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Function stacking windmill

 
pollinator
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My son came up with an interesting idea for function stacking on a windmill.

fig a) windmill of whatever type you like
fig b) extra stability achieved by adding guy wires
fig c) plastic sheeting over the guy wires helps to direct surface wind up into the blades
fig d) plastic sheeting also serves as a greenhouse (plus shelter for power bank)

What do you think?
stacked_fn_windmill.png
[Thumbnail for stacked_fn_windmill.png]
 
master gardener
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If it's windy enough to have a functional windmill, my guess is that you would need much more than 4 guy wires to hold the plastic. Maybe think in terms of how a yurt is built only the top "circle" of the yurt would be just below the windmill's pivot point? The more the plastic can flap and gust, the shorter its lifespan from my experience.

I know there's some reason that putting a windmill on top of a house is not recommended, but I don't know if that's because of 1. noise, 2. houses aren't built for the stress involved, 3. danger if the windmill blades fail, or 4 some other reason or a combo of reasons. Since your drawing has a dedicated windmill support as the starting point, that eliminates #2. If you don't spend hours in the greenhouse (or are prepared to wear hearing protectors if the noise bothers you) you wouldn't be stopped by #1. I don't know what the risk from #3 is, but please investigate it before risking someone's' life.
 
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What is the original function of the windmill?

Is it to provide electricity or to pump water?

In holland bases of windmills are enclosed so looking at those structures may provide some information.

I agree with Jay's comments. I live where it is very winding and plastic sheeting would not work here.

Making a solid greenhouse that might withstand your area's wind, rain, snow, etc. might work if installing the windmill blades somewhere as the holland windmills might work.

I feel your son has a great idea which just needs some refinements.
 
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I think you've got a great son! Congratulations.
 
Jay Angler
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#2 Son suggests this idea might work better with a vertical axis windmill. The "Just have a Think" fellow did a video about a new version of one that they were hanging off street poles, so it's an area with ongoing development.
 
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Some have had success with a horizontal cage type windmill on the peak of a roof where the prevailing wind blows up the roof.  So when designing a greenhouse think about prevailing wind and elevations to see if such function stacking is possible.  Wind is a degrading force so as others mentioned the design has to be resistant to those forces.
Encouragement to keep researching both windmill and greenhouse design with a view of compatibility.
 
pollinator
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I wouldn't use plastic sheeting. But, having buildings around that are shaped to channel air towards the windmill sounds like a good idea.
 
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Adding plastic sheeting will add to the windload on the structure.  More guy wires will help that.  Covering the guy wires with something that won't wear the sheeting e.g. low pressure irrigation pipe, might be an idea.  Cable stayed towers move a little as the wind changes but the sheeting may be fixed at the base.

Consider differences in thermal expansion of plastics and metals.  The taller the tower the more it might matter.

Taller towers are better for wind energy production.  Note they have intermediate guys that might cause problems in the greenhouse.

One reason for not putting wind turbines on a roof is turbulence created by the building.  Sloped plastic sheeting to ground level shouldn't create much turbulence at the tower head.

Consider how you will service the tower, the guys and the turbine when it is needed.  It would be good not to have to remove the sheeting in order to do this.

Consider whether putting a power system (electronics, batteries, and maybe high voltage DC and AC) inside a hot and humid atmosphere is a good idea.  It is actually done with greenhouse automatic controlled equipment but water and electricity are not always a good mix.

The air leaving the turbine should be as unrestricted as possible.  This might affect where the sheeting goes in relation to the turbine.

The thought of stacking functions is a great one and should help you establish how the problem you have is related to the solution you propose.

Have a look at prior art.  There has been a lot of stuff done on the West Coast in the last 50 years or so.  It is highly likely that some of what you propose has been tried before.  Worth looking at so you can make new mistakes rather than repeat old ones.

What about adding a thermal convection tower (Spain(actual), Australia(proposed))?  How would a tower a kilometer high go?  Or some form of solar concentrating collector mounted on the tower (don't forget the servicing issues)?

What I want you to do is to just consider what you think about the comments above without worrying about whether I think you are wrong or right.  I might be wrong, or irrelevant, or whatever.  If my comments help, good.  If not, not. Keep up the thinking.  It is not as common as you might hope.
 
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Hi Clyde,

Welcome to Permies.
 
                              
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Hi, I never post, but here is my $0.02CAD.

I wouldn't worry too much about trying to "get more wind" to the turbine.  Pushing wind around is a very complex thing.

When you see a truck going down the road with a tarp flapping in the "wind", that tarp is absorbing energy..... costing more fuel to move said truck.  I think the same would be true of the plastic sheeting at the base of your tower, if it is flapping in the wind, it is taking energy out of the surrounding wind.  Maybe it's wind energy that wasn't going to reach the blades anyway, but maybe it is....

Like I said, directing wind around is not simple stuff.  Consider wind tunnel testing on cars; Did you know that often what is done to the back of the car makes more difference than the front when trying to reduce drag?  Neat.  This is also neat  
 
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Just about every professional windmill advertisement I've seen talks about how the windmill blades must be high enough to get out of the turbulent surface wind area.  That they need clean laminar flow wind to perform well.  The angled plastic would most certainly increase the air turbulence, and would have a negative impact instead of a positive one.  
 
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Interesting vertical axis turbine.   https://harmonyturbines.com/wordpress/
 
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Sounds good in theory, but have you any idea how much force a moderate wind will exert on a plastic "sail"? That's why boat sails were made of stout canvas, and still those sails would sometimes part under a strong enough wind. Try it, maybe your winds will be lighter!
 
pollinator
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You have a smart, thinking kid, my friend. It is hard to figure out just how tall it would be or how large you plan to make the blades, but assuming that all is in synch, it is a pretty good idea.
You posited 4 guywires.
What if the structure could be more Teepee-like? That would make it cheaper and non "residential", which would be easier to "permit". Also, it is easier to resist the wind if there are many facets [rather than 4] to this teepee.  
I would also favor heavy canvass rather than what might be a plastic 'sail' flapping and eventually ripping.

A long time ago, I bought a couple of these advertising canvasses such as you see on the side of a road.  There are companies that specialize in recycling these large plastified waterproof sheets. [and you know they resist the elements since they are on billboard!
They can come in 40'X 40'. Maybe larger even. The one I got was made of 2 sheets, vulcanized together and had grommets every 4 ft. which made it easier to attach. I'm still using them between some garden beds I have, and it's been 10 years +.
The best idea is to be able to protect any electrical stuff under the contraption.
You didn't mention the general purpose of your windmill although getting electricity is obvious. If you used it to pump water to irrigate some other area of your property, that  would be a pretty cool setup too: The pump, I presume under the teepee, would be protected from the weather/ frost, depending where you live. [And some pumps that have to get primed each time don't freeze, any way, so...]. Tell your kid to keep it up!
Good thinking!
 
Jerry Sledge
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New and used vinyl tarps.
https://www.billboardvinyls.com/
 
Cécile Stelzer Johnson
pollinator
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Jerry Sledge wrote:New and used vinyl tarps.
https://www.billboardvinyls.com/



Thanks, Jerry. I think mine came from Michigan, but yes, that's exactly what I was thinking.
 
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