Abstract:
A photovoltaic system includes multiple strings of solar panels and a device presenting a DC load to the strings of solar panels. Output currents of the strings of solar panels may be sensed and provided to a computer that generates current-voltage (IV) curves of the strings of solar panels. Output voltages of the string of solar panels may be sensed at the string or at the device presenting the DC load. The DC load may be varied. Output currents of the strings of solar panels responsive to the variation of the DC load are sensed to generate IV curves of the strings of solar panels. IV curves may be compared and analyzed to evaluate performance of and detect problems with a string of solar panels.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/053,784, filed on Mar. 22, 2011, which is incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    The invention described herein was made with Governmental support under contract number DE-FC36-07GO17043 awarded by the United States Department of Energy. The Government may have certain rights in the invention. 
     
    
     TECHNICAL FIELD 
       [0003]    Embodiments of the subject matter described herein relate generally to solar cells. More particularly, embodiments of the subject matter relate to generation and analysis of solar cell current-voltage (IV) curves. 
       BACKGROUND 
       [0004]    Solar cells, also known as “photovoltaic cells,” are well known devices for converting solar radiation to electrical energy. They may be fabricated on a semiconductor wafer using semiconductor processing technology. A solar cell includes P-type and N-type diffusion regions. Solar radiation impinging on the solar cell creates electrons and holes that migrate to the diffusion regions, thereby creating voltage differentials between the diffusion regions. In a backside contact solar cell, both the diffusion regions and the metal contact fingers coupled to them are on the backside of the solar cell. The contact fingers allow an external electrical circuit to be coupled to and be powered by the solar cell. 
         [0005]    A solar cell may be characterized by its IV curve, which is a plot of the solar cell&#39;s output current for a given output voltage. The IV curve is indicative of the performance of the solar cell.  FIG. 1  shows example IV curves of a solar panel, which comprises a plurality of interconnected solar cells mounted on the same frame. The IV curves of  FIG. 1  show current-voltage characteristics with dependence on solar insolation and temperature of the solar panel. 
         [0006]    Solar cell IV curves of a solar panel may be manually generated by technicians using appropriate test equipment. Typically, a technician may measure output current and voltage of a solar panel to get IV curves for the solar panel for that particular time of day. To generate IV curves for a new solar installation, which may comprise hundreds of solar panels, several technicians are needed for several days. After installation, new IV curves for the solar installation may need to be periodically generated to verify the performance of the solar panels in accordance with contractual obligations. The new IV curves are again manually generated by technicians. 
       BRIEF SUMMARY 
       [0007]    A method of automatically generating and analyzing solar cell current-voltage (IV) curves is disclosed. The method comprises sensing current generated by a first string of solar panels in a plurality of strings of solar panels, each string of solar panels in the plurality of strings of solar panels comprising a plurality of serially-connected solar panels, each solar panel in the plurality of serially-connected solar panels comprising a plurality of serially-connected solar cells mounted on a same frame, and sensing current generated by a second string of solar panels in the plurality of strings of solar cells, wherein sensing current in the first and second strings of solar panels comprises sensing current with a sensing device comprising a first field sensor adapted to sense current in the first string of solar panels and a second field sensor adapted to sense current in the second string of solar panels. 
         [0008]    A sensing device is also disclosed. The sensing device comprises a first current sensor adapted to non-invasively detect the current of a wire, a second current sensor adapted to non-invasively detect the current of a wire, a control device adapted to control the first and second field sensors, and a communications port controlled by the control device and adapted to receive and transmit signals and to receive power, wherein the first and second field sensors are powered by power from the communications port. 
         [0009]    A photovoltaic panel string monitoring system is also disclosed. The system comprises a first string of solar panels comprising a plurality of solar panels connected in series, a second string of solar panels comprising a second plurality of solar panels connected in series, a combiner box connecting the first and second strings of solar panels, and a sensing device comprising first and second current sensors, the first current sensor adapted to determine a first current in the first string of solar panels and the second current sensor adapted to determine a second current in the second string of solar panels. 
         [0010]    These and other features of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A more complete understanding of the subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
           [0012]      FIG. 1  schematically shows example IV curves of a solar panel. 
