WO2012143892A2

WO2012143892A2 - Methods and system for detecting defects of at least a photovoltaic device

Info

Publication number: WO2012143892A2
Application number: PCT/IB2012/051981
Authority: WO
Inventors: Joachim Ufheil
Original assignee: Somont Gmbh
Priority date: 2011-04-20
Filing date: 2012-04-19
Publication date: 2012-10-26
Also published as: EP2700108A2; WO2012143892A3

Abstract

Disclosed are methods and system for controlling connection process of at least a connector to at least a solar cell. The method comprises the steps of: heating at least the solar cell, electrically connecting the connector to at least the solar cell, cooling down at least the solar cell, inspecting at least the solar cell for detecting a defect during cooling, and controlling the connection process to avoid at least the defect.

Description

METHODS AND SYSTEM FOR DETECTING DEFECTS OF ATLEAST A PHOTOVOLTAIC DEVICE

FIELD OF THE INVENTION

[001] The present invention relates generally to manufacturing of solar modules, and, more particularly, to methods and system for detecting defects of atleast a photovoltaic device in a cost effective, secure, and efficient manner.

BACKGROUND OF THE INVENTION

[002] Solar cells also, called photovoltaic cells or simply cells, are semiconductor devices which transform light in electrical power. Nowadays the bulk of the commercially sold solar cells are crystalline solar cells, for example, mono or poly crystalline or hetero junction, which consist of doped silicon wafers. However, such individual solar cell generally produce a relatively low energy output, accordingly, in order to obtain a desired high energy output, a significant number of solar cells, in the form of strings or matrix, are interconnected to form a solar module (also referred to as 'solar panel'). In particular, individual solar cells are connected in series to provide a desired output voltage. The series blocks of solar cells in turn are connected in parallel to provide sufficient current output for the particular application. Solar cells are connected in series to limit the current. Current makes wire warm, thereby dissipating energy. Voltage can be dealt with more easily.

[003] In order to establish electrical contact with such cells, a metallization layer is applied on the backside and on the topside of these cells or wafers. Usually the backside metallization covers the whole backside area whilst the topside metallization consists of very narrow fingers and two or more wider bus bars.

[004] The solar cells are interconnected with metal ribbons (also referred to as 'connector'). The topside metallization of one cell is linked to backside metallization of the next cell, by placing a ribbon on the bus bar of a solar cell, heating the ribbon and the bus bar, so that the solder (which is normally provided as a coating on the ribbon) melts and then letting the ribbon and solar cell cool off again to form an electrical contact. This process is known as stringing and is used to connect each row of strings to form a matrix solar module. The ribbons usually are soldered on the cells in order to minimize contact resistivity and to get a uniform electrical contact over the whole bus bar. The back of one cell is electrically connected to the front of the next solar cell. [005] This process poses a problem that due to different thermal expansion coefficients of the ribbon and the solar cell, thermal stress is induced in the solar cell after soldering when the solar cell and ribbon are cooling down. For crystalline solar cells this stress can lead to a special type of micro cracks called conchoidal fractures of the solar cell surface. These fractures break off chips of the surface of the solar cell. This chipping may destroys the structure of part of the active surface of the cell and it may interrupt the contact between a finger and the solar cell or even break off a finger, interrupting all current flow in that finger. This chipping effect occurs mostly if the cell is heated too much and/ or if the cell cools down too quickly.

[006] The heating depends on multiple factors, for example, firstly on the contact of the soldering means to the solar cell, for example, as a soldering head wears down or gets dirty, the heat contact to the solar cell decreases. The operator may increase the temperature of the head to compensate for this. If for some reason the head get clean (dirt drops off, is cleaned, wears down in a positive manner), too much heat may be applied to the solar cell. Secondly, the heating also depends on the type of ribbon and also the batch it comes from. One ribbon may conduct heat better than the other. This may be due to the solder coating being applied to the ribbon in a slightly different way, the use of slightly different materials, say the copper of the ribbon or the shape of the ribbon. Also the content of the solder may vary.

[007] Thirdly, the heating also depends on the type of solar cells and also the batch it comes from. The bus bar on the cell may be a little bit thicker or less thick, changing the heat conductivity properties. Also material properties may vary.

