Continued from General Contractor Uses Drone Technologies for Solar Panel Inspection (1)

Finds 4 failure types

Four types of failures are mainly found by drones. They are classified into "damage," "string defect," "dirt" and "cluster failure." "Damage" refers to cracking of solar panel cover glass (Fig. 4). Overheating is observed at multiple locations inside a panel in many cases.

Fig. 4: Examples of "damage" (source: Shoken)

The company believes that "cracking of glass causes water intrusion into the panel, generating abnormalities at various locations inside the panel and resulting in overheating." "String defect" refers to a state where power generation stops on a string unit basis (Fig. 5).

Fig. 5: Example of "string defect" (source: Shoken)

In this state, power is not transmitted from the defective string when power is generated by the solar panels, due to a fuse blowing inside a combiner box, disconnection or other reasons. The defect is detected easily from temperature distribution images shot by drones.

"Dirt" refers to dirt on solar panel surfaces such as bird droppings, causing the amount of power generated by the cells (power generation elements) to decrease under such dirt (Fig. 6).

Fig. 6: Example of "dirt" (source: Shoken)

"Cluster failure" refers to a cessation of power generation from a cluster, which consists of multiple cells and forms part of a panel such as 1/3 of a panel, resulting from activation of a bypass diode caused by a decline in the output of cells due to a problem of some kind (Fig. 7).

Fig. 7: Example of "cluster failure" (source: Shoken)

Cluster failure is known as a defect easily discovered from temperature distribution images shot by drones. In an inspection performed by the company, cluster failure was discovered in 60 of about 1,600 panels at a power plant operated by an external company and uses panels made by foreign manufacturers, for example. On the other hand, no cluster failure was discovered in panels made by two domestic manufacturers, according to the company.