Seeing Heat: What Can We Learn Using Thermal Imaging on Solar Sites?

Thermography has become an essential diagnostic tool in solar PV operations and maintenance, providing technicians with a glimpse into problems often invisible to the naked eye. This powerful inspection method is so effective at revealing critical electrical issues that it’s specifically required by the NFPA 70B Standard. Using thermal imaging cameras, O&M professionals can quickly scan vast arrays of modules to identify anomalies before they escalate into costly failures or safety hazards – issues that would otherwise require extensive manual testing.

In this short excerpt from the NFPA 70B: A New Standard for Electrical Equipment Maintenance course, HeatSpring instructor Brian Mehalic explores thermal imaging in solar applications and how this technology helps maintenance teams pinpoint module performance and safety issues. From detecting offline strings and short circuits to identifying failed bypass diodes and damaged cells, thermography offers invaluable insight into PV system health that changes how we approach solar maintenance.

Transcript and photos below.

 So diving into some of those things, we can see with the thermal camera, we can see hot cells on individual modules.

We can see strings and sections of modules that are offline. In that image on the bottom left there, you can see several strings of modules that are all hotter than everything else. Modules that are not operating appear hotter than the modules around them. 

You can also see a couple of smaller, narrower subsections of modules that are hotter and those are not operating as well. In fact, there we have bypass diodes conducting, which may be because there’s an issue with the module or it may be because a bypass diode is doing its job. 

What is that? It’s to route current around parts of modules that are shaded, soiled, or perhaps damaged to prevent overheating them. We can clearly see those individual sections, usually one third of a module that’s not operating.

We can see that patchwork pattern we saw in the previous slide. This is characteristic of a short-circuited string of modules, where we have a looping current in there and all of the cells are kind of lighting up at different levels based on how much of that current they can or cannot pass in that short circuit.

Drilling down further, I talked about those bypass diodes that we could see thirds of a module or sections of a module is not conducting. Here, you can actually see the bypass diode in the junction box on the back of the module itself warming up and giving off heat because it is passing current through it instead of that third of the module that’s being bypassed.