Method and apparatus for electrically accessing photovoltaic modules

An apparatus and a method for testing and/or conditioning photovoltaic modules. The apparatus includes a set of contacts for contacting electrical conductors of the module and a testing and/or conditioning system for testing and/or conditioning of the module and measuring parameters associated therewith.

FIELD OF THE INVENTION

Embodiments of the invention relate to the field of photovoltaic power generation systems, and more particularly to methods and systems used to test and/or condition photovoltaic modules during manufacture.

BACKGROUND OF THE INVENTION

Photovoltaic (PV) modules convert solar radiation to electrical current using the photovoltaic effect. During manufacturing of the modules, minor variations in process parameters may result in modules having dissimilar performance characteristics. Dissimilar performance characteristics are undesirable because the design and performance of a photovoltaic array may rely on each module performing according to product specifications. Therefore, it is desirable to manufacture modules that exhibit similar performance characteristics when installed in the field. Moreover, it is desirable to manufacture modules that maintain similar performance characteristics over the life expectancies of the modules. An efficient way to test and/or condition manufactured modules is desired.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments that provide a system for inline testing and conditioning of PV modules while they are manufactured. These embodiments are described in sufficient detail to enable those skilled in the art to make and use them, and it is to be understood that structural, logical, or procedural changes may be made to the specific embodiments disclosed without departing from the spirit and scope of the invention.

FIG. 1illustrates a bottom perspective view of a PV module100according to an exemplary embodiment. The PV module100may have any suitable geometry. For example, the PV module100may have a width of about 60 cm, a length of about 120 cm, a thickness ranging from 5 to 8 mm, and a weight of about 12 kg. The PV module100includes a plurality of layers between front and back covers that form a plurality of interconnected PV cells that generate electrical current from solar radiation.

The PV cells within the PV module100are electrically connected to a cord plate110attached to a back cover120of the PV module100. The cord plate allows external connections112and114to be connected to internal conductors of PV module100. As illustrated inFIG. 2, during manufacturing of the PV module100, positive and negative lead foils232and234, which are electrically connected to the PV cells, are brought out of the PV module100through a hole230in the back cover120. The positive and negative lead foils232and234are brought out near the front edge280of the PV module100. In a subsequent step in the manufacturing process, the cord plate110is attached to the back cover120and external conductors are electrically connected to the positive and negative lead foils232and234within the cord plate110. Positive and negative lead foils232and234may be formed of any suitable material such as, gold, silver, copper, aluminum, or other conductive metals. In one embodiment, the positive and negative lead foils232and234may be formed of conductive tape.

FIG. 3aillustrates a diagram of a testing and conditioning system (TCS)300according to an exemplary embodiment. The TCS300includes an enclosure302, a conveyor310, a testing and conditioning unit (TCU)318, and a system controller330.

The enclosure302has a box shape and includes a bottom303, a top304, a first opening306on one side and second opening308on an opposite side. The first and second openings306and308are large enough to allow the conveyor310and the PV module100atop the conveyor310to pass there through. The enclosure302is designed to limit access to the PV module100and other parts of the TCS300to prevent an operator or other object from conducting current applied to the PV module100during testing and/or conditioning. As illustrated inFIG. 3cthe enclosure302further includes first and second access doors307and309that are used to access the interior of enclosure302for maintenance. The access doors307and309allow an operator to remove broken modules or to repair components within the enclosure302. Additionally, the enclosure302may include solenoid-locking safety switches390to secure the access doors307and309and thereby secure the enclosure302during testing. The enclosure302may also contain a perimeter sensor that detects whether the access doors307and309are secure. The enclosure302is connected to and communicates with the control panel335through communication cable352, which in turn communicates with the system controller330through communication cable350. The enclosure302may provide information regarding the status of the enclosure302to the system controller330via the control panel335, such as, whether the perimeter of the enclosure302is secured.

The conveyor310passes through the enclosure302and through the first and second openings306and308in the direction of arrow316and supports a PV module100. The PV module100is positioned on the conveyor310with the leading edge382of the PV module100facing the opening308. Furthermore, the PV module100is positioned on the conveyor310with the PV module's100positive and negative lead foils232and234facing the top304of the enclosure302and the PV module's100front edge280facing into the page. A scanner314may be positioned outside the enclosure302and below the conveyor310to read an ID of the PV module100as it is brought into the enclosure302. The PV module100ID may be a bar code or any other computer readable identification system.

