windmill dangers.

[Fla._Deadheader]

 I would say you need to control the driver of the Alternator.  What do you plan to use to power the Alternator

[Radar67]

I have an idea about using the wind to power the alternator, but not with a traditional windmill. Picture a squirrel cage blower fan, but on a larger scale and different blade configuration, with the alternator in place of the motor. I will most likely have to gear or belt drive it to get the rpm where they need to be, but in a high wind situation, need something to slow it down or shut it down to keep from burning the alternator up.

[pineywoods]

Speaking of controls, does anyone know of a speed control that would keep say an alternator from going over a certian rpm?

Radar, I assume you are thinking windmill driven alternators. the old farm-type windmills used a mechanical governor which swing the tail vane around to point the windmill head less into the wind. Didn't work too well,especially with gusty winds.
I think on the big windmills, the pitch of the blades is controlled by an electric motor, hence some speed control. In theory, the blades can be set to zero angle to stop rotation completely. But that ain't nowhere near close enough. To connect a generator of any type to the power grid, the frequency and phase of the generator output has to match the grid perfectly, otherwise spitzensparken und fusenpopen. output of the actual alternator is usually multiphase ac which gets rectified down to dc. The final output is done with a honkin big electronic inverter.
The DIY crowd has available plans for a low-speed homemade alternator built from a car brake drum and a bunch of husky magnets out of microwave ovens. Makes multi-phase ac, frequency and voltage vary depending on rotation speed. That's rectified to dc and used to recharge a battery bank.

[chainspinrunner]

I live in Western New York Southern Erie county and we just had a couple hundred Vesta units put in in a few counties to the south in the past 2 years and these projects are on mostly private farm and forest land. These windmills are fairly new and have not been tested against mother nature yet. I can see a failure resulting in major damages in such a rural area. Some of these turbines are right on top of the farms and close to residences, snowmobile trails, hunting land, etc...
 Has anyone heard of major damage to ares such as this.

[Fla._Deadheader]

  Radar, what you are describing is a VAWT (Vertical Axis Wind Turbine). For ALL info you could possible want, go here.

  http://www.fieldlines.com

[Radar67]

FDH, the VAWT is very similar, except I plan to have the cyclinder on the horizonal, like a long oversized hamster wheel. A tail to keep it pointing the right direction is planned, but it will not furl.

[moonhill]

Radar67, are you concerned with the unit itself turning too fast or the extra power coming from it?  One of my mills has a heater, like a toaster, using the extra energy, if it is making too much.  It also twist in strong winds lessening the surface area of prop facing the wind, in effect slowing the rpm's.   My other smaller one, 404, has flexible blades that torque/twist, distorting them so they don't catch and this spins it in the wrong direction in hi gusts, it makes quite the noise when this happens and real windy days it goes on and on.  Sometime we have to reverse the polarity via a switch in the house, this is a break and it doesn't produce electricity when in this mode but I do sleep better.   

Tim

[Radar67]

My concern is not with the power produced, but the speed of the components at high wind. A car alternator usually runs within a range (rpm) on an automobile, I don't know at what speed damage would occur or electrical components start burning out, so I figure to govern the max speed the unit components can turn.

Speaking of automobiles, when the battery on a car is completely charged while driving, where does the extra power from the alternator go? Everything I have read on windmills says you have to have a heater or something to burn the extra (as moonhill described) when the batteries are fully charged and you are producing more power than you are using.

[Fla._Deadheader]

 Difference is, on a car, the regulator drops down the output to a minimum. On a Windmill, the load is used to help control speed of the prop. No load, and the mill COULD runaway, in high winds. That's why auto furl is a MUST on Wind equipment.

  Not sure how you will auto furl that cross mounted squirrel cage rig you want to try. Never heard of ANYONE doing it that way.

[Gary_C]

An automotive alternator produces alternating current that is converted into direct current by the diodes. The voltage in your battery is controlled by the regulator that simply turns the field voltage on or off which starts or stops all charging. The regulator is set to turn off the alternator field at about 13.5 volts. So when the field voltage is turned off, all charging stops and there is no output from the alternator.

The problem with using the alternator as a electricial generator is they are not rated or built for continous output. You will see that now on all rebuilt alternators when they have tags that say they are not to be used as a battery charger, only as a maintainer of a battery. The heat generated during continous operation will destroy the alternator.

For example with a 1000 amp-hr battery that is discharged to only 200 amp-hrs remaining, if you hooked up a 80 amp alternator, which is a very large alternator, it would take the full output of that 80 amp alternator for 10 hours to recharge that battery with no other load on the electrical system. But 10 hours of continous output will overheat that alternator. That is why the rebuilders will give you instructions to use a regular battery charger to recharge a badly discharged battery before installing the replacement alternator. And if you fry a rebuilt alternator, they can tell.

[LeeB]

I just now looked at this thread for the first time. I'm afraid I have to disagree with one of the earlier posts

I'm with Harold's thoughts on this too...as for me, the greater (est) danger is getting into the auto, and onto the highway. Be safer to be in the military in Iraq.

Any of you ever been in a taxi in the middle east? 

[Ianab]

The problem with using the alternator as a electricial generator is they are not rated or built for continous output. You will see that now on all rebuilt alternators when they have tags that say they are not to be used as a battery charger, only as a maintainer of a battery. The heat generated during continous operation will destroy the alternator.

So it would be a good idea to modify the regulator so the alternator produced less than it's maximum output? An 80 amp alternator should be able to produce 40amps continous I assume. And size the windmill for a 40amp alternator.

