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Page last updated at 09:49 GMT, Friday, 5 September 2008 10:49 UK

When the wind doesn't blow

Danish wind farm
The answer to Britain's energy demands... on blustery days at least

By Simon Cox
BBC News

By 2020, more than a third of Britain's electricity will be generated by wind power, according to government plans. But what happens on calm days?

On a clear summer's day the Horns Rev wind farm off the coast of Denmark could almost double as a tourist attraction. Watching the rows of 200 foot white steel turbines turning gently in the wind, occasionally catching the afternoon sun is beautiful, almost hypnotic.

To see it properly you need a helicopter, as it's in the middle of the North Sea. I had hitched a ride with Bent Johansen, who manages the operations of Danish turbines for the energy company, Vattenfall. For him the future of wind is off-shore.

"Horns Rev can produce as much power as all our 300 onshore turbines put together," says Mr Johansen.

The Investigation's report on renewable energy for the UK is broadcast on Radio 4 on Thursday, 4 September at 2000 BST
Or catch up using the iPlayer

Horns Rev is currently the biggest off-shore wind farm in the world, covering an area of over 20sq xkm. In the next decade Britain will be seeing its own versions of Horns Rev cropping up off the coastline.

The government estimates about 35% of electricity will need to be generated from wind power by 2020, to meet an EU target. This will mean a massive increase in the amount of wind power generated, from 2% at present to 35%.

It's a big leap, admits Maria McCaffery of the British Wind Energy Association, "but we believe it is possible".

Denmark is the poster boy for wind power - 20% of the electricity it generates comes from wind, it claims. Horns Rev can provide enough power for 150,000 homes. On the day I visited it would be lucky to power a village. So what does Denmark do when the wind doesn't blow?

The answer is on the giant screens which dominate the control room of Energinet, the Danish national grid. Peter Jorgensen, the vice president of Energinet, directs me to the map of Scandinavia which fills one vast screen. On it are the unique energy connections Denmark has to its neighbours in Norway, Sweden and Germany.

This allows them to import power when it's not windy or export it when they have too much.

Exporting wind

"It would be very difficult to run the system without the inter-connectors, we are very dependent on our neighbours", Mr Jorgensen concedes.


The Investigation: Wind Power

Denmark is proud of the fact that a fifth of its electricity comes from wind. But Hugh Sharman, an energy consultant, says this figure should be treated with caution. Sifting through the charts in his crow's nest office overlooking the Jutland peninsula in Denmark, a different picture emerges.

"Every time the wind is high, the exports are high. Every time the wind is low, of course there are few exports". Mr Sharman says more than half of Denmark's wind power is exported - so it only actually uses nine percent of the wind energy it generates. If the Danes couldn't do this, their system wouldn't work.

The UK, however, doesn't have this option. There is a link to France and one being planned to Holland but these won't able to shift the amount of power needed to balance our system. Peter Jorgensen believes it can, but it won't be cheap.

"You could build a system that would balance on it own," says Mr Jorgensen, "but it would be very costly"

Giant batteries

Other options for Britain would be to store its wind power in giant batteries, but this is difficult and very expensive.

Instead the UK will need to look at back-up power stations for the many days when it is not windy enough . In the short term that will come from fossil fuel generation, says Nick Rowe, an energy campaigner with Friends of the Earth.

Scroby Sands windfarm
British version - Scroby Sands windfarm in Norfolk

"It does not mean we will need the fossil fuel generation all the time but it means they need to be turned on when necessary."

This back-up will probably have to be gas-fired power stations as these are the easiest to turn off and on.

But this will mean a "dash for gas" - a resource that Russia, hardly Britain's most cooperative ally, has in spades.

Dieter Helm, professor of energy policy at Oxford University, says Britain could find itself badly exposed. It would be "about the worst possible thing that one could conceive of given what's going on in Russia and given our dependence on Russian gas supplies".

It could also prove costly. The energy company, E.On recently estimated back-up power could cost up to 10bn per year across all the energy suppliers. That would add 400 to the average annual household energy bill.

But supporters of wind power like Maria McCaffrey believe it will make energy cheaper.

"We don't have to pay for wind power it just comes to us naturally and is totally sustainable. The expectation is that it will in time drive down the basic cost of energy and actually help the fuel poverty situation."

The government accepts it is a challenge to manage energy security and price rises but it is fully committed to reaching the 2020 target. And what happens if we don't? The EU is expecting this to become a legally binding target within the next year so we could be hauled before the European courts of justice and face huge fines, which of course would come out of your pocket.

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