Yawn Here we go again with claims of getting 3 times as much power by putting a fancy hoop around the wind turbine and mounting it at ground level. And people will get fooled again and lose their money again.
Here’s a link to the story last time they tried it, in New Zealand
Buy a Tristar charge controller (UK only)
From: Mike Allen
Subject: Re: A Wind Turbine Recipe Book
Date: 12 April 2013 10:53:18 BST
To: jytte
I recieved the book yesterday and when it arrived I thought ‘this isn’t worth £12’.
But how wrong I was once I’d opened the envelope and settled down to read the contents with a cup of coffee. 3 hours later the coffee was stone cold and I was still reading the book.
Loads of info to be getting on with.
I’ll email Hugh when my terbine is up and running with some pics.
Thanks a lot.
Michael.
I wish that link to the article and video were working.
Admittedly my first impression upon seeing the idea was – booo-gus! Then maybe about 4 years ago on nhk’s science view they showed a rather convincing demo (sorry I couldn’t find such an old video now). A toy prop spun by a wind source that can easily seen to speed up when the shroud was placed around it. Just like a vehicle that has lower pressure areas at the rear (“base”) causing drag, it is possible to create drag near the rear of the turbine with the diffuser ring that decreases back side pressure of the turbine for increased rotational speed. Now granted it doesn’t scale up to any appreciable size very well, and there may still be something missing from such a simple demo (like higher velocity but lower torque), but to date, it changed my mind.
Yes it does work in theory and you can indeed obtain an increase in output for a given area, but in practice it is much easier to increase the swept are of the blades than to build that huge thing. The fact that you can find no trace of this project now (seven years on) kind of says it all really. Taller towers and larger blades work better.
I agree with your assessment. It seems completely impracticable to put a shroud around a large turbine given that for one thing, it induces a large drag force imposed on the support structure. Still, at my harbor I see a number of yachts with those small turbines for which it might be suitable – the benefit also that it protects inadvertent collision with the blade.