Vattenfall has started construction of the Kentish Flats Extension, which is the only offshore wind farm being built in UK this year.
Located off the Kent coast, the extension project is expected to cost more than £150m.
It will involve installation of 15 wind turbines at 8km distance from the coast.
The project is an extension of the 90MW Kentish Flats offshore wind facility, which has been operating since September 2005.
Vattenfall project director for Kentish Flats Extension Matthew Green said: "A number of large vessels will be offshore Herne Bay and Whitstable this summer as we add 15 turbines to the existing 30 at Kentish Flats.
"It doesn’t get much tougher than this: piling foundations 30m into the seabed; installing 139.6m-tall turbines weighing 600t over 8km off the coast; and, completing on schedule and to budget with, most importantly, maximum emphasis on safety."
First power from the 49.5MW scheme is expected to be available later in the year.
Permission for extending the capacity of the existing farm was received in February 2013.
Once operational, the extended offshore wind development will be able to meet the power requirements of nearly 35,000 UK households.
Vattenfall UK country manager Piers Guy said: "It’s important the UK pipeline keeps delivering, and Kentish Flats Extension does that in a modest way, so that British suppliers can maintain a foothold in the sector and help capture the significant economic opportunities that go with it."