Patent Publication Number: US-2013249588-A1

Title: Device and method for testing a solar module

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 102012102456.1 filed Mar. 22, 2012. 
     FIELD 
     The invention concerns a device and a method for testing a solar module. 
     BACKGROUND 
     By means of a solar module it is possible to transform light into electric power. Solar modules consist of a plurality of interconnected solar cells. The power generated by the solar cells is collected by means of long metal bands and collected to a connecting zone having a positive and a negative terminal. Frequently, solar modules are equipped with so-called terminal boxes in the range of the connecting zone from which the power generated can simply be taken, 
     During or after production solar modules have to be tested in order to recognize defective or damaged solar cells or insufficient electrical connection between the solar cells. Different testing methods are known and customarily used for this purpose. When using the so-called electroluminescence method the solar module is supplied with voltage. The light emitted by the solar cells is captured by one or several cameras and then analyzed. For example, the electroluminescence method was described in the U.S. Pat. No. 7,601,941, wherein here merely particular solar cells were tested. In a different well-known method the solar module is irradiated (“solar simulation”), the electrical parameters of the solar module thus irradiated are captured, resulting in a current-voltage characteristic. In the methods mentioned above, the solar module has to be electrically connected with the respective test device. 
     The published application EP 2 330 631 A1 discloses a test device for testing a solar module according to the electroluminescence method. The test device has a plurality of cameras which can be displaced by a motor. The solar module reaches the test device, is stopped at a predetermined position in the region of the opening of a darkroom equipped with the cameras and then connected with a power source for the electroluminescence test. This test device has several disadvantages. For example, it has a comparatively complicated design and is interference-prone. In addition, the test method is expensive and time consuming. 
     Therefore it is the objective of the invention to avoid the disadvantages of the known devices and to provide an arrangement and a method for testing a solar module that are especially characterized by improved efficiency. In particular, it is intended to reduce the duration of the testing method. By means of the arrangement, it should especially be possible to perform an electroluminescence testing method or solar simulation. Furthermore, the arrangement should provide the possibility of selectively testing solar modules with different testing methods (for example, electroluminescence methods, solar simulation). Ultimately the arrangement should be easy to manage and operate. 
     SUMMARY 
     The arrangement for solving the above problems is characterized in that it comprises a test device with a transfer unit by means of which the solar module can be transported through the test device. For example, by means of the transfer unit the solar module can be transported through an irradiation unit for performing a solar simulation, or through an imaging unit equipped with one or several CCD cameras for performing the electroluminescence test. Moreover, the test device comprises a device for tapping parameters of the solar module (subsequently also called “tapping device”), for example, to perform solar simulation. Alternatively or possibly additionally, the test device can comprise a device for supplying electricity to the solar module (“supply device”), for example, to perform an electroluminescence method. The tapping and/or supply device is designed to generate an electrical connection in such a way that, during the process of transporting the solar module through the test device, the tapping or supply device comes in direct or indirect contact with the solar module. Accordingly, when transporting the solar module with the transfer unit an automatic contact takes place between the solar module moving in transport direction and the tapping or supply device which is preferably stationary at least during the transport process. With such an arrangement the period of testing a solar module can be considerably reduced. The electrical connection is generated merely through the contact of two components and not, for example, through a plug connection. Therefore, the test device can have a simple structure and is easy to use. 
     In a first embodiment the test device can comprise an irradiation unit for irradiating the solar module. For this purpose, the above-mentioned device is designed as a tapping device for tapping parameters of the solar module irradiated by means of the irradiation unit. With such a design, the tapping device comes in direct or indirect contact with the solar module when the solar module is passing the irradiation unit, allowing for a simple and optimal solar simulation. In this way, it is especially easy to tap the voltage and current of the irradiated solar module in order to determine the current-voltage characteristic. 
     Alternatively or additionally, the test device can comprise an imaging unit for optically capturing the solar module in a monitoring area. In this case, the device can be designed as supply device by means of which voltage can be applied to the solar module. With this arrangement, an electroluminescence test can be performed in an easy and efficient manner. For this purpose, the supply device is designed in such a way that the solar module comes directly or indirectly in contact with the supply device when the solar module passes the monitoring area or when the solar module is transported through or past the imaging unit. 