[008] If solar cells are damaged by chipping and this is not recognized, and the cells are used to form strings, matrices and finally modules. The later the chipping is detected, the more cells are damaged and later have to be replaced. If the damage caused due to chipping is repairable, this has to be done manually by hand, costing much time and resulting in undefined process quality because the quality is not as constant as can be expected of a machine. If the damage is not detected at all, it may lead to the solar module with lower total output power thereby reducing the sale price of the solar module. The problem may also not become visible until the module has been sold and installed and then it has to be replaced.

[009] The chipping can interrupt fingers. Since stresses are highest close to the bus bar, the chipping is most likely to occur there. If one finger is broken, during electroluminescence imaging no current will flow through the broken finger to the bus bar. This makes the area adjacent to that finger appear dark (the current would make the solar cell light up a little as if it were a light emitting diode). The chipping can be recognised by the presence of a number of dark areas in the image.

[0010] The prior art discloses numerous techniques for detecting solar cells defects, for example, US Patent application 20050252545 discloses methods and apparatus for detecting solar cell defects by applying a forward-biasing electric current through a silicon solar cell or a group of interconnected solar cells for a short duration and then analysing the resulting thermal image of each cell with an infrared (IR) camera. The method is particularly useful in assembling solar cell arrays or modules in which large numbers of cells are to be wired together. Automated module assemblers are disclosed in which the solar cells (or strings of solar cells) are tested for defects prior to final module assembly.

[0011] The features of conventional techniques for detecting solar cells defects are complex and deficient, thereby, necessitating the need for a new technique which is simple and reliable in operation.

[0012] Accordingly, there exists is a need of means for detecting solar cells defects and controlling manufacturing process of the solar module, which solves the problems in the prior art, with simple technologies process and prevent solar cells from getting damaged and damaged cells being used down stream in the manufacturing process in a cost effective, environmentally safe, and secure manner.

SUMMARY OF THE INVENTION

[0013] In view of the foregoing disadvantages inherent in the prior art, the general purpose of the present invention is to provide an improved combination of convenience and utility, to include the advantages of the prior art, and to overcome the drawbacks inherent therein.

[0014] In one aspect, the present invention provides a method of controlling connection process of atleast a connector to atleast a solar cell. The method comprises the steps of heating the solar cell, connecting the connector to atleast the solar cell, cooling down the solar cell, inspecting atleast the solar cell for detecting a defect during cooling, and controlling the connection process to avoid atleast the defect. The connector is coupled to bus bar of the solar cell electrically or mechanically. Atleast one connector connected to the solar cell is connected to a second solar cell.

[0015] In another aspect, the present invention provides a system for controlling atleast a connection process of atleast a connector to atleast a solar cell. The system comprises atleast a heating unit for heating atleast the solar cell, atleast a connection unit adapted for connecting atleast the connector to atleast the solar cell, atleast a cooling unit adapted for cooling down atleast the solar cell, atleast a inspection unit adapted for inspecting the solar cell for detecting a defect, and atleast a control unit adapted for controlling the connection process as to avoid the defect. The connection unit is capable of connecting the connector with the solar cell electrically or mechanically. The control unit capable of indicating any improper action during the connection process.

[0016] These together with other objects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The advantages and features of the present invention will become better understood with reference to the following more detailed description taken in conjunction with the accompanying drawings in which:

[0018] FIG. 1 illustrates a schematic diagram of a photovoltaic cell;

[0019] FIG. 2 illustrates an exemplary string ;

[0020] FIG. 3 illustrates a flowchart of a method for detecting defects of atleast a photovoltaic device, according to an exemplary embodiment of the present invention;

[0021] FIG. 4 illustrates a flowchart of the plotting of the sound spectrum, according to an exemplary embodiment of present invention;

[0022] FIG. 5 illustrates an image of an exemplary time series, according to an exemplary embodiment of the present invention;

[0023] FIG. 6 illustrates a graph between amplitude and frequency, according to an exemplary embodiment of the present invention;

[0024] FIG. 7 A illustrates an exemplary chipping on the solar cell; [0025] FIG. 7B illustrates the amplitudes of the Fourier transform over time for different frequencies, according to an exemplary embodiment of the present invention;

[0026] FIG. 8 illustrates a system for controlling atleast a connection process of atleast a connector to atleast a solar cell, according to an embodiment of the present invention;

[0027] FIG. 9 illustrates an inspection unit adapted for detecting a defect, according to an exemplary embodiment of the present invention; and

[0028] FIG. 10 illustrates the mechanical shield, according to an exemplary embodiment of the present invention.

