An irradiance level At least 600 W/M2 is needed to inspect Solar PV. This is the amount of energy falling on the surface of the modules, therefore any metering equipment should be placed in the same plane.
You can of course obtain some thermal patterns at lower irradiance, but to be able to fully check for all anomalies such as junction box failures for example, then the module has to be ‘working hard’ and producing a sufficient amount of energy.
Does this mean inspections should only be in the hot summer months? NO! PV modules work very well when they’re cooler, and they will often provide some of their peak outputs during cold sunny days. There are often many days in the UK during early spring or late autumn which are very good for PV production and therefore thermal inspections.
The displayed graph shows a good day in FEB where there was >600w/m for most of the day.
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