     The tapping or supply device can involve a contact bar on which a contact surface attached to the solar module can glide or slide along during the transport process. When solar modules have several connecting zones arranged next to each other in transport direction, it is also possible to provide several contact bars. When the solar module with the transfer unit can be transported in a transport direction through the test device, the contact bar extends preferably in the transport direction. By means of the contact bar, it is possible to generate an electrical connection between solar module and test device over a comparatively long period of time. Instead of providing contact bars that extend in the transport direction, different components can be used as tapping or supply devices which touch only briefly the contact surface attached to the solar module. In order to ensure a safe and interference-free operating method, it can be of advantage when the contact bar comprises a feed section produced through a curve. Furthermore, the contact bar can comprise a straight contacting portion adjoining the feed section and extending in the transport direction. Moreover, the contact bar can also be bent open at its rear end (in relation to the transport direction). 
     In particular, it can be advantageous when the contact bar is formed of at least one strap-shaped profile element consisting of steel, copper or any other electrically conductive material. The contact bar can comprise two adjacent profile elements. By means of the pair of profile elements, the positive terminal and the negative terminal can be connected on an individual basis, respectively. 
     For a large-scale application, it can also be advantageous when the tapping or supply device can be positioned by means of an adjustment mechanism located in the test device. As a result, it is possible to test different size solar modules with the same test device. 
     When by means of the irradiation unit a lighting zone in the solar module can be irradiated, it can be of advantage to arrange the contact bar in the transport direction overlapping to the lighting zone. The overlapping relates to a top view on the test device (vertical viewing direction). 
     During the transport process, the tapping or supply device can come in direct contact with the connecting zone or its conductive paths. At the same time, the connecting zone can have exposed conductive paths where the metal bands connecting the solar cells are bundled. However, it can be of special advantage when the arrangement comprises a contact device that can be temporarily attached to the solar module in the area of the connecting zone, by means of which contact device the solar module can be electrically connected with the tapping or supply device. The contact device can be used also when the solar module comprises an already wired terminal box in the area of the connecting zone. Consequently, by means of the contact device an indirect contact takes place between solar module and tapping or supply device. After completing the test the contact device can simply be removed. Based on its weight, it can be especially advantageous merely to place the contact device on, or attach it to the solar module. 
     Consequently, the contact device can provide the contact surface that can be moved during the transport process along the contact bar in gliding or sliding manner. At the same time, the contact surface can be advantageously arranged in the area of an upper surface of the contact device. The contact device can comprise a plastic housing. By means of said housing, the contact device is electrically insulated to the outside so that operating personnel can easily and safely grab the contact device. In addition to simplify handling, a further advantage involves that it is virtually impossible that the active surface of the solar module is mechanically damaged by the tapping or supply device and especially by the contact bar. 
     The contact device can comprise at least one contact pin for directly contacting a conductive path of the connecting zone of the solar module or an electrical input, for example, in the form of sockets for connecting a solar module pre-assembled with a terminal box. Usually, solar modules have two conductive paths involving one terminal (positive, negative), respectively. Therefore, the contact device preferably comprises two contact pins for contacting the conductive paths. Therefore, the contact device can have a contact pin for each conductive path. In order to improve the contact quality to the solar module, the contact device can have two, three or more contact pins, respectively, each of which is attached to a conductive path of the solar module, or touches it when disconnected. 
     In order to generate a sliding contact to the guide rail, the contact device can comprise at least one contact element that resiliently adjoins, or can adjoin, the contact bar. The contact element can consist of steel, preferably stainless steel, copper or any other electrically conductive material. At the same time, the contact element forms an advantageous contact surface which contacts the contact bar in a sliding manner during the transport process. To provide the suspension, it is possible to use for each contact element one or several compression springs or any other means of resilience. The spring-loaded contact element can be stored in a movable manner in a housing, especially in a plastic housing. Such an arrangement ensures an excellent electrical connection between the solar module and the test device. For example, the contact element attached to the respective terminal and the at least one corresponding contact pin can be connected with one another by means of an electric wire. 
