Efforts are being made to improve the efficiency of solar panel inspection by using drones (unmanned aerial vehicles). Nearly all the companies that conventionally made such efforts were power producers, companies related to the solar power generation business including O&M (operation and management) service providers and drone operators.

These companies have expertise and strengths in solar power generation or drone operation and have been improving the technologies and services, aiming for accurate and more effective solar panel inspection.

Recently, slightly different cases have been emerging. Some companies began to utilize their experience of using drones efficiently in other fields such as civil engineering surveys and the knowledge cultivated through operation of their own solar power plants for solar panel inspection.

General contractor Shoken Co Ltd of Otsu City, which mainly handles civil engineering, first started such operations at its mega (large-scale) solar power plants (See related article) (Fig. 1).

Fig. 1: Flying a drone in Shoken Ishibe Solar Power Plant (source: Nikkei BP)

The company does not offer the solar panel inspection service to external companies. It is currently also carrying out validations at nearby solar power plants as part of its technical verification efforts.

The company first started using drones in the civil engineering business, its core business. Drones are mainly used to improve the efficiency of measurement before working out plans and to report the progress to clients in the civil engineering field. The idea of including solar panel inspection as an application target of drones, in addition to civil engineering, came up partially because Tomotsugu Chihiro, the executive officer and solar business director at Shoken, was effectively using a drone personally.

Visual inspection of panels is included in the monthly inspection items performed by the company for its solar power generation business. It took about a half day for the visual inspection in the company's mega solar power plant with an output of approximately 2MW. The company wanted to improve the efficiency of such work.

There is a big difference between the use of drones in civil engineering and their use for solar panel inspection. Aerial images shot by normal visible light cameras are normally employed when drones are used in the civil engineering business. On the other hand, aerial images shot by infrared cameras are mainly used for solar panel inspection because the purpose is to understand temperature distribution in panels.

Therefore, up-to-date knowhow, in addition to technologies and knowledge on drones obtained from experience in the civil engineering business, is required, such as that on infrared cameras and appropriate flying height. Specifically, it is important to increase the number of panels that can be shot in one image, considering the resolution of the mounted infrared camera while maintaining the clarity of the images at the required level.

The knowhow for finding solar panels with a high defect possibility from aerial temperature distribution images was accumulated from the two mega solar power plants that the company operates.

The flying routes are set in advance and drones fly automatically over the sites.