           [0013]      FIG. 2  schematically shows a photovoltaic (PV) system in accordance with an embodiment of the present invention. 
           [0014]      FIG. 3  schematically shows a PV string in the PV system of  FIG. 2 , in accordance with an embodiment of the present invention. 
           [0015]      FIG. 4  schematically shows a data collection and control computer in the PV system of  FIG. 2 , in accordance with an embodiment of the present invention. 
           [0016]      FIG. 5  shows a flow diagram of a method of automatic generation and analysis of solar cell IV curves in accordance with an embodiment of the present invention. 
           [0017]      FIG. 6  schematically shows a string current monitor block in accordance with an embodiment of the present invention. 
           [0018]      FIG. 7  schematically shows a diagram of a string current monitor block in accordance with an embodiment of the present invention. 
           [0019]      FIG. 8  schematically shows current field sensors in accordance with an embodiment of the present invention. 
           [0020]      FIG. 9  schematically shows a plurality of strings of solar panels and a string current monitor block in accordance with an embodiment of the present invention. 
           [0021]      FIG. 10  shows a flow diagram of a method of automatic generation of solar cell IV curves in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    In the present disclosure, numerous specific details are provided, such as examples of apparatus, components, and methods, to provide a thorough understanding of embodiments of the invention. Persons of ordinary skill in the art will recognize, however, that the invention can be practiced without one or more of the specific details. In other instances, well-known details are not shown or described to avoid obscuring aspects of the invention. 
         [0023]    Techniques and technologies may be described herein in terms of functional and/or logical block components and with reference to symbolic representations of operations, processing tasks, and functions that may be performed by various computing components or devices. Such operations, tasks, and functions are sometimes referred to as being computer-executed, computerized, software-implemented, or computer-implemented. In practice, one or more processor devices can carry out the described operations, tasks, and functions by manipulating electrical signals representing data bits at memory locations in the system memory, as well as other processing of signals. The memory locations where data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties corresponding to the data bits. It should be appreciated that the various block components shown in the figures may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of a system or a component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. 
         [0024]    “Coupled”—The following description refers to elements or nodes or features being “coupled” together. As used herein, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically. Thus, although the schematic shown in  FIG. 7  depicts one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the depicted subject matter. 
         [0025]      FIG. 2  schematically shows a photovoltaic (PV) system  200  in accordance with an embodiment of the present invention. In the example of  FIG. 2 , the PV system  200  includes a plurality of PV strings  210 , a PV inverter  220 , and a data collection and control computer  201 . 
         [0026]    A PV string  210  may comprise a plurality of solar panels that are electrically connected in series. The direct current (DC) output of the PV string  210  is electrically coupled to a device that presents a DC load to the PV strings  210 . In the example of  FIG. 2 , that device is the PV inverter  220 , which converts the DC output of the PV strings  210  to sinusoidal alternating current (AC). The AC output of the PV inverter  220  may be applied to a power grid or power distribution of a customer structure (e.g., residential, commercial, industrial), for example. A PV string  210  may include a controller  211  configured to monitor and control solar panels in the string and to communicate with other components of the PV system  200 . In one embodiment, a PV string  210  wirelessly communicates with the PV inverter  220  over a wireless mesh network. A PV string  210  may also communicate with the PV inverter  220  over other types of communications networks without detracting from the merits of the present invention. 
         [0027]    The computer  201  may comprise a computer configured to collect operational data from the PV system  200  including electrical current, voltage, temperature, solar insolation, and other information indicative of the performance and operational status of the PV system  200 . The PV inverter  220  may include a communications module  221  for communicating with components of the PV system  200 , including combiner boxes  212  (see  FIG. 3 ), controllers  211 , and the computer  201 . The PV inverter  220  may communicate with the computer  201 , combiner boxes  212 , controllers  211 , and other components of the PV system  200  over a wired or wireless computer network, which includes the Internet. 
         [0028]      FIG. 3  schematically shows a PV string  210  in accordance with an embodiment of the present invention. In the example of  FIG. 3 , the PV string  210  includes a combiner box  212  and a plurality of solar panels  214 . A controller  211  and environment sensors  216  allow for monitoring and control of the PV string  210 . 