The movement of the conveyor310is, controlled by a conveyor controller312. The conveyor controller312operates the conveyor310to bring the PV module100into the enclosure302and align the PV module100with the TCU318. A presence sensor366located beneath the conveyor310and connected to the conveyor controller312is used to determine when the PV module100is aligned with the TCU318. The conveyor controller312also is connected to and communicates with the control panel335through communication cable353. The conveyor controller312sends status information to and receives commands from the system controller330via the control panel335.

The TCU318includes a contact unit320and a power unit340. The contact unit320has contact pads324and325that respectively contact the lead foils232and234of the PV module100during testing and conditioning of the PV module100. The power unit340provides an electrical bias to the PV module100and measure voltage and current on the PV module100during testing and/or conditioning of the PV module100. The electrical bias may be constant voltage, constant current, variable voltage, variable current, pulses of constant current, pulses of constant voltage, alternating constant or variable current and constant or variable voltage, or any combination thereof. In one embodiment, a relay may also be utilized with the power unit340to provide electrical bias to the PV module100.

The contact unit320is positioned within the enclosure302between the conveyor310and the top304of the enclosure302. The contact unit320includes a plunger switch322, first and second contact pads324and325(as illustrated inFIG. 3b), and an edge sensor326. The plunger switch322is used to sense the presence of a module100below contact unit320while the edge sensor326is used to align the contact pads324and325over the positive and negative lead foils232and234respectively of the PV module100in a direction perpendicular to the direction of PV module100conveyance during testing and conditioning of the PV module100. The plunger switch322, edge sensor326, and first and second contact pads324and325are further illustrated and described with respect toFIG. 4. A control panel335is provided to operate and control the contact unit320. The control panel335is also connected to and communicates with system controller330through communication cable350. The control panel335may also connect to the power unit340via communication cable351, contact unit320via communication cable352, and the sensors (e.g.360and366), scanner314, and conveyor controller312via communication cable353. The contact unit320sends status information to the control panel335, and ultimately the system controller330and receives commands from the system controller330via the control panel335.

FIG. 3billustrates a top view of the diagram ofFIG. 3aaccording to an exemplary embodiment with the contact unit320in a home position. The contact unit320resides in the home position during periods when the PV module100is not being conditioned or tested. In the home position, the portion of the contact unit320positioned closest to the conveyor310is maintained at least 2.5 inches from the conveyor310. This clearance distance prevents the contact unit320from scratching or otherwise damaging the PV module100when it is brought in and out of the enclosure302. When a PV module100is brought into the enclosure302, the conveyor310positions the PV module100so that the contact unit320is centered between the leading and trailing edges382and384of the PV module100. Centering the contact unit320between the leading and trailing edges382and384of the PV module100aligns the contact pads324and325with the lead foils232and234in the direction of PV module100conveyance. As mentioned above, the edge sensor326is then used to center the contact pads324and325and align them with the lead foils232and234.

Referring again toFIG. 3a, the power unit340is located outside of the enclosure302and is connected to the contact unit320by positive and negative wires344and346. In another embodiment, the power unit340may be contained within the enclosure302. The power unit340supplies current and voltage to the PV module100by way of the contact unit320and positive and negative wires344and346. More particularly, the power unit340supplies current and voltage to the positive and negative lead foils232and234of the PV module100by way of the contact pads324and325of the contact unit320. When the power unit340is enabled by the controller330, current flows between the power unit340and the PV module100. When the power unit340is disabled by the controller330, current stops flowing from the power unit340.

The power unit340may operate in a constant current mode with a current set point ranging between 0 to 11.0 amps with an accuracy of +/−0.15 amps. The power unit340may also supply an adjustable voltage that ranges between 0 and 300 volts. In total, the power unit340may provide up to 3300 watts of power to the PV module100. In another embodiment, the power unit340may also operate in a varying current mode with a current set point ranging between 0 to 11.0 amps with an accuracy of +/−0.15 amps and a voltage ranging between 0 and 300 volts. Furthermore, in another embodiment, the power unit340may operate in a mixed mode and provide varying levels of current and voltage.

