Inspects 'CIS' solar panels that drone inspection companies avoid

CIS compound solar panels are used in some of the solar power plants of external companies where the company shot aerial images.

CIS panels are generally excluded from the targets of solar panel inspection services by drones, because there are almost no CIS panel failure modes that can be discovered from aerial temperature distribution images at present. However, such an undertaking is easy for Shoken because the company has yet to commercialize the service and is not paid for the service. The company, with the cooperation of power producers, shoots aerial photos aiming to validate the technologies.

At present, "cracks in the glass" of CIS solar panels are almost certain to be discovered (Fig. 8).

Fig. 8: Example of cracks in glass of CIS panels (source: Shoken)

CIS panels are black on the surface. When the cover glass is cracked and the cracks extend like a spider's web, many spots on the panel become white. It is easy to identify panels with broken glass because of the contrast. Interestingly, temperature distribution is also abnormal in four panels that are in the same row as the panel with broken glass.

The company shoots aerial videos in black and white. The aerial videos are checked in real time by a mobile terminal on the ground. When abnormal temperature distribution is discovered, still images of the area are shot from the ground.

The images can be colored and the temperatures can be indicated by using software for analysis. When a defective panel is enclosed by a rectangle on the screen displayed by the software, using the temperature measurement function of the software, the area with the highest temperature inside the box is indicated by a red triangle and the area with the lowest temperature is indicated by a blue triangle. The lowest temperature, average temperature and highest temperature in the box are displayed in the top left of the screen.

CIS panels with broken glass and panels in the same row as such panels with abnormal temperature distribution are higher in temperature than other panels, and this can be confirmed by using the software function.

CIS panels are connected in series and in parallel to form a string. Five panels are connected in series and four circuits of connected panels are connected in parallel in many cases. The array normally consists of four rows, with five panels connected in series in one row, and the panels in multiple rows are frequently connected in parallel.

Judging from such a situation, it is estimated that power is not transmitted to four panels that are connected in series with a CIS panel with broken glass, stopping power transmission from the panels.