         [0029]    A solar panel  214  comprises electrically connected solar cells mounted on the same frame. In one embodiment, each solar panel  214  comprises a plurality of serially-connected backside contact solar cells  215 . Only some of the backside contact solar cells  215  have been labeled in  FIG. 3  for clarity of illustration. Other types of solar cells, such as front contact solar cells, may also be employed. 
         [0030]    Each PV string  210  comprises a plurality of serially-connected solar panels  214  coupled to a combiner box  212 . The output of the PV string  210  is electrically connected to the PV inverter  220  by way of the combiner box  212 . The output voltage of the PV string  210  may thus be sensed by a voltage sensing circuit at the PV inverter  220 . 
         [0031]    In the example of  FIG. 3 , the combiner box  212  includes sensor circuits  213 . The sensor circuits  213  may comprise electrical circuits for sensing the amount of electrical current flowing through the solar panels  214  of the PV string  210  (and hence the output current of the PV string  210 ) and for sensing the output voltage of the PV string  210 . The sensor circuits  213  may be implemented using conventional current and voltage sensing circuits. The sensor circuits  213  may be located in the combiner box  212  or integrated with a solar panel  214 . The sensor circuits  213  may transmit current and voltage readings to the controller  211  of the PV string  210  over a wired or wireless connection. In another embodiment, the output voltage of a PV string  210  is directly sensed at the PV inverter  220 . 
         [0032]    The environment sensors  216  may comprise an irradiance sensor and/or temperature sensor. The environment sensors  216  are shown collectively as outside the solar panels  214 . In practice, an environment sensor  216  may be located in individual solar panels  214  or a location representing the PV string  210 . 
         [0033]    An irradiance sensor senses the amount of solar irradiance of insolation on one or more solar panels  214 . The irradiance sensor may comprise a plurality of solar cells separate from those of the solar panels  214 . The output current of the irradiance sensor solar cells is indicative of the amount of solar insolation on the panel, and is sensed by an associated electrical circuit and provided to the controller  211 . An irradiance sensor may be mounted on individual solar panels  214  or a location representative of the location of the PV string  210 . 
         [0034]    The environment sensors  216  may also comprise a temperature sensor. The output of the temperature sensor is indicative of the temperature of a solar panel  214  or a location of the of the PV string  210  where the temperature sensor is located. The output of the temperature sensor may be provided to the controller  211 . 
         [0035]    The controller  211  may comprise control circuits, such as a maximum power point optimizer, and communication circuits for sending and receiving data between components of the PV string  210  and the PV system  200  in general. The controller  211  may receive sensor outputs from the sensor circuits  213  and environment sensors  216  over a wired or wireless connection. The controller  211  is configured to communicate the sensor outputs to the communications module  221  of the PV inverter  220 , which provides the sensor outputs to the computer  201 . 
         [0036]      FIG. 4  schematically shows a data collection and control computer  201  in accordance with an embodiment of the present invention. The computer  201  may have less or more components to meet the needs of a particular application. The computer  201  may include a processor  401 , such as those from the Intel Corporation or Advanced Micro Devices, for example. The computer  201  may have one or more buses  403  coupling its various components. The computer  201  may include one or more user input devices  402  (e.g., keyboard, mouse), one or more data storage devices  406  (e.g., hard drive, optical disk, USB memory), a display monitor  404  (e.g., LCD, flat panel monitor, CRT), a computer network interface  405  (e.g., network adapter, modem), and a main memory  408  (e.g., RAM). The computer network interface  405  may be coupled to a computer network, which in this example includes the Internet. 
         [0037]    The computer  201  is a particular machine as programmed with software components  410  to perform its function. The software components  410  comprise computer-readable program code stored non-transitory in the main memory  408  for execution by the processor  401 . The software components  410  may be loaded from the data storage device  406  to the main memory  408 . The software components  410  may also be made available in other computer-readable medium including optical disk, flash drive, and other memory device. The software components  410  may include data collection and control, logging, statistics, plotting, and reporting software, 
         [0038]    In one embodiment, the computer  201  is configured to receive data from the communications module  221 , controller  211 , and/or other components of the PV system  200 . The computer  201  may receive sensor data from the PV strings  210  directly or by way of the inverter  220 . The sensor data may include output current of a PV string  210 , output voltage of a PV string  210 , and environmental conditions (e.g., temperature, solar insolation) of a PV string  210 . 
