Use of thermal imaging cameras in photovoltaic systems

Photovoltaic systems should do their job for decades. Unfortunately, the aging process leads to various defects and even partial failures. Many of these defects can be traced back to the boom times of solar systems. Less qualified personnel on duty led to consequences that can still be felt today - from insufficient solar yields and processing errors to safety and fire risks. But a lightning strike can also cause defects. Thermal imaging cameras are used to detect irregularities quickly and easily. Thermal imaging cameras quickly locate thermal abnormalities so they can be resolved.

Inspection of a photovoltaic system

Photovoltaic systems are checked easily, quickly and efficiently using thermal imaging cameras. During operation, thermal irregularities are identified that indicate defects.

It is important that the solar system is in operation and converts solar energy, otherwise the individual modules will not heat up. The guide value is 50% of the nominal power.

Normal findings

Benign irregularities are called normal findings. There are white spots on the thermal imaging camera display. These are screw connections, basic structures of the system and also connection boxes (usually connected to the back of the system). Normal findings should be ignored in the analysis.

Hot spots and defects

Hot spots and defects are detected through the thermal imager's ability to sense temperature differences. A thermal sensitivity of 100 mK is sufficient for this. The thermal sensitivity describes the smallest temperature difference that can be perceived with the camera.

There will always be some minor thermal differences. However, as soon as larger differences are visible, deviations of 2 K, the said point should be examined more closely.

In the case of defects, the total resistance of the cell sometimes increases. The cells are placed in series to output a high voltage. As a result, the same current flows through all cells. In the defective cell, the increased resistance leads to heating, making the defect clearly visible on the thermal imaging camera.

Defects can also be caused by lightning. The bypass iodes are destroyed in the process. They are visible on the IR images due to strong heating.

Hot spots indicate hot spots in the silicon semiconductor. They become punctiform, in the "measles" pattern, visible on the thermal imaging camera.

Handling of the device

For the simple thermal requirement of an inspection of photovoltaic or solar modules, one can disregard the sometimes high range of functions of the thermal imaging cameras.

It is important that the emission coefficient is set on the thermal imaging camera and adapted to the object to be examined. This describes how much heat an object emits compared to a black body (idealized material that perfectly absorbs and reflects heat).

The FOV (field of view) plays an equally important role. It describes the section that a camera can record from its surroundings. Devices that have a small FOV are more suitable for small objects with large distances and vice versa.

Purchasing a thermal imaging camera

When buying a thermal imaging camera, make sure that you have a large field of view. This allows you to control large modules at close range. The camera also has to cover a high temperature range. In addition, a high sensor resolution is essential for testing photovoltaic and solar systems. In comparison to damaged insulation in the house, detail is required for the electronics - it should have a minimum resolution of 300 x 200 pixels.