The energy debate: Wind

Can we harness enough of its strength to solve Britain's power crisis?

Riding a rubber inflatable dinghy out to sea feels like being lashed to the bow of a galleon. You get soaked fast by the bursting waves. Sea salt stings the eyes and face. The wind is deafening as the boat picks up speed, skimming over the water and leaping into the air - hanging there for two or three seconds - before slamming back down, sending a judder through the pelvis and driving air out in a grunt. This must be what it was like for Tony Blair when he rode the same small orange rubber boat, the 12-seater Warlock Voyager, out of Whitstable Harbour last week to see the wind farm seven miles out to sea.

"You may feel a bit of a pull backwards," said the skipper Graham Hall before we set off to replicate the journey. He wasn't joking. The waves are almost non-existent today, apparently - a swell of no more than half a metre - but they don't seem that way to a landlubber holding on for dear life. There is no time to be sick, though: the motion is like a series of punches to the midriff.

Mr Blair has had a stomach-churning week, but for one morning he got away from it all - with only colleagues, aides and detectives, a press boat and two police launches for company.

"People told me to give him a little nudge over the side, but he seemed like a decent, ordinary guy," said Graham, as he strapped on my lifejacket at the jetty. "I asked him if he could let me off taxes for the rest of my life." Being at his mercy on this bucking boat would make most people promise Graham anything, but the Prime Minister is a stronger man. "He said no. But he was nice about it."

Graham works for Bayblast, which runs tourist trips out of Whitstable most days. People want to see seals or the strange Maunsell sea forts built on stilts during the Second World War; but since last summer they also want to get up close to the Kentish Flats. The offshore wind farm is the largest in Britain. The 30 turbines seen from a distance are mesmerising, their slender blades turning slowly and apparently generating enough electricity in a year to run 100,000 homes. In doing so, they produce 223,000 tons less harmful carbon dioxide than a coal-fired power station would.

Mr Blair made the boat trip to announce his Government's second energy review in three years, the main substance of which was the desire to build new nuclear power stations - but boats and windmills make a better photo opportunity. "One of the reasons for coming here," Mr Blair said, "is to say nuclear is only part of the answer."

Later that day, the Secretary of State for Trade and Industry, Alistair Darling, promised to force energy suppliers to buy more from renewable sources: 20 per cent of electricity by 2020 (compared to 4 per cent now). New planning rules will make it easier to build wind farms and put up turbines on ordinary homes. The Conservative leader, David Cameron, has already received permission to erect one on his £1.1m Edwardian home in a north Kensington conservation area, despite complaints from neighbours. The environmental auditor Donnachadh McCarthy said it could save the Camerons up to £100 a year in electricity bills, but they will have to be careful when they use it.

"If his wind turbine is the same as mine, he will get between one and two kilowatts of power a day. But it does not all come in at the beginning of the day, and if he needed 800 watts to use the washing machine, he would have to wait something like three hours for the turbine to generate that much energy." (Or he could flick a switch and use the normal supply.) Domestic turbines cost from £1,000 to £3,000, so a saving of £100 a year will mean a windmill takes 30 years to pay for itself. But it will do so much more quickly if energy experts are right and electricity prices rise dramatically.

Britain is running out of power. North Sea gas supplies are dwindling and our nuclear reactors getting old. Replacing them will take a long time, but energy shortages won't wait. Wind farms can be built far more quickly - although they have also generated passionate opposition, particularly when built on previously unspoilt land in Wales and Scotland. The campaign group Country Guardian has described them as "monstrous, alien industrial structures".

Feelings are strong on both sides, but the independent Sustainable Development Commission produced a report on the pros and cons of wind power last year. It found "no major technical barriers" to windmills providing all the power the energy review is now demanding - but warned that this would cost considerably more than electricity from a coal-fired power station. One estimate is a cost to the average consumer of £28 a year. But windmills produce none of the carbon dioxide believed to be the main gas responsible for global warming. So supporters argue that it is cheaper to pay for windmills than buy cheap power stations that speed up the greenhouse effect and indirectly cause towns to be flooded by rising sea levels, for example.

Their opponents say the two things just do not correlate, because the science of global warming is uncertain and cutting CO ₂ may not prevent it anyway.

The main technical objection is that the electricity grid needs a constant supply, yet the wind does not blow all the time. The SDC investigated this. "Wind blows at variable speed, variable intensity and sometimes not at all," it said, but the variations were forecastable, allowing the assertion that "variability is not a problem for the electricity grid".

The SDC was also dismissive of the threat to nature - despite claims from the Royal Society for the Protection of Birds that rare eagles have been killed by the whirling blades - claiming this could be avoided with careful planning. But wildlife concerns are holding up a wind farm on the Isle of Lewis, among others. And it is during the planning process that the fury hits the fan.