The power unit340further includes voltage sensor347and current sensor348used to measure the voltage and current within the PV module100during testing and/or conditioning of the PV module100. For example, in a testing mode, the power unit340may measure the voltage and/or current generated by the PV module100when the PV module100is exposed to light. In a conditioning mode, the electrical bias provided by the contact unit320to the PV module100during a conditioning event may be monitored by the voltage and current sensors347and348. Using voltage sensor347, the power unit340measures the voltage between the positive and negative lead foils232and234of the PV module100. In another embodiment, the power unit340uses the voltage sensor347to measure the voltage on a voltage divider that corresponds to the voltage between the positive and negative lead foils232and234. Using the current sensor, the power unit340measures the actual current flow within the PV module100.

The power unit340is connected to and communicates with the control panel335through communication cable351. The power unit340receives commands from the system controller330via the control panel335and the power unit340sends data, such as voltage and/or current measurements, and status information to the system controller330via the control panel335.

The TCS300may further include first and second temperature sensors360and362(as illustrated inFIG. 4) within the enclosure302. The temperature sensors360and362are positioned above the conveyor310and are centered between the leading and trailing edges382and384of the PV module100. For example, as illustrated inFIG. 4, the first temperature sensor360is positioned one-quarter of the length464of the PV module100from the front edge280of the PV module100and the second temperature sensor362is positioned three-quarters of the length464of the PV module100from the front edge280. The first and second temperature sensors360and362are used to measure the temperature of the PV module100before, during, and after testing. In one embodiment, the temperature sensors360and362may be non-contact pyrometers. In another embodiment, the temperature sensors360and362may be contact sensors that move into and out of contact with the PV module100. The temperature sensors360and362are connected to and communicate with system controller330via the control panel335to send the temperature readings of the PV module100.

As illustrated inFIG. 3a, the system controller330is connected to and communicates with various components in the TCS300through communication cable350and the control panel335according to one embodiment. In another embodiment, the system controller330may communicate with components in the TCS300using a wireless network, Bluetooth, or other means of communication. In yet another embodiment, the system controller330may communicate with some of the components in the TCS300using a wired connection and other of the components using a wireless connection.

The system controller330controls the operation of the TCS300, executes self-diagnostics, and may interface with a plant-wide communications network. In particular, the system controller330may support the TCS's300operational functions, diagnostic systems, process parameters, status reporting, program download functions, and program upload functions. To allow for self-diagnostics, the system controller330may include diagnostic software to allow for trouble shooting causes of process alarms. For example, the software may store alarm histories that include event details such as the type of alarm, the time stamp of the alarm, and the time stamp of the TCS300reset following the alarm. The diagnostic software may also allow for viewing and trouble shooting of machine functions through the network connection.

The data that is received by the system controller330from the TCS300may be collected, displayed, transmitted, and stored. For example, data concerning the PV module100, including testing and conditioning data, may be displayed on a console398to an operator. The data may also be transmitted and stored in a database396. The data may be transmitted to the database396by way of a network server. For example, in one embodiment, the server may be an OPC server and the database396may be an SQL database. Furthermore, the data may be stored in a process table within the database396. Within the table, an entry may be created for each PV module100that is processed by the TCS300. For example, module ID, electrical current set point, actual electrical current, start time stamp, end time stamp, start voltage, end voltage, start temperature, end temperature, and equipment status may be stored for each PV module100.

The data may be collected and continuously uploaded to the database396in real-time. Alternately, the data may be collected and stored locally within the system controller330and periodically uploaded to the database396. In one example, data may be uploaded at the end of each testing and/or conditioning cycle. The uploaded data may include raw data collected from the sensors. Alternately, the uploaded data may also include data processed by the system controller330. As described above, data may be uploaded from the system controller330to the database396. Data may also be downloaded from the database396to the system controller330. In one embodiment, the system controller330is a programmable logic controller. In another embodiment, the system controller330is a computer.

FIG. 4illustrates a detailed front view of the contact unit320and the PV module100within the TCS300according to an exemplary embodiment. As illustrated inFIG. 4, the contact unit320is mounted on horizontal rails470and a vertical rail472to allow the contact unit320to move laterally and vertically.

