Wind Turbines with circular shroud all way round rotar blades

makeorbrake · 21-01-2014 01:08PM #1

As per the thread title, I've come across a wind turbine which has a wrap around all the way round it. i.e. Think of a circular outer frame - surrounding the complete rotar.

Is there anything tangible in the systems that they offer? For those that are not familiar with this, they claim 100% increase in energy produced due to the nature of the design of their units and payback periods 'as little as 5 years'.

Anyone here more knowledgeable on the subject care to critically appraise?

NB. I've amended this thread to remove company name following advice from the mods. Therefore, if you have an inkling as to suggest name of provider, then please hold back on that - don't post it up.

Jayzesake · 23-01-2014 06:12PM

Hi makeorbrake,

sorry, can't offer any enlightenment on those, but I'd be interested to know more too. Can you pm me a link?

Thanks

freddyuk · 23-01-2014 08:41PM

This contact of mine is in the Superhome scheme in UK. He has exactly that in his garden. i have no idea of the data but I can ask him for it. Click on the wind tab.
http://www.eastangliarenewables.yolasite.com/

However the company has gone bust so this may be a clue to performance.

makeorbrake · 24-01-2014 01:39AM

@Jayzesake: PM sent.

@freddyuk - what you linked to is more or less what I had come across - although the ones I came across came in different sizes and I suspect the smallest one - which was for domestic was slightly bigger than the one in your link...i *think*...

freddyuk · 24-01-2014 01:41PM

Concensus is they do not work and the company selling them has been resurrected here http://www.skwindtronics.com/ and has possible issues according to some links I have seen.
I would personally walk away.

makeorbrake · 24-01-2014 01:55PM

@freddyuk: Thanks for that. I hoped that wasn't the case but it figures that it is. If the claims they make were real, I'm sure this would be much much bigger news.

richie123 · 26-01-2014 02:12PM

i wouldnt think its a flash in the pan..at last a turbine thats actually efficient and works this company has won awards for this. technology will be available early 2014 according to its website.Will be interesting to see wat kind of warrantys and how expensive these new types of turbines will be!!(note i have no connection with this midlands based company whats so ever!)

quentingargan · 27-01-2014 10:46AM

Folks - I think we are confusing two different turbines here. Windtronics is a model that has been on sale in the UK for a few years. The OP here is talking about a machine being developed in Ireland. Both have an outside cowling.

There have been a few turbines with cowlings developed. I don't know much about either, but it is nice to see entrepreneurship and research going on in relation to small wind in Ireland, despite the lack of incentives here. In the long term, small wind has potential to be a major export product - especially in developing regions of the world where micro-grids will provide power in to areas not served by a national grid.

makeorbrake · 27-01-2014 10:59AM

quentingargan wrote: »

There have been a few turbines with cowlings developed. I don't know much about either, but it is nice to see entrepreneurship and research going on in relation to small wind in Ireland

Of course it is great to see - and I really want to believe in what they are claiming. If what they say is true and they are achieving 100% increase in energy produced by comparable systems without the cowling, then surely that would be a game changer?

I'd just love to see some independent verification of what they are claiming..

quentingargan · 27-01-2014 11:03AM

makeorbrake wrote: »

I'd just love to see some independent verification of what they are claiming..

Times have changed since the days when turbine manufacturers could publish a power curve based on theoretical outputs. The MCS process in the UK, which is a major market, requires independent testing to EN61400. Most major markets require this as well.

There are problems with the system - not least a cost of about €100k to do the tests - but anyone doing research does so knowing that their performance claims will be verified by this test. So I think that raises the bar enough that nobody is going to invest in developing a product on the assumption that they can sell it without this verification of their claims.

freddyuk · 27-01-2014 11:28AM

Thanks for clarifying that Quentin. Are we allowed to investigate further hereon or can you PM any details? I have not come across the company.

quentingargan · 27-01-2014 11:41AM

PM Sent. Q

quentingargan · 27-01-2014 11:48AM

By the way, I don't think this is a product that is commercially available as yet - it is an interesting concept.

So although the moderators requested the name of the company be snipped by the OP earlier in this thread, maybe they would consider allowing an exception here?

Capt'n Midnight · 28-01-2014 11:58PM

makeorbrake wrote: »

For those that are not familiar with this, they claim 100% increase in energy produced due to the nature of the design of their units and payback periods 'as little as 5 years'.