[0029] Like reference numerals refer to like parts throughout the several views of the drawings. DETAILED DESCRIPTION OF THE DRAWINGS

[0030] The exemplary embodiments described herein detail for illustrative purposes are subject to many variations and structure and design. It should be emphasized, however that the present invention is not limited to particular system or method for detecting defects of atleast a photovoltaic device and controlling connection process of atleast a connector to atleast a solar cell, as shown and described. Rather, the principles of the present invention can be used with a variety of photovoltaic device testing and manufacturing process controlling methods and structural arrangements. It is understood that various omissions, substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but the present invention is intended to cover the application or implementation without departing from the spirit or scope of the its claims.

[0031 ] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details.

[0032] As used herein, the term 'plurality' refers to the presence of more than one of the referenced item and the terms 'a', 'an', and 'atleast' do not denote a limitation of quantity, but rather denote the presence of atleast one of the referenced item. The term 'device' also includes 'engine' or 'machine' or 'system' or 'apparatus' or 'unit'. [0033] The terms 'photovoltaic device' includes atleast any one of a wafer, a solar cell, a string, a matrix, and a solar module. The term 'solar cell', 'photovoltaic cell', and 'cell' may also be used herein interchangeably to refer the same thing. Solar cells may be of any technology such as thin film, crystalline, hetero junction or HIT etc. The terms 'ribbon' and 'connector', may be used herein interchangeably. The connector may be a sheet of any material provided with conductive pathways. The terms 'contact area', 'contact', 'bus bar' and 'finger' may also be used herein interchangeably to refer to the same thing. The ribbons may be connected directly to the fingers.

[0034] In an exemplary embodiment, the present invention provides methods and system for detecting defects of atleast a photovoltaic device and controlling connection process of atleast a connector to atleast a solar cell. The system of the present invention may be mass produced inexpensively and provides user an easy, robust, efficient, secure, cost effective, environment friendly and productive way of solar cell testing.

[0035] In an exemplary embodiment, the present invention provides a method for detecting defects of atleast a photovoltaic device and controlling connection process of atleast a connector to atleast a solar cell. The method comprises the steps of heating the solar cell; electrically connecting the connector to the solar cell; inspecting the solar cell for detecting atleast a defect; and controlling the connection process as to avoid these defects. The connector may be electrically or mechanically coupled to bus bar of the solar cell. Atleast one connector connected to the solar cell is connected to a second solar cell.

[0036] According to an exemplary embodiment, the present invention provides a system for detecting defects of the photovoltaic device and controlling process of atleast a connector to atleast a solar cell. The system comprises atleast a heating unit adapted for heating atleast the solar cell, atleast a connection unit adapted for electrically or mechanically connecting the connector to atleast the solar cell, atleast a cooling unit adapted for cooling down atleast the solar cell; atleast a inspection unit adapted for inspecting the solar cell for detecting a defect when the solar cell cools down; and atleast a control unit adapted for controlling the connection process as to avoid the defect.

[0037] Referring to FIG. 1 which illustrates a schematic diagram of an exemplary photovoltaic cell 10. The photovoltaic cell 10 has a top surface with a plurality of fingers 12 and two bus bars 14 connected across the fingers 12 to collect the electric charge generated. A metallization layer 16 may be applied usually to the whole bottom surface of the photovoltaic cell 10. The bus bars 14 at the top surface and the metalized layer 16 of the bottom surface, may act as two terminals of the photovoltaic cell 10 to establish atleast one of an electrical and mechanical contacts with other electrical members in an electric circuit.

[0038] Referring to FIG. 2 which illustrates an exemplary string 20. In order to get higher power, a number of solar cells are interconnected and assembled in the string 20. The string 20 consists of several solar cells 10a, 10b and 10c, which are electrically or mechanically connected in series. In the string 20, the topside metallization of one solar cell 10a may be linked to backside metallization of the next solar cell 10b, using metal connectors 22. These connectors 22 usually are soldered on the bus bars 14 of the solar cells 10a, 10b and 10c in order to minimize contact resistivity and to get a uniform electrical contact over the whole bus bar 14.

