wind power science experiment - seeking input

muldoon · December 11, 2009, 12:40:45 AM

So it is science fair season and my daughter has expressed an interest in wind power this year. I have been a reader on other-power for several years and all around science dork for most of my life. So I figure we're probably in pretty good shape to make a simple wind generator and light up a bulb. I intend to wire up a very simple motor/generator (DC) with copper coils and neo dynium magnets and put a prop on it and let her play with hand turn, wind turn, maybe even the kitchen sink to represent hydro power. Thats all good and I think I'm ok with that. I feel fairly confident we can juice up an LED or maybe even a flashlight battery.

However, I also am thinking of it in a slightly larger scale, and doing some research on what else we can do aside of the science fair itself to really dig into the nuts and bolts of it. I looked at the home made windmills and AC alternator designs, the stators and rotors. Great stuff, a little daunting but cool. I also stumbled across several commercial oriented "science kits" designed to teach properties and principles for school age children of albeit older children. Some of them quite fascinated me, and I got to planning and thinking about it and have come up with an idea I have never seen pursued.

Before I kick this can any further, I wanted to post my thoughts to this forum. I know there are several on the alternative energy kick, and several wind power enthusiasts as well. I am looking for criticisms and perhaps ideas or things I had not thought of before building in an attempt to avoid any mistakes I may not be aware of.

I don't like heights, and I don't like spending a bunch of money. I don't want to mess with towers and guide wires, and I prefer smaller than larger. If a workable design is possible, I would rather cheaply clone it and run it in series/parallel on a smaller scale adding in pieces than a single large dollar investment.

I have to say this learning kit fascinates me.
http://www.picoturbinesite.com/whwitukit1.html
and details
http://www.learnonline.com/pdf/Whirlybird%20Wind%20Turbine%20User%20Manual.pdf

It is a whirlybird attic vent plan that uses the Lomanco heavy duty B1B12 roof ventilator as the prop, with a mounted rotor containing magnets. On the stationary side is a stator with 12 coils producing a 3phase AC alternator. The vent itself has heavy duty thrust bearings and is allegedly good to 150 mile wind, the bearings are lifetime guaranteed and sealed. No maintenance and great weather protection. The plan itself is a little on the light side using bar magnets and rather weak gauge windings. When I say on the light side, I mean it's mickey mouse - as is - one would be lucky to see 8-10 volts from it and very minimal amperage.

My thought is to follow the basic idea using rare earth heavy duty 2" magnets from otherpower and 14 gauge windings. Have the 3 phases dump into an AC delco 150amp (6 diode) bridge rectifier (from a GM alternator) and then use that for charging DC batteries. I will add a zener inline to keep the battery from trying to spin the blade, but thats it as I see it. As everything is AC voltage, use SER service entrance 12/3 romex to the batteries, where the rectifier would be. From the rectifier on the DC power side use #4 gauge wire into the terminals. I do not have plans for a charge controller, looking for advice if it is absolutely necessary.

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It seems to me that while the vent is not on a tower, nor is it a true "prop based" windmill, it could be quite effective. The two I have on my house spin all the time. By using very strong magnets and a decent set of windings I am thinking it might be worth pursuing.

Like I said above, looking for criticisms, ideas, warnings, and the like. So I'll be honest, some of my worst ideas come when I'm just thinking... I wont take any offense if this is a bad plan. Thanks I appreciate any thoughts on it the forum as to offer.

MountainDon · December 11, 2009, 12:49:08 AM

I don't like towers either. I believe the theory is sound. I do wonder though, how the turbine will react to the heavier load imposed by the stronger magnets? I guess that's where some experimentation is in order.

As for the charge controller, if this works, then worry about it.

December 11, 2009, 01:23:12 AM

The tower should be 30 feet taller than nearby objects - trees etc as a minimum. This should tell you some about it - I designed mine off of it.

http://www.bergey.com/Products/XL1.Tilt.IM.4.pdf

Many used treadmills have a permanent magnet motor that makes a good generator with little else to build and can many times be had cheap. Not all are DC motors.

