mean a comparatively long test duration for individual solar cells or photovoltaic modules, the average test duration per solar cell or photovoltaic module can be significantly reduced according to the invention, which thus helps to reduce manufacturing costs, but nevertheless a realistic evaluation of the degradation of Solar cells or photovoltaic modules under the influence of high voltage allows.

In the first and second method step, respectively, a first or second electrical voltage is preferably applied between the solar cell and a counterelectrode or between the cell matrix of a photovoltaic module and a counterelectrode. For this purpose, the solar cell or the photovoltaic module with the back expediently rests on a grounded bottom plate, wherein the aforementioned first or second voltage is applied by means of a counter electrode to the front of the solar cell or the photovoltaic module. In particular, an elastic, electrically conductive plastic which is suitably pressed against the front side of the solar cell or of the photovoltaic module is suitable as counterelectrode. The counterelectrode expediently lies on the entire surface on the front side of the solar cell or of the photovoltaic module and becomes this

Purpose pressed by a pressure plate or the like against the front of the solar cell or the photovoltaic module. The counter electrode does not necessarily have on the entire surface of the front of the solar cell or the Photo voltaic module abuts, but does so according to a further preferred embodiment.

In the first method step, an accelerated test is preferably carried out, during which the potential-induced degradation is accelerated by increasing the temperature and / or voltage and / or air humidity. For this purpose, it is particularly preferred that the temperature prevailing in the first process step is greater than 60 ° C and more preferably 85 ° C, with a high relative humidity prevailing, preferably greater than 60% and more preferably 85%. To further accelerate the test, the surface of the

Photovoltaic modules are sprayed with water or covered with wet cloths. Solar cells or photovoltaic modules, which are absolutely stable for a sufficiently long time in this accelerated test, which can easily be influenced by predefining the length of the first predetermined time interval, are deemed to be stable for the entire module life according to the invention. Only for those solar cells or modules, which are evaluated as possibly unstable, a further test is made in the subsequent second process step, in particular under simulation of realistic operating conditions. For further acceleration in the first method step, the first voltage is a

DC voltage and is preferably at least -500 V and more preferably about - 1000 V. It has been found that with such high negative voltages between the solar cell and a counter electrode or the cell matrix and the frame of a photovoltaic module, a potential-induced degradation sufficient can be quickly determined by measurable electrical characteristics, so that can be deduced with sufficient probability on the overall behavior during the module life.

For frameless modules, conductive clips, tape or the like are attached to the modules. These are instead of the frame with the positive pole of the

Voltage source connected. The first time interval may be at least one week, preferably about four weeks. Over the first threshold value, the percentage of solar cells or photovoltaic modules to be subjected to the further second process step can be significantly varied. A first predetermined threshold value of at least 1%, more preferably at least 2.0%, and even more preferably about 5.0%, has proven to be sufficient for a meaningful evaluation of the solar cells or photovoltaic modules.

According to a preferred embodiment, parameters or physical parameters acting on the solar cell or the photovoltaic module are varied stepwise or gradually periodically on the basis of predetermined day and night lengths in order to simulate realistic application conditions. Thus, for example, based on an application in Central European regions in the summer, a corresponding day length of about 12 to 16 hours and a night length of about 12 to 8 hours can be used as basis and in these time intervals other parameters or quantities, such as temperature, relative humidity, to the solar cell or the photovoltaic module voltage applied and / or incident light power gradually or gradually, for example, an actual day or night profile approximate, be varied periodically, in accordance with the total daily length. Such test conditions can also be easily logged and defined in the form of a standard.

To simulate the daily parameters, a voltage of at least -300 V and more preferably of about -400 V can be applied to the solar cell or the photovoltaic module, in particular during the predetermined day length, or be illuminated with a predetermined incident light power and during the predetermined night length Voltage of 0 V (storage without application of voltage) or a vanishing light output prevail. By the latter, the regeneration of the solar cell or the solar module is taken into account overnight. Accordingly, the ambient temperatures may also be varied, for example, at least 45 ° C and more preferably about 75 ° C during the predetermined daylength, and lower during the predetermined nightlength, preferably 15 ° C. Such parameters can be easily adapted to the climatic Conditions of the target site to be adapted and readily specified and simulated in a conventional climate chamber.