[0039] Referring to FIG. 3 which illustrates a flow chart of a method 100 for controlling connection process of atleast a connector 22 to atleast a photovoltaic device 10, for example, the string 20. The method 100 starts with a step 110 of heating of atleast two solar cells 10a and 10b. Each of the solar cells 10a and 10b may have atleast one bus bar 14. The heating of the solar cells 10a and 10b heats the bus bar 14 to prepare the solar cells 10a and 10b to form atleast one of an electrical and a mechanical connection among them.

[0040] At a step 120 the two solar cells 10a and 10b may be electrically or mechanically coupled by applying the connector 22 on the heated bus bar 14 of each of the two solar cells 10a and 10b. The heated connector 22 may be soldered to the solar cell as to form atleast one of an electrical and a mechanical connection with the bus bar 14 on cooling.

[0041] At a step 130 the two solar cells 10a and 10b are cooled down actively or passively. This allows the soldered electrical connection to form and the string 20 may be inspected during the cooling down phase for detecting any defect caused by the soldering process. Generally, the inspection of the string 20 may be carried out to detect any chipping 17 (as shown in FIG. 7 A) which leaves a special fingerprint. The chipping 17 may occurs during cooling after the connection of the connector 22 and the bus barl4. The cooling down may be done automatically or actively.

[0042] As, the defects themselves are not corrected, accordingly, a necessary corrective action may be taken at a step 140 if any defect is recognized during step 130.

[0043] According to an exemplary embodiment of present invention, the method 100 is capable of detecting atleast a defect from any one of a micro crack, a chipping 17 of the solar cell surface at the electrical or mechanical connection or any combination thereof.

[0044] According to an exemplary embodiment of present invention, the step 130 of inspecting the string 20 for detecting a defect may comprises the step of generating atleast one of a 2D image and a 3D image. A camera may be adapted to provide atleast one of the 2D image and 3D image. The camera includes atleast one of a 2D camera and a 3D camera. The 2D image and the 3D image may be used to recognize chipping 17, which leaves a special fingerprint (as shown in FIG. 7 A). The 2D image may include atleast one of a normal image, a line of pixels, a thermal image, an electro or photo luminescence or any combination thereof. The 3D image may include a stereo vision, a time of flight, a triangulation, any kind of range image as known from the state of the art or any combination thereof.

[0045] The camera may use atleast one of a time of flight using pulsed or continuous wave, stereo imaging using atleast one of multiple cameras a spatially structured light, interferometry or any other technique. The chipping 17 may create holes which may have two essential features that may be recognized with the 3D camera, for example, first the depth of the holes and second if the fingers 12 of atleast any one of the solar cells 10a, 10b, 10c of the string 20 are interrupted, the fracture may be seen in the 3D image.

[0046] Atleast one of the 2D image and the 3D image may be taken from atleast a range near atleast one of the connector 22 and a connection area of atleast a connection of the connector 22 with atleast any one of the solar cells 10a, 10b, 10c of the string 20 (atleast the bus bar 14). The range includes atleast one of a range along these areas less than 1cm, a range less than 5cm, a range less than 5mm, a range of 2mm or any combination thereof.

[0047] In an exemplary embodiment of present invention, the step 130 of inspecting the string 20 for detecting a defect may comprises step of recording atleast a sound for generating atleast a sound spectrum. The sound spectrum is a representation of usually a short sample from a larger time series 40 (as shown in FIG. 5) of a sound in terms of the amount of vibration at each individual frequency. It is usually presented as a graph of either power or pressure as a function of frequency. The power or pressure is usually measured in decibels and the frequency is measured in Hz or kHz. Atleast one of the sound and the sound spectrum may be analyzed to detect any defect which may occur during the cooling of, for example, the solar cells 10a, 10b, 10c. With generating the sound spectrum, the recording of sound and converting this recording into spectral representation is meant, not the active generation of sound.