         [0039]    The computer  201  may be configured to control the DC load presented to the PV strings  210 . For example, the computer  201  may be configured to send a control signal to the inverter  220  such that the inverter  220  presents a particular DC load to the PV strings  210 . A PV string  210  changes its output current based on to the DC load presented to it. By varying the DC load presented by the inverter  220 , and receiving data indicating the corresponding output current and voltage generated by the PV string  210  for particular DC loads, the computer  201  is able to plot IV curves for the PV string  210  under various conditions and for different output current and voltage levels. 
         [0040]      FIG. 5  shows a flow diagram of a method  500  of automatic generation and analysis of solar cell IV curves in accordance with an embodiment of the present invention. The method  500  is explained using the PV system  200  as an example. As can be appreciated, the method  500  may also be employed in other solar cell installations with a relatively large number of solar panels. The steps of the method  500  may be repeatedly performed to allow for real-time monitoring of the PV system  200 . 
         [0041]    The method  500  includes sensing the output voltage (step  501 ) and corresponding output current (step  502 ) and insolation (step  506 ) of a PV string  210  in the PV system  200 . The output current of the PV string  210  may be sensed by a current sensing circuit installed in a combiner box  212  or integrated in a solar panel  214 . Similarly, the output voltage of the PV string  210  may be sensed by a voltage sensing circuit installed in the combiner box  212  or integrated in a solar panel  214 . The output voltage of the PV string  210  may also be sensed at the PV inverter  220 . Various output voltage-current pairs may be sensed over a relatively long period of time, or by varying the DC load presented to the PV string  210 . Each current and voltage measurement may include solar insolation for that measurement. 
         [0042]    The sensor data indicating the sensed output voltage, current, and solar insolation of the PV string  210  may be received by a controller  211  in the PV string  210 , and then transmitted to the computer  201  directly or by way of the PV inverter  220 . Sensor data for a particular PV string  210  may be collected periodically in real-time, such as every few minutes. The sensor data may include additional information, such as time and date stamps indicating when the output voltage and current were sensed and environmental conditions (e.g., solar insolation and temperature) at the time the output voltage and current were sensed. 
         [0043]    The computer  201  may periodically receive sensor data of each of the plurality of PV strings  210 . The computer  201  may generate IV curves for each PV string  210  using the sensor data (step  503 ). The IV curves may indicate output voltages, corresponding currents for particular PV strings  210 , and dependence factors, such as corresponding solar insolation and/or temperature of the PV strings  210 . As a particular example, each IV curve for a particular PV string  210  may indicate current and voltage at a solar insolation. The IV curves may be generated for sensor data taken over a period of time, such as over a week, month, or year. The sensor data for generating IV curves may be filtered based on collected solar insolation and/or temperature data. For example, the sensor data may be filtered such that only sensor data taken at particular solar insolation and/or temperature are used to generate IV curves. 
         [0044]    In one embodiment, IV curves generated from sensor data are employed to evaluate the performance of a PV string  210  in real-time (step  504 ). For example, the computer  201  may compare an IV curve having recent current-voltage data against a baseline IV curve or a reference IV curve to determine if the PV string  210  meets performance standards. The baseline IV curve may be the IV curve of the PV string  210  as originally installed and the reference IV curve may be dictated by contractual requirements. The IV curve comparison may indicate whether the PV string  210  is degrading, e.g., lower output current at a particular output voltage, or still meets expected performance standards. Automatically sensing output voltages, output currents, and corresponding environmental conditions, and then automatically generating corresponding IV curves advantageously allow for evaluation of the performance of the PV string  210  in real-time. By comparing recent and past IV curves of the PV string  210 , performance degradation trends may be detected before the degradation becomes a full blown failure. 
