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Groundbreaking 'spinning' wind turbine wins UK Dyson award

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About 35 years ago I first saw a fantastically simple DIY omnidirectional wind turbine.

 

Take an oil drum. Cut it in half vertically down the centreline.  Mount the two halves side by side facing opposite ways on a vertical axis.  Whatever way the wind blows it will always rotate the same direction.

 

This just sounds like a refined version of that principle.

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31 minutes ago, ProDave said:

This just sounds like a refined version of that principle.

Yes and no - the idea looks like it was to accept wind from any direction including up and down so if you put it on the side of a tall building it can operate in the updraft. Their Ptypes are 3D printed which means they can have air passages of all shapes and forms inside.

Edited by MikeSharp01

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Vertical wind turbines have historically not performed well but it hasn't stopped people from trying! Be interesting to see an installed version and the actual energy it produces, in an urban environment. There's also no way to "furl" if the wind gets too high unlike modern turbines, risking structural damage. Best of luck to them though....one free with every vacuum cleaner perhaps?!

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11 minutes ago, mike2016 said:

There's also no way to "furl"

That was one of the design considerations - as in it never needs to furl, one of the designers (inventors) was on R4 Today this morning and he mentioned that it can work in very high winds so keeps on generating even though the more traditional turbines have had to shut down.

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There are two main types of vertical axis wind turbines, and they both have different upper limits. 

 

The Dyson ones, like the "cut in half oil barrel" ones, are variations on the Savonius design (see here: https://en.wikipedia.org/wiki/Savonius_wind_turbine ) that use drag as the motive force and have the advantage of simplicity, they cannot easily over-speed in high winds, they don't need to point into the wind and they can still operate reasonably well in "dirty air" (i.e. air that's pretty turbulent, such as in urban areas).  The disadvantages are significant, though.  Because they can only ever deliver power equivalent to the differential lift and drag of the side facing the wind, their overall efficiency will be well below the Betz Law limit***.  The other disadvantage is that their main bearing takes a very high bending and shear load when operating, or just held stationary, in very high winds - a much greater load than an equivalent power axial turbine.

 

The other type of vertical axis turbine uses lift as the primary means of extracting power, like the Darrieus rotor (see here: https://en.wikipedia.org/wiki/Darrieus_wind_turbine ) and can be a fair bit more efficient - in theory they could be as efficient as axial blade wind turbines and, like them, operate at close to the Betz Law limit***, which so far has seen wind turbines that run at up to about 48% mechanical efficiency (there are electrical losses and transmission and conversion losses that reduce that a bit).  In practice, there hasn't been as much investment into developing Darrieus designs, for a host of reasons, including the complexity of some of the rotating components, the challenges of servicing them, and just the fact that an immense amount of money has already been invested in developing axial blade wind turbines, so there's no real incentive to invest in Darrieus  type machines.

 

The Dyson device seems to be fairly and squarely in the "chocolate teapot" category as far as I can see.  Urban wind turbines have a host of problems not associated with the design, such as noise, vibration, finding safe and secure mounting locations for them on or around buildings as well as the inevitable return on investment conundrum.  A Savonius rotor type design, even if highly optimised, as I'm sure Dyson has done, is still going to be a very low efficiency device, and that, combined with the much lower overall wind speeds in urban areas (buildings create drag which slows down the low level wind speed a lot), means that the net output for any given free air wind speed is likely to be too low to generate a worthwhile amount of power.  I wish him well, but feel that this is another idea that won't take off commercially.

 

 

*** The Betz Law limit is an interesting concept that can be a bit hard to get your head around at first.  In essence, Betz started from the standpoint that any wind turbine device could never extract all of the available power in the wind flowing through it, because if it did, there would be still air behind the turbine device.  The problem with that is, if the air is still behind the wind turbine device, then how can there be air flowing through it to generate power? 

