The short answerA drone thermal inspection photographs the solar system with a thermal camera while it is generating. A faulty panel heats differently from its surroundings, so faults can be found across a large area without going panel by panel.
A solar system can lose output with no sign visible to the eye. A faulty cell, a failed diode or a disconnected string looks like any other panel from the outside, but they stand out in a thermal camera.
What does the inspection reveal?
| What the image shows | What it may be |
|---|---|
| A small hot spot in one cell | A faulty cell, a crack or local dirt |
| One third of a panel hotter | A bypass diode problem |
| A whole panel hotter | A panel that is disconnected or not properly connected |
| A whole row of hot panels | A disconnected string |
| A hot pattern at the bottom of panels | Dirt build-up, among other causes |
Important: the image points to a suspect, and the final diagnosis is made on site by whoever maintains the system.
Why use a drone?
- Area. In a large facility, checking every panel by hand takes a long time.
- Precise location. A University of Messina study describes a flight with a GNSS RTK receiver that links each thermal image to a location, in order to locate faulty modules.
- Safety. High roofs can be viewed without climbing onto them.
Under what conditions is the inspection reliable?
Thermal differences appear when the system is generating, so shooting conditions determine the quality of the result:
- Sufficient irradiance. IEC TS 62446-3, the standard for thermographic inspection of PV systems, requires at least 600 watts per square metre on the module surface.
- Stable skies. Passing clouds change the output in the middle of the shoot.
- Moderate wind. Strong wind cools the panels and reduces the differences.
- A running system. Make sure the system is connected and generating during the flight.
- Resolution and angle. Flight height and camera angle affect what can be detected, and sun reflections.
What should a good report contain?
- A map of the facility marking every finding.
- A thermal image and a regular image of each finding.
- Classification by type and severity, to prioritise repairs.
- Shooting conditions: date, time and weather.
- A list the maintenance team can work from.
When choosing a provider, ask to see a sample report. A good report is worth more than beautiful images.
When should you inspect?
- After installation, as a baseline before handover.
- When output has dropped and it is not clear why.
- Before a warranty period ends, while repairs can still be demanded.
- After an event such as a storm or hail.
- As part of periodic maintenance, according to your maintenance plan.
What about wind turbines and designing new systems?
The same drone also serves for integrity checks and surveys of wind turbines, and for survey and 3D modelling of a site before designing a photovoltaic system. All of this is on the energy services page.