         [0045]    In one embodiment, IV curves generated from sensor data are employed to detect and troubleshoot PV string failures (step  505 ). For example, the computer  201  may analyze a recent IV curve to detect a present or pending open circuit or short circuit condition. A short circuit condition is characterized by an IV curve where an output voltage is low for a corresponding high output current. A short circuit condition indicates that there is a short in the PV string  210  (e.g., a solar panel  214  is shorted or developing a short). An open circuit condition is characterized by an IV curve where an output voltage is high for a corresponding low output current. An open circuit condition indicates that the series connection of the solar panels  214  in the string is open. The threshold for low or high current or voltage may be set for particular installations. The computer  201  may compare current-voltage pairs of an IV curve to thresholds to determine if the PV string  210  presently or will soon have a short circuit condition or open circuit condition. 
         [0046]      FIG. 6  illustrates an embodiment of a string current monitor block for use with PV system  200 , described above. Unless otherwise described below, numerical indicators refer to similar components and elements described above. The sensor or sensor circuits  213  can include an embodiment of the string current monitor block, such as illustrated here. With additional reference to  FIG. 7 , the sensor  213  can include a printed circuit board (PCB)  250  supporting a plurality of current sensors  255 . The current sensors  255  can be connected to or coupled to a microcontroller  260 . The microcontroller  260  can also interoperate with, and the sensor  213  can also include, communication ports  270 , a power source  275 , and a sensor power switch  280 , as well as other modules or processor devices such as a temperature sensor  299 , or others not illustrated, such as memory devices, an analog-digital (A/D) converter, a translator device, an A/D converter reference, and so on. In certain embodiments, such as the illustrated embodiment of  FIG. 7 , one or more of such devices can be integrated, such as the microcontroller  260  which includes an A/D converter and communications module appropriate for receiving and providing signals using the communications ports  270 . 
         [0047]    The current sensors  255  can include Hall Effect field sensors adapted with sufficient sensitivity to determine current in a wire from a string of solar panels  210 . There can be more than one current sensor  255  on each sensor  213 , such as the twelve current sensors  255  illustrated in  FIG. 6 , and each current sensor  255  can be coupled to the microcontroller  260 . In one embodiment, there is a current sensor  255  for each string of solar panels  210  which is connected in the combiner box  212 , the sensor  213  additionally positioned within the combiner box  212 . Therefore, as few as two current sensors or as many sensors as there are strings of solar panels, without limit, can be present on the sensor  213 . The current sensors  255  can measure current in a wire associated with the current sensor  255  in a non-invasive manner, such as by not penetrating the wire. A Hall Effect field sensor can accomplish such a measurement. 
         [0048]    A current sensor  255 , like any of the sensors or sensing devices described herein, can provide to the microcontroller  260  any of a variety of signals, such as a voltage signal or a communications signal, which conveys information regarding the current being measured. Thus, for example, in one embodiment, the current sensor  255  can provide to the microcontroller a voltage level which is indicative of the current being measured by the current sensor  255 . In such an embodiment, the voltage signal can be converted to a current measurement either by the microprocessor  260  or by another device to which the voltage level is provided. In another embodiment, the current sensor  255  can provide a signal which conveys a direct measurement of the current being measured by the current sensor  255 . 
         [0049]      FIG. 8  illustrates an example of wires  258  passing through a first  255  and second  256  current sensor, where the sensors are Hall Effect field sensors. By measuring the magnetic field surrounding the wires  258 , the electric current flowing through the wires  258  can be separately determined by each of the first and second current sensors  255 ,  256  for each of the individual wires. There is no need for a direct electrical connection to the current in the wire to measure the current. 
         [0050]    With reference again to  FIGS. 6 and 7 , the microcontroller  260  is shown as a single device integrated with an A/D converter, although the functions can be performed by different devices or modules in other embodiments. The microcontroller  260  can include a processing element, as well as digital memory storage, communications devices, or other elements or devices necessary to perform the functions described herein. Although the microcontroller  260  is illustrated coupled to various different elements of the sensor  213 , such as the communications ports  270  and current sensors  255 , in embodiments, the different components of the sensor  213  can be interconnected and coupled together in any manner which enables practice of the functions described herein. 
