Cloud-to-ground lightning flash density and the number of lightning flashes hitting wind turbines in Japan

The current status of the Japanese coastal region shows that winter lightning has seriously damaged wind turbines owing to its larger electrical charge than summer lightning. In Japan, 64% of serious wind turbine damage occurred in winter. Typically, lightning flash density is used to evaluate lightning risk in an area. Herein, we discuss the extent of lightning damage on wind turbines in Japan and cloud-to-ground (CG) lightning flash density based on the Japanese Lightning Detection Network, the largest lightning location system in Japan. Consequently, we found no correlation between the number of lightning flashes hitting wind turbines and summer lightning ground flash densities in the surrounding areas of a wind turbine. Approximately 95% of the lightning flashes that hit the turbine occurred in winter. The probabilities of lightning flashes hitting wind turbines were 0.12% in summer and 5.6% in winter. We developed a map showing the probability of lightning flashes hitting wind turbines in Japan. The probabilities obtained using this map were quite similar to the CG lightning flash density in winter. Therefore, we propose that lightning risk for wind turbines should not be evaluated based on the annual CG lightning flash density in Japan.