[0048] Referring to FIG. 4 which illustrates a flowchart of a method 400 for plotting of the sound spectrum, according to another exemplary embodiment of present invention. The method 400 starts with a step 410 of recording atleast a sound signal in a continuous fashion to record the chipping sound. The sound may be recorded by a sound recorder, e.g., microphone 541 (as shown in FIG. 9). The sound produced when chipping 17 occurs may be used to recognize the chipping 17 (FIG. 7A). The microphone 541 may be placed near the cooling soldered electrical or mechanical connection and sound signals may be recorded during the cooling period with respect to time. The sound signals recorded with respect to time may form a time series (as shown in FIG. 5).

[0049] At a step 420, the recorded sound, for example, Fourier transformed and the sound spectrum, is plotted with respect to time. The time series 40 may be Fourier transformed, preferably using tapering (also referred to as 'windowing'). Since the peaks of the cracking sound are very small, tapering needs to be done to avoid artificial abrupt changes in the time series masking the small peaks need to be detected. At a step 430, analyzing the plotted sound spectrum to recognize the defect. If the time series 40 is analyzed directly, peaks or burst shorter than 0.1, 0.05 or 0.01 seconds may be assigned to defects. The recording itself may be analyzed. Further, the recording may not have to be the Fourier transform.

[0050] Referring to FIG. 5 which shows an image of an exemplary plotted time series 40. In the image, the needle like peaks visible are recognized as the sound produced during micro cracking or chipping 17 (as shown in FIG. 7A). It may be observed from the FIG. 5, that a typical peak may only be 0.02 seconds wide.

[0051 ] In another exemplary embodiment of present invention the sound signal is recorded with a sampling rate of 44 kHz and above. As may be seen from FIG. 7B, a 44 kHz sampling rate results in a maximum recognizable frequency of 22 kHz due to the aliasing effect.

[0052] In another exemplary embodiment of present invention, the sound may be recorded for a plurality of frequencies including frequency in a range of 5 kHz to 30 kHz. The chipping sound may be detected if over a range of frequencies the sound spectrum is high, e.g. equally divided. The preferable frequency range may be 5 to 30 kHz, more preferably from 10 to 20 kHz and most preferably from 13 to 17 kHz.

[0053] Referring to FIG. 6 which illustrates a graph between amplitude and frequency, according to an exemplary embodiment of the present invention. Preferably, when most points of the sound spectrum lay above 70%, 80% or 90% of the peak power value of that range then the peaks in the time series, that may come from the chipping 17, may be very narrow. Meaning that in their Fourier transform, they are represented by many frequencies.

[0054] Referring to FIG. 7A which illustrates chipping 17 on the solar cells 10, according to an exemplary embodiment of the present invention.

[0055] Referring to FIG. 7B which illustrates the amplitudes of the Fourier transform over time for different frequencies, for a signal characteristic to the occurrence of micro cracks and chipping 17. The horizontal axis is the time and the vertical axis represents the frequency. The amplitudes for different frequencies are given by color. The vertical stripes are the peaks representing the chipping sound: short burst of many frequencies.

[0056] An algorithm for recognizing the chipping sounds may be run on multiple frequencies. Preferably the results of these algorithms may be used to recognize chipping, e.g., by means of a voting or ranking algorithm such that results from a number of algorithms must be positive to recognize chipping 17, building an average or a median.

[0057] In another exemplary embodiment of present invention, the method 100 may further comprises a step of cancelling ambient noise. The ambient noise may be recorded and e.g. it's power spectrum may be calculated and used for filtering. In its simplest form, the ambient noise may be used to indicate if a valid cracking sound detection is possible or not. For this, also the microphone 541 may record sound when it is sure that no chipping 17 occurs. Also an additional microphone 541 for ambient sound may be used. In a more sophisticated form, the ambient sound is used by the filter for recognizing the cracking noise. Filters such as Wiener filters or deconvolution filters may be used.

[0058] In an exemplary embodiment of the present invention, at the step 140 of the method 100, the necessary corrective action giving an alarm and warning to interrupt the manufacturing of the string, transferring the manufacturing process of the string 20 to a safe mode, wherein the safe mode is atleast one of a slower mode, controlling the manufacturing process automatically or any combination of these actions. Giving an alarm and warning to interrupt the manufacturing of the string 20 and transferring the manufacturing process of the string 20 to a safe mode may be done automatically or manually.