Windpower · December 11, 2009, 07:47:46 AM

well you did ask for my opinion......

quote from page 4 of

http://www.learnonline.com/pdf/Whirlybird%20Wind%20Turbine%20User%20Manual.pdf

"The Whirlybirdtm Wind Turbine is not a toy. Assemble and operate it
responsibly"

I disagree, it is a toy.

I my opinion of these "Live off of the grid for $100 and 2 weekends of work" websites are outright fraud

I think this whirlybird is in the same category as these

http://www.earth4energy.com/
http://www.homemadeenergy.org/?hop=gccg101
http://energy2green.com/

vertical axis drag type of wind devices are useful for some applications (like a roof mounted air vent)

but are a very poor choice for generating electrical power. They have a very slow rpm limit due to the very low tip speed ratio and so require some sort of 'gear up" to produce any meaningful power. They simply capture a very small fraction of the power of the wind.

I think this has been beaten to death over the last 40 years

IMO William Kamkwamba designed a much better charger than the Whirlybird toy. At least it produced enough power to charge cell phones and light his family's house so he could read at night.

http://williamkamkwamba.typepad.com/williamkamkwamba/photos.html

RainDog · December 11, 2009, 09:27:45 AM

Gotta be one of the coolest photos I've seen in a while, Windpower.

Muldoon, alternative energy sources, and all things green, are hot right now, so it's a timely project. Just earlier this week my 11 year old son won at his school's science fair and is going to county with something similar.

One thing my son learned, and kinda wishes he'd have known, is that the judges care a lot more about the presentation board, abstract, and notes than they do the hands-on project itself. The project caught their eye, yes, but after that it was all about the presentation of data. Make that display sing!

Anyhow, good luck, and keep us posted on y'all's ideas and progress.

December 11, 2009, 10:48:17 AM

Muldoon, keep in mind that depending on how tightly coupled the field is with your coils, and how much power you are trying to extract, this will set the torque load on your rotor assembly.

So if you are trying to get additional power out of the turbine, expect to need additional torque somewhere. If you don't have reduction gears, chances are that tightly (magnetically) coupled generation will stall your rotor under any sort of load.

The Savonious (sp?) generators are interesting, but very low efficiency with the magnets whirling by coils that are spaced fairly far from them. If you want to get more power out, you need to increase field strength, improve coupling, increase coil inductance and decrease coil resistance. IF it sounds hard to optimize this, it is.

Want power? Big blades, strong wind, and a tight generator.

A room mate of mine in college made and interesting savonius turbine out of a couple of pickle buckets. He used the lids as the top and bottom, and cut the sides out of the sides of the bucket. He mounted skateboard wheels on their bearings to attach to a piece of threaded rod going throgh the assy, and it worked very well. But keep in mind that the torque recovered is very low without gearing.

Good luck! this sounds like fun.

Squirl · December 11, 2009, 01:37:45 PM

I have been away for a while (tied up in a hearing) so I have not had a chance to post my wind turbine project. I would definitely go with a permanent magnet DC motor for the turbine, especially your first one and a child's science project. It depends on what you are trying to show. Are you trying to show the power of the wind or how a generator works? I have taught these as two different lessons to a high school green energy club.

I will be up front that I do not particularly like the whirly bird design. Windpower is right in my opinion. One drawback is it is very small so it only captures a small wind swept area so the maximum theoretical power is exceptionally small. In addition to that, it is a VAWT design which has the problem of facing lots of drag and spinning slowly. This gives you a very small captured amount of power out of even the potential power. It is only good for turbulent winds on roof tops. The investment in materials is huge compared to the power output. It is not cost effective. IIRC, these things cost $50 or more plus magnets and wire. Also the power is 3 phase AC, so to convert it to DC you need three rectifiers. For $100 in materials you could build a HAWT that puts out twice the power.

"I don't like heights, and I don't like spending a bunch of money. I don't want to mess with towers and guide wires, and I prefer smaller than larger. If a workable design is possible, I would rather cheaply clone it and run it in series/parallel on a smaller scale adding in pieces than a single large dollar investment."

As I stated before VAWT are good for turbulent winds but they are almost never cost effective in power production per watt. I have looked and tried to design many, many, many different kinds. When I added up the costs of materials and compared it to the potential output and expected output, I keep coming back to a HAWT.

