Thermal hotspots over PV module after thermal imaging! What to do?
Well, a quick visual inspection of these modules can eliminate some obvious possibilities of soiling, shadows, glass cracks, burnt connectors, back sheet bulging, browning etc. What if there are no visual signs? Very often field technicians measure Voc and Isc of the suspected modules to classify them as faulty or not. Is this enough to conclude the module health condition?
Here is a unique case wherein thermal hotspot over module recorded severe electrical degradation:
An interesting phenomenon was observed by AirProbe team while inspecting one of the 2-year-old utility solar PV site.
Underperforming blocks were targeted for root cause analysis of degradation. Visually all the modules in the block appeared healthy. Local O&M had performed rigourous cleaning and multi meter tests over modules to understand the primary cause, the problem persisted. AirProbe team took this as a challenge to determine the root cause.
The thermal image of several tables (as in fig below) reflected multi cell hotspots over PV modules. Moreover, the Voc and Isc of the modules appeared to be same and normal. Interestingly, the Vmp values were unexpectedly lower dropping down the power output of the module. The electrical mismatch in the solar cells were so severe that the overall string operation was affected. Further, these modules were randomly spread across the site in series with healthy modules, that effectively brought down the system performance. Note that the bypass diodes are not activated!
In general, O&M teams at the site perform Voc and Isc tests over modules and conclude on the positive health conditions of the module leaving such faults unnoticed! This is where 100% thermal imaging using drones provides a complete clarity over module health with speeds as high as 20-30 MW scan per day. Further IV tracing of affected modules can pin point the electrical degradation cause and corrective actions such as replacement, warranty / insurance claims could be made accordingly.
We through AirProbe wish to bring this technology transformation for efficient O&M in solar industry. Do get in touch with us for more knowledge sharing interactions over PV performance improvements - www.airprobe.in
Thanks to local O&M site associates site for the support during the inspection.