There were no objections to the two giant propellers that loom over the Ford plant in Dagenham, East London, but that is a heavily industrialised site, very different from Saddleworth Moor or Romney Marshes, where plans have been thwarted by locals. The tactic for most of the 1,634 turbines built so far has been to go for really isolated places, but there may not be many of those left if wind is going to produce five times as much energy as it does now by 2020. That is a big if. The British Wind Energy Association says it is possible, but only if Mr Blair backs up commitment with very big grants and subsidies.

Getting to the Kentish Flats from Whitstable takes 10 minutes in the Warlock Voyager. As we get closer, the perspective changes and it is possible to see that the turbines stand in five lines of six, in a diamond pattern. Each tower is as wide as a lighthouse at its custard-coloured base, which has a metal landing platform and a door. Inside is a ladder and a simple basket lift, says Michael Keam, who used the dinghy to run spares or act as a rescue boat while the turbines were being built. Half a dozen are motionless today, probably because there are maintenance engineers working high up behind the propellers.

The company that runs the wind farm is Swedish, but "all the men who worked on this are from Whitstable - or Kent anyway," says Michael. Some trawlermen claimed the wind farm would stop them fishing, "but I think they were just after a bit of money. Nobody ever fished out here. It was just a sandbank with nothing going on." The water is only five metres deep, so tankers coming close would run aground long before they hit a windmill.

We are in among them now, where other boats are not permitted. Graham cuts the engine and allows the dinghy to drift towards the base of a tower. The boat sways on the waves and the tower seems to move too, reaching overhead as if to touch the sun, a flat silver disc behind the clouds. Then a giant blade cuts across and starts to fall - and it feels as if it will keep falling down on us until that sharp blade divides the boat in two. We duck, instinctively, but the blade passes overhead with a loud tearing sound, a soft but ominous va-voom . Then it is gone ... until the next blade.

The campaign group Country Guardian describes the noise from living near one of these things as "an insidious, low-frequency vibration that's more a sensation than a noise. It defeats double-glazing and ear plugs, coming up through the ground or through the floors of houses and manifesting itself as a ripple up the spine, a thump on the chest or a throbbing in the ears." However the report by the Sustainable Development Commission said that once windmills were up, "communities often find that noise is not a problem". It is not an issue at all if they are built out to sea, as many of the new ones will be, but that is complicated and expensive.

"We had better get back," says Graham, looking towards black storm clouds over the Isle of Sheppey. He guns the engine and we leap the waves again, leaving behind the men who may still be inside those windmills. Luckily for them, the storm clears quickly. Looking back from on shore at Tankerton Slopes half an hour later, the sky looks grey but calm. The wind turbines are clearly visible, far more so than they were in the artistic impressions published for the public consultation.

The pleasure of looking out to sea, usually, is that the eyes can settle on a featureless horizon, a reminder of the true scale of things. But these windmills stop that: they draw the gaze and enclose the seascape, making it feel smaller. "Rubbish," says the lady in the tea chalet, who sees them every day. "They're lovely. It's free wind out there - it blows constantly here, let me tell you - and we need the power don't we?" Margaret, a pensioner walking a dog on the grassy slopes, shakes her head. "They're OK but they have a novelty value, don't they? If they were everywhere you looked, like pylons, wouldn't we feel different then? Wouldn't that spoil it?"

HOW A WIND FARM WORKS

1. Each of the rotor blades at the Kentish Flats wind farm is 45 metres long. They turn at an average speed of 8.7m per second.

2. Three blades are attached to a hub and spinner 70m above sea level. The speed of rotation depends on the density of the air, the speed of the wind and the angle of the blade.

3. Behind the hub is the nacelle, which resembles the cab of a crane. In here is the gearbox, which is directly attached to the three rotor blades.

4. The energy produced by the turning blades is transferred from the gearbox to the generator, where it is transformed into electricity. This is carried by cables to a sub-station onshore in Kent.

5. The turbines are remotely controlled by computers at the wind farm's office in Whitstable, seven miles away.

HOW WIND POWER COULD GROW

128 wind farms are operating in Britain today with

1,634 individual turbines producing

1,694 MW of energy in a year, which is enough for

950,000 homes, and saves the

3.8 million tons of carbon dioxide a coal-fired power station would make.

4 per cent of the UK's energy needs are currently met using renewable sources such as wind, wave and solar power, but...

20 per cent will be provided in this way by 2020 if the Government meets the target declared in the Energy Review.

24,000 new turbines may have to be built to meet this target.

11,000 turbines are already under consideration through the planning system.

£16bn is the investment required to meet the target.

£28 is the average predicted rise in an electricity bill per year if this happens.