Electric Generators for Wind Turbines 1

[Sparweb]

I have a wind turbine on the drawing boards that I want to prototype this summer. It is a Vertical Axis WT, sized to produce about 1kW (I hope). I expect it to turn more slowly than typical VAWT's (just based on some analysis at this point), something like 60 RPM, with lots of torque instead (lots and lots of torque).

Does anyone have suggestions about selecting generators for it? I'm a bit out of my expertise on the electrical side.

On the safety side, I'm thinking of using an old disc brake from my car to stop it when necessary. Can this be done electrically instead? (or does that just cause a safety problem of its own?)

Thanks, in advance, for any help you can offer.


Steven Fahey, CET

 

[itsmoked]

Hello SparWeb you future bird murderer! Just kidding
our paper was just making a big fuss over the birds killed by Altamont Pass wind farms in CA. Expurts were arguing as to the actual numbers/year which ran from 400 to 6,000.. (Come on what's the actual number?!?!)

At any rate that's an interesting project you have. The disk brake is an excellant idea though I wouldn't use the one off your car. One problem is that your average disk brakes are hydralic which isn't real good for emergency/maintenance applications due to hydralic leak down. You might look for a mechanical disc brake like the type used on cars for the rear parking brake feature.

Next the cheapest generator would be a vehicle alternator. Fairly reliable too. But you haven't stated what you are going to do with the power. Do you need 12VDC or 120VAC? Are you going to try running household appliance stuff or only garage or workshop or??? There are many different possibilities out there. Some cheap some expensive, but truly effective.

More info please.

 

[byrdj]

This site my help give you some ideals

http://wind.dynalias.com/indexg.html

 

[Sparweb]

Since I'm trying to make a "proof of concept" machine, I think the way to go is 120V running a bank of 100W light bulbs. I could switch them on one at a time to progressively load up the turbine.
The alternative - DC - is a bit easier because, as you say, auto (or aero) alternators are easy to come by and already designed for the task at hand. What should I choose to load a DC generator? Adding an inverter to go back to the light bulb idea would work, but it's more complicated and the power loss thru the inverter gets in the way of measuring the turbine's performance.
Any other opinions on the topic are very welcome!

The point of the project is to find a way to get over the "self-starting" problem that Darrieus and other vertical axis WT's have. I have a few alternatives in mind, and I want to create a turbine that I can adapt to try a variety of solutions. I won't claim that all of the ideas are my own - some come from a few university papers that I've read.

Mechanical brakes - Maybe the disc brakes from a mountain bike or motorcycle would be more appropriate.

Thanks byrdj for the link.


Steven Fahey, CET

 

[itsmoked]

Hi SparWeb,

Okay you're using it for research..

I have used the lightbulb method myself. It works well but it has some problems in your case. Remember you generally need to keep an AC generator running at one speed. This is why most small wind or water generators run DC generators so the frequency/speed control is removed from the whole process.

I would think you would be MUCH better served with a 12VDC car alternator that you gear way up with a single belt. So the alternator spins about 2,000-3,000RPM


Then you run the output to a large rheostat that you can *continuously* vary, unlike light bulbs.

You stick an ammeter in the line, and a voltmeter across the rheostat.

From these two meters you just multiply their two readings together and you have the windmills power output.

Later if you want to see *light* either stick in one or more headlights or ? You can also stick in an inverter and create your 120VAC without the really large mucking about with trying to accurately control the mill's speed.

You said 1000W. You need an alternator rated at 1000W/12V = 84AMPS So find one rated at 100Amps, a pretty common value.

The rheostat will take a little looking around to find for cheap but they exist. I have two and didn't pay for either.

http://www.eletele.com.br/Reostatos_e.htm#Reostatos Toroidais

http://www.mechtric.com.au/Pdf/Rheostat/Rheostat.pdf

http://www.jenkins.com/jenkins/controls/ohmite.htm

Oh yeah the brake ... A good large diameter mountain bike mechanical disk brake would probably work. Personally I would use a car rear mechanical disk brake from a junkyard and I would grab the brake application lever out of the car too. As this would be one less thing you have to fabricate. A car's applicator will be self locking something a bicycle will not be. This would let you click on *some* brake and if it's a car brake it will take a whole lot of abuse. For instance, build your mill with the car brake and you can run it a bit by just applying a few clicks of brake drag. Once that is all working you can proceed to the generator angle.

