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SNOOPY, Good post thanks for the explanation. I am inclined with the little bit of engineering study i did to still question two blades instead of four, or more. Its a bit like a car engine two cylanders vibrate more than six. The Dutch windmills had four blades never two i still am inclined to think that they have it wrong. My limited knowledge in this field tells me they have it wrong, the more blades the less noise, and vibration the blades can still be feathered in strong wind gusts. I wont buy in i am already exposed with TPW in this field but will keep an open mind on the company.
macdunk
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quote:
Now why can't a three bladed windmill 'teeter'? ...
... Of course balancing the wind forces on a two rotor wind blade isn't trivial either, but it is much easier than trying to do the same on a three bladed design.
Is this what they actually told you Snoopy?
Hinging rotating blades is a common practice to cope with differential and varying loads across multiple blades. The single (lifting) rotor helicopter did go really anywhere until this idea was applied.
The advantage of the windflow two blade design is the simplicity of the hinging mechanism. However using a constant velocity joint sort of arrangement it could be applied to a three or (to keep duncan happy) four or whatever blade design. The theory is simple the actual practice of applying it to several tonnes swirling round a horizontal axis is a little! more involved.
You may also be interested to know that the rotor (independent of the number of blades) balances itself out without any clever control device.
The big issue here, which blew the prototype apart, is that it can only cope with a finite degree of imbalance (upto when the hinge reaches the limit of the hinge movement). Exceed that and you need to go out and pick up the pieces.
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quote: Originally posted by Paper Tiger
Is this what they actually told you Snoopy?
Not in those exact words. You got the output from the Snoopy 'paraph****ometer'. The see-saw analogy was mine.
quote:
Hinging rotating blades is a common practice to cope with differential and varying loads across multiple blades. The single (lifting) rotor helicopter did go really anywhere until this idea was applied.
The advantage of the windflow two blade design is the simplicity of the hinging mechanism. However using a constant velocity joint sort of arrangement it could be applied to a three or (to keep duncan happy) four or whatever blade design. The theory is simple the actual practice of applying it to several tonnes swirling round a horizontal axis is a little! more involved.
I appreciate your powered flight acumen on this matter Paper Tiger.
However, what I think the Windflow people were trying to tell me (and I stand to be corrected) was that a wind turbine tends to be an order of magnitude larger than these transport applications. So the differential blade loading of wind gusting is much more of an issue.
Also with a plane or a chopper you can simply 'go with the flow' if a really strong gust of wind gets up. A wind turbine is anchored to the ground and so it must take the full force of whatever the wind throws at it.
quote:
The big issue here, which blew the prototype apart, is that it can only cope with a finite degree of imbalance (upto when the hinge reaches the limit of the hinge movement). Exceed that and you need to go out and pick up the pieces.
The wind turbine is programmed to shut down above a certain wind speed. I think I am correct in saying that it was stationary when it blew apart. The Windflow people know this because of the electronic data logging equipment on it. Something was mentioned about the bolting assembly on the nacelle being redesigned.
SNOOPY
To be free or not to be free. That is the cash-flow question....
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quote: Originally posted by duncan macgregor
SNOOPY, Good post thanks for the explanation. I am inclined with the little bit of engineering study i did to still question two blades instead of four, or more. Its a bit like a car engine two cylinders vibrate more than six.
I don't think your analogy is quite right Macdunk. Car cylinders are generally in different geometric planes turning a crankshaft. It is the out of balance forces and moments in the different geometric planes that gives an internal combustion engine its balance (or not so to speak). IIRC the 'straight six' cylinder engine is a theoretically perfectly balanced layout, whereas any smaller number of cylinders, or a V6, is not.
The windmill blades are all in one geometric plane.
Perhaps a more valid comparison would be with a radial aero engine. I don't think it matters much how many cylinders you have in a radial aero engine. It won't have large out of balance forces operating inside it.
quote:
The Dutch windmills had four blades never two I still am inclined to think that they have it wrong.
There may be some argument for four blades being more efficient. Certainly the commercial prop aircraft I see tend to have four blades and not two.
However, in the case of a wind turbine the power source is 'free', so efficiency isn't the number one goal. The goal is to extract as much power as you can from the wind available, and that can but doesn't always mean working your blade at maximum efficiency.
Of course if you had four blades, then the total blade structure you are supporting would be twice as heavy, and that has other implications for costs.