The contact unit320, as illustrated inFIG. 4, is in an aligned position above the PV module100. To begin testing and/or conditioning of the PV module100, the contact unit320moves from the home position, into the aligned position, and then into contact with the PV module100. Specifically, the first and second contact pads324and325are moved into electrical contact with the positive and negative lead foils232and234of the PV module100.

To place the contact unit320into contact with the PV module100from the home position, the contact unit320first moves laterally, i.e. parallel to the back cover120of the PV module100, in the direction of arrow490along the horizontal rails470to the aligned position. The contact unit320moves laterally until either the edge sensor326detects the front edge280of the PV module100or the contact unit320reaches an end position along the horizontal rails470. If the end position along the horizontal rails470is reached, as determined by a horizontal position sensor494, the contact unit320returns to the home position and indicates to the system controller330that it was unable to detect the edge of the PV module100. If the edge sensor326detects the front edge280, the contact unit320stops moving laterally and commences to descend toward the PV module100along the vertical rail472. In one embodiment, the edge sensor326may be a photo eye sensor capable of identifying the location of the front edge280of the PV module100with an accuracy of 3 mm. In another embodiment, the edge sensor326may be another type of sensor.

The contact unit320descends toward the PV module100until the contact unit320reaches an end position along the vertical rail472as determined by a vertical position sensor496, such as a Hall Effect sensor. With the contact unit320at an end position along the vertical rail472, the first and second contact pads324and325are in contact with the positive and negative lead foils232and234respectively. The system uses the plunger322to verify that the contact unit320is on the PV module100and infers that first and second contact pads324and325are in contact with the positive and negative lead foils232and234respectively. The plunger322extends lower than the first and second contact pads324and325by a known distance492and is fixed to the contact unit320by a plunger spring423. As the contact unit320descends toward the PV module100, the plunger322contacts the PV module100before the first and second contact pads324and325contact the positive and negative lead foils232and234. As the contact unit320continues to descend with the plunger322in contact with the module100, the plunger spring322is compressed. A proximity switch sensor498detects the compression of the plunger spring322, which indicates that the contact unit320contacted the module100. The contact unit320then indicates to the system controller330that contact has been made.

In another embodiment, the contact unit320may use sensors to determine the vertical distance between the PV module100and the contact pads324and325and place the contact pads324and325into contact with the PV module100. Various devices may be used to move the contact unit320along the horizontal rails470and the vertical rail472. For example, in one embodiment, air cylinders may be used to move the contact unit320. In another embodiment, servos, an electric motor, or a hydraulic system may be used. Furthermore, different mechanics may be used to move the contact unit320horizontal and vertically. For example, air cylinders may move the contact unit320vertically, while an electric motor may move the contact unit320horizontally. In any event, the placement and design of the contact unit320should be controlled to limit the pressure applied by the contact unit320to the PV module100. For example, in one embodiment, the pressure applied by the contact unit320to the PV module100should be limited to 25 lbs of force over a 6 square inch area.

FIG. 5illustrates a method500implemented by the TCS300to test and/or condition the PV module100inline during manufacture of the PV module100according to an exemplary embodiment. To begin, in step505, the system controller330waits to receive confirmation from the enclosure302that the doors307and309are closed and the enclosure302is secured. Once the system controller330confirms that the enclosure302is secured, in step510, the system controller330indicates to the conveyor controller312to bring the PV module100into the enclosure302. The conveyor controller312operates the conveyor310to bring the PV module100into the enclosure302. The PV module100is brought into the enclosure302after the back cover120of the PV module100has been installed and the lead foils232and234have been brought out of the hole230of the back cover120and folded back onto the surface of the back cover120. In one embodiment, the PV module100may be brought into the enclosure302from a laminator that installs the back cover120. To install the back cover120, the laminator typically heats the PV module to between 100 and 200 degrees Celsius. As a result, the PV module100enters the enclosure302with a temperature between 20 and 200 degrees Celsius.

