Huge parts intended for an offshore wind farm have been spotted being delivered to Sheerness Docks.

A large green crane was seen off the town’s coast on Tuesday prompting people to ask on Facebook what it was.

We can reveal that it was lifting equipment for a 15-turbine extension to the Kentish Flats wind farm, 8km off Whitstable and Herne Bay, which started construction at the weekend.

The Swedish state-owned firm behind the project, Vattenfall, is using the Port of Sheerness as the storage and reloading harbour for the foundation structures.

Barges, each carrying the components for two foundations at a time, are being brought across the Channel from Antwerp and moored in the harbour.

They are then picked up by the crane vessel, Neptune, which is operated by GeoSea.

Following the short transit to the wind farm site, monopiles – deep foundations – are hammered into the seabed and the secondary structures are lifted over them.

The Kentish Flats extension is the only UK offshore wind farm to be built in UK waters in 2015 and is expected to cost more than £150m.

All turbines are expected to be deployed this summer with power from the scheme expected to be generated later in the year.

Once completed, it will provide enough electricity to power 35,000 UK households a year.

Matthew Green, Vattenfall’s project director for the Kentish Flats extension, said: “A number of large vessels will be offshore at 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 30m into the seabed, installing 139.6 metre tall turbines weighing 600 tons over 8km off the coast and completing on schedule and to budget with, most importantly, maximum emphasis on safety.”