Dutch Style Windmill

[PHinker]

   I'm kicking around the idea of building a dutch style windmill on our 40 acre property.  Of course, those designs were aimed at milling grain or pumping water but I would like to find a way to generate electricity.  Even a modest setup would have an enormous swept area so it seems that gearing up to usable shaft RPMs isn't completely unreasonable.

   What I'm thinking is the design would look authentic on the outside but the inner workings would be considerably altered.  First, there's no reason for the main shaft or any of the middle or lower floor machinery.  Everything could be contained in the cap so the middle and lower floors could be used for a shop and an office.  One thing I haven't been able to find yet is a detailed description of the fantail.

   Sail design is another issue.  I haven't been able to find any data on the efficiency or tsr in that sort of blade.  Some of the later designs included shutters to help with managing high wind conditions.  My guess is that I'll end up replacing the traditional sails with a more modern blade design.

   I've talked with my local electric co-op and they are open to hearing about over-driving an induction motor and tying it to the grid.  The electric company has what they call a Net Billing program which is indistinguishable (by me) from 'detent metering'.  Their current policy is that they'll allow customer generation for a system up to 25kW.  You pay retail for anything you use and they'll pay you last year's wholesale rate for any surplus you produce.  They're currently trying to get through a proposed change where customer systems of 10kW and less get paid the retail rate for any surplus produced.

An alternative to over-driving an induction motor would be using a more standard setup like a 'Windy Boy' grid-tie inverter.  The problem I see with this is that those systems seem to want a high input voltage with a fairly narrow range (e.g. 400-600vdc) so I'm a bit unclear as to how to generate that over a wide range of wind speeds.

[snuffy]

"One thing I haven't been able to find yet is a detailed description of the fantail."

I believe those were turned into (or out of) the wind manually by spinning the cap.  Some even had a tiller like device supported by a wheel, behind (downwind) from the building.

[Titantornado]

Like this?

Though this one turns the whole structure, it wouldn't be hard to make it just operate the upper "cap" of the structure itself.

[snuffy]

Can't see your picture !?

[Titantornado]

Ha, how 'bout that.  Worked when I did the preview, but not anymore.  Here's the link to the webpage it's from: http://www.windmillworld.com/millid/2336.htm

[PHinker]

Yes, thanks.  I understand the function of the fantail, which is to rotate the cap into the wind, but I haven't found details as to how these worked other than a brief blurb about the fantail driving a worm gear and it taking an hour to turn the cap house 180 degrees at full speed.

[wdyasq]

Well, the Dutch windmills used an airfoil and lift type airfoils. The 'fan' to turn the cap commonly drove a gear through a set of reduction gears. There are some modern Wind turbines with similar turning gear.

Ron

[ghurd]

I don't know if gearing is always needed.

Thicker magnets, more magnets, and more copper?

Cost is always an issue, but maybe a smaller percentage of the whole system.

Gears cost money, lower efficiency, wear out, etc.

Figure the cost of the system.

Add a lot of money for the extra magnets and copper.

Subtract a lot of money for the gearing and related parts.

A few 100 for more magnets and copper.  A few 100 for a lawn tractor rear end and stuff.

Starting in low wind, with less maintenance and higher efficiency... Priceless.

G-

[Stonebrain]

This might be interesting

http://bernard.garibal.free.fr/fonct/index.htm

cheers,

stonebrain

[Titantornado]

Well, the fantain device would seem pretty simple to build.  The most difficult single piece would be the component to turn the turret.  A giant ring gear doesn't seem monetarily ideal.  So, I've seen chain hoists that have pulleys in them that are designed for chain. The way I'd do it, is to have a groove in the circumfrence of the turret, with one of these pulleys located next to and in line with the groove in the turret. A chain would be fitted to run in the groove and through the pulley in a continuous loop. The tension can be set by adjusting the distance of the pulley from the turret.  You'd want it set with very little slack, but not taught.  Some sort of "teeth" should be made into the groove to prevent slipping.  I have a few ideas how I'd do that, like bolts installed perpendicular to the groove, so they pass partway through the groove, for the chain to "grab" onto.  Or even to just run lag bolts into the groove, radially from the hub.  The lag bolt's head would provide the gripping surface. Though, this way seems more hacky to me. You'd only need a minimum of two "teeth" placed opposite each other in the turret groove, which would assure no less than one tooth is gripping at any time.  I'd add more than that, simply to assure good holding power against the forces of nature.

So, to get the power of the fantail to the chain pulley.  Two 90 degree transistions would be required.  Here's how I'd do it.  I'd use two automotive differentials. Something that uses swing arms.  Because I have a Miata, I know the rear differential is ideal for this purpose, being very compact, lubricated, and designed for heavy loads.  I'd weld the planetary gears so they can no longer turn. From the fantail's shaft, I'd run it to where the driveshaft would normally connect. One of the axle outputs would run back to the turret with a driveshaft.  Back in the turret, I would have the incoming driveshaft connect to the driveshaft connection of the other differential, and the chain pulley connected to one of the axle outputs. (not sure how the differential will like being laid with it's axle outputs oriented vertically, but it's not like were running it in a car anymore)

Configured like this, you have three steps of gearing down.  Through each differential, and the third through the chain drive.  So lets figure out what the reduction would be.  I believe the standard Miata dif is 4.10:1, and lets say our turret groove is six feet in diameter, with the chain pulley being six inches in diameter, giving a 12:1 ratio. The fantail to turret revolution ratio would be about 202:1.  Increasing the turret groove to eight feet in diameter would make the ratio 269:1.

Seems like a junk yard could get you this setup pretty cheap.  Two difs, a pulley from a beat chain hoist, 25 feet of chain, some pipe for a driveshaft, and a bit of misc hardware.

Sounds like a project that I'd like to help build.