Vattenfall said it will begin construction in 2015 of the up to 51MW second phase of the Kentish Flats project, provided it reaches a final investment decision in favour of the plan.
The Swedish utility said a decision about which turbine model to deploy has not yet been made. If 3MW turbines are chosen, then 17 units would be needed.
The project's near-shore location might make the choice of larger models with a higher rated capacity unacceptable, due to impacts on local sea views.
The existing Kentish Flats offshore wind farm has a capacity of 90MW, powered by 30 Vestas V90 3MW turbines. It has been generating power since 2005. The second phase would cost more than £150 million (€180 million), according to Vattenfall, and would increase the generating capacity of the combined wind farm by up to 56.7%.
"We welcome the Secretary of State’s timely decision. Kentish Flats' Extension will make a major contribution to generation from Vattenfall’s large fleet of offshore wind capacity in UK waters and help the delivery of UK climate change and renewable energy obligations," said Goran Loman, Vattenfall project manager.
Vattenfall has been working with an airport in southern England to mitigate the potential impact on operations from the expansion.
The Kentish Flats Extension (KFE) project site lies 7 kilometres off the Kent coast, in the Thames estuary. The airport is located in north-east Kent, close to Ramsgate. The two parties are working on addressing the turbines' effect on the airport's radar system.