What could be more clean and natural than harvesting energy from the power of wind using gigantic turbines? Environmentalists have dreamed of this since at least the Thirties, when a Nazi German inventor called Dr Franz Lawaszeck theorised how to solve his country's energy problems at a stroke.

He wrote: 'Wind power, using the cost-free wind, can be built on a large scale. Improved technology will, in the future, make it no more expensive than thermal power . . . the wind towers must be at least 100 metres high, the higher the better, ideally with rotors 100 metres in diameter.'

Wind power was all the rage among Nazis, many of whom shared the party's fanatical commitment to the environment. Other big fans included Hitler's favourite commando, Otto Skorzeny.

General Electric plans to build the world's largest wind turbine - twice as high as Big Ben

After an eventful war — which included springing Mussolini from his mountain-top jail in a daring glider operation and planning a (happily abortive) assassination attempt on Churchill, Roosevelt and Stalin — the plucky SS-Obersturmbannführer settled in Spain where he spent his later years campaigning on behalf of the nascent wind industry.

But it has taken until now for the Nazis' dream of a world powered by wind to become even remotely plausible.

In the Thirties, Lawaszeck's scheme foundered for practical reasons: those giant turbines would have required 27,500 tons of steel each, approaching the amount used in the battleship Scharnhorst.

Today, though, huge turbines, even bigger than the ones Lawaszeck envisaged, can be built more efficiently using tubular steel and concrete (for the towers) and carbon fibre (for the blades). At last, the era of Big Wind is upon us, with a new generation of turbines that are bigger — and create more electricity — than ever before.

Danish firm LM Wind Power, a supplier of components to the industry, has since 2016 offered blades 290ft (88.4 metres) long — bigger than the wingspan of an Airbus A380, or nearly twice the length of an Olympic-sized swimming pool

Danish firm LM Wind Power, a supplier of components to the industry, has since 2016 offered blades 290ft (88.4 metres) long — bigger than the wingspan of an Airbus A380, or nearly twice the length of an Olympic-sized swimming pool.

Perched on a rotor, they will sweep an area the size of three football pitches and — according to the manufacturer — pull the same weight as 16 African elephants, and each year produce electricity equivalent to the annual consumption of 'around 10,000 homes — that's a whole town'.

Which may sound like a lot except that you would require about 7,500 such turbines to supply the UK at peak time, and in any case, the intermittent nature of wind can't generate an uninterrupted supply to a single house.

These monsters, however, will shortly be dwarfed by the world's biggest turbine model — the Haliade-X 12 MW — which will soon be tested by GE Renewable Energy at Blyth, Northumberland.

Standing 853ft (260 metres) tall with 351ft-long blades (107 metres), it will produce electricity equal to the annual consumption of 16,000 homes. The size of such a turbine will make it too obtrusive to site on land. But one possibility is that it could be erected in large numbers far offshore, in an area such as Dogger Bank — a shallow stretch of the North Sea about 60 miles off the coast.

This is the proposed location of a giant wind farm being developed by the Dutch firm TenneT.

Standing 853ft (260 metres) tall with 351ft-long blades (107 metres), it will produce electricity equal to the annual consumption of 16,000 homes

With a man-made island to house its substations, and many hundreds of turbines, it could theoretically have a capacity as huge as 30GW (gigawatts), though because of its low productivity it would still only generate energy equal to about a third of the UK's needs, and would contribute little, or nothing, to security of supply.

What does this all mean for the future of energy? If wind power's advocates are to be believed, something extraordinary.

The average power capacity needed to meet electricity demand at any moment for the UK is 36GW, with a summer low in the 20s and a winter peak of 62GW.

So that 30GW Dogger Bank project alone — if it ever comes to fruition — ought nearly to be enough to supply much of Britain's electricity needs.

Imagine: no more 'dirty' fossil fuel power; just thousands of offshore turbines swishing in the distance, generating free, 'low carbon' electricity until the end of time.

So runs the theory. But then, as with so many utopian schemes, there are huge catches — starting with the eye-watering cost.

Electricity produced by onshore wind costs twice as much as conventional gas-fired electricity generation; offshore wind three times as much. The only reason the wind industry is viable is because of the massive subsidies it receives. Subsidies raised silently from your energy bill.

British Gas has said that by the end of this year, green taxes will add a fifth to the average fuel bill. Iain Conn, boss of parent company Centrica, said: 'It is going to be, in our estimates, about £200 on everyone's bill which is getting on for 20 per cent.'

By 2020/21, according to the Office for Budget Responsibility (OBR), the total cost of all the subsidies for renewable electricity will be nearly £11 billion a year, and wind power will be taking more than half of that. And don't be taken in by that ad campaign by Greenpeace and a coalition of environmental groups and electricity suppliers last year, claiming that the cost of wind energy is plummeting to the point where it's now cheaper than fossil fuel power.

No it's not. The ads were withdrawn as the result of a successful complaint to the Advertising Standards Authority, because they were deliberately misleading propaganda, based on projected costs, not real, current figures.

In fact, Professor Gordon Hughes, of the University of Edinburgh, and his colleagues showed in a recent study published by the Global Warming Policy Foundation think-tank, that the capital costs of new offshore wind farms do not appear to be falling and indeed appear to be still rising as wind projects move into deeper waters.

