Windmill

[Hello]

I am thinking of constructing a small windmill (4 to 5 feet high), and covering the blades with solar cells, to generate electricity from both wind and sun and charge some batteries. Has anyone seen a project like this published, or have any ideas on the subject? Thanks!

[Externet]

Hi.
It will work very well when the sun faces the cells and vibration does not break them and brushes be reliable and when the surface of the cells be aerodynamically curved.
Miguel

[josmith]

It's a great idea if you live in an area where the wind starts in the east and gradually shifts to the west during the day.

[jwax]

I like the hybrid concept, but some compromise would have to be met between solar output,wind output, and somewhere in between.
Solar cells are available as a flexible film so they could be bonded to the blades, but have relatively low efficiency.
Nice project for the magazine!
John

[Dean Huster]

Here's the rain on the parade ... we've already had some sprinkles ..... I sure don't see tracking the sun and tracking the wind as two things that will ever synchronize. Even if the wind did follow the sun as josmith suggested, I really don't see the wind blowing straight down at high noon! And with the cells on the impellers, you'll have to have slip rings to deliver the power.<p>I'd suggest that it would be more cost-effective to have a windmill on a tall tower (it's amazing how much stronger the wind is at 40 feet than it is at 5 feet) and a sun-tracking solar array on a separate frame.<p>Dean<p>[ September 27, 2004: Message edited by: Dean Huster ]</p>

[Externet]

¿What happened, Dean?

The design could be nicely enhanced with mirrors tracking the sun aiming the face(s) of the windmill or tracking deflectors re-directing the wind towards the sun incidence angle.
But won't work on any calm nights...
Miguel

[Dean Huster]

"¿What happened, Dean?"<p>I'm getting slow in my old age. What happened where?<p>
"But won't work on any calm nights..."<p>Now, wait a minute. What if there's a full moon?<p>Dean

[Chris Smith]

Make a cover over the wind mill and cover that with solar cells? <p>No need for aero dynamic anything, Water wind mills use flat blades like dog eared fence slats.

[Dean Huster]

In the book Wind and Windspinners, a windmill design that used steel barrels cut in half from top to bottom and interleaved with three such sets set vertically on the same axis with a 60°shift for each pair was used for a "directionless" windmill.<p>Dean

[rshayes]

The windmill Dean is describing is a type called a Savonius Rotor. Try typing "savonius" into google.
There are several descriptions on the internet of this type. Many seem to be in Australia.

[Joseph]

Oh yes, I have seen the plans for one of those. Australia sounds like a good flat location for tapping into wind power.<p>I edit so much because I get large size fonts only after posting. <p>[ September 29, 2004: Message edited by: Joseph ]</p>

[Bob Haller]

My best friend has a 14 foot blade windmill in his yard he uses to charge 12 volt batteries.<p>He uses old car batteries because the energy generated is worth less than the cost of replacing batteries. were in pittsburgh, in the right spot it might work. but solar cells on the blades, forget it. ruin the aerodynamics and a hazard if a cell or its mount come off. my friend had ice build up once it flung the ice sheet 1/2 mile and could of killed a person if it hit them.<p>you absolutely need a robust overspeed limiter, he has paddles that come out in too high wind to slow things down. also remember they can be noisey when they run, which will be spring fall and winter storms. for much of the year you will have to charge the batteries so they dont go bad.<p>my friend bill had hassles with the shadow of the blade turning bugging the neighbors, it passed over their window.<p>they can be fun, as a exhibit but energy wise they arent a winner.

[haklesup]

Inspired by these posts about putting solar cells on a windmill, my creative sap started running a bit. (especially when pointed out that a windmill can be a noisy eyesore.)<p>Imagine a tree-like structure with leaves made up of photo-electric cells and with stems and branches made up of piezo-electric strips (configured to generate tiny charges when flexed).<p>The "leaves" would be arranged to minimize self shading and give maximum exposure to the sky at all angles.<p>When the wind blows, the leaves would flutter, causing the piezo-electric stems to contribute charge.<p>All the power is collected in the "Trunk" and delivered to the load at the base.<p>If one cared to estimate the surface area of the leaves, the percent exposed to the sun and the efficiency of the cells, the power derived from the photo cells could be calculated in a straightforward manner.<p>What I am not sure of is the piezo electric part. How much charge would a 2 inch "leaf stem" contribuite in a mild breeze? and Can this charge be efficiently collected and stored?<p>Anyone have a good sense of how efficient such a system could ultimately be? <p>No doubt such a tree made of today's materials would be very expensive and make barely enough energy to run it's own christmas lights at night but with materials of tomorrow and high volume, could such a tree be in our futures?<p>search on "piezo electric generators", they do exist in various forms.<p>I think maybe the tree idea has been tried but without the piezo twist.