As the PV module100enters the enclosure302, a previously read ID of the PV module100is sent to the system controller330so that the system controller330may customize the testing and/or conditioning for the individual PV module100. As the conveyor310brings the PV module100further into the enclosure302, the presence sensor366senses the PV module100and sends a signal to the conveyor controller312which stops the conveyor310. The PV module100is now aligned in the direction of PV module100conveyance beneath the contact unit320and above the temperature sensors360and362as illustrated inFIG. 3b. The conveyor controller312then sends a signal to the system controller330that the PV module100is aligned. In step515, the system controller330commands the conveyor controller312to disengage the conveyor310so that no movement of the PV module100may occur during testing and/or conditioning of the PV module100.

In step520, the system controller330determines if the doors307and309are closed and if one or more start criteria for the testing and/or conditioning of the PV module100have been meet. In one embodiment, the start criteria may be programmed into the system controller330by the operator before hand. In another embodiment, the start criteria may be set by the operator using the console398in real time. In yet another embodiment, the operator may override programmed start criteria in real time using the console398.

In one embodiment, start criteria may include the temperature of the PV module100falling within a specified range, such as between 20 and 200° C. The system controller330may determine the temperature of the PV module100using the temperature sensors360and362. If the temperature of the PV module100is above 200° C., the system controller330may wait for the PV module100to cool before continuing. Additionally, if the temperature of the PV module100is outside the specified range, the system controller330may determine the start criterion has not been met. In another embodiment, the start criteria may include the TCS300having an allotted amount of time, such as between 0 and 10 minutes, to perform the testing and/or conditioning during the manufacturing process. For example, the start criteria may indicate that 5 minutes is needed to perform testing and/or conditioning during the manufacturing process. If the system controller330determines that there is only 3 minutes to perform the testing and/or conditioning, then the start criteria would not be met.

If the start criteria cannot be met, the method500advances to step580. Otherwise, in step525, the system controller330commands the contact unit320to place the contact pads324and325into contact with the lead foils232and234as explained with respect toFIG. 4. If the contact unit320is unable to place the contact pads324and325into contact with the lead foils232and234then the method500advances to step570. If contact between the contact pads324and325and the lead foils232and234is established then, in step530, the system controller330commands the power unit to output power.

Once the power unit is enabled, in step540, the electrical contact between the contact pads324and325and the lead foils232and234is verified. To verify the electrical contact, the system controller330commands the power unit340to supply an electrical bias to the PV module100through the contact pads324and325. For verification, a low current, for example 0.25 amps may be used. For testing and/or conditioning purposes, the current supplied by the power unit340may range between 0 and 11 amps and the voltage may range between 0 and 300 volts. After the electrical bias has been applied for a set amount of time, for example, 5 seconds, the power unit340measures the current and voltage of the PV module100and sends the data to the system controller330. The system controller330compares the measured current and voltage to set thresholds to determine if the PV module100is faulty or if the contact between the contact unit320and the PV module100is not sound. For example, in one embodiment, a PV module with a measured current below 20 milliamps or a measured voltage below 20 volts would be considered faulty or as having an unsound contact between the PV module and the contact unit320. If the measured current and voltage are found acceptable, the method500advances to step550. If either of the measured current and voltage levels is found unacceptable, the method500advances to step560. Furthermore, if during step540the system controller330receives data indicating that the enclosure302is no longer secured, the method500advances to step560.

In step550, the PV module100is tested and/or conditioned using electrical bias provided by the power unit340as controlled by the system controller330. The electrical bias applied to the PV module100during the testing and conditioning may be constant, alternating, pulsating, or any combination thereof. Additionally, the system controller330may adjust the testing and/or conditioning procedures and conditions based on information known about the PV module100being tested and on feedback received during the testing and/or conditioning procedure. For example, data on the PV module100may be collected during the manufacturing processes that occur before the testing and/or conditioning of the PV module100. This collected data may then be used when selecting parameters for the testing and/or conditioning of the PV module100. For example, information relating to a vapor deposition process for the PV module100, such as the temperature and chemical composition of the melt material, may be stored in the database396. Based on this stored data, the testing and/or conditioning may be adjusted. Furthermore, the system controller330may adjust the testing and/or conditioning procedures and conditions based on real time operator input received through the console398.

