Gale-force winds snap wind turbine propellers in Japan

Propeller blades on three wind-turbine generators in Iwate Prefecture snapped after being exposed to gale-force winds. Nagasaki Shipyard and Machinery Works, a division of Mitsubishi Heavy Industries Ltd., which produced the turbines, is examining them to determine how the accident occurred. Kamaishi-based Tomen Power said it was possible the blades of the propellers had cracked after being struck by lightning and then snapped when being exposed to strong winds on Wednesday.

Officials said one of the damaged wind turbine generators was located in the Iwate Prefecture city of Tono, and the other two in the town of Otsuchi. The generators - three of 43 placed at altitudes of between 800 and 1,000 meters - each consisted of a pole 68 meters high and three propeller blades measuring 29.5 meters in length. The three propeller blades that snapped had broken near their base, officials said. One propeller was damaged near its tip. Strong winds were recorded in Iwate Prefecture, with the wind speed in Morioka reaching 31.7 meters per second, a record for February. Strong winds were also blowing in the area where the generators were located. The propeller blades are built to withstand wind speeds of up to 60 meters per second, and are set to switch off automatically when the wind speed reaches 25 meters per second or more.