 

There are some who have argued that the formula Betz came up with to describe the maximum mechanical power extraction efficiency of any wind turbine device may not be wholly valid, and I can think of a few ways in which the limit he proposed might possibly be broken, as curiosities only, but for all intents and purposes the Betz Law limit works well as a practical limit on device efficiency.  In simple terms, this limit means that every the very best wind turbine cannot extract more than about 59% of the available power in any free stream of wind. 

 

For those that want to do the sums, Betz Law is described in more detail here: https://en.wikipedia.org/wiki/Betz's_law

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To be fair to Mr Dyson, I don't think he or his company has anything to do with this design. The designers have won a 'James Dyson Award' which is given out by his charitable trust.

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1 hour ago, mike2016 said:

There must be an upper limit and where do those stresses go at that speed?! Good article here that goes into pros and cons. Maybe they've cracked it but I'd be skeptical until they publish verifiable data from a real world trial.....

Not even sure it has to be mounted on a vertical axis, only going on what the chap said this morning and awaiting some real results is something of a must. However we might conjecture given that they envisaged its max size as about 1-2m in diameter . If it is a sphere, and that is essentially what it looks like, and has an axis (which I guess it must) then the stresses will go into the bearings to support it and the structure of the sphere itself in terms of the resultant centripetal forces trying to tare it apart, given its max envisaged size I don't see an upper wind speed limit being in there because it cannot physically furl so only breaking will do it and its 'windage' (for want of a better word) stationary and rotating will perhaps be approximately the same, while their turbine is much smaller than other things in the environment that successfully  stand in any presented wind across the planet. However Betz may well apply as it approaches a different aspect of the operation.

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You can mount a Savonius device like this horizontally, or at an angle and it will still work OK.

 

The Betz Law limit for a device of this type is a lot lower than the ~59% maximum efficiency for a theoretically "perfect" device for extracting power from the wind.  It's roughly half the Betz limit, so a maximum theoretical mechanical efficiency of just under 30%, and an estimated maximum practical efficiency (if developed to the same level as variable pitch, variable blade twist, axial turbines) of less than 25%.

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I get the impression that a good analogy for this turbine wrt to a typical one is like going for a east-south-west solar array rather than a south one - you get less peak but more width.


So horses for courses. They seem to want to sell this to people in flats for the deranged urban winds of the metropolis.

 

I would say that it would be interesting to have this made from a sheet material or spokes and fabric, rather than a plastic matrix.

 

Could it be delivered flat as an unfolding space-frame, perhaps even made from a properly reusable material?

 

Ferdinand

 

Edited by Ferdinand

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@JSHarris summarises things nicely above but it should also be pointed out that the amount of energy available in the wind varies tremendously with the wind speed. It's that energy which the Betz law says what proportion you can extract. The available energy is proportional to the cube of the wind speed so wind at 6 m/s has 8 times as much energy as at 3 m/s. An increase from 6 to 8 m/s doesn't sound a lot but it more than doubles the amount of energy available. Or, to put it another way, the decrease in wind speeds caused by buildings and so on really stuffs turbines even if they're cleverly designed to deal with the turbulence.

 

Maybe one day somebody will design something which is actually useful for this sort of thing but it's really not worth wasting much time on until they (or, better, somebody else) produces good figures for actual power production.

 

The reason it's cubed is kinetic energy is proportional to the square of the speed and the amount of air you get through the turbine disk is proportional to speed as well.

Edited by Ed Davies
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Very true @Ed Davies.  Sometimes trying to simplify stuff as an attempt at clarity leads to technical inaccuracy, and I didn't want to get bogged down in the "power is proportional to the square of velocity and energy is proportional to the cube of velocity" stuff, for fear of the post being too long and too technical for some!

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On 05/09/2018 at 18:37, JSHarris said:

the post being too long and too technical for some!

 

I like branflakes 😐.

 

Do windturbines require PP beyond a certain point or are they considered as non permanent structures and exempt for soem reason. Obviously the massive huge ones are a different question. Just thinking of a relevant domestic sized one.

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1 hour ago, Big Neil said:

Do windturbines require PP beyond a certain point or are they considered as non permanent structures and exempt for soem reason.