Ok Here are some of my recommendations. First check out.
http://www.kidwind.org/
and
http://www.otherpower.com/toymill.html
For the science project.

The motor-
I agree with most of what the other power people recommend but not always to get started. For quick and cost effective small scale power generation I recommend small scooter motors on ebay. They go for around $20 and are PM and DC. This will get you generation a decent amount of power off the bat. They are rated between 100-300 watts which is around the amount of power you will be generating from a small turbine. The treadmill motors are rated for 1-2 KW and will have more cogging. I never understood why people advocate these huge motors with small blades. Using a DC motor, there is a quick success feeling that I like (and most kids do to) that is encouraging to keep going. For a very small all PVC school project I would go with a hobby motor. With a simple resistor you can wire it directly into an LED array for power generation.

The blades
While yes hand carved blades are most efficient the cheapest easiest and fastest way to get started is PVC blades. More blades = more torque and more drag for a slower speed. Not good for power production without gearing, better for water pumping. There are many diagrams here:
http://www.builditsolar.com/Projects/Wind/wind.htm
They are exceptionally easy to cut and need the minimal amount of equipment and tools. All you need is a 4 or 6 in pvc pipe form Home cheapo. ($14 - $26) And a $15 jig saw from Wally world. I started working with a jig saw when I was 10 so this is simple enough for a child to do. The normal ratio is 5 to 1 length to diameter so a 4 in diameter pipe would have 20 in blades 6 in - 30 in.

For the hub you can use a metal cutting circular saw blade, just blunt the edges cutting some concrete or a grinder. Or you can use a piece of metal and just cut a circle out of it and drill a hole in the center.
then just screw the motor to a 2x4 and put a tail on it.

So for around $60 in materials you could have a wind turbine without the tower that has to potential of putting out some real power. You could build a small stand out of PVC for indoor display for a science fair.

Raindog makes a good point. What age group is this for? What lessons, scientific principles do you want this to display?

muldoon · December 11, 2009, 01:56:49 PM

great comments, I knew this was a good place to ask.

MtnDon - the stronger field by the magnets is a concern and I also am curious how it will effect the vent in low wind. I'll just have to see what happens.

Glenn - Deep down I know your right, and that to capture any real wind I need to be up above any obstructions. My curiosity still niggles me. My thinking is to put it on a base in the back of my truck with the wind collecting side just above the cab in height. Attach multimeter and perhaps use a bike computer to track rpms and track it at 5miles per hour, then 10, 15, 20, etc. With some luck I can at least get an idea of any potential this thing has. Perhaps then put some load on it and track the rpm drop at the same speeds. If the answer is it needs to be elevated to be useful then I agree that's just what it would need to be. I imagine this type of test would at least answer the question?

Windpower - thank you for your thoughts. Just a few things tho, the link I sent is not a "power your house for 100 dollars" link. It is a science experiment for schools to use for teaching middle and high schools about wind power. They also sell a breadboard with ammeter/voltmeter with about a dozen or so experiments relating to wind speed, airspace between magnets and coils, load increases and such. I realize it is not intended for real work as-is. However, my curiosity with the simpleness of it leads me to wonder if the idea could benefit from a more beefed up approach. Instead of using a heavy VW brake assembly, use this platform. I also have a hobby that is wraught with fraud and it is something I am quite passionate and vocal about. Probably far too often. I understand the frustration, however I just want to be clear that I am not selling anything here, nor I am trying to mis-represent my goals or any potential gains from this. Like I said in my original post I don't think I have ever seen it attempted, and I still don't see a clear reason why it is doomed to complete failure. Your post, while appreciated doesn't lead me to that conclusion either.

Raindog - Shannon is in 3rd grade this year, I don't know how much of all of this is going to make it into her project for school. Certainly we will do something with a goal of getting a led or Christmas light lit and make the display around that. I am thinking more of an extra-extra curricular to take something simple to the next level. And hopefully do it without going in hundreds and hundreds of dollars. Would appreciate any ideas you have on the display. Do you have any pictures of the one you guys did or ones that won?

