The world's biggest offshore wind farm off the Kent coast in Britain has been officially opened. Swedish energy giant Vattenfall which built the farm 12 kilometres off Foreness Point in Thanet said the 100 turbines are expected to generate enough electricity to power 240,000 homes. In all, up to 341 turbines will be installed over a four-year period. Construction work at the 780 million pound wind farm began two years ago and was completed in June. The 380 feet tall turbines are spread over an area of more than 35 sq kilometres and are visible from the shore on a clear day. There are currently about 250 wind farms operating in the UK.