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My limited knowledge in this field tells me they have it wrong, the more blades the less noise, and vibration the blades can still be feathered in strong wind gusts.
The 'noise point' was brought up. There is no denying that wind turbines do make a noise. The plan is to keep the noise 'broad spectrum' wherever possible. That means no annoying 'high pitched whine' or 'deep rumble'. Standing right next to the device -in admittedly low wind- we got a periodic 'deep woosh' as the blades went around. I wouldn't describe it as unpleasant any more than the sound of waves crashing in on a beach is unpleasant. Since 'the crash', Windflow have had another look at the gearbox design and have been able to make it quieter. I wasn't aware of any gearbox noise last Sunday, but that could be because the blade speed was so low on the day.
Having said that, noise annoyance can be a subjective thing.
The two houses that were closest to the turbine had no problems with turbine noise. The third closest house did. I for one would not be game enough to go and tell he/she of the third house that they are wrong.
quote:
I wont buy in I am already exposed with TPW in this field but will keep an open mind on the company.
Fair enough. Once the business model is proved you may find that NZ Windfarms will be 'put on the block' and a company like Trustpower might end up owning them anyway!
SNOOPY
To be free or not to be free. That is the cash-flow question....
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Snoopy:
It would be worth your while reading the WTL report on the event.
The turbine was rotating (but shutting down). I accept that this was an extreme event and understand what they have applied various remedies and that you can not cover every eventuality.
PS You do not need to be corrected.
PPS I have worked out what a paraph****ometer is, don't you just love the american's sense of sensibility and decorum?
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Banned
quote: Originally posted by Paper Tiger
quote: Originally posted by pimpit
The cheapest wind generator you can get in nz is $585.
It generates 200w at 40m/s wind speeds.
To get 1kw you need to have it running for 5 hours at top speed.
To buy 1kw hour off the power grid is only 17c.
I believe wind generator's have very poor rate of return for the investment.
40m/s = 144km/h
BTW Are we talking about the windmill or the cow?
Definately not viable. On windless days that is why you need to cow there.When the cow farts it can generate some power but the fart tax at then works out more than the money genreated by the windmill. And that aint no bull.
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Forgive me guys for going slighly off topic, but i think rather than windmills we should place turbo pods anchored in the bottom of rivers, and harbour entrances. Out of sight no noise continuous power. MACDUNK is on to it drawings at the ready first prototype on the [ahem] horizon. We have rivers rushing to the sea harbours filling up and emptying out a little bit of thought a few bob thrown my way from you lot and we are in business. macdunk
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Off topic too but wasn't there a New Zealand company about 15 years ago that tried producing mini hydro power devices? They had some mini turbine that could be placed in rivers without dams and produce power for 600 homes or some such. Can't remember the name...
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quote: Originally posted by Halebop
Off topic too but wasn't there a New Zealand company about 15 years ago that tried producing mini hydro power devices? They had some mini turbine that could be placed in rivers without dams and produce power for 600 homes or some such. Can't remember the name...
Well Lads its all been done before the USA gov spent heaps on it main trouble beside`s heaps more is the constante flow required it vary`s all the time so does the generation Factor.. [8D]
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Too stay off topic for another post.
If you want to use the flow of rivers build a damn dam and cope with the RMA.
If you want to go tidal then try synchronising the orbit of the moon with the peak demand of the consumers of New Zealand.
Meanwhile NZ Windfarms keep telling us how well the IPO offer is going but we can still apply for shares.
PS The announcement "NZ Windfarms Talking Corner Stone" is not a break-through in communications.
PPS I am looking forward to NZ Windfarms adding more variety to the Palmerston North vista*.
*Anybody know whether this windfarm will be visible from Woodville?
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The problem with wind, riverflow, tidal flow, waves and even the sun is that you cant guarantee it will be there when you need it. that is why you will always need dams/thermal/nuclear.
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Theoretically trading starts today in the heads (NWF) and options (NWFOA) for this one.
I am not expecting the turnover as for U2 tickets.
Actually I am not expecting this to trade at all.
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as a follow on from my last post well over a month ago, today sees the first trade in the head shares: 2,000 @ $1.20.
Still no trade in the options.
Disc: none
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On campbell tonight, dosent look too good. Can see plenty of potential opposition to the things.
I certainly wouldnt want them nearby
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Did not see the programme but I have just seen the five turbines currently installed of which only three were operating.
They certainly look a little odd when compared to the three bladers of their TrustPower neighbours and the big Genesis turbines further along.
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