If you compare a three blade turbine with a six blade one then you'll probably find a 100% improvement

In wind farms the cost of the generator is only 1%-3% of the overall cost. And wind is free so efficiency gains don't really mean a lot.

Ducts work by capturing more wind. But you need to use more materials , and there is a much higher wind loading so you need stronger towers. With large on shore turbines three is the magic number. Three blades means less vibration than two (or even one :eek:) but a greater swept area than than using more blades.

Perhaps using two blades on a floating platform might be more efficient because you have to take into account a pounding ocean and no fixed base. Other than that all large production wind turbines use three blades without ducts. It would certainly make towing out a semi submersible design a lot easier

Also have a read of
http://www.gizmag.com/dodgy-wind-turbines/27876/

makeorbrake · 29-01-2014 01:33AM

Capt'n Midnight wrote: »

If you compare a three blade turbine with a six blade one then you'll probably find a 100% improvement

In wind farms the cost of the generator is only 1%-3% of the overall cost. And wind is free so efficiency gains don't really mean a lot.

Ducts work by capturing more wind. But you need to use more materials , and there is a much higher wind loading so you need stronger towers. With large on shore turbines three is the magic number. Three blades means less vibration than two (or even one :eek:) but a greater swept area than than using more blades.

Ok, I didn't realise this. So more blades = more power but less stability but with significantly more outlay on the unit due to additional blades?

I've checked back again with the system in question, and the pics of their systems seem to be 3 blade turbines. Does that mean that perhaps there is something in this - without there necessarily being increased outlay for their product (there's no indication of pricing yet).

Capt'n Midnight · 29-01-2014 09:18AM

makeorbrake wrote: »

Ok, I didn't realise this. So more blades = more power but less stability but with significantly more outlay on the unit due to additional blades?

I've checked back again with the system in question, and the pics of their systems seem to be 3 blade turbines. Does that mean that perhaps there is something in this - without there necessarily being increased outlay for their product (there's no indication of pricing yet).

More blades = more stability
More blades = slower speeds and higher torque. Look at the old wild west wind pumps , like the turbofan of a jet engine. Lots of torque to mechanically couple a water pump.

A three blade fan can't hope to capture energy from all the air that flows through , the blades are simply too narrow, but the outer tips of the blades are further away so you have a greater swept area.

If you increase the number of blades by two , you could get 100% more power. If you double the length of the blades you increase the swept area by a factor of four.

Ducting works. Almost all jet engines these days use turbofans.

However, helicopters even things like the Osprey V22 which spends most of it's life as a plane don't because it's a lot of dead weight to carry around.

The number of propeller driven aircraft with ducts is very small. And the Tu-95 / Tu-144 don't use them. And they are big, heavy, fast and inefficient. Huge Contra-rotating propellers. And they can still cruise at over 850Km/hr if you put the foot down.

What I'm surprised at is the lack of winglits on turbines. Most new airliners have the vertical surface at the tip of their wings to reduce vortex / wind spilling off the end - maybe it's just useful when travel above Mach 0.8 , but they could offer some of the advantages of ducts at a fraction of the cost.

16-02-2014 01:59AM

Hugh Piggott wrote:

Building a duct that forces the air through a smaller
diameter rotor at high speed.
It simply isn't worth all the extra material involved in
building a duct like that. The wind tends to divert
around it so you don't gain as much as you would
think. It is actually more effective to build a
conventional blade rotor with larger diameter, than to
make a duct. Some big companies have spent a lot of
their investors’ money finding this out.

.

forestgray · 19-02-2014 08:25PM

Capt'n Midnight wrote: »

If you compare a three blade turbine with a six blade one then you'll probably find a 100% improvement

This is completely untrue. Although there would be a marginal increase in efficiency, it wouldn't be anything near 100%. Any increase in efficiency due to increased number of blades is dominated by a law of diminishing returns.

By way of example. ..
If I remember right a single and two blade turbine design are about 60% and 75% as efficient as a three blade design respectively.

19-02-2014 10:20PM

Going from one blade to two = 6% efficiency increase, two to three is a 3% increase.
Balancing the centrifugal moments is why three blades are most popular, reducing mechanical wear this is often the motive of the added material expense. With fewer blades higher rotational speeds can be achieved.

Wind Turbines with circular shroud all way round rotar blades

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