It's really only in that occasional situation where you have flat battreries AND a day of strong wind. But better to design the system so it does't melt down when that does happen.

Another popular alternative to an car alternator is a Fisher and Paykel washing machine motor. It has a neat Stator of coils that can be rewired for 12 volt, and a big plastic hub with magnets that spin around it. All good bits for making a generator.
http://www.yourgreendream.com/diy_instructions.php

Ian

[bandmiller2]

Their is a type of windmill that can be built from a 55 gal drum or multiples of the same.Slice a drum in half the long way slide the two halves half way apart and mount on a verticle shaft.Wind comes in feeds around like a water turbine and spins the drum.I forget the name and have never done it myself.The type of windmill that is like a hamster wheel was built years ago out on the prarie i think called a jumbo they were crude and not very efficient but worked.Frank C.

[Tom]

You really have to be careful with those windmills in a windy area.  There was some in S. Florida, back before the turn of the century, that got got spun up in hurricane.  They got to going so fast that they took off and flew seven hundred and thirty square miles of pasture, cattle and all, across the Gulf of Mexico to Texas.  They changed the brands and used the pasture on the King Ranch.  We were left with Okeechobee.

Somebody told me that Louisianna used to have a bunch of windmills on a big 630 square mile ranch just north of New Orleans one time.

Texas used to be mostly salt water marsh and rats untill all this windmill stuff got started.  You'll notice that they mostly pump oil.  Probably to keep all that new ground stuck in place.  The King Ranch was one of the biggest benefitters.  All they had was Blue Bulls until after the great windmill debacle.

[StorminN]

Radar, there's a couple of different schools of thought... are you planning to charge batteries, or tie to a grid?

If you're charging batteries, you'll need a diversion controller and a dump load for when the batteries are full. I don't know the specifics on duty rating of alternators and burning up homebuilt stators, but the guys over at Otherpower (the link deadheader gave) will know for sure...

The other option is to physically limit the rotation... and if you don't want to make it furl, just about your only option is a brake. If I were doing it DIY, I would look at the electronically-actuated brakes from trailers. Depending upon the size of your rotor (and the size of the brake you use), these could probably stop it. Then your next problem is making sure you have a tower that can withstand the force of a stopped, non-furled turbine at the top of it, in strong winds... but, this has been done!

Case in point... I found a commercially-made turbine from the mid 1980's for sale here, told my friend he should buy it, and he did. It's an Enertech 1800... 1.8kW turbine, asynchronous grid tied (ie., AC motor), 12 foot diameter, three fixed blades, downwind prop (no furling).

The way it works is... it has a little anemometer that mounts up the tower, just below the turbine. The turbine has a prop, a 32:1 gearbox, a disc brake, and an AC motor. When the anemometer senses that the wind is >7mph, the control box (pretty simple relay box) releases the electronic disc brake, which allows the prop to start spinning... at the same time, the control box puts 120VAC power to the AC motor / generator... which gets the prop to speed... 109rpm or so, IIRC. When the prop comes up to speed, a relay kicks in, and it's now asynchronous... it's a fixed speed machine, so when the wind tries to overpower the motor spinning, the motor resists... and voila, power is sold back into the grid.

This continues on until the wind either drops below 7mph, or climbs to above 40mph... at which time comes the tricky part... when the anemometer senses that the wind has been over 40mph for a certain amount of time (I forget how long, maybe 1 minute?) the control box applies the brake and the 12 foot rotor comes to a stop, until time that the anemometer senses the wind has dropped again. Yes, there must be a tremendous amount of force applied to the top of the tower from a 12 foot prop stopped in 40mph+ winds... something like >1,200lbs side force, I'm told... but I haven't done the math myself. Think a guyed tower, something like an 80' Rohn 45g.

For your case, if you're charging batteries, I would get a simple diversion controller (like a Trace/Xantrex C40) and wire it so that the trailer brake is part of the the diversion load... this might take a bit a fooling with, but with a relay and a 12VDC source, you could most likely stop the turbine... and without the turbine spinning, there would be no heat to deal with. For that matter, depending on your normal charge controller, you might be able to run the brake relay right off an aux circuit on the charge controller, trigger it at a certain voltage setpoint, like 14.8V on a 12VDC system (on something like an Outback MX60).

-Norm.

[petefrombearswamp]

Bandmiller,
That type of windmill was in the Mother Earth News in the 70's
It was called the savonius super rotor, using two or three 55 gal drums.
I planned to build one, but "procrastination is the thief of time"
Here it is 2009 and I still haven't done it.
Pete

[logwalker]

You can believe it or not but I think more force is applied to the tower when the rotor is spinning than when stopped. When turning it is more efficient. At least that is what happens in water with a boat propeller. Joe

[StorminN]

You can believe it or not but I think more force is applied to the tower when the rotor is spinning than when stopped. When turning it is more efficient. At least that is what happens in water with a boat propeller. Joe

You know, Joe... that makes sense... I do believe it! Perhaps the 1,200lb force figure I read was for the spinning rotor at under 40mph...

-Norm.

[sawdust]

I just got my copy of Homebrew Wind power. They have a explanation of why many designs are either inefficient or impractical. Over the years they explain that all have been tried.

http://www.freeenergy.ca/news/127/ARTICLE/1224/2007-03-06.html

This link is to one of their designs that was posted years ago. part one.

Their book is excellent reading.

I had one of my rotors come apart in a real high wind... sounded like my 12 guage.

sawdust