Work has begun on a £150 million extension to a wind farm off the coast of Kent.

Vattenfall, the Swedish energy company, has started construction on 15 new turbines in its Kentish Flats wind farm about 8km off the coast of Whitstable and Herne Bay.

The wind turbines are expected to be completed this summer and will be the only wind farm to start building offshore in UK waters this year.

It increases the size of the 30-turbine farm, which has been operational since 2005, by 50%.

Once complete it will be able to generate enough electricity to power 35,000 homes a year .

Project director 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.

“We hope local people will be able to follow the construction and take a great interest in what is a challenging and complex engineering exercise.

“It doesn’t get much tougher than this: piling foundations 30 metres into the seabed; installing 139.6 metre tall turbines weighing 600 tonnes over 8km off the coast; and, completing on schedule and to budget with, most importantly, maximum emphasis on safety.”

Piers Guy, Vattenfall’s UK country manager, 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.”

“We hope local people will be able to follow the construction and take a great interest in what is a challenging and complex engineering exercise..." - Matthew Green, Vattenfall

It has been a busy few weeks for Vattenfall, which began the wind farm extension on Saturday.

Earlier this month the company hired Ramsgate-based BEC, a construction firm, to build an extension to its Kentish Flats offices, based in the Thanet town’s harbour.

Building is due to be completed this summer, and will also employ several Kent-based subcontractors including PKR Services, Grummant Heating, Total Electric, Metalfab, B&H Brickwork, RFV Gasking Carpenters, Complete Roofing and All-Access Scaffolding.

Mr Green added: “Kentish Flats Extension is probably one of the biggest inward investments in Kent this year. It’s important the local economy benefits.

“That’s why Vattenfall, and our key suppliers, will support local business where we can. So we’re delighted to be working with Ramsgate-based BEC and its local suppliers on the extension to the operation and maintenance facility.”

Rob Barlow, managing director of BEC, said: “Vattenfall’s support of local business like BEC is to be really welcomed.

“Investment in wind energy is an opportunity for construction firms like BEC. We employ 17 local builders – and we are using other local firms – so this contract to build the site office extension for Kentish Flats Extension secures work for many people.”