In addition, the prevailing relative humidity in the second process step can be selected to be comparatively high, for example greater than 60% and more preferably 85%. According to a further embodiment, if a degradation is detected after the first method step, the first method step is continued until the change in the electrical parameter or the high-voltage degradation derived therefrom is within a predetermined range that can be variably set and, for example, 4% to 10%.

According to a preferred embodiment, the electrical parameter is a voltage-current characteristic (UI) and / or a parallel resistance of the solar cell or of the photovoltaic module and / or the electric power actually generated for a predetermined incident light output or the efficiency of the solar cell or solar cell of the photovoltaic module.

According to a further embodiment, for further acceleration at least during the first process step, an electrically conductive elastic plastic, preferably foam, rubber or silicone, pressed onto the front of each solar cell or the respective photovoltaic module and a DC voltage greater than -50 V and In particular, the order of magnitude of several -100 V can reach, for example, about -1000 V, between the conductive plastic and the respective solar cell or the cell matrix applied in each photovoltaic module. During the high-voltage degradation process, the respective solar cell or the respective photovoltaic module is preferably arranged directly on a grounded ground plate, for example made of stainless steel. The DC voltage is preferably applied uniformly to the front of the respective photovoltaic module. Surprisingly, it has been found that real operating conditions can be well simulated by these test conditions. In particular, leakage currents can be detected simply and reliably, without the respective photovoltaic module being exposed to a moist environment or even to a permanent stream of water needs. Rather, according to the invention, the respective solar cell or the respective photovoltaic module can be reliably tested virtually under dry conditions. The solar cells can thus continue to be used immediately after passing the test for installation in photovoltaic modules, without expensive purification and further processing processes would be required to make the respective solar cells even suitable for further installation in photovoltaic modules.

The high voltage can be applied to the conductive plastic via a high voltage electrode, wherein preferably the entire back of the conductive plastic layer, so the front of the solar cell or the photovoltaic module facing away from the back of the plastic, at least in the solar cell or the photovoltaic module directly opposite area completely coated or coated with a conductive layer, in particular a metal layer or metallization. So charges can be evenly distributed.

To provide reliable test conditions, the electrically conductive plastic is preferably subjected to a predetermined pressure distributed uniformly over the entire surface of the respective solar cell or of the respective photovoltaic module, wherein the pressure is preferably chosen so that the plastic retains its elastic properties and thus for a re-test is reusable. Care should be taken to a certain minimum pressure in order to ensure a full-surface investment of the plastic on the front of the respective solar cell or the respective photovoltaic module. This pressure may be, for example, at least 0.3 kPa.

As electrically conductive plastics are in particular plastics based on styrene or polyurethane or foamed plastics, such as foams, produced in particular under inert gas atmospheres, in particular noble gas atmospheres. Also suitable is conductive rubber or silicone.

For uniform distribution of the pressure on the entire surface of the respective solar cell or the respective photovoltaic module while the pressure by means of a on the Be applied back of the conductive plastic acting insulating plastic plate. In this case, in particular a fiber-reinforced plastic plate can be used, which allows a comparatively high flexural rigidity and thus a homogenization of the pressure even with local force on the plastic plate.

According to a further embodiment, the voltage, preferably a DC voltage, is applied from a high voltage source by means of at least one electrode connected to the back, i. with the front of the respective solar cell or the respective photovoltaic module remote side, the conductive plastic is connected and contacted.

For uniform distribution of the pressure, in a further embodiment, in each case two photovoltaic modules are pressed against one another with the conductive plastic between them. In this case, the conductive plastic is contacted at least one point laterally.

According to a further embodiment, the electrical parameter of the solar cell is measured by means of a measuring electrode, which passes through the conductive plastic by means of an insulating sleeve, in particular a plastic sleeve, and is in contact with the front side of the respective solar cell. For contacting the front side of the solar cell, a contacting contact may be sufficient. In this case, the thickness of the conductive plastic can vary, for example, depending on the test conditions to be realized or due to the pressurization. Thus, the measuring electrode sleeves are preferably designed height adjustable.