NM - that is essentially what MtnDon was getting at above as well if I understand him correctly. My intention after doing the windings is to compress the stator and cast it in resin to get as flat a surface with minimum height required over the magnet surface - maybe 1/8th inch? Reducing resistance in the coils would be done with larger conductor, however that also reduces the amount of coils. Like you said - everything is a trade off right. Just like your roommates plan, sometimes just because something doesn't use the traditional materials and techniques doesn't mean something wont work.

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I do have a wind question that I am unable to figure out. Most documentation I have read is very explicit that you always need to have a load on any wind power driven turbine. The reasoning I have seen for this is that with no load the turbine will just spin itself faster and faster until it flies apart. Curious if that is a factor in this design as I don't think a vent is subject to the same forces as a prop or blade design. I also have read that as speed increases without a load to slow it down the voltage in the alternator can climb and climb - perhaps to the point of demagnetizing the magnets? I don't know quite how all of this works mathematically so I am at a loss of whether or not I need to even be bothered by it. Appreciate any thoughts on the subject.

Thanks again

glenn kangiser · December 11, 2009, 02:07:44 PM

muldoon, for close to the ground and smaller wind, the Savonius type rotors geared up to get charging speed - maybe with a multi-v serpentine belt would possibly be better. They don't care as much about the turbulence caused by ground objects. A double one offset 90 degrees would be self starting. Multi-v belts can be used on flat pulleys - no problem. They of course will not transfer as much horsepower but that is not a problem in this case. They also don't waste much horsepower in transferring which is important in this case. They currently use them as replacements for the fan belt (flat) for my 1919 Dodge.

I also encourage you to continue your experiments with the vent as it will get you primed to go on to bigger and better things. Your understanding will increase as you experiment with it.

December 11, 2009, 02:37:35 PM

Squirl - thanks for the thoughts. Good to have you back on the forum.

She's 8, the core principles I want her to take away are the relationship between energy, electricity, magnetism, electromagnetism - (the motor/generator inverse relationship). Once that fundamental principle is there, move on to ways of harnessing natural sources to provide the kinetic energy to drive the generator, in this case primarily wind. My goal is that we look at a dozen or so things in the real world and see the same windings, same spinning process, and same end result so that she gets an appreciation for how much of the things she sees everyday really work. ie look at the alternator in a car, the windings in a small motor from a toy, etc. We have talked about fossil fuels and she has told me that we will run out - how an 8 year old learns these things on her own I do not know. I think this is a good opportunity to get her thinking about these things on a science level instead of just a consumer level. I dont want to make the content real heavy - but I do want to try to put the spark in her about it.

As for goals for the actual project, any measurable amount of power is fine - however I would like to make it actually useful if possible. If she could charge her cheapy mp3 player or the like with a dc source I think it would really drive the points home. Another point I forgot to mention is that I already have the whirlybird - it flew off somebodies house in the neighborhood during hurricane Ike and has been in my backyard shed for over a year. It does not add any cost to the project. Perhaps that's one of the reasons I liked the idea. That being said, if I spend 100 dollars and the goals are met I don't really mind - it's a cheap investment in what the real goals are for this thing.

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Glenn - I'll look into the savonius design and see what lessons can be learned there. In the meantime I'll just keep pondering and moving along. Moving from the general to the specific if you will.

Squirl · December 11, 2009, 03:46:07 PM

I didn't realize that you already had the parts. By all means go for it.

I keep wanting to do a VAWT with a car axle as the axis and a concrete base. I just can't find the time or justify the resources.

8. The simplest sounds like a hobby motor with pvc blades and a PVC stand. Personal electronics (cell phones, mp3 players) use a tiny amount of electricity and it would probably work. A 12 in blade in 10 mph of wind should put 5 watts out.

glenn kangiser · December 11, 2009, 03:54:29 PM

Hey Squirl, I missed your post somehow. Great info - thanks. I can tell you know that of which you speak.

muldoon, I would suggest that you also have her study basic electrical theory and how automotive charging systems worked on the older stuff.. I found quite a bit of easy to understand theory in the older tractor and automotive books - back when the industry was trying to explain it to mechanics.