Performance Testing

Our performance testing crew will ensure that you get a complete and accurate analysis of your entire pv system.  Using the Sol-Metric I-V Curve Testing equipment, we can detect and anyalyze any performance loss in your solar system.  We will submit a complete data analysis which includes a performance percentage of each string.  A report will also be included as to any suggestions or recommendations to improve performance of your pv system. Our PE Electrical Engineer will review all findings and will issue a professional report of solar array performance.

I-V Curve Measurement and the Solmetric PV Analyzer

The I-V curve (current versus voltage) represents all possible operating points of a PV module, string or array at existing environmental conditions. The curve starts at the short circuit current and ends at the open circuit voltage. The maximum power point, located at the knee of the I-V curve, is the operating point that delivers the highest output power. It is the job of the inverter’s maximum power point tracking circuit (MPPT) to find that point as irradiance and temperature change. The PV (photovoltaic) curve (power versus voltage) is zero at either end and a maximum at the knee of the I-V curve. Any impairments that affects the shape of the I-V curve will reduce the peak power value and diminish the value of the array.

What is the background of I-V curve tracing in the PV industry?

I-V curve tracing has been used for decades in PV R&D, manufacturing, and field testing. It is the most comprehensive measurement that can be performed on a PV module, string or array. Today, it is the availability of an affordable, compact, rugged, and easy to use curve tracer that has changed the game in PV system testing. The Solmetric PV Analyzer allows the user to compare the measured I-V curve with the predictions of built-in PV models, giving immediate indication of the health of the array. The companion Data Analysis Tool makes quick work of analyzing and displaying the test results for kilowatt to multi-Megawatt PV projects. Some PV Analyzer users have adopted this test method to reduce their test times, others to gain deeper insight into PV system performance. Together, these are a winning combination.

What are the benefits of I-V curve tracing?

Reduced test time

I-V curve tracing measures array performance with a single electrical connection at each combiner box, and a single measurement per string. After isolating the combiner box from the rest of the array and lifting the string fuses, the curve tracer is connected to the combiner box buss bars. One at a time, the fuses are inserted and the strings measured. Data is saved electronically. A single I-V curve sweep by the PV Analyzer takes less than a quarter of a second, and the cycle time including saving of data takes less than 15 seconds per string. There is no need to return to the array again later to measure operating current on each string, because the I-V measurement has already determined the maximum power and the maximum power current and voltage.

No need to bring the inverter on-line to test PV string performance

Traditional test methods required the inverter to be brought on-line in order to measure the operating current of each string under load. I-V curve tracing eliminates this requirement by measuring the performance of each PV string under all load conditions. This means you test the array once, earlier in the project, avoiding the long wait to bring the inverter on-line.

Reduced start-up and commissioning risk

Testing the array before the inverter is brought on-line means less risk of array-side problems showing up during start-up or commissioning.

More detailed measurement results

I-V curve tracing is the most comprehensive test possible for PV arrays. In addition to measuring the short circuit current and open circuit voltage, it uniquely measures the maximum power point of each string. In fact, the PV Analyzer measures 100 points along the I-V curve. With this resolution, the measurement can detect more physical effects that may be degrading the performance of the system. The PV Analyzer uses a sophisticated PV model to predict what the shape of the I-V curve should be, taking into account the existing irradiance, module temperature, module brand and part number, the sun’s incident angle, wire length and gauge, and so on. Any deviation in the shape of the I-V curve compared with the on-screen model gives important clues to the nature of the impairment for troubleshooting purposes.

Efficient data management

I-V curve measurement data is saved electronically, eliminating data recording errors. The Solmetric I-V Data Analysis tool automatically produces a family of displays of array performance across a population of measurements, making it easy to visually demonstrate that PV strings are performing consistently and in line with expectations. If performance issues exist, the tool quickly draws attention to the problem strings.

Detailed performance baseline

PV arrays are extremely robust and reliable but performance does gradually degrade. Occasionally a module will fail. I-V curves captured and stored at start-up or commissioning time give you a detailed baseline against which to compare future measurements over the life cycle of the PV system. Module degradation and failures are easily measured and documented, facilitating module warranty claims. Questions of workmanship or claims about problems dating back to installation time are easily resolved by referring to baseline data. Taken as a whole, these advantages reduce the costs and risks associated with PV system construction and testing, and provide a baseline for ongoing maintenance.

More efficient troubleshooting

Curve tracing is an invaluable tool when troubleshooting PV strings, detecting excess series resistance, low shunt resistance, module mismatch, or shorted bypass diodes directly from the shape of the I-V curve. To find a bad module in a string, just measure the string repeatedly with a different module shaded in each instance. All of the measured curves will look alike except for the one in which the failed module was shaded. The Solmetric PV Analyzer has features that these analysis techniques easy.

Why is the Solmetric PV Analyzer (PVA) the best choice for measuring I-V curves?

The Solmetric PV Analyzer combines an affordable, compact, fast, and easy-to-use I-V curve measurement tool with built-in PV performance modeling and STC translation capability, allowing users to immediately determine whether a PV module or string is performing to its potential. If it is not, the shape of the I-V curve provides critical information about potential causes of the performance problem. Advanced data analysis tools make fast work of analyzing data and generating reports for system stakeholders. And if it is ever needed, responsive technical and application support is at your service. The Solmetric PV Analyzer is also specifically designed to accurately measure high-efficiency PV modules, allowing time for the charge distribution in the modules to shift as the load voltage changes, to avoid distortion of the I-V curve.