Alternatively, at back contact solar cells in the device at least two separate contacts on the back.

Preferably, the sheet resistance of the conductive plastic, ie the specific resistance / thickness, in the range between and 10 ⁵ to 10 ¹¹ Ω / sq, to ensure uniform charging of the surface of the solar cell or the photovoltaic module. Another aspect of the present invention further relates to the use of a method as described above, in the production of photovoltaic modules, wherein only such solar cells and finished completed photovoltaic modules may actually be used or delivered, their change in the electrical characteristic or the high-voltage degradation derived therefrom either does not exceed the first predetermined threshold value after the first method step or does not exceed a second predetermined threshold value after the second method step. In this case, according to a further embodiment, the second predetermined threshold value may be less than or equal to the first predetermined threshold value.

figure description

The invention will now be described by way of example and with reference to the accompanying drawings, from which further features, advantages and objects to be achieved will result. Show it:

1 shows a schematic representation of a measuring structure for carrying out the method according to the invention;

FIG. 2 is a schematic flow diagram of a method according to the invention; FIG. and

Fig. 3 possible performance curves of solar cells or photovoltaic modules under test conditions according to the inventive method.

Detailed description of preferred embodiments

First, the basic structure of a measuring device 15 for carrying out the method according to the invention is described below with reference to FIG. 1, namely the example of measuring the high voltage degradation of a photovoltaic module 8. The photo oltaik module 8 is placed on a grounded ground plate 16, the preferably made of a stainless steel. On the bottom plate 16, the back of the photovoltaic module 8 is located. If the edge of the frame (not shown) protrudes from the rear side covered with the foil, can in the central region of the Photovoltaic module 8 may be provided a raised portion, the full area of the back of the photovoltaic module 8 is applied directly.

As shown in FIG. 1, an electrically conductive, elastic plastic 1 is pressed onto the front side of the photovoltaic module 8, ie onto the transparent glass cover pane. This preferably has a sheet resistance (= resistivity / thickness) in the range between 10 and ⁵ to 10 ¹¹ Ω / sq. The photovoltaic module 8 facing away from the rear side of the conductive plastic 1 or the front of the pressure plate 7 may be provided with a metal plate or metallization (shown in Fig. 1 without reference numerals). The elastic plastic 1 is uniformly pressurized by means of a pressure plate 7, preferably made of a fiber-reinforced plastic. Thus, there is a full-surface investment of the plastic 1 on the top of the photovoltaic module 8, wherein at the same time a constant electric potential difference between the pressure plate 7 and the cell matrix in the photovoltaic module 8 is generated. More specifically, the constant electric potential difference is generated by applying a suitable voltage, preferably a high voltage, to the metal plate or metallization, wherein the back of the photovoltaic module 8 rests on the grounded base plate 16 over its entire area. The pressure plate 7 serves not only a pressurization, but also an isolation to the environment. For applying the high voltage to the metal plate or metallization, at least one high-voltage contact electrode 17 extends through the pressure plate 7 as far as the metal plate or metallization, which is in each case connected to a high-voltage source 20. The high-voltage contact electrode 17 is suitably screwed into an insulating contact sleeve. The high voltage contact electrode 17 is electrically isolated from the pressure plate 7.

Alternatively, with the same construction, which is typically smaller in dimension but smaller in construction, the method can also be applied to at least one non-encapsulated solar cell. In this case, at least one insulating contact sleeve 18 is screwed into the pressure plate 7, into which a measuring contact is inserted, which contacts the front side, in particular the front side metallization of the solar cell to be evaluated in order to derive the electrical characteristic. For back contact solar cells without Vorderseitenmetallisierang are alternatively located in the device at least two separate contacts on the back.