This new generation of mega-turbines, we're told by green advocates, will solve most of these problems. Bigger blades and taller towers mean they'll be able to capture the more plentiful wind that blows at higher altitudes, unlike the smaller turbines beset by 'low wind days' (one in every 5.6 days according to energy union GMB) when they're generating little, if any, power. Thus they will become more cost-effective.

Also, being far out at sea, they won't alienate all those rural voters who can't stand having wind turbines industrialising the countryside, disturbing their sleep and killing bats and birds.

Despite its huge cost, offshore wind remains a vital part of the Government's energy strategy — its best hope of meeting its EU-driven CO2 reduction obligations, under the 2008 Climate Change Act. But according to John Constable, of the Renewable Energy Foundation, this is a chimera.

So that 30GW Dogger Bank project alone — if it ever comes to fruition — ought nearly to be enough to supply much of Britain's electricity needs

Wind energy, he says, will never be a solution because of 'fundamental physics: wind, by its nature, is a low density and intermittent flow of energy. Correcting those deficiencies to supply reliable electricity to consumers means huge capital expense in the turbines and in the electricity system as a whole'.

Making turbines bigger and putting them out at sea only makes things worse. They are much more expensive to erect and maintain in a remote, hostile environment, and have a much shorter working life.

Analysts have known for years that rising repair costs would mean the economic lifetimes of turbines were way under the 25 years promised by the industry.

In February this year, Danish offshore wind operator Ørsted admitted it might have to repair the blades of more than 600 turbines, after just a few years on the water, at a cost of about £1million per turbine.

And the bigger they are, the worse this is going to get, for all sorts of reasons.

These machines are already dealing with large forces, putting huge loads on their components. Making them bigger just increases the problem, and not just because of increased weight. Wind shear — the difference in wind speed at different heights — leads to uneven loading at the top and bottom of the blade radius and causes huge strain on the working parts. This is really difficult and very expensive engineering.

Then there's the erosion of the blades, due to high-speed impacts with small particles, dust, ice and salt. Ørsted is replacing those blades because their edges had become rough, and as any engineer will tell you, when a wing gets rough it becomes unstable.

Then there's the wind industry's dirty little secret: according to some concerned ecologists, those spinning blades could be killing millions of birds and protected bats every year.

In Spain alone, one survey estimated, up to 330 birds and 670 bats are killed per turbine per year; a survey in Sweden put the bird death toll as high as 895 per turbine. The wind industry denies these estimates, which are hard to confirm, not least because the areas below the turbines where the bodies might be found are often jealously guarded.

But those figures are for onshore wind turbines. It's likely that fewer birds are killed offshore because they are more scarce.

Indeed, according to a recent study at Vattenfall's Thanet wind farm seven miles off the coast of Kent, just six collisions were recorded on video and radar over a two-year period — an average of one every four months.

The industry (which funded the Vattenfall study) is desperately trying to persuade us all that there isn't a problem. But the RSPB, which has historically leaned over backwards to help the industry, is finally losing patience and has just rejected the latest impact study.

Concerns have also been raised about the damage done to other marine wildlife by offshore wind turbines. There is evidence to suggest the turbines' lower frequency noise is disrupting the sonar of whales and dolphins, causing them to beach and die. Another offshore wind farm was implicated in the death of baby seals found stillborn on the beach nearby.

But if wind is really so expensive, inefficient and environmentally damaging, why does our Government remain so committed to it?

Largely because of the lobbying of a hugely powerful industry. An industry desperate not to lose its extraordinarily generous subsidies.

For example the (mostly foreign) owners of the London Array — the largest wind farm in the world, off the coast of Kent, which was opened by David Cameron in 2013 — receives about £190 million a year in subsidies, on top of selling electricity they make. That sort of windfall, forgive the pun, ensures the industry presses its case with ruthless efficiency.

It is now under real pressure. The Treasury has put a moratorium on new subsidies until the middle of the next decade at the earliest, and the wind industry is trying to survive by pretending that falling generation costs have made them economically viable. Secretly, they are hoping for a change of policy (Jeremy Corbyn?) and a stonking carbon tax.

This latest propaganda about 'bigger', 'better', 'faster' new mega-turbines is designed to keep us and the politicians in the industry's thrall.

Even now, they are building the new biggest wind farm in the world, called Hornsea Project One, off the Yorkshire coast. It will have 174 turbines over a 240-square mile area, each 620ft high (189 metres). And that's before we get on to Hornsea Projects Two and Three, which are already in the pipeline and which, you can bet, will be still larger and with even more monstrous turbines.

As the Renewable Energy Foundation's John Constable explains: 'All this is designed to give the illusion that there has been massive technological progress in the industry when in fact the major problems remain unsolved: the energy in the wind is of low quality. Turning it into high quality, reliable energy for the consumer is still very expensive indeed.'

Yet the propaganda often finds a ready audience because so many want to believe, against all the evidence, that wind must be a preferable alternative to our gas-fired turbines, vanishing set of coal-fired plants or ageing nuclear reactors.

We don't want to hear about the intermittency of the wind, which makes it so problematic as a reliable source of power for an advanced economy and means we need alternative generating capacity as well.

Nor about all the pollution — and extra CO2 — generated by the gas-fired back-up for when the wind's not blowing. Nor all those birds and bats being killed. Nor the capitalist fat-cats getting rich off all the subsidies we have to pay them.

As those Nazis believed in the Thirties, so today's Greens — and the attendant climate industry — would have us believe today: that wind is the kinder, cheaper, cleaner, more natural solution to our energy problems.

Well, it isn't.