     The contact device can have a lower surface facing the solar module. The contact device can comprise means arranged in or on the lower surface that protect the upper surface of the solar module against scratching and/or fix the position of the contact device on the solar module. The scratch protection means can consist of an elastic material and preferably have a tubular, deformable design. 
     The contact device can be placed manually on the solar module. However, it is also possible that the test device comprises a pick-and-place unit by means of which the contact device is automatically placed on and removed from the solar module (after completing the test). 
     The transfer unit can comprise means of transport for supplying preferably in a lying position the solar module to the irradiation unit and/or to the imaging unit and means of transport for removing preferably in a lying position the solar module from the irradiation unit and/or from the imaging unit. 
     The means of transport can be designed as conveyor bands on which the solar modules are placed and transported in a simple and gentle manner in the transport direction through the test device. Each of the conveyor bands can comprise endless belts and two guide rollers. Additional rollers for supporting the belts of the conveyor band can be arranged between the guide rollers. However, it is also possible to use different means of transport. For example, the test device could comprise feed rollers driven by a motor and freely rotating rollers, on which the solar modules can be placed and transported. 
     The means of transport can be interrupted in the region of a monitoring area. In the monitoring area, the solar module can be optically captured with the imaging unit. In the case of a test device equipped with a contact bar extending in the transport direction, it can be advantageous when the contact bar extends across and is overlapping the entire monitoring area. The transfer unit can comprise two conveyor band units (supply conveyor band, discharge conveyor band). Each conveyor band unit can comprise at least two conveyor bands arranged in parallel to one another, and the solar modules can be placed on the edges of the conveyor bands. In the case of large- scale solar modules, it can be advantageous when a third conveyor band is arranged approximately in the center between the two conveyor bands. 
     According to the invention, the method involves the following steps: advantageously, the solar module is transported through the test device by using the transfer unit of the test device described above. The solar module transported through the test device is irradiated with artificial light and the parameters of the irradiated module are tapped by means of a tapping device which comes in direct or indirect contact with the solar module to generate an electrical connection. In this way, a simple and fast solar simulation can be performed with the solar module, thus testing the solar module. As an alternative to solar simulation, it is also possible to perform an electroluminescence method. For this purpose, the solar module to which voltage has been applied by means of a supply device is optically captured by an imaging unit. In order to generate the required electrical connection, the supply device comes in contact with the solar module during the transport process of the solar module through or past the imaging unit. In other words, the electrical connection is generated merely by the transport process. The solar module does not have to come to a stop in the test device in order to apply voltage to the solar module, which would delay the period of testing. 
     The direct or indirect contact comes about in that a contact or a sliding contact takes place between a stationary supply device, or a stationary tapping device, and the moving solar module. For an indirect contact, it is possible to use the contact device described above. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The subsequent description of embodiments and the drawings show further characteristics and advantages of the invention. It is shown: 
         FIG. 1  is a top plan view of a solar module; 
         FIG. 2  is a cross section view of a test device according to the invention for testing the solar module shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of the tapping device shown in  FIG. 2  with contact bars for contacting the solar module; 
         FIG. 4  is a perspective view of the test device shown in  FIG. 2 ; 
         FIG. 5  is a perspective, detailed view of the contact device shown in  FIG. 3  coming into contact with the contact bars; 
         FIG. 6  is a different perspective of the contact device shown in  FIG. 5 ; 
         FIG. 7  is a rear perspective view of the contact device shown in  FIG. 5 ; 
         FIG. 8  is a top plan view of the tapping device shown in  FIG. 3 ; 
         FIG. 9  is an alternative to the arrangement shown in  FIG. 8 ; and 
         FIG. 10  is a further alternative design of tapping device for testing the solar module. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. 