The plastics used in the construction or foams, cables, etc. are designed for temperatures up to about 130 ° C, wherein the plate spacing between pressure plate 7 and bottom plate 16 for the application of the method to solar cells between 10 and 20 mm is adjustable. The contact sleeves 18 are therefore designed to be height adjustable. So that the conductive elastic plastic material 1 does not slippage laterally during the test, positioning means, for example in the form of lateral projections, are provided on the pressure plate 7, which hold the plastic in its position.

As shown in FIG. 1, the bottom plate 16 is connected to a ground potential and the high voltage contact electrode 17 is connected to a high voltage source 20.

For the application of the method to solar cells, each measuring point which is formed via the measuring contact 18 is connected via an oppositely arranged Zener diode pair Z1... Z40 for protection against undesired voltage peaks during the measurement parallel to the measuring device 22, in particular a digital multimeter , switched. If voltages of, for example, greater than 12 V or less than -12 V occur during the measurement at the measuring contacts 18, then the anti-serially arranged Zener diode pair breaks through and closes the circuit briefly. With the aid of the multiplexer 21, the electrical parameters at a plurality of discrete measuring points 18, which correspond to the aforementioned contact sleeves, can be measured sequentially and in a predetermined time sequence by the respective measuring contact 18 is switched on or switched through. The output signals of the measuring device 22 are passed to an evaluation device 23, for example a computer, which evaluates the measured data obtained and / or graphically processed.

According to Fig. 1, the entire measuring range including the bottom plate 16, the electrically conductive, elastic plastic 1 and the pressure plate 7 in one

Climate chamber 19 is arranged, in which suitable environmental conditions can be simulated, in particular elevated temperatures of for example 85 ° C and / or a predetermined relative humidity of, for example, 85%. Complementary or Alternatively, only the conductive plastic 1 and / or the solar cell to be measured or the photovoltaic module to be measured can be kept at a predetermined temperature, for example greater than 40 ° C.

For a rapid test in the first method step, a voltage of preferably several -100 V, for example -1000 V, is applied between the conductive elastic plastic 1 and the solar cell or the photovoltaic module to be tested. By means of the climatic chamber 19 are at the same time, for further acceleration, a high temperature of greater than 60 ° C and a high relative humidity greater than 60%, for example, a temperature of 85 ° C and a relative humidity of 85% set. The conductive elastic plastic 1 shown in FIG. 1, which is pressed onto the front side of the solar cell or the front module cover, thereby serves to further accelerate the test, at least during the first method step. Alternatively, the photovoltaic module front can also be sprayed with water or covered with wet cloths. To increase the conductivity, the water may contain salts. Repeatedly at certain intervals, the photovoltaic module is disconnected from the voltage and determines the electrical characteristic, in particular a voltage-current characteristic (UI) and / or the parallel resistance (dark and / or bright characteristic), and / or actually generated electrical power at the onset of a predetermined light output. Alternatively, the measurement of the parameter can also be done without disconnecting the voltage. This is in particular the preferred method in the measurement of the characteristic of at least one solar cell to be tested, d. H. Voltage-current characteristic (UI) and / or the parallel resistance (dark characteristic and / or bright characteristic), and / or the actually generated electric power at the onset of a predetermined light output.

A method according to the present invention will be described in more detail below with reference to FIG. 2. First, in the first method step, a so-called accelerated test is carried out, as has already been described above. If no degradation occurs within a specified period of, for example, 4 weeks or the degradation does not exceed a predetermined first threshold, for example, 1%, more preferably at least 2.0% and more preferably about 5.0%, the solar cells or the Modules as stable and the others Procedure is aborted. However, if degradation occurs and, in particular, the degradation exceeds a predetermined threshold, as stated in particular above, then the accelerated test is continued until the degradation of the solar cell or module power is within a predetermined range, especially if the degradation is greater X is X (eg X = 4%) and Y is less than or equal to Y (Y = 10%). Thereafter, the first process step ends.