Current and/or voltage measurements may be taken during the testing or conditioning process by the power unit340and sent to the system controller330. The measurements may be taken at set time intervals. For example, the measurements may be taken every 15, 30, or 60 seconds, or after any other reasonable time period. Once testing and/or conditioning is commenced, the system controller330also monitors stop conditions to determine when the testing and/or conditioning should end. Stop conditions may include measurable quantities, such as, the temperature of the PV module100falling below a set point, the voltage on the PV module100rising above a set point, the duration of the testing and/or condition lasting for a predetermined period. If one of the stop conditions is fulfilled, the method500advances to step560. The stop conditions may be preset or determined in real time by the operator. Furthermore, if during step550the system controller330receives data indicating that the enclosure302is no longer secured, the method500advances to step560.

In step560, the system controller330commands power unit340to stop providing power. Then in step570, the system controller330commands the contact unit320to return to the home position. In step580, the system controller330sends a signal to the conveyor controller312to move the PV module100out of the enclosure302. The conveyor controller312operates the conveyor310to bring the PV module100out of the enclosure302. It should be understood that additional steps may be performed in the method500as described. Furthermore, some of the steps may not be performed, or the steps described may be performed in a different order.

The TCS300may include more than one TCU318to allow the TCS300to process more than one PV module at a time. For example, as illustrated inFIG. 6, the TCS600may include five TCUs318spread along the conveyor310to enable the TCS600to test and/or condition five PV modules100a-100esimultaneously according to an exemplary embodiment. In this embodiment, the five PV modules100a-100eare brought into the enclosure302at the same time along the conveyor310. The system controller330controls the testing and/or conditioning of each PV module100a-100eindividually and may change the testing and/or conditioning performed on an individual PV module100a-100ebased on the data previously collected for the PV module100a-100eor based on the information collected during the testing and/or conditioning of the PV module100a-100e. Furthermore, the system controller330may change the testing and/or conditioning for each individual PV module100a-100ebased on input from the operator.

The TCS300operates to test and/or condition every PV module100a-100eindependently. For example, if one of the five TCUs318is unable to locate or contact its corresponding PV module100a-100e, the remaining PV modules100a-100eare tested and/or conditioned. Likewise, if one of the PV modules100a-100efails the initial testing, the remaining PV modules100a-100eare tested and/or conditioned. Additionally, the TCS300continues testing and/or conditioning each PV modules100a-100euntil a stop condition is fulfilled for that individual PV module100a-100e. For example, if the PV module100ehas met its stop condition, the testing and/or conditioning on the PV module100ewill stop while the remaining PV modules100a-100dcontinue to be tested and/or conditioned. The remaining PV modules100a-100dwill continue to be tested and/or conditioned until they fulfill a stop condition. In this example, after fulfilling the stop condition, the PV module100eperforms steps560and570. When all five PV modules100a-100ehave fulfilled their stop conditions and completed steps560and570, the TCS300performs step580and the testing and/or conditioning of the PV modules100a-100eis completed.

In another embodiment, the TCS300operates to test and/or condition each PV module100a-100edependent on the condition of the remaining PV modules100a-100e. For example, once the stop condition for one of the PV modules (e.g.100a) is fulfilled, testing and conditioning for every module100a-100emay stop. Likewise, in this embodiment, the TCS300may not perform testing and conditioning on any of the PV modules100a-100eif one of the TCUs318is unable to locate or contact one of the PV modules100a-100e.

A system700may also be implemented where multiple TCSs600are operated in parallel. For example, as illustrated inFIG. 7, the system700may include eight TCSs600a-600hoperating in parallel according to an exemplary embodiment. The system700may simultaneously test and/or condition forty PV modules individually periodically, for example, every ten minutes. In this embodiment, each of the TCSs600a-600hare controlled by a single system controller730. Furthermore, each of the TCSs600a-600hhas a console398that allows an operator to control the testing and conditioning of each PV module100within the individual TCSs600a-600h. Additionally, the TCSs600a-600hmay operate independently of each other so that the conditions and situations in one TCS600a-600hdoes not affect the operation of the remaining TCSs600a-600h. In another embodiment, a system controller may be used to control and operate each TCSs600a-600hindividually. In yet another embodiment, a single console398may be used for all of the TCSs600a-600h. Other embodiments may use more or fewer TCSs as required by the system700.

While embodiments have been described in detail, it should be readily understood that the invention is not limited to the disclosed embodiments. Rather the embodiments can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described without departing from the spirit and scope of the invention.