       FIG. 1  shows an exemplary solar module  10  that can be tested with the test device described below. The solar module comprises a plurality of solar cells  11  which are arranged on a glass plate. The solar cells  11  are electrically connected with one another by means of soldered metal bands  12 . On one side of the solar module  10 , the metal bands  12  are conducted to a connecting zone  13 , and there they are combined into two conductive paths  14 . The solar module  10  comprises an optically active surface and an opposite rear side. At least most of the solar modules currently used have the connecting zone  13  on the rear side. 
     It is certainly also possible to test with the invention-based test device other embodiments of solar modules, as well as solar modules in various stages of production. It is possible to insert a plastic sheet between the glass plate and the solar cells  10  which fuses when laminating the solar module. Usually additional layers are arranged on the rear side of the solar cells before the solar module is laminated. The test can also be made after a solar module has been laminated. However, this has the disadvantage that defects can no longer be corrected. Also known are so-called thin-film modules in which the semiconducting material of the solar cells is directly applied to the glass plate. The test device described below can also be used for testing such types of modules. 
       FIG. 2  shows a lateral cross-section of the test device (depicted with numeral  1 ) for testing a solar module  10 . The test device  1  shown comprises an imaging unit  5  for optically capturing the solar module from below and an irradiation unit  2  for irradiating the solar module from above. Furthermore, the test device  1  comprises a transfer unit  3  by means of which the solar module  10  can be transported in a horizontal plane in a direction e through the test device between the imaging unit  5  and the irradiation unit  2 .  FIG. 2  also shows the monitor of an evaluation unit  7  by means of which the images taken with a camera  17  can be analyzed. 
     Basically, the irradiation unit  2  consists of a light source  15  (depicted symbolically), which is arranged in a darkroom or housing  18  and provides a lighting zone. By means of the irradiation unit  2 , the solar module  10  can be exposed to artificial light, and the current and voltage values thus obtained can be recorded for determining a current-voltage characteristic. For this purpose, the test device  1  is equipped with a tapping device  4  extending in the direction e, which is subsequently shown and described in more detail. However, the same device  4  can be used to apply voltage to the solar module in order to perform an electroluminescence test. The imaging unit  5  equipped with the camera  17  is used to record the electroluminescence processes. As a result, it is possible to use the arrangement shown in  FIG. 2  to perform with one and the same equipment two different test methods (i.e., electroluminescence test and solar simulation). 
     The tapping device (depicted with numeral  4 ) can be used for supplying power, as well as for tapping electrical parameters. It is certainly also possible to provide a simplified test device which is configured to perform only one of the test methods described above. Consequently, the test device could comprise either an imaging unit for optically capturing the solar module or an irradiation unit for irradiating the solar module. With the device  4 , power would be supplied for performing the electroluminescence test or for tapping electrical parameters (solar simulation). As a result, a test device arranged for performing the electroluminescence test would not have an irradiation unit with a light source on the same side as the imaging unit  5 . 
     In the embodiment shown in  FIG. 2 , the test device comprises a darkroom or housing  16  with a light source  24  directed to the passive rear side of the module, resulting in background lighting. The positions of the solar cells of the solar module  10  illuminated by the light source  24  could be measured by means of the camera  17  and an image processing software, this making it possible to detect broken solar cells or solar cells damaged in any other way. In simpler embodiments of the invention-based test device, the transmitted light arrangement with the light source  24  has been eliminated. 
     The transfer unit  3  of the test device  1  comprises conveyor bands  8  and  9  that are arranged on the input side and output side respectively. Each of the respective conveyor bands  8 ,  9  is provided with two guide rollers  27  and  27 ′. One, respectively, or possibly both of the guide rollers can be powered by a motor. Support rollers  28  are arranged between the guide rollers  27 ,  27 ′ to support the belts of the conveyor bands, 
     The test of a solar module  10  is performed with the optically active side facing downward. On the solar module  10  a contact device  6  is temporally located on which is moved together with the solar module. On one side, the contact device  6  is electrically connected with the solar module  10 . On the other side, the contact device  6  has to be connected with the test device  1  so that the solar module can be tested. For this purpose, the contact device  6  comprises a contact element  33  which comes in contact with the stationary tapping or supply device (depicted with numeral  4 ) and which moves in the direction e. Depending on whether the contact element  33  presses against the tapping device, a gliding or sliding contact comes about during the transport process. Obviously, the solar module  10  does not come in direct contact with the tapping device  4 . The contact takes place in an indirect manner by means of the contact device  6  that can be temporarily attached to the solar module. After performing the test, the contact device  6  is again removed from the solar module  10 . 
