The turbine described on the last page was of a geared type. You can also have gearless types. Here's a diagram of a German design:


Principles of Wind Power

Go Back

They are becoming the dominant type in offshore wind farms as tests indicate that they are in fact more efficient than geared ones. Leading the field is the German firm Siemens, who seem to have a mission statement to dominate the World's technical market as they've got a finger in every pie. Not bad for a company that started as makers of telegraph equipment and installed the first electric street lights in Godalming.


I digress. This type of turbine is also called a direct drive, and you can see why. The rotating part drives around a magnet, which rotates round a coil section, thus creating a dynamo which generates electricity.

Of course it doesn't matter what sort of turbine you've got if you haven't got a tower to put it on. The taller you can get the tower, the better because the wind at higher altitudes isn't liable to suffer intererence rom the ground and as such will maintain more of a constant speed and direction. The ones at Royd Moor are35 metres (about 115 feet) tall from the bottom of the tower to the centre of the hub. They're very slender too. They are the freestanding tubular type, and are by far the most common found; other types include the lattice (looks rather like a radio mast) and the guyed, which is a long steel pole held in place by guy wires.


The freestanding tubular is popular because you can create an access chamber in the centre through which you can climb up the inside to do inspection and maintenance. However, the higher the tower, the greater the material needed to make the tower, otherwise they buckle. There are also severe cyclic forces at work as the turbine turns, causing a horizontal moment load to the foundations as well as the vertical one when still. Put simply, the wind tries to blow the tower over; and the higher the tower the easier this will be. You can combat this by restraining the rotation.


A HAWT cannot operate for this reason (amongst others) at a windspeed greater than about 56 mph. Nor can it do it effectively at a windspeed lower than 14 mph.  In fact in the UK any kind of wind turbine will only generate for limited periods; it will produce about 21% of what it actually could do over its lifetime.


Theoretically a wind turbine can extract a maximum of 59.3% of the energy of the wind and turn it into electricity. This is known as  Betz's Law.


 If  you converted all the energy in the wind hitting the turbine wind speed afterwards would be zero. But, if the wind doesn't move out  of the turbine,  no more can get in . To keep wind flowing through,and thus get energy, some wind must move out with energy left in it. It's just over 40% of the initial energy that's needed for this, giving us a Betz limit of 59.3%.


There's a LOT of really intense mathematics backing up this fact. You can check it if you like. But unless you like being up to your armpits in theoretical mathematical modelling I'd take Betz's word for it if I were you. In any case, since this is based on a theoretical ideal rotor which has neither a hub nor drag, and has an infinite number of blades, where the flow is axial and has no heat transfer,  has no wake effect- oh and it's mastless-  it doesn't bear any resemblance to real world mechanics at all. Betz of course is one of Clever Clive and the Sciency Misfits closest friends.


Real turbines won't achieve anywhere near the Betz limit. The very, very best of them will struggle to extract 45% of the wind energy and turn it into electrical. In fact, on average, the figure is about 28%.


In the United Kingdom, the windiest months are the winter ones, rising in December and falling in March. At this time, the turbines on a wind farm will produce a good deal of electricity doing about 38% of their capacity factor. In summer, this drops dramatically, and over the whole year the turbine will produce about 21 % of what it could do. So, it's a fifth of 60% of the energy of the wind: 12% of the energy of the wind is extracted.


How Green is my Spinny?


Now, throughout this article I've been very good. I haven't tried to bias my writing, I've presented facts and technical details and where possible avoided colouring with my opinions on the matter. This is where I let myself off the leash. If you are of the persuasion that likes to think it's environmentally friendly, either stop reading at this point or prepare yourself for a shock. You have been warned. A rant is forthcoming.


Wind power is the worst idea since Eve said to Adam "darling, I've made you an apple pie for pudding". It is truly, deeply awful. If a malevolent imp had come along and said "I'll think I'll find a way to completely and utterly bugger things up for good" it could not have done better than to invent these noisy, EMF spurting bird mashers and sprinkle them generously around the World.


Fact why wind power is rubbish number 1: (this subtitle is an indication of how unbiased this is......)


