WC Archive

Careful with your units!

You probably mean 2500 kilowatts not kilowatt hours.

Actually, I *do* mean kilowatt-hours. From the product description:

We have chosen to specify the turbine in terms of expected annual kilowatt-hour production in Class 2 (30 meter) wind resource.  We think this is more useful than specifying in terms of power output in a wind speed that rarely occurs in the low wind resource typical of SWT.  The WPU-2500 will produce 2500 kilowatt hours in Class 2 (30M) wind. 

The WPU-2500 would typically be called a “1500 Watt” Turbine in the industry.  It would be rated at 1500 watts at about 13 meter/second.  Thirteen m/s is about 28 mph, which rarely occurs where most of the population in developed countries lives.

Thanks for keeping an eye on the details, though -- it's important to get these things right. I'll amend the front page to make the kw/hr use more clear.

What do you mean by "new model"? It looks pretty much like the good old "Darrieus-Rotor" (invented 1929 by Georges Darrieus).

Sigh, yet another vertical axis wind turbine claiming world-changing characteristics. Wind Sail are to be congratulated for keeping their efficiency numbers in the realms of the possible. Many companies have sprung up claiming efficiencies (Cp) of greater that 16/27, the Betz Limit, or theoretical efficiency limit of a wind turbine.

Reducing the tip speed ratio reduces the efficiency of the device, so the Wind Sail's Cp of 28% at 12m/s is quite a bit lower than a typical horizontal axis machine (like the Lagerwey LW900, which has a Cp of 34% at 12m/s).

This machine is miles ahead of the modified Savonius (drag) turbines that some manufacturers are touting. But still, very few knowledgeable wind engineers would advocate roof-mounting a wind turbine. There are issues with turbulence and vibration, not to mention that built-up areas tend to be quite sheltered.

I also take issue with their claims about fewer bird kills. Any structure kills birds. Buildings and windows kill over 5000x more birds than wind turbines, and cats more than 1000x (source: http://www.awea.org/faq/tutorial/wwt_environment.html#Bird%20and%20bat%20kills%20and%20other%20effects. ). It would be a very dizzy raptor that could sit on top of a running vertical axis wind turbine.

Vertical axis machinery is not some magical energy source suppressed by The Great Conspiracy. They were the subject of huge development projects in the 1970s and 1980s. There were problems with fatigue, higher costs, and lower operating efficiencies than horizontal axis machines. I design wind farms for a living, and I don't know of a single utility-scale vertical axis machine that is operating, let alone available for commercial purchase.

The aerospace industries have had limited success in developing viable wind turbines. NASA, Boeing and MAN all tried developing machines, but could never bring a machine to market. It's interesting to note that most of the successful companies now manufacturing wind turbines started out in agricultural engineering, not aerospace.

The only thing that realy matters with a turbione is is it cheap and is it durable. If its both then you have a hit.

What killed alot of early designs was maintenance costs.

Sigh. Another defensive HAWT advocate.
Notes
1) Wind Sail is NOT proposing utility scale application. The Russians have proposals in this area, but no WS work is underway.
2) What matters in SWT is cost per kwh, not efficiency, etc.
3) Japan specifically is examining placing small turbines on top of buildings. When you have no oil, you get interested.
4) As recently as one year ago, old Flowinds were still in operation at Altamont pass. Next time I fly over, I will look to see if this is still true.
5) Agree bird kill is mostly hype.

I don't think that anyone who is serious about VAWT's would claim that they are a source of anything other than a cost effective alternative to HAWT's. The trouble comes trying to over come the prejudice that pervades the industry. It is good to see that you understand the value of measuring the output of wind turbines over the course of a year. I have long thought that the current method to be at best misleading. However that's the way the industry does it so i guess we'll just have to go along with it. Tell me..does -your machine self start?