       FIG. 3  shows the tapping device (depicted with numeral  4 ) by means of which the electrical parameters of the solar module can be sensed and power can be supplied to the solar module for performing the electroluminescence method. The tapping or supply device  4  comprises a contact bar  20  that extends in the transport direction e. The contact bar  20  comprises two parallel profile elements  21 ,  21 ′ which can consist of an electrically conductive material, for example, of steel, preferably of stainless steel, or copper. To some extent as a counterpart to the contact bar  20 , the solar module  10  includes the contact device  6  in the area of the connecting zone  13 . On the upper surface of the contact device  6  facing the contact bar  20  two contact elements corresponding to the profile elements  21  have been arranged, which contact elements strike and touch the contact bar  20  or its profile elements during the further process of transport in the direction e. The contact device  6  rests on the rear side of the solar module in the area of the connecting zone  13  opposite of the optically active side. 
       FIG. 3  shows also that the front and rear ends of the profile elements  21  and  21 ′ are bent upwards. The front bent up end of the contact bar  20  forms a feed section (depicted with numeral  22 ). The feed section  22  is followed by a straight section  23  which is basically coplanar to the upper surface of the solar module  10 . In the embodiment at hand, the profile bar  20  is attached at the remaining test device (not shown here) via three suspension points by blocks  25  consisting of insulation material and electrically connected (in a manner not shown) to the test device (for example, via cables or wires). Furthermore, the test device can comprise an adjusting device (not shown) by means of which the profile bar  20  can be moved back and forth to be able to adjust to different sized and types of solar modules. The direction of movement which basically runs perpendicular to the transport direction e is indicated with a double arrow f.  FIG. 8  shows the outlines of the adjustment mechanism. For example, when the size of the solar module  10  changes and with it the connecting zones or the position of the attached contact devices  6 , the contact bars  20  have to be moved (moving direction indicated with an arrow f). Smaller solar modules and contact bars moved to adjust to the changed conditions are indicated with dotted lines. 
       FIG. 4  shows constructive details of the test device  1 .  FIG. 4  shows the test device  1  in which the darkroom  16  with the background lighting has been removed to better demonstrate the structure and mode of action of the test device. The transfer unit  3  comprises a supply unit with three conveyor bands  8 ,  8 ′,  8 ″ and a discharge unit with three conveyor bands  9 ,  9 ′,  9 ″. The solar modules  10  are placed in lying position on the three conveyor bands  8 ,  8 ′,  8 ″ or  9 ,  9 ′,  9 ″ arranged in parallel. 
     Between the conveyor bands  8 ,  8 ′,  8 ″ or  9 ,  9 ′,  9 ″ there is a gap which forms a monitoring area  19 , over which gap the solar module can be moved safely without any danger of tilting. The camera housing  18 , in which the cameras  17  required for testing are fixed or movably mounted, is located below the gap. This arrangement of conveyor bands makes it possible that a wide strip of the solar module  10  can be received without being obscured by any transport elements. 
     The test method is performed in the following manner: the solar module is transported together with the transfer unit  3  through the test device  1 . For solar simulation the solar module  10  transported through the test device  1  is irradiated with artificial light and the parameters of the irradiated module are sensed during the transport process by means of the tapping device  4  which comes in contact with the solar module  10  to generate an electrical connection. Thus, the electrical connection required for testing is generated merely through the transport process. In this case indirect contact comes about through a mere contact between the stationary tapping device  4 , on the one hand, and the moving solar module  10 , on the other hand. For the electroluminescence method the electrical connection between solar module and test device is generated in an analogous manner. 