If, due to the selected measurement intervals at which the electrical parameter is measured, the actual power degradation should then be greater than Y, the solar cells or modules are partly regenerated in an intermediate step until the power degradation lies in the required range between X and Y. For this purpose, it can first be queried whether the degradation is greater than or equal to Y. If this is not the case, the accelerated test is continued and the method returns to the block "continue test." If the degradation is greater than or equal to Y, an regeneration of the solar cell or the photovoltaic module takes place in an intermediate step, in particular when storing the solar cell or the photovoltaic module without applying a voltage (0 V) and at a temperature of 25 ° C or at elevated temperature and / or reverse voltage (reversed voltage).

Finally, if the performance degradation in the required range between X and Y, begins in a second step of the test under realistic climatic conditions. For this purpose, on the basis of predetermined day and night lengths, parameters or physical variables which act on the photovoltaic module and thus the solar cells are varied stepwise or gradually periodically. By way of example, the temperature may be 15 ° C. for an assumed night length and the solar cell or the photovoltaic module may be stored without application of voltage (0 V) and the temperature may be at least 45 ° C., for example 75 ° C., for a given daylength , Be and the voltage applied to the solar cell or the photovoltaic module voltage at least -300 V, for example -400 V, amount or additionally a predetermined light power incident on the front bar of the solar cell or the photovoltaic module. The relative humidity may be at least 60% at the same time, preferably 85%. If the solar cells or photovoltaic modules in this time exceed a performance degradation (for example, a threshold Z = 6%), so these are considered unstable and are discarded. If the aforementioned threshold value Z is not exceeded, then the solar cell or the photovoltaic module is considered stable and the test procedure is terminated. FIG. 3 shows the measured power curve of solar cells or photovoltaic cells.

Modules as an example during a test. Plotted is the actual electrical power generated at a predetermined incident light power, based on the corresponding power at the beginning of the test, plotted over the duration of the test. The first process step can be carried out, for example, for 18 days and for acceleration at temperatures of 85 ° C, a relative humidity of 85% and

Applying a voltage of -1,000 V are executed. Subsequently, the test is carried out under realistic conditions of use, for example 75 ° C during the day / 15 ° C at night, 85% relative humidity, -400 V day / 0 V at night. Shown are two possible time courses, on the one hand a curve approaching inversely exponential to a relative power of 96% and on the other hand a curve approaching inversely to a limit value of approximately 89.5%. As can be seen in FIG. 3, the measuring points during the second method step can be extrapolated into the future with high significance, ie to the value to which the respective electrical characteristic actually approaches. This limit can easily be read from a graph or calculated. Based on this limit, the actual performance degradation is then evaluated. If this is greater than a second predetermined threshold (Z), the modules are not considered stable, otherwise stable. Another important aspect of the present invention is a

Measuring device for performing the aforementioned measurement or evaluation method directed, as shown by way of example in FIG. 1.

Another important aspect of the present invention is further directed to a method of manufacturing solar cells or photovoltaic modules having a plurality of such solar cells using the aforementioned measurement method. For this purpose, first solar cells are formed by means of a suitable manufacturing process. Subsequently, the solar cells are evaluated individually or in groups by means of the measuring device shown in FIG. In such a method, only such solar cells continue to be used, for example, ready-packed or further processed into photovoltaic modules whose change in the electrical characteristic or the derived high-voltage degradation does not exceed the first predetermined threshold either after the aforementioned first step or after the aforementioned second step does not exceed a second predetermined threshold.

In a method for producing photovoltaic modules, the photovoltaic modules can initially also be formed by means of a suitable manufacturing method. Subsequently, the photovoltaic modules are each evaluated by means of the measuring device shown in FIG. In such a method, only such photovoltaic modules continue to be used, for example ready-to-use packaged, whose change in the electrical characteristic or the high-voltage degradation derived therefrom does not exceed the first predetermined threshold either after the aforementioned first method step or after the aforementioned second method step a second predetermined one Threshold does not exceed.