[0059] Referring to FIG. 8 which illustrates a system 500 for controlling atleast a connection process of atleast a connector 22 to atleast a photovoltaic device 10 and detecting defects of the photovoltaic device 10, according to an exemplary embodiment of the present invention. The system 500 comprise atleast a heating unit 510 adapted for heating a plurality of solar cells 10a and 10b, atleast a connection unit 520 adapted for electrically or mechanically connecting atleast the solar cells 10a and 10b, atleast a cooling unit 530 (also referred to as 'base') adapted to retain and cool off the string 20, atleast an inspection unit 540 adapted to inspect the string 20 for detecting a defect, and atleast a control unit 550 adapted to take a necessary corrective action when the defect or any abnormality is recognized. The control unit 550 may only be capable of indicating any improper action during the connection process, e.g., to an operator. Each of solar cells 10a and 10b may have a contact area 14 (also referred to as 'bus bar'). [0060] According to an exemplary embodiment of present invention, atleast one of the heating unit 510 and the cooling unit 530 may further comprise atleast one of a metallic plate at a fixed temperature and a conveyor (not shown) to move the solar cells 10a, 10b,.. over the metallic plate from a hot area to a cool area or from a cool area to a hot area respectively. The metallic plate may have a fixed temperature. The conveyor may be adapted to move the string 20 over the metallic plate from a hot area to a cool area. The conveyor may also used as the heating plate to keep the temperature at a desired level. The string 20 may be transported from a region where they are heated and or soldered onto the cooling plate. The cooling plate may get progressively cooler in the direction of movement. As the solar cells 10a, 10b, 10c, ..etc., may move to cooler areas, they cool down in controlled manner.

[0061 ] According to an exemplary embodiment of present invention, the connection unit 520 for electrically or mechanically connecting the solar cells 10a and 10b may include atleast one of a metal ribbon, soldering ribbon, a soldering rod, a heating plate, a heating press, an IR-heater, a hot air nozzle, an oven or a combination thereof.

[0062] Referring to FIG. 9 which illustrates the inspection unit 540 adapted for inspecting the solar cell 10a, 10b, 10c or the string 20 for detecting a defect, according to an exemplary embodiment of the present invention. The inspection unit 540 may comprise atleast one of a microphone 541 capable of recording a sound signal, a signal converter, preferably an analogue to digital converter 542 is capable of converting the sound signal into a series of numbers, a computing unit 543 adapted to compute atleast a spectrum such as Fourier spectrum of the series of numbers, an analyzer 544 adapted to recognize the defect from the sound recorded by analyzing the sound spectrum or any combination thereof. Other transforms may be used as well such as a wavelet or cosine transform, or any other transform useful to detect characteristics of the sound that is representative for the defects. Multiple microphones may be adapted to localize the position where the chipping 17 occurs and to ensure that one microphone 541 is always close enough to the chipping 17 to ensure good recording. The inspection of the string 20 may also be carried out by an analogue system.

[0063] Referring to FIG. 10 which illustrates a mechanical shield 545, according to an exemplary embodiment of the present invention. The mechanical shield 545 may covers atleast the microphone 541 to avoid disturbance and background noise during recording of the sound signal.

[0064] According to an exemplary embodiment of the present invention, the microphone 541 may be located at any one of the location from a list of locations including the connection of atleast one of the connector 22 and the solar cells 10a and 10b and the cooling unit 530, a region on the string 20 having temperature drops from 180°C to 30°C, or a region on the string 20 having e.g. a temperature drop rate ranging from 5°C per /minute to 15°C per minute.

[0065] The microphone 541 may be placed in the range where the cooling after soldering takes place. It has been recognized that chipping 17 (as shown in FIG. 7 A) occurs most in the region where the temperature drops from 80°C to 50°C. The microphone 541 may therefore be placed in the region of the cooling unit 530 where atleast one of the solar cells 10a and 10b is cooled down from 180°C to 30°C, preferably from 120°C to 40°C, and more preferably from 80°C to 50°C.

[0066] The rate of cooling may play an important role. The faster the change, the more stress in the material and the more chipping 17 (as shown in FIG. 7A) occurs. It may therefore be beneficial to place the microphone 541 in a location where the temperature of the solar cells 10a, 10b drops more than 5°C per minute, preferably more than 10°C per minute and more preferably more than 15°C per minute.

