Wind power may be one of the cleaner, greener energy sources available, but turbine and blade failures point to dangers that were not anticipated.

David Campbell and his family were asleep in their farmhouse in Northern Ireland when the 16-foot blade from the wind turbine crashed through the roof of his home one windy night in January last year.

"It was like a bomb hitting the roof," he told the Belfast Telegraph. "It shattered the tiles and the blade disintegrated itself." Campbell was not the only person to see the direct effects of a turbine failure.

Just over a year later, in February, a 200ft Vestas wind turbine near the Danish city of Århus disintegrated spectacularly in high winds when a blade came loose and smashed into the central tower, causing the whole structure to collapse.

The incident was captured on video camera and footage has been viewed thousands of times on YouTube. Just two days later a turbine close to the town of Sidinge, in Denmark, sent a blade flying more than 300ft before it hit the ground. Keld Boye, a farmer whose land is near the structure, told Danish television: "I drive my tractor and my wife rides horses out there. Just think if we'd been out there when it happened."

After Denmark's climate minister demanded an investigation, authorities found the blade loss was caused by a lack of maintenance: regular checks on bolts in the turbine had been neglected. The Danish government announced mandatory service checks for every one of the 5,000 wind turbines in the country.

Turbines in Britain - there are 2,000, almost all of which are onshore - aren't immune from failure. A 200ft turbine at a wind farm in Kintyre collapsed last November in a 50mph wind. Following that, 26 wind turbines across Scotland were shut down as a precautionary measure while the broken structure was examined. Then the following month in Cumbria, a 100ft steel turbine crashed to the ground.


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