Measurement technology for sun tracking systems

In the solarindustry, non-contact temperature measurement aids in the continuous monitoring of the production processand thus helps improving the production procedure. By detecting slightest changes in the thermal behavior, possible malfunctions can be detected and solved easily and reliably. The thermal imagers of Optris are especially suited for these tasks. Thermal imagers are not the only option, though

Infrared cameras are essential instruments for the quality control of solar cells. One possibility of testing is the periodical modulated exposition of the solar cells to light (Illuminated Lock-In Thermography). The separation of charge within the solar cell leads to leakage current at defective parts and thus to local hot spots. The hot spots can be detected by the infrared camera.


The process and product temperature is a very important physical indicator within almost every industrial manufacturing process. This applies for the solar industry, too. Infrared cameras of Optris used for industrial services are achieving higher importance within the solar industry due to new developments within the area of infrared sensing technology as well as reductions in price.

Especially within the solar industry the production and monitoring of solar modules relies on numerous thermal processes. The compact and fast optris XI 400 is therefore often used for visualizing and monitoring the process.


Temperature monitoring for brazing processes

Temperature allocation of wafers for the production of solar modules is captured during string brazing. This assures a reliable and efficient assembling process. Temperature measurement takes place on the silicium surface which is connected to the braze point. That’s how the quality of the homogeneity of the brazing is measured. Challenges during the monitoring of the brazing processes are: the adequate local resolution and the temporally resolution as the heating of the braze points can take place in less than a second. With a resolution of 382 x 288 pixels as well as a frame rate of 80 Hz for the whole picture the optris PI infrared camera has developed into a suitable device.
Both illustrations above show examples of an inductive braze process within the solar cell production. First, the solar cell is entering the braze area. Above the cell are two metal bands which are marked by the white arrow in the left illustration and which are going to be brazed with the cell. Afterwards the induction heating elements lower to the wire and press the wire onto the solar cell. Through creating an induction area the wire heats up and connects with the solar cells metal contacts. As shown bin the right illustration the heat energy process within the solar cell is seen quite clearly. At this stage it is important not to exceed a certain temperature in the silicium as the possibility of the wafer to splinter due to inner frictions remains very high.

Temperature monitoring of laminating processes

A further area of application for the optris PI160 thermal imager is the thermal monitoring of laminating processes after the single wafer has been brazed to a string. A process conduct based on thermal monitoring can provide consistent temperature allocations across the panel area during the heating and cooling down phase. Thereby the laminating process will be less stressful for the solar cells and the laminating film – the rate of defective goods can clearly be decreased.

Screenshot of PI Connect software

Function control of solar cells


Contact free measuring infrared thermography is an essential instrument for the function control of solar cells. One possibility of the function control is the periodical modulated exposition of the solar cells with simultaneous observation with an infrared camera – the Illuminated Lock-In Thermography. The separation of charge generated through the exposure of light into the solar cell leads to leakage at defective parts. Those results in locally bordered heating of the cell can be detected with the optris PI160 thermal imager as a hot spot. The set up of the process is schematically shown in the following illustration.


Another inspection method is the Dark Lock-In Thermography. The solar cell will be connected with the power supply unit and will than react with heat emission. The thermographical camera can support the localization of areas with low product quality by measuring the surface temperature.