Wouter, possibly a stupid question: Does slowing, or increasing the rpm change the amount of vibration? 15rpm isn't very "fast", but I'm sure those tips are hauling butt.

Phill,
There is a research project underway here in Florida looking at exactly that, using the Gulf Stream in stead of tidal flows.

These windparks were mostly installed between 2004 and 2007, between you visit. And there are going to be more.

I think there were only a handful of individual turbines in 2004 if any !

Construction is progressing at an alarming rate.

And while I'm happy to work on them, I'm not really ready to accept a whole horizon full of them.

To me the clear horizon over the western egde of the sea symbolized space, freedom and something untouched by humans and I enjoyed looking at it that way. Now it is more and more boxed in with these windparks.

But there is no way around it, we need them as the best solution, cutting down on energy consumption, is an impossible sell to most people.

Wouter

Probably more of interest is a station using the tide itself. I think they have one of those in France for over 30 years now. France has some huge tide in certain places. Basically it is very similar to a hydro electrical dam but you just reverse the flow twice a day.

Tides in NL are too small for that.

Another project of interest is wave-stations.

Another interesting project (for TaipanFC) is something that is planned in Malaysia. Two tall office buildings that are spaced apart in the such a way that they form a venturi. Right between the towers their are cross bridges so people can go from one building to another and between these bridges there are those smaller wind turbines that Timbo mentioned.

Wouter

Not really, it will mostly change the frequency at which these disturbances occur.

Of course if you REALLY slowed it down then the aerodynamic forces will become alot smaller as well and so too the disturbance. However energy yield will drop sharply below some turning rate and then you win nothing. The turbines are already optimized as it is.




Easy to calculate :

rotor blade length = about 50 mtr.
15rpm = 15 * 2*pi rad/min * 1/60 sec = 0.5*pi rad/sec

tip velocity = 50 mtr * 0.5*pi rad/sec = 25*pi mtr/sec = about 75 mtr/sec = about 300 kph or 200 Mph.

Wouter

Got some links or documentation on that Gulf Stream project ?

Would like to read some more about it

Wouter

Wouter,
here is a link to an NPR article about the project:
NPRGulfStreamproject

Link to the project web site:
FAUprojectwebsite

There is also a new technology under reseach called Reverse Electro Dialysis.
Basically they can draw power from the chemical reaction that occurs when saltwater meets freshwater.

http://www.redstack.nl/RS-Pres01/RS-pres_bestanden/frame.htm
http://www.onderzoekinformatie.nl/nl/oi/nod/onderzoek/OND1309967/

[quote
Another interesting project (for TaipanFC) is something that is planned in Malaysia. Two tall office buildings that are spaced apart in the such a way that they form a venturi. Right between the towers their are cross bridges so people can go from one building to another and between these bridges there are those smaller wind turbines that Timbo mentioned.

Wouter [/quote]

All sorts of things like this being considered round the world. With new London buildings having to use 10% renewable fuels, then creating venturis for turbines is worth considering. Just would want to know how noisy this would be when working in (or living near) the building.

Arie,
Interesting stuff.
I know zip about sources of natural energy.
From the zip I like solar.
There used to be a chap on a goffer with a solar cell to keep him out of the sun.
I would see him down the shops frequestly many miles away from where he lived.
I think he passed away because I have not seen him for years.
Anyhow with the increase in petrol prices I think a device for personal transport that is solar powered would be great.
So I have started working on a solar powered trike.
I suppose it has already been done but still it should be a lot of fun.

I am not an engineer either....They are still a ways off making this commercially viable, but it is sure interesting....one of their major concerns at this point is the potential damage to sealife: I guess the larger diameter turbines could do some real damage to the swimming critters <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />
Keep us posted on the solar trike!

Wouter, a long long time ago ( over 30 years ) I was working with a guy who was experimenting with horizontal turbines rather than vertical. Basically he had 4 wing sections on long horizontal poles, the wings were set up so they started to tilt when over a certain speed making them less efficient and thus governing the speed. His big problem was to get them spinning in low winds to then create lift which powered them up. His reasoning was that a small wing section on a long pole generates a lot of force rather than the inefficiencies of a propellor, much easier and simpler to build as well. Anyway why has this type of turbine not developed rather than the props we know of today

Sounds alot like a Darrieus rotor.



http://en.wikipedia.org/wiki/Darrieus_wind_turbine

The patent on it was given out in 1931, yes indeed, 1931.

Most of us know it by its curved version, as a result of the movie waterworld.






In my opinion it is a very elegant design, even magical with its vertical axis of rotation and it being totally independent of wind direction and speed. I mean how can it actually work like that ?

The reason is pretty simple but you won't figure it out for yourself that easily.

And water world was right in its usage. It is one of the very best rotor designs for a vehicle. It points straight up and works irrespectibally of the direction the vehicle is heading; it is said to even work when travelling directly into the wind ! But I've never seen any proof of the latter.

Is that the type you mean ?

Wouter

Yes your top picture is similar, why when they should be really efficient are they not being developed, I think they work because of the apparant wind they generate.

As far I can fathom props should / are really inefficient

Please read the wikipedia article that was provided.

Should answer most questions you have.

The only thing I missed in it was a comparison between energy yields (efficiency) between different rotor designs. Here the Darrieus is pretty good but the standard three bladed (upwind) rotors are still more efficient.

Wouter

Wouter-Your research is very interesting. Are there any of those mega windmills operating now? 100 meter span is huge. I know I met a guy here in town that builds windmills and ships them all over the world though I can't remember the company's name. But having the Tennessee River on there door step makes shipping much easier.

yes. Although the smart rotor concept is still in research and/or feasibility study stage.

Here is a windpark with 104 mtr diameter rotors. Notice the scale of the tugboats !




These pictures will give an even better feel of scale, notice the two persons standing on the stabilized walkway and the dinghy at the very foot of the tower. The stabilized platform uses a setup also found in flight simulators. It's base is made up from 6 very large hydraulic actuators that are computer controlled to keep the walkway level with the doorway in the tower when there are rougher seas.

Phill, these are actually the turbines that you have seen off the coast of Zandvoort. It is the windpark off "Egmond aan Zee".



Wouter

How about using the waves?

http://12degreesoffreedom.blogspot.com/2008/02/wave-and-tidal-energy-potential.html

http://seattletimes.nwsource.com/html/localnews/2003931009_wavepower07m0.html

http://www.mms.gov/offshore/PDFs/WaveTidal%20Energy_1-RobertThresher.pdf

Must be a lot of turbulence downwind of them. If the disturbance stretches for 20 times the height.. Dont put the race course too close to them. Say goodbye to any interesting birds as well.

I am waiting for them to drop these ocean current stations in the Gulf Stream and subsequently screw up its flow and the then fall out as Europe goes into a deep freeze. <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />

That ought to make the water wars over irrigation and river flow look like nothing.

And now back to our regularly scheduled program-----