         [0051]    Thus, the microcontroller  260  can, through coupling to the communications port  270 , receive signals from the controller  211 , inverter  220 , or other device which controls the sensor  213 . The microcontroller  260  can also provide response signals through the communications port  270 , therefore enabling the sensor  213  to respond to a command from a remote controlling device to energize the current sensors  255 , sense the current of one or more wires passing through the current sensors  255 , and send a signal communicating the measurement to the remote controlling device. Additionally, the communications port  270  can be coupled to a power source  275  of the sensor  213 . The power source  275  can be controlled by the microcontroller  260  to operate the various components of the sensor  213  using power received through the communications port  270 . One such communications port can be a RS-485 connector, though other ports receiving power during communication can be used. Thus, in certain embodiments, the power source  275  can be coupled to a sensor power switch  280  for providing power from the communications port  270  to each current sensor  255 . In certain embodiments, the sensor  213  can be arranged such that power, including electrical power, is supplied to each current sensor  255  simultaneously, whereas in other embodiments, power can be selectively supplied to each of the individual current sensors  255 . 
         [0052]      FIG. 9  illustrates an embodiment of the sensor  213  coupled to the controller  212 . The sensor  213  is positioned such that wires  295  from each string of solar panels  210  passes through a current sensor  255 . As shown, twelve current sensors  255  can be used with twelve strings of solar panels  210 , where each string of solar panels  210  is combined in a combiner box. By powering the sensor  213  from a communications port, the sensor  213  can simultaneously determine the current through each of twelve strings of solar panels  210 , increasing the ease of automation of IV curve generation. Moreover, because the power used to operate the sensor  213  can come from a communications line connected to one or more of the communications ports  270 , a separate power line from either a PV string or the controller  212  is not necessary. In this way, multiple sensors can be powered from a single communications and control device, such as the controller  212 . 
         [0053]      FIG. 10  illustrates a flowchart of a method for using a sensor, such as sensor  213 , to automatically generate IV curves. The various tasks performed in connection with process  600  may be performed by software, hardware, firmware, or any combination thereof. For illustrative purposes, the following description of process  600  may refer to elements mentioned above in connection with  FIGS. 6-9 . In practice, portions of process  600  may be performed by different elements of the described system, e.g., current sensor  255 , microcontroller  260 , or communications port  270 . It should be appreciated that process  260  may include any number of additional or alternative tasks, the tasks shown in  FIG. 10  need not be performed in the illustrated order, and process  600  may be incorporated into a more comprehensive procedure or process having additional functionality not described in detail herein. 
         [0054]    One method of using a sensor, such as sensor  213  described above with reference to  FIGS. 6-9  can be in response to receiving  610  a control signal using or with a communications port  270  of the sensor  213 . In response, the microcontroller  260  or other control device can operate at least a first  620  and second  622  current sensor to sense the current in respective first and second strings of solar panels, or solar strings. In certain embodiments, the first and second current sensors  255  can be powered by power received through the communications port  270  of the sensor  213 . 
         [0055]    In some embodiments, it may be sufficient to determine only the IV curve of the first string of solar panels. In such an embodiment, the voltage of the first string of solar panels can also be measured  630 . The solar insolation of the first string of solar panels can additionally be determined. From this information, a first IV curve can be determined  650  and communicated  660  via a response signal using the communications port  270 . In certain embodiments, the IV curve need not be determined, and all sensed information can be directly reported, such as current information from the sensor  213 , to a controller, including the controller  212 , and the IV curve determined remotely. 
         [0056]    In certain embodiments, after performing current sensing steps  620 ,  622 , the second string of solar panels can have its voltage sensed  632  and solar insolation sensed  642  independently from the first solar string. This information can be used to generate 652 a second IV curve independent from the first IV curve. In such embodiments, the IV curves can be reported together in step  660 . In some embodiments, however, the sensed information from each or any of steps  622 ,  632 , and/or  642  can be provided via a communications signal to the controller  212 . In this way, the sensor  213  can either provide the IV curve directly or information which can be coordinated with other inputs, such as the voltage and/or solar insolation information to determine an IV curve. 
         [0057]    Methods and apparatus for automatic generation and analysis of solar cell IV curves have been disclosed. While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.