In summary, a test method is thus disclosed with which meaningful parameters can be reliably derived within a relatively short time and a reliable prediction can be made with regard to the performance during the entire service life of the solar cell or of the photovoltaic module. Based on the test results, individual solar cells or photovoltaic modules can be sorted out. LIST OF REFERENCE NUMBERS

1 conductive elastic plastic

7 pressure plate

8 solar cell or photovoltaic module

15 measuring device

16 base plate

17 high voltage contact electrode

18 measuring contact

19 climate chamber

20 high voltage source

21 multiplexers

22 UI meter (digital multimeter or 4-quadrant source)

23 evaluation device (computer)

Claims

claims

A method for evaluating the high voltage degradation of at least one solar cell or a photovoltaic module (8), in which method

in a first method step, a first electrical voltage is applied between the solar cell and a counterelectrode or between the cell matrix of the photovoltaic module and the counterelectrode and an electrical parameter of the solar cell or of the photovoltaic module is measured after a first time interval has expired;

the solar cell or the photovoltaic module is transferred to a second method step, if the change in the electrical characteristic or the high-voltage degradation derived therefrom exceeds a predetermined first threshold, and

the solar cell or the photovoltaic module in the second method step is subjected to ambient conditions other than during the first method step and an electrical parameter of the solar cell or of the photovoltaic module is measured, with which the high-voltage degradation of the solar cell or of the photovoltaic module is evaluated.

2. The method of claim 1, wherein with the other environmental conditions during the second process step realistic operating conditions of the solar cell or the photovoltaic module are simulated, which vary over time.

3. Method according to claim 2, wherein parameters or variables acting on the solar cell or the photovoltaic module for simulating realistic application conditions are varied stepwise or gradually periodically on the basis of predetermined day and tail lengths.

4. The method of claim 3, wherein the parameters or quantities acting on the solar cell or the photovoltaic module at least one of the solar cell or the photovoltaic module comprises applied electrical voltage and an ambient temperature.

The method of claim 4, wherein the voltage applied to the solar cell or the photovoltaic module electrical voltage is a DC voltage.

The method of claim 5, wherein the voltage applied to the solar cell or the photovoltaic module DC voltage during the predetermined day length is at least -300 V and during the predetermined night length is 0 V and / or

the prevailing ambient temperature during the predetermined day length is at least 45 ° C, and lower during the predetermined night length.

The method of claim 1, wherein in the first process step further, an elevated temperature of greater than 60 ° C and a high relative humidity greater than 60% is applied, preferably a temperature of 85 ° C and a relative humidity of 85%.

Method according to one of the preceding claims, wherein the first electrical voltage is a DC voltage which is at least -500 V and preferably about - 1000 V.

Method according to one of the preceding claims, wherein the first predetermined time interval is at least one week and preferably about 4 weeks and wherein the predetermined first threshold is at least 1%, preferably at least 2% and more preferably 5.0%.

10. The method according to any one of the preceding claims, wherein the prevailing relative humidity in the second process step is greater than 60% and is preferably 85%.

11. The method according to any one of the preceding claims, wherein at least the second method step is carried out in a climatic chamber (19).

Method according to one of the preceding claims, wherein the first method step is carried out until the change in the electrical characteristic or the high-voltage degradation derived therefrom is within a predetermined range.

The method of claim 12, wherein the change in the electrical characteristic or the high voltage degradation derived therefrom is in a range between 4% and 10%.

14. The method of any one of the preceding claims, wherein the electrical characteristic is a voltage-current characteristic (UI) and / or a parallel resistor (Rshunt) and / or the actual power generated at a predetermined light output of the solar cell or the photovoltaic module.

15. The method according to any one of the preceding claims, wherein a conductive elastic plastic (1) on the front of the solar cell or the photovoltaic module (8) is pressed and this is used as a counter electrode, msbesondere the electrical voltage between the plastic (1) and solar cell or cell matrix is applied in the photovoltaic module.

16. The method according to claim 15, wherein the plastic (1) with a predetermined and uniform over the surface of the respective solar cell or the respective

Photovoltaic module distributed pressure is applied.

17. The method of claim 16, wherein the pressure of the plastic (1) against the solar cell or the photovoltaic module is greater than 0.3 kPa.

18. The method according to claim 16 or 17, wherein the pressure is equalized by means of a plate (7) over the surface of the solar cell or the photovoltaic module (8).