[0067] The chipping 17 (as shown in FIG. 7A) mostly occurs in the region close to the bus bar 14. The reason for this is that the stress is highest at there, the stress on the solar cells 10a, 10b is exerted by the bus bar 14 and the connector 22 soldered. If a camera is used to detect chipping 17, only this range of atleast one of the solar cells 10a and 10b has to be monitored. When using a microphone 541 to record sound, it may be placed near to the connector 22.

[0068] Since the cracking noise stops after a certain time, atleast one of the solar cells 10a and 10b having had this problem must be marked. The marking of atleast one of the solar cells 10a and 10b may be done mechanically or electronically. The mechanical marking may include atleast one of spray, sticker, indicator etc. In electronically marking, position of atleast one of the solar cells 10a and lObis recorded and the string 20 is put aside. Further, a display or indicator indicating the damaged cell 10a, 10b, .. may also be adapted in the electronic marking. Further, in an exemplary embodiment, atleast a marking unit is adapted for carrying out the marking.

[0069] In various exemplary embodiments of the present invention, the operations discussed herein, e.g., with reference to FIGS. 1 to 10, may be implemented through computing units such as hardware, software, firmware, or combinations thereof, which may be provided as a computer program product, e.g., including a machine-readable or computer-readable medium having stored thereon instructions or software procedures used to program a computer to perform a process discussed herein. The machine-readable medium may include a storage device. For example, the operation of components of the system 500 and apparatus 540 may be controlled by such machine-readable medium. [0070] In other instances, well-known methods, procedures, components, and circuits have not been described herein so as not to obscure the particular embodiments of the present invention. Further, various aspects of embodiments of the present invention may be performed using various means, such as integrated semiconductor circuits, computer-readable instructions organized into one or more programs, or some combination of hardware and software.

[0071 ] Although a particular exemplary embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized to those skilled in the art that variations or modifications of the disclosed invention, including the rearrangement in the configurations of the parts, changes in sizes and dimensions, variances in terms of shape may be possible. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as may fall within the spirit and scope of the present invention.

[0072] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions, substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but is intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

Claims

CLAIMS What is claimed is:

1. A method for controlling connection process of atleast a connector to atleast a solar cell, comprising the steps of:

heating atleast the solar cell;

electrically connecting the connector to atleast the solar cell;

cooling down atleast the solar cell;

inspecting atleast the solar cell for detecting a defect during cooling; and

controlling the connection process to avoid atleast the defect.

2. The method according to the claim 1, wherein the defect includes atleast one of micro-cracks and chipping of the solar cell surface.

3. The method according to the previous claims, wherein the step of inspecting the solar cell further comprising the step of generating atleast one of a 2D image and a 3D image.

4. The method according to the previous claims, wherein atleast one of the 2D image and the 3D image is taken from atleast a range near atleast one of the connector and a connection area of atleast a connection of the connector with the solar cell.

5. The method according to the previous claims further comprising atleast one of the steps of recording a sound, generating a sound spectrum, analysing the sound, analysing the sound spectrum, cancelling ambient noise or any combination thereof.

6. A system for controlling atleast a connection process of atleast a connector to atleast a solar cell, comprising:

atleast a heating unit for heating atleast the solar cell;

atleast a connection unit adapted for connecting the connector to atleast the solar cell;

atleast a cooling unit adapted for cooling down atleast the solar cell;

atleast an inspection unit adapted for inspecting the solar cell for detecting a defect when the solar cell cools down; and

atleast a control unit adapted for controlling the connection process as to avoid the defect.

7. The system according to previous claims, wherein the cooling unit is capable of cooling down atleast the solar cell actively or passively.

8. The system according to previous claims, wherein atleast one of the heating unit and the cooling unit comprising atleast one of a metallic plate at a fixed temperature and a conveyor to move the solar cell over the metallic plate from a hot area to a cool area or from a cool area to a hot area respectively.

9. The system according to previous claims, wherein the inspection unit comprising at least any of: a sound recorder capable of recording atleast a sound signal;

a signal converter capable of converting the sound signal into a series of numbers;

a computing unit adapted to compute atleast a spectrum; and

an analyser adapted to recognize the defect from the sound recorded, or any combination thereof.

10. The method of controlling manufacturing process of atleast a solar module having a plurality of solar cells using atleast one of the system and the method of one of the previous claims.