Cyclone Erica puts turbines to the test

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Wind plant operators in France's overseas tropical territories are counting the costs and learning the lessons of dealing with tropical storms after Cyclone Erica struck the islands of New Caledonia on March 14. Erica was stronger than the three previous cyclones in the region, with an average wind speed of 40 m/s and wind gusts reaching 56 m/s.

Three of the four groups of turbines in New Caledonia are operated by French company Vergnet, which specialises in smaller turbines for storm prone regions. All three escaped with minor damage. The fourth larger scale plant, Plum, consisting of 20 Vestas V27 and V29 turbines operated by the utility Electricité et Eau de Calédonie (EEC) suffered far more damage.

Eight new turbines had been installed at the end of 1999 bringing the total capacity to 4.5 MW, with an output sufficient to meet 35% of the electricity needs of the Mont Doré community where it is sited. Sixteen of the turbines mounted on fixed lattice towers were put out of action by the cyclone. Vestas dispatched technicians to the site as soon as it could to assess the damage and decide on what to do.

"Five were extensively damaged," says Charles Dugué of Vestas France. They will have to be dismantled. On eleven others, the nacelles have been taken down to perform repairs safely. "The aim is to get the turbines back into operation as soon as possible," adds Dugué. On the islands, the cost of the damage has been estimated at 50% of the original investment capital. Investigations by EEC's insurer are underway.

Vergnet's smaller units fared much better. The company says its wind farm managers received the storm warning on March 12 and were able to put emergency procedures into effect the following day. Vergnet's turbines are all mounted on tilt-down towers, which can be raised and lowered on guy ropes and tied to anchors on the ground in extreme conditions. The most recently built and largest of the Vergnet wind clusters, Col de Prony, suffered most. Its ten 220 kW turbines use 50 metre lattice towers. They were all tilted and tied down, but two turbines were still pushed off their stands and anchor plates bent under excessive loads.

On the Ile de Pins, which endured the worst winds in living memory and where the church tower was brought down, none of the three 60 kW Vergnet turbines mounted on tilting tubular towers were damaged. Vergnet's third wind farm in New Caledonia, on Lifou island, was not in Erica's path of destruction and the nine 60 kW turbines were unaffected.

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