Two tools—an infrared thermometer and a pyranometer—are indispensable for accurately predicting a PV array’s production. An infrared thermometer (from $50) can take the array’s temperature with fairly accurate results. Its laser pointer helps to aim for measuring an object’s infrared (IR) energy, which is translated into a corresponding temperature and displayed on the thermometer. Infrared thermometers are also called IR thermometers, laser thermometers, noncontact thermometers, or temperature guns. The reflection from a module’s glass surface may interfere with an IR thermometer’s accuracy since it has a relatively low emissivity. When possible, take the measurement on the back of the module, which has an emissivity approaching 1, closer to the default settings on most basic IR thermometers.
A pyranometer (about $135 for a simple handheld unit) measures how much sunlight is hitting the site. Most use the electricity generated by a small, internal, and calibrated PV cell to measure the sun’s irradiance. Although this tool is costly, it’s a worthy troubleshooting tool for the pro, as it can be very difficult to predict PV performance without one.
IV curve tracers are becoming more widely available, and used for troubleshooting and commissioning. They analyze the voltage, power, and current characteristics of PV modules in real-world conditions. They can find and verify underperforming modules and series strings relatively quickly and easily. However, with a nearly $3,000 price tag, they are mostly used by larger PV companies and other professionals.
Infrared cameras (also known as IR cameras and thermal imaging cameras) can be helpful in finding and verifying trouble spots within PV arrays, wiring, and modules. Like IR thermometers, they read infrared energy to show the temperature of different objects in the field of view, and then display the heat differences as a colored image. High-resistance areas will heat up (in wire connections, within modules, etc.) and can show up as “hot spots,” making locating trouble areas fairly straightforward. But IR cameras require training to use effectively and with basic models starting at $1,000, they are also mostly for professional use.