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Blowby-blow account

Cover story: Renewable energy

Expect to see wind turbines sprouting on schools, town halls and council houses following Chancellor Gordon Brown's announcement of a £50M fund to encourage microgeneration in public buildings last week.

Last year Britain became one of only eight countries to install more than 1GW of wind-energy generating capacity. This sounds impressive until it is considered that the UK's 1.3GW of installed capacity can be expected to deliver just over 400MW of power. This is equivalent to a paltry 1% of the country's electricity requirement. To hit the government's target of producing 10% of the country's energy from renewable sources by 2010, 7GW of additional capacity must be brought on line in the next four years.

To most, the challenge of delivering so much generating capacity looks nigh impossible.

Yet the output of wind farms has doubled since 2004 and schemes with the potential to produce 3GW of power are under construction or have been given the go ahead. A further 10GW is up for planning permission. Allowing for an operating ef'ciency of 30%, these schemes combined will deliver an additional 3.8GW of capacity - well over half way to the magic 10% 'gure.

Wind scheme promoters have had success in bringing projects to fruition by proposing larger installations, enabling them to sidestep local planning processes by getting consent for schemes from the Of'ce of the Deputy Prime Minister.

British Wind nergy ssociation head of communications Alison Hill says that exponential growth of wind generating capacity is being hampered by 'a bottleneck in components supply.

'There is a global shortage of turbines, which means the feasibility of some projects is being reassessed.' Hill also says that the development of offshore wind schemes has been slower off the mark than expected. She insists, however, that the 'slack can be taken up by onshore', and that the 2010 target can be met.

Others are more sceptical.

Queen Mary and West'eld College electrical engineering professor Michael Loughton believes that wind's unreliability limits its potential. When the wind dies down a baseline supply must for sourced from elsewhere, he says.

But Sinclair Knight Merz wind power group manager Paul Van Lieshout notes that 'there is a close correlation between wind and energy demand. Wind blows when it is coldest; demand is greatest when it is windiest.' Power distributor National Grid claims it could comfortably cope with supply 'uctuations with up to 20% of electricity coming from wind.

Van Lieshout believes that moving from relatively small, diversi'ed wind farms towards larger concentrations could ease intermittency issues: 'As soon as you start thinking in terms of wind power stations - about large, centralised generating capacity - you create a signi' cant level of control.' He wants to see concentrations of 1GW-installed capacity, delivering 300MW, equivalent to the output of a medium-sized gas-'red power station.

'With modern turbines you can control how much energy is coming out, ' Van Lieshout says. 'If we were to get a large proportion of electricity on the grid supplied by wind it might be possible to throttle back in periods of low demand and crank up to meet peak demand.' Meanwhile, energy investors such as power 'rm E.ON and contractor Amec are pushing the government to encourage expansion of wind power by changing the electricity trading market. Wind generators are penalised for providing a variable supply by being paid lower electricity prices than conventional generators. And they want a long-term policy framework, without which investors are reluctant to build new generating capacity of any kind.

E.ON chief executive of'cer Paul Golby says: 'Investors want a clear signal that policy will be stable and give fair terms to low-carbon technologies. As a company we have the capital to deploy on low-carbon generation, but we need a long-term legal and ' nancial framework.'

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