 

[Sparweb]

Smokey, you're full of good ideas. Parking bake, headlights, alternator... what am I building here?!

Never heard of a rheostat that can dissipate 1kW. Not your garden-variety Radio Shack volume knob. I'll follow your links and see what they've got.

Thanks a lot!

Steven Fahey, CET

 

[itsmoked]

And don't forget to pick up a Cataclizmikcreosphere too.

 

[mexelec]

Hi Sparweb,

I've been searching about VAWT's for a while, I'm considering a VAWT but with a variable diameter in order to increase tork and reducing the speed.
I agree with the DC alternator option and wish you luck
Please let us know about your development

 

[alehman]

Don't forget you'll need some muffler bearings too!
Sounds like a fun project.

Oh, and you may need more than 3000RPM to get 1000W from a car alternator. If you can take high frequency AC, you can disconnect the internal rectifiers and bring the winding leads out directly. The windings are 3-phase.

 

[itsmoked]

heheh muffler bearings.. I was thinking what the heck is he talking about???

Yeah alehman is correct you probably would want to spin the alternator at least 4,000RPM.

Speaking of using light bulbs for loads.... been-there-done-that!

Seriously!!

Here's a few shots to spice up your day.. or night.

I was asked to build a 14 channel power PID controller.

Each channel was 1000 Watts.

I wanted to test it before delivery.

How to test it...hmmmm

14,000 Watts....hmmm

What's cheap?

Costco light bulbs!!

I picked up 140 of them.

I wasn't about to socket that many so I soldered to the base and tie-wrapped to the threads pigtails. Then I lumped 10 into one wire pair for each channel. 1000 Watts each ta-da!


Here's a front pic of a 19 inch rack mount power controller I designed and built from scratch.

I did it at home, when my spare bedroom was a laboratory. (Now I have a commercial place.)

Here's a top view of the controller. SSR city. I also had current monitoring of each channel, a master contactor, fault lights, happy lights, fault lock out, communications and a multiloop controller. Temp sensors were thermocouples.

Here are the light bulbs.. during the day.
I learned many things.. Like 14kW is a lot of heat! After running for 30 seconds the solder would start melting on the bulbs in the middle of clusters... this would cause the hot leads to spring off, easily finding the threaded bulb bases and instantly shorting. The controller got fault tested!!

This lead to the use of a large fan and careful bulb spacing. Note the trailer hitch wire hold down and the trusty waffle iron load cell.

At night it was spectacular.. This picture doesn't do it any justice at all because the camera stopped way down to get the shot. 14kW of lamps lit up the 120ft Redwood tree down the street so brightly that its true color was present. When these lamps started modulating it was breathtaking.

The unit tested okay and I ended up making about 40 of them.

So yes light bulbs do work, but are a pain to set up.

 

[alehman]

Quite impressive loadbank, itsmoked. Is the hose there just in case of a problem? A bit off-topic, but what does one do with a 14-channel power PID controller?

 

[Warpspeed]

I agree a 12v or 24v dc system is a lot more practical and electrical safety comes into this as well. The battery side of things is easier too.

The big problem with Darius and other vertical machines is as you say, the low operating Rpm, and the high torque. One system I have seen was to use a complete car rear axle with one side removed from the differential. That will give you a vertical pillar with a brake and sturdy bearing at the top. The handbrake cable can be used to lock the system when required, and the brake drum will keep the rain out to a certain extent if it is sealed with silicone.

The system I saw was a Savonius made from cut down 55 gallon oil drums mounted on long pipe arms.

At the base, the original differential spider gears can be welded up. The crown wheel and pinion will give you a very high torque right-angle drive output with an initial speed step up of around 3:1 to 4:1

The diff will also provide a strong locating point for a very large diameter drive pulley (or sprocket) to run your car alternator at a suitable speed. Hint, a bicycle chain is going to be more efficient at this than a V belt.

It might all look a bit agricultural, but it will be very robust and low cost, and well within the capabilities of a good practical handyman.

