More than half of Britain's wind farms have been built where there is not enough wind

It's not exactly rocket science – when building a wind farm, look for a site that is, well, quite windy.

But more than half of Britain’s wind farms are operating at less than 25 per cent capacity.

In England, the figure rises to 70 per cent of onshore developments, research shows.

Experts say that over-generous subsidies mean hundreds of turbines are going up on sites that are simply not breezy enough.

Britain’s most feeble wind farm is in Blyth Harbour in Northumberland, where the nine turbines lining the East Pier reach a meagre 4.9 per cent of their capacity.

Another at Chelker reservoir in North Yorkshire operates at only 5.3 per cent of its potential, the analysis of 2009 figures provided by energy regulator Ofgem found.

The ten turbines at Burton Wold in Northamptonshire have been running for just three years, but achieved only 19 per cent capacity.

Europe’s biggest wind farm, Whitelee, near Glasgow, boasts 140 turbines. But last year they ran at less than a quarter of their capacity.

The revelation that so many wind farms are under-performing will be of interest to those who argue that they are simply expensive eyesores.

Michael Jefferson, the professor of international business and sustainability who carried out the analysis, says financial incentives designed to help Britain meet green energy targets are encouraging firms to site their developments badly.

Under the controversial Renewable Obligation scheme, British consumers pay £1billion a year in their fuel bills to subsidise the drive towards renewable energy.

Turbines operating well under capacity are still doing well out of the scheme, but Professor Jefferson, of the London Metropolitan Business School, wants the cash to be reserved for the windiest sites.

He said: ‘There is a political motivation to drive non-fossil fuel energy, which I very much respect, but we need more focus.’

He suggests that the full subsidy be restricted to turbines which achieve capacity of 30 per cent or more – managed by just eight of England’s 104 on-shore wind farms last year.

Those that fall below 25 per cent should not be eligible for any subsidy. Professor Jefferson said: ‘That would focus the mind to put them in a sensible place.’

Britain has 2,906 wind turbines spread over 264 sites. But a further 7,000 are planned for the next 12 years to meet European targets on cutting greenhouse gas emissions.

Nick Medic, of Renewable UK, which represents the wind industry, said talk of efficiency was ‘unhelpful’.

He added: ‘Other types of energy, from hydro to nuclear, operate at 50 per cent efficiency at best due to factors including maintenance shut downs and fluctuating demands.’