It's not green. Not in the least. The oils and glues used in the construction of these collosal monstrosities are made of fossil fuels and mashed dead animals. The foundations need tons of concrete and they have to be built nowhere near town centres, which inevitably means they go up on greenfield sites. The vibrations from the turbines transmit down the towers, and into the ground. Wildlife does not like it much. You can't have tall trees; they sap wind energy. Wildlife doesn't like that much either; and neither does the soil. Eventually you end up with fallow land.



Fact why wind power is rubbish number 2:


We could supply all of England and Wales with the energy they need from wind. By fitting as many turbines as we can into Scotland and Northern Ireland. We wouldn't have room for the Scots and the Irish though.



Fact why wind power is rubbish number 3:


The turbines are dangerous. I'm not saying bits will break off and go flinging through the air. That hardly ever happens. What does happen is the blades get iced up in cold weather. They're at their peak of performance from the end of December to the beginning of March. Oh dear. Because when they begin to turn, the ice, which is clinging on to the blades, becomes dislodged eventually. If the blades are turning quite fast, guess what happens? That's right, it goes flying off in an unpredictable direction, and if anything made of meat happens to meandering around in the radius it could easily get an express delivery of rapidly moving rock-hard water flung from this whirling trebuchet to the back of the head. Consequently the areas where wind farms are have to be closed to ramblers when there's a danger of ice fall. And woe betide any farmer who puts his sheep there.




Fact why wind power is rubbish number 4:


They kill lots of birds, they really do. The Americans think that 200,000 a year are mashed up in the aerofoils as they spin round and there's no reason to doubt them.



Fact why wind power is rubbish number 5:


It's a great big electric motor spinning backwards stuck hundreds of feet up in the air. It produces bucketfuls of electro-magnetic interference. The MOD had conniptions a few years ago because some turbines were interfering with radar signals. Not just any old radar signals either. Oh no. These were the ones watching out for Russian air activity over the North Sea. So we wouldn't know there was a squadron of Bears coming to drop bombs on York until they flew over Scarborough. Nice.

Royd Moor is near Penistone. Penistone is part of Barnsley, though people in Penistone will not admit it. They say it's near Sheffield. That speaks volumes about Barnsley. In Barnsley they don't get much right, but give them credit where it's due, on the day they gave planning permission to build Royd Moor Wind Farm, one of the councillors must have had a drink of Red Bull because they insisted that the company that built it must, if it became apparent that it was interfering with TV and radio signals, build a repeater.

You can see Emley Moor from Penistone, in fact in some parts you can't miss it. At the very instant Royd Moor went operational, some people lost their TV signals and had poor radio too. BBC engineers call this a Q5 situation, which means complete loss of comprehensible sound and vision. Previously it had been Q1 (perfect).


Fact why wind power is rubbish number 6:


In the UK, the government is subsidising wind farms. It's making providers buy ROCs which means they've got to get a percentage of their supplies from renewable resources. This is proving expensive, and the suppliers are passing the costs to consumers. It's thought that at this rate, thousands of people in the UK won't actually be able to afford to run more than basic electrical appliances. So, no washing machines, no tumble dryers, no hoovers and probably no kettles. All so we can build wind farms that aren't going to be any use to us in 20 years.


You may have gathered from the above that I don't like wind farms. They're big and ugly, they spoil the scenery for miles around, they chase away wildlife and they aren't up to the job is my opinion. I am however, according to  HM Government, in a minority, as 80% seem to support them.


I still say that we can't have a modern, industrialised nation powered entirely by gusts of rapidly circulating air. I think that if the current mania for renewable resource continues, the UK will be plunged into a national crisis by 2030. I maintain that we need nuclear power stations. And yes, I know there's a risk of an accident, but apart from Chernobyl, which was jerry built by cowboys using margarine tubs and old bubble-gum, there's never been a major incident yet.  I like electricity. I make my living by it. I don't want to see it consigned to history and have to become a stonemason or a blacksmith. Certainly not when the reason is to satisfy Nick-bloody-Clegg and his gang of eco-mentallists.

In conclusion, I say there's no future in the wind, and we need to be investing in tried and tested resources instead.



Article and rants by Ian Lang Feb 2012

Previous Page