wind power

[johnyb]

 hi all I,m mostly curious I dont remember who posted poower from the win d chart my ? pertains to that chart. I seen in  another post that a 10 ft diameter blade at 20 mph wind produces .94 % of a horse power. This chart shoes many different size blades but the ten ft blade shows that in 20mph wind it produces inthe neighbor hood of 500 watts  which is .66 % of 1 horse power  why the discrepency almost athid difference  am I missing something   thank you in advance asuming mags are 1 x2 x1/2 n 45

[TheCasualTraveler]

Hello johnyb,

     Looks like your fairly new to the forum. When you go to the page to submit a posting there is a box below the post area that says, "Preview Post". I will often click on it up to 10 times to make sure my post is spell checked, coherent and reads well. Just a thought.

[Flux]

A reasonable figure for a home made prop of 10ft diameter in a 20 mph wind when running on the peak of its power curve is probably about 1.2 hp.

The snag is that that with conventional loading directly into a battery with a cut in near 7mph is that at 20 mph with a high efficiency alternator you are hard in stall and the prop may be down to 1/4 hp or less. The best compromise you can manage is to lower the alternator efficiency to something like 50%. This reduces your potential 1.2hp to .6hp and you will be significantly stalled so you won't be running the prop at its peak power point so if you manage about 400W you are in fact doing quite well.

Unless you have some means of matching the load for the various wind speeds you can't hope to get anywhere near the full prop power over a wide wind speed range. You can improve the high wind power at the expense of low wind performance but unless you live in a very high wind area it doesn't pay off in terms of energy capture.

Can't see where magnets come into this discussion, it's a fundamental problem of matching a variable speed prop to a fixed speed alternator. Buy a mppt controller and you can actually get your 1hp at 20mph .

Flux