Further doubt has been cast on the government's plans for bioenergy by a charity sponsoring research into renewable technologies.

Publishing new research this week, the Renewable Energy Foundation said the government's expectation that three-quarters of the 2010 bioenergy target would be supplied by wind power was "unrealistic".

John Constable policy director of the charity, which has voiced its concern over wind turbines in the past, said wind turbines were a politically visible gesture that made the public feel something was being done. "While turbines in the Shetlands run at an impressive 50% of their theoretical maximum capacity, in other areas they perform less well."

Mr Constable cited data from two UK plants, Dagenham, in Essex, which runs at 19% and the Barnard Castle plant, in County Durham, running at just 9%.

He also suggested the variation in power produced by turbines would present difficulties in achieving a smooth delivery of power to the National Grid.

"Using Met Office data we found that power swings of 70% within 30 hours were the norm in January," said Mr Constable.

"By 2010 the government plans to provide 10% of energy requirement from renewable energy. This rises to 15% by 2015 and 20% by 2020. I doubt these targets will be met unless other forms of power are given greater attention and investment," said Mr Constable.

"The government must invest more in other forms of renewable energy such as biomass. Coal-fired power stations are already capable of co-firing using biomass such as short-rotation willow. This can provide a more predictable delivery of power," he added. 

 The reports are available at www.ref.org.uk Click on UK RENEWABLE ENERGY DATA in the sidebar then follow links.