19. The method of claim 16 or 17, wherein the pressure over the surface of the first photovoltaic module (8) by means of a second photovoltaic module, which is pressed against the first photovoltaic module (8), is equalized, wherein the conductive elastic plastic (1) between the two photovoltaic

Modules is located.

20. The method of claim 19, wherein between the cell matrix of the second photovoltaic module (17) and the conductive, elastic plastic (1) is also applied an electrical voltage.

21. The method according to any one of claims 15 to 18, wherein the DC voltage from a high voltage source (20) by means of at least one electrode (17) to a front side of the solar cell or the photovoltaic module (8) facing away from the conductive plastic (1) becomes.

22. The method according to any one of the preceding claims, wherein the front side of the photovoltaic module in the first process step and / or in the second process step is covered with water or sprayed with water.

23. The method according to any one of the preceding claims, wherein the front side of the photovoltaic module is covered with wet cloths.

24. The method of claim 22 or 23, wherein the water or the water of the wet wipes contains salts to increase the electrical conductivity.

25. The method of claim 22, 23 or 24, wherein the water or the water of the wet tissues is used as the counter electrode.

26. The method according to any one of the preceding claims, wherein a module frame of the photovoltaic module is used as a counter electrode.

27. The method according to any one of the preceding claims, wherein the conductive plastic is a styrene or polyurethane-based plastic or a foamed plastic is, for example, a foam produced in particular under inert gas atmospheres, in particular noble gas atmospheres.

28. The method according to any one of claims 1 to 26, wherein the conductive plastic is a conductive rubber or silicone.

29. The method according to any one of the preceding claims, wherein the conductive plastic does not stick, in particular does not adhere to the solar cell or the photovoltaic module.

30. Use of the method according to any one of the preceding claims in the production of solar cells or photovoltaic modules, wherein only such solar cells or photovoltaic modules may be used, their change in the electrical characteristic or derived therefrom

High-voltage degradation either does not exceed the first predetermined threshold after the first method step or does not exceed a second predetermined threshold after the second method step.

31. The use of claim 30, wherein the second predetermined threshold is less than or equal to the first predetermined threshold.

32. Device for evaluating the high voltage degradation of at least one solar cell or a photovoltaic module (8), in particular for carrying out the method according to one of claims 1 to 29, with

a grounded bottom plate (16) which is designed such that a rear side of the solar cell or of the photovoltaic module (8) rests thereon,

a pressure plate (7) for exerting a pressure against the bottom plate (16),

a voltage source (20) for generating an electrical voltage, a counterelectrode (1), which is conductively connected to the counter electrode (1) in order to be supplied with the electrical voltage, and

a measuring and control device (23), wherein the measuring and control device is designed so that

in a first method step, a first electrical voltage is applied between the solar cell and the counterelectrode or between the cell matrix of the photovoltaic module and the counterelectrode and an electrical characteristic of the solar cell or of the photovoltaic module is measured after a first time interval has expired;

the solar cell or the photovoltaic module is transferred to a second process step if the change in the electrical parameter or the high-energy degradation derived therefrom exceeds a predetermined first threshold value,

the solar cell or the photovoltaic module in the second method step is subjected to ambient conditions other than during the first method step, and

an electrical characteristic of the solar cell or the photovoltaic module is measured, based on the high voltage degradation of the solar cell or the photovoltaic module is evaluated.

33. The apparatus of claim 32, wherein the counter electrode (1) made of an elastic, electrically conductive plastic) is formed between the pressure plate (7) and on the bottom plate (16) resting solar cell or one on the bottom plate (16) Photovoltaic module (8) is arranged and pressed by the pressure plate (7) against the solar cell or the photovoltaic module (8).

34. Use of the device according to claim 32 or 33 in a device for producing solar cells or photovoltaic modules, wherein only such solar cells or photovoltaic modules may be used, their change in the electrical characteristic or derived therefrom high-voltage degradation either after the first process step the does not exceed the first predetermined threshold or does not exceed a second predetermined threshold after the second method step.