Building a Wind-Power Generator

You will need to do some homework to better understand the limitations of automotive type alternators. One that is not mentioned often is related to you wanting to use a vertical shaft orientation. All automotive units are designed to run with shaft horizontal. The units do not contain thrust bearings. A 100 Amp alternator has a rotor of sufficient weight to cause early wear as the ball bearing takes the whole end load in addition to the normal radial load. We ran into the same problem when trying to retro fit outboard motors with high output alternator.

It works .. for a while . . . but the bearings wear out prematurely.

Try and look in the archives of CR4 This subject has been discussed countless times

Good luck.

THANKS FOR THE INFO, I HADNT CONSIDERED THE THRUST BEARING FACTOR. I WILL TRY OTHER ARCHIVED SITES FOR THIS PROBLEM.

I feel that the bearing problem is fixable, just dismantle the unit and get the type numbers of the bearings, then look for replacements that can accept axial and radial loads.

Or as a possible alternative leave the radial (the standard bearings for a horizontally mounted alternator) bearing in the pulley end as radial and install a single roller bearing for axial and radial loads at the other end.....

Do remember to observe correctly all the correct ways of installing so as to not damage the bearing before usage, eg. no hammering of the bearing on either the inner or outer where such hammering will transfer energy into the balls/rollers.....

In my very limited experience, provided that the housing and shaft are clean, the bearings will slip on, maybe a little too easily (for ease of manufacture), therefore clean the surfaces and bearing and use bearing loctite to keep them fixed in place. They must never ever turn in the housing.

A bigger problem that you have to face is speed and mechanical resistance of the alternator. Many auto alternators need to turn at 2000 rpm to give a reasonable output, this is highly variable, testing of a few different scrapyard units (mark each carefully with its origin vehicle for future reselling of the not needed unnits), may give you one with a lower machanical resistance and a reasonable output at low rpm.

May I suggest that you look for a Japanese car unit as old as possible, why ? you may ask, well you need one with a low current output (relatively) as possible, to enable you to make the windmill of a reasonable size and not huge.

Well why will it need to be huge, simple, you will have problems of getting your windmill to revolve at more than 200 rpm, this may/will need to be stepped up via pulleys to produce the needed rpm at the alternator.....the mechanical resistance of the alternator (most have magnets and are very "notchy" and have a high resistance to being turned), will be increased dramatically simply by the pulley multiplier needed for speed, imagine starting off on a bike, going up a hill in top gear.......

The usage of DC motors "backwards" to make a voltage is not to be recommended as the brush position will be radially wrong to work as a generator!!! Unless it is a high quality motor where you can move the assemby to get the correct pickup point.....They also need high rpm to get any sort of output....

A really old DC Dynamo from a 50's vehicle and the control box is one possible method to go, but the need for two meters simultaneously and a large amount of (now lost) knowledge to set it up precludes that method for me.......remember that many were positive earth if you go that way........

There are websites showing how to build your own alternator that works at low revs and torque, have a search around....

I would recommend a spiral Savonius windmill for ease of use, ease of installation and general usage with no need to turn for wind direction.......make it at least twice the size that you feel you may need.......3 times will be better......

Good luck and keep us informed please.

Andy, does this windmill spin faster than the horizotal type and what about its torque?

Look at Wikipedia for a more detailed look at:-

Savonius Wind Turbines

Best wishes and keep us informed....

Thanks Andy!

This looks a v. good design in a house hold application especially for its immunity to turbulent wind conditions and it is no more eye saw than the propeller types.

I noticed that propellers can be a real eye saw when they spinning in day time as well as much more dangerous to birds.

Just an opinion.

A company in the USA makes them look like an out house!!! No danger to birds either.

Andy; it ain't as easy as you make out. We had a potential military contract but foundered on the problem of finding suitable bearings that were drop-in substitutes for what was already being used.

And the military was simply not interested in a custom made cobble up. As far as they were concerned the alternators had to be off-the-shelf. unfortunately the stock alternators that did have the right bearings simply did not have enough output current. We needed somewhere in the neighborhood of 6 - 8kW of output power from replacement alternators.

If not from the outboard engine manufacturers then from established third party vendor. I spent considerable time with bearing suppliers looking for suitable substitutes.