       FIG. 5  shows a condition in which the solar module  10  is electrically connected with the test device. For each conductive path  14  or terminal, the contact device  6  comprises, for example, three tappet-like contact pins  31  which come in contact with or touch the conductive path. The contact pins  31  for each terminal have the advantage that the required electrical connection is ensured even when the operating personnel do not precisely place the contact device  6 . However, in principle, one contact pin for each terminal would be adequate. On the other side, the contact device  6  has the two contact elements  33  which touch the profile elements  21 ,  21 ′ of the contact bar  20 . The contact elements  33  are spring-loaded in the direction of the surface normal of the upper surface of the solar module  10  and are slightly pressed downwards at the start of the transport process when entering the contact bar  20 . The contact elements  33  thus pressed down generate a sliding electrical contact to the bottom side of the profile of the contact bar  20  when the solar module  10  is moved in the transport direction e. The contact pins  31  can also be spring-loaded in order to ensure that all contact pins are contacted. However, the total amount of the spring force is so small that the contact device  6  cannot be lifted off the module. The contact device  6  comprises a plastic housing  30 . The contact elements  33  are located in the region of the upper surface and the contact pins  31  are located on the opposite lower surface of the housing of the contact device. For each tapped terminal, the respective contact pins  31  are electrically connected with the appropriate contact element  33  (for example, via wiring behind a removable cover plate  38 ) inside the housing. 
     In  FIG. 6 , the plastic housing  30  has been opened up in the area of the contact element  33 , making it possible to view a compression spring  35  of the spring-loaded contact element  33 . The spring-loaded contact element  33  is resilient and can be moved relative to the housing  30 , whereas each contact element  33  is spring-loaded with a compression spring. 
     According to the embodiment at hand, the contact device  6  merely has to be placed on the solar module  10 . Because of its weight it remains at the position where it was placed. Additional means for fixing the contact device are not required. The bottom view representation displayed in  FIG. 6  shows deformed elements  34  on the bottom side  37  of the contact device  6 . Said deformed elements  34  protect the upper side of the module  10  against scratching. In addition, because of the increased friction, the scratch protection elements  34  preferably consisting of elastomer have the purpose of fixing the contact device  6  in the position in which it was placed on the solar module. The deformable elements  34  have a tubular, deformable profile. It is also possible to design the scratch protection elements  34  as flexible, solid profiles consisting of elastomer. As a result, it is almost impossible for the contact device to get out of place. When the testing method is completed, the contact device  6  is simply removed and placed on the following solar module to be tested. As shown in the subsequent figure, the contact device  6  comprises two contact elements  33  which are attached to a respective terminal of the connecting zone  13 . 
       FIG. 7  shows a top view of an alternate contact device  6  which can be used with the test device  1  described above. This contact device  6  is appropriate to be used for solar modules that have been pre-assembled with terminal boxes. These solar modules have been provided with cables and plugs to be connected in a solar system. Instead of using contact pins, like in the embodiment described above, the electrical connection between solar module and contact device is generated by using an electrical connection in the form of connector sockets  32 .  FIG. 7  also shows that the contact device  6  is provided with two contact elements  33 ,  33 ′. Contact surfaces  36  of the contact elements that can glide along the contact bar are designed, for example, as planar surfaces. The contact surfaces  36  of the contact elements can have a convex or pointed design, resulting in a linear or punctiform mechanical contact between the contact element  33 ,  33 ′ and the contact bar  20 , instead of a wide-area contact. 
     In the embodiment shown in  FIG. 8 , the contact bars  20  can be selectively moved laterally by means of an adjustment mechanism in the direction f transverse to the transport direction e. Instead of such a mechanism, it is also possible to provide adjacent contact bars. In the embodiment shown in  FIG. 9 , the tapping or supply device  4  comprises two additional rows of contact bars offset towards the inside (depicted with numerals  20 ′,  20 ″). 
     The test device could also comprise contact bars  20  which are aligned transverse to the transport direction. Such an arrangement is shown in  FIG. 10 . Here, the tapping or supply device  4  comprises three adjacent contact bars  20 ,  20 ′,  20 ″. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.