 

Depends where you are. In Scotland they are permitted development as long as they're at least 100 m from anybody else's curtilage. That's for microgeneration which is up to 50 kW so potentially quite a substantial turbine.

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4 minutes ago, Ed Davies said:

Depends where you are. In Scotland they are permitted development as long as they're at least 100 m from anybody else's curtilage. That's for microgeneration which is up to 50 kW so potentially quite a substantial turbine.

interesting. Can anyone in the know please post a link to a domestic product which might produce the same average power as lets say a 10KwP solar setup as an example. Just so i can look at a real example instead of product surfing

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PV will have a capacity factor around 10%, i.e., averaged over a year it'll produce about 10% of its “peak” output. A wind turbine will do a bit better but in the south of England I'm guessing not much more than about 20% so to match 10 kWp of PV you'd want a turbine around 5 kW. The one that springs to mind is the 6 kW Proven, now sold by Kingspan.

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I like the idea of combining Pv & wind generation as it dramatically improves the window for providing power. However a neighbor has a turbine installed in his field and it is remarkably noisy, not something that would be tolerated in a built up area. Fortunately we are rarely downwind of it. The (lack of) noise claims made by https://thearchimedes.com/ piqued my interest, but they have gone very quiet, and we would never get PP for it on our new site. 

I do wonder if district systems based on geothermal heat will ever take off, apparently the conditions in Cornwall are good for it, but I would imagine the setup costs would be prohibitive for the foreseeable future. 

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On 31/01/2019 at 13:55, Ed Davies said:

 

Depends where you are. In Scotland they are permitted development as long as they're at least 100 m from anybody else's curtilage. That's for microgeneration which is up to 50 kW so potentially quite a substantial turbine.

I could manage that distance --Iwill check 

any good small turbines out there -

seems to be a lot round here that have stopped working --supplier gone bump  or just too unreliable mechanically

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2 minutes ago, scottishjohn said:

any good small turbines out there -

seems to be a lot round here that have stopped working --supplier gone bump  or just too unreliable mechanically

I am in a top spot for a wind turbine, no adjacent property  for miles, open to the sea facing south west, with hills on either side that funnel the wind straight at my property. But finding the funds and knowing your spending it wisely  are a couple of big hurdles I still need to cross...... anyway back to work. 

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40 minutes ago, scottishjohn said:

any good small turbines out there

 

The classic robust off-grid turbines are the Provens, now sold by Kingspan. The smallest is 2.4 kW (branded as 3.6 kW or so by Kingspan, I think). The next larger one is the 6 kW. (They then tried to stretch it to a much larger one, 15 kW, I think but had a problem with the manufacturing of the shaft which basically sank the company. The MD, Gordon Proven, died of a heart problem and Kingspan bought them out.) When they were Proven the problem with them was that they had so many agents around the country that none did enough business to be able to afford to stock spares and Proven wouldn't deal with end users directly. I don't know how this has changed since Kingspan took over. There are examples all over the Highlands, one 6 kW which has been running for years just down the road from my site. Paul at the end of the road swears by them - I've lost track but I think he has two.

 

Further down the size scale it gets a bit harder to find reputable designs which are suitable for windy sites. The two I've had my eye on are Futurenergy and Leading Edge The best I can say is that both have been around for a while and have been used with reasonable success. Futurenergy had a good reputation for customer support though I haven't been in touch with any users for a while.

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hi, 

 ok after talking to border hydro ,who also are supplier of kingspan wind turbines 

its a non starter  if you have grid electric --only really worth considering if off grid 

35k ballpark ,for 6kw turbine  fitted

20years to  payback --then it will be about worn out .LOL

 

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But a) do you really need the 6 kW? and b) the “fitted” probably includes a lot of concrete in the ground that you could probably do yourself/get done a lot cheaper.

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One of the many troubles with small wind is the cost of the towers. Its just crazy expensive to get up into the wind economically. Hence a lot of provens for example are on 6m towers, which is hopeless, you want to be at least quadruple that IMO, preferably more. 

 

Let's not even talk about the blades flying off yet.. 

 

 

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