A Savonius rotor can generate huge torque if the buckets are mounted on long arms. The car axle solves a lot of the mechanical problems, and it could all be done almost for zero cost too.

 

[itsmoked]

Warp that's a great suggestion. Deals with a whole lot of infrastructure stuff right off the bat. I would probably change the axel oil to something much thinner like 20W. Also you have to deal with where the oil sits in the sideways axle. Probably needs to be way over filled and re-vented higher.


Hi alehman,

They use those controllers in the machines that make flat panel displays. There is a process phase where you must heat the large thin glass sheets to a closely controlled temp before depositing chamical layers on them. The *ovens* are 13 shelves (14 heaters) in a vacuum chamber that the glass pauses in to be heated. The sheets of glass where 30" X 30". The latest are now 60" x 72" and about 1/16" thick. Nice and fragile and all handled in a vacuum by robots.

 

[mexelec]

Here's an interesting forum about wind energy

http://www.odysen.com/forums/viewforum.php?f=117

Hope it could be useful for you

 

[pennpoint]

itsmoked
Very impressive photo's. Very nice applicaton to the 100w (X 14) bulb load. In addition whats that thingy next to the "waffel Iron" looks like a electromag device.
BTW are you located out West? Cause I seen this brite light back awhile ago.
I can imagine the bulbs clinking together from the fan air and then breaking too! Well you made it work and thats what counts. Good on you.

Best Regards
pennpoint

 

[itsmoked]

Thanks pennpoint! The thing next to the W.Iron is just a receiver trailer hitch used to pin one of the 4AWG wires down as it was trying to control the 'lay' of my bulb string. It weighs about 30#.

I'm 75mi south of San Francisco. heheh

Actually many times the bulbs clacked together I would flinch but I never lost one.

Oh, the hose just lives there I wouldn't dream of spraying it on an electrical conflagration. I'd use that 30# Purple-K dry extinguisher in the shed door, to the left (red).

mexelec; THAT is a nice forum...

 

[Sparweb]

Hey fellas,

Thanks for bringing up a lot of fun ideas. Warpspeed, I see you're familiar with both the Darrieus and Savonius VAWT designs. Have you come across any alternative types? Each of the above two have weaknesses, and I'm playing with mathematical models of a design that will overcome them.

I also like the suggestion of using an auto rear axle - my concept drawing isn't that different, fundamentally.



Steven Fahey, CET

 

[Sparweb]

I just found out about variable speed controller units for electric motors. Could this work?

Steven Fahey, CET

 

[jraef]

Work for what?
As standard, they are omni-directional in that they are used to run the motor, but not use power from an overhauling motor to feed back to the line. There are "regenerative" VFDs, but because they are back-to-back inverters they are essentially twice the price and twice the losses. Some VFDs can be fed with DC, so with a DC power source and a little creativity they can be used as an inverter, but a plain inverter would cost you less, so why?

BTW, back to your question as to how to put a load on a DC generator? Light bulbs don't know the difference between AC and DC, only the voltage level fed to them. So if you get your hands on a 12V generator, just go buy some 12V light bulbs. Many hardware stores carry them, marine and RV accessory stores as well. From a proof-of-concept standpoint you want the most direct route from turine to load, so any kind of electronic device in between will add losses that may interfere with your results.

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla

 

[Warpspeed]

SparWeb, I used to be really into alternative energy scene a few years back. I have seen some wonderfully creative ideas in this field.

Savonius rotors are self starting, simple, and easy to make and are probably the easiest and cheapest for a do it yourself project. As the fuel (wind) is free, overall mechanical efficiency is probably not as important as it may at first seem. Another aspect is repair of storm damage. It is not going to be a complete disaster if a fifty dollar junk wind machine gets completely demolished.

Darius rotors are much more high tech, but supporting it at the top is a problem never that easy to solve.

For feeding power back into the grid, the best system I have seen used a dc wind machine and battery, coupled to a fully bi-directional sinewave inverter. This inverter being a stepped sinewave of typically thirty steps.

These inverters are truly bi-directional and can easily handle reactive loads very effectively because of that feature. Also the ratio of dc/ac input/output voltage is continually variable so they make excellent battery chargers. They can also supply a fully regulated ac voltage from a varying dc source.