Update on the MagWind Levitated Vertical Wind Turbine
Ok, let's take another approach. Mag-Wind says its wind turbine will produce 5 kW at a rated speed of 28 mph (12.5 m/s). To produce that much power at that wind speed it would need to be 281% efficient! Yee ha. That's some windmill. Modern wind turbines, at best, can deliver 40% of the energy in the wind at any specific wind speed. This turbine has a specific rotor loading of 3,360 W/m2 of rotor area. Let's compare that to the over rated AirX. The AirX is somewhat smaller so we won't compare actual production, just rotor loading. Remember, the AirX doesn't even deliver what is promised. The specific rotor load for the AirX is about 400 W/m2. The Mag-Wind claims to produce from its rotor almost ten times more power than the AirX which can't even meet its performance claims. Ouch. I've never seen such outlandish claims before-and I've seen a lot of them.
Link: Wind-Works.org
Via TreeHugger
1 Posted 2007-02-05 23:04:21 by Chris (becky@nt.net)
Well without trying a magwind to verify claims, sounds like someone just wants to sound smart.
im sure mag lev trains, HV engines and even gas savers all have !smart! people trying to prove they dont work but they do.
ps just that fact that it still produces power in high winds that would normally break or stop any other wind generator from producing power must mean something.
prop or turbine... sounds like only a pilot would know...
2 Posted 2007-02-07 14:33:43 by keivn houston (househacker.com@urly-bird.com)
From the original post: "So, how is it possible to make as much electricity as we do with only a 4-foot sweep? We use the roof of a house or other building to extend our reach and increase the volume of air reaching the sails of our VAWT. This gives us the effect of a larger surface area without actually having a larger vane."
Perhaps the fact that the roof of the house funnels wind into the rotor, means that all of your calculations that depend on area are off.
Remember: according to standard aerodynamic equations, bumblebees can't fly.
3 Posted 2007-02-20 12:00:53 by EM
Actually, according to standard aerodynamic equations and models, it is well understood how bumbleebees fly. Please stop spreading inaccurate myths found in 'inspirational' emails.
One (of many) source:
http://www.news.cornell.edu/releases/March00/APS_Wang.hrs.html
4 Posted 2008-10-23 09:10:17 by Kevin Borich (kevin@kevinborich)
Does anyone know if it really works? If it
does where do I get one from?
cheers kev - insearch of!
5 Posted 2009-02-10 11:32:42 by Ben
What you need to understand is Mag-Wind's "roof effect" is simply a fancy word for a wind funnel.
That, and you can't quantify wind energy simply on wind speed. eg. How much energy is available for extraction if you're blowing through a straw at 12.5m/s? How much energy is available for extraction if the coast of a small city is being blown by a 12.5m/s wind?
Wind speed needs to be considered together with cross sectional area if it's to be used as an indicator of potential energy, because you're extracting kinetic energy from a moving air mass. So if you're talking wind energy, you *have* to talk about its mass.
What MagWind is doing is using the entire cross section of the house to act as a giant sail to funnel all that moving air mass and direct it at the wind turbine's sails. If you put their vertical turbine in the desert, or any other large flat surface, then yes, your calculations would hold; but they'd definitely not hold if placed at the end of a gigantic wind funnel, because the wind cross-sections are drastically different, and therefore collect differing masses of air.
Hope this clarifies things a bit. Remember, kinetic energy is 0.5mv^2. Don't forget it's about the wind's mass as well as its speed. MagWind is simply using the roof to funnel more air mass to strike its turbine's vanes.
6 Posted 2009-02-10 11:37:06 by Ben
As an example,
If you blow through a straw, the air leaves the straw at about 5m/s. But, the air leaves your lungs at a speed that's definitely lower. MagWind would call this "straw effect".
Or even partially covering the tip of a hose. The water flows through the hose at a constant rate, but leaves the end of the hose at a much higher speed and pressure. MagWind would call this "thumb effect".
7 Posted 2009-06-25 16:45:47 by Kevin
So what does this mean in laymans
terms? I cannot see anything going on
recently at their website - I guess that
says it all, but thought I'd ask anyway.
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