I have recently started to build my own CNC machine and bearings play a large part.

I have found out that the big companies like SkefCo have bearings in different types and qualities for all sizes. Its just getting them ordered and delivered in small quantities that are a problem with many distributors, who want big orders for all special sizes...

Get hold of the big companies catalogs.

Also, check to see if youz can take a slightly wider bearing without problem.

Another method would be to redesign the bottom end cap and add an Axial bearing at that point.

I have done something similar for my CNC machine, a single radial bearing with an Axial bearing either side of it, that way the axial loads are transferred to the frame and do not ruin the radial bearing!!!!!

What's wrong just using a cone roller bearing?

That's very durable in front wheels and seeing them also used as head-stock bearings.

Nothing. That is what I was trying to do in the first place. The catch being I needed such a bearing as a drop in replacement for the existing bearings. The contract to supply a military application meant we could not indulge in remachining the existing casting. Or in doing any other modifications that was complicated and time consuming. That would have driven up the cost and negated the principle of OFF-THE-SHELF procurement. OTS procurement rules means they can buy a replacement or repair part from any supplier using an industry standard part number or cross reference number. The military has learned their lesson about $700 hammers and $200 toilet seats. If you want to sell them something unique as a sole source supplier you had better have something really unique and extra ordinary and be able to guarantee a 20 year supply.

We were in fact trying to replace just such a product. It had been bought about 10 years previously and subsequently proved deficient and prone to break downs. Bearing failures were among the most frequent causes. Being single source also meant they cost dearly and could not be second sourced from a competetive alternate supplier. Then the original company went bankrupt.

If I had wanted to spend $100+ per bearing X 2 for one alternator, no doubt I could have found something. But do you as a hobbyist want to spend that much just for one component of a complex assembly to test if the concept works as expected.

Since you are just making one off and it is just for your own use, then by all means modify and adapt whatever you wish. In fact go ahead and use an automotive alternator without modification. It will work long enough to serve as proof of concept. You may not even rack up enough hours to cause premature failure befre you find a better way to do it. I'm accustomed to designing stuff that has to last 20 years or more. I tend to make it as bullet proof as possible.

As an alternative, separate the vertical rotor of the wind mill from the vertically oriented alternator shaft. Support the wind rotor on a separate thrust bearing pillow block. Now you are no longer carrying the wind rotor weight directly on the alternator ball bearing.

You probably need some kind of speed ratio change in any case. An automotive alternator has to spin at around 2000 RPM to produce anything useful and spin at 5000 to deliver its rated output. A wind rotor will never turn that fast. Even airplane propellors never turn faster than 2400 RPM at ful throttle. So you need to insert some kind of speed up gear box or belt / pulley arrangement. Now you only need to worry about the weight of the alternator rotor itself. Even the ball bearing will stand up to that, for a while at least.

Check out the spiral configuration used by helixwind. It is independent of wind direction and compact.

I know that this kind of turbine can and has been built but I think the biggest problem is the small amount of energy available in the wind near a typical house. Unless you live on top of a hill, on the coast, or at least in open countryside, the turbine will only operate at about 10% capacity factor on average, with long calm periods when no electricity is generated. Also, unless you gear up the generator with a gear box or belt drive, the rotation speed of the turbine will be too low for the alternator. If you make the turbine large enough to capture a meaningful amount of energy, its diameter will be so large that its rotation rate will be rather low. For example, if the turbine is 1m in diameter and 1m tall,and it is designed for a wind speed of 10m/s, then at a power coefficient of 0.2, it will produce about 120 Watts. However, with generator, gearbox/belt losses and battery charging losses, this will only be about 80 Watts. Then with variable wind speeds next to a typical house, the average power delivered will only be about 8 Watts. At 1m diameter and a tip speed ratio of 1 for a Savonius type turbine, the design rotation speed will be 191 RPM.

I think your strategy of a vertical axis turbine is a good one at low heights where the wind is turbulent and often changes direction rapidly.

Batteries are also expensive and a weak point in many designs. - That is if you propose to keep the wind-powered system separate from grid electricity. From what I have read, nickel-iron batteries seem to be the best for this kind of application if you expect your system to last more than 5 years.

For building your own wind turbine, try this forum...

http://www.fieldlines.com/section/wind

boB K7IQ