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10-26-2009

How I home-built an electricity producing Wind turbine. Part 1

Mike Davis

Several years ago I bought some remote property in Arizona. I am an astronomer and wanted a place to practice my hobby far away from the sky-wrecking light pollution found near cities of any real size. I found a great piece of property. The problem is, it's so remote that there is no electric service available. That's not really a problem. No electricity equals no light pollution. However, it would be nice to have at least a little electricity, since so much of life in the 21st century is dependant on it.

One thing I noticed right away about my property is that most of the time, the wind is blowing. Almost from the moment I bought it, I had the idea of putting up a wind turbine and making some electricity, and later adding some solar panels. This is the story of how I did it. Not with an expensive, store-bought turbine, but with a home-built one that cost hardly anything. If you have some fabricating skills and some electronic know-how, you can build one too.

Let me state up front that I probably won't be able to help you out much if you decide to build your own wind turbine. This web site has become insanely popular, often taxing the bandwidth limits of the server. I get dozens of requests for help each day. I simply don't have time to answer the majority of them. Most of the questions and requests I get are the same ones over and over again. I have crated a FAQ to handle these repetitive questions. Please read it before emailing me. Simple questions, not covered by the FAQ, which only require a quick and simple answer may get replies if time permits. However, there is no way I can help you out with complex issues, teach you electronics theory, help you locate parts, build a charge controller for you, or custom design a system for you. There just aren't enough hours in the day. Sorry. 

 
Update: Here is a video of the wind turbine in operation.

I started the process of designing my wind turbine by Googling for information on home-built wind turbines. There are a lot of them out there in an amazing variety of designs and complexities. All of them had five things in common though:

  1. A generator
  2. Blades
  3. A mounting that keeps it turned into the wind
  4. A tower to get it up into the wind
  5. Batteries and an electronic control system

I reduced the project to just five little systems. If attacked one at a time, the project didn't seem too terribly difficult. I decided to start with the generator. My online research showed that a lot of people were building their own generators. That seemed a bit too complicated, at least for a first effort. Others were using surplus permanent magnet DC motors as generators in their projects. This looked like a simpler way to go. So I began looking into what motors were best for the job.

A lot of people seemed to like to use old computer tape drive motors (surplus relics from the days when computers had big reel to reel tape drives). The best apparently are a couple of models of motor made by Ametek. The best motor made by Ametek is a 99 volt DC motor that works great as a generator. Unfortunately, they are almost impossible to locate these days. There are a lot of other Ametek motors around though. A couple of their other models make decent generators and can still be found on places like Ebay . This web site talks about the virtues and vices of various Ametek motors when used as generators.

http://www.tlgwindpower.com/ametek.htm

There are probably lots of other brands and models of permanent magnet DC motors available that will work well as generators. Permanent magnet DC motors work as generators, but they weren't designed to be generators. So they aren't great generators. Some types of motor are a lot worse than others. When used as generators, motors generally have to be driven far faster than their rated speed to produce anything near their rated voltage. So what you are looking for is a motor that is rated for high DC voltage, low rpms and high current. Steer away from low voltage and/or high rpm motors. You want a motor that will put out over 12 Volts at a fairly low rpm, and a useful level of current. So a motor rated for say 325 rpm at 30 Volts when used as a generator, could be expected to produce 12+ volts at some reasonably low rpm. On the other hand, a motor rated at 7200 rpm at 24 volts probably won't produce 12+ volts as a generator until it is spinning many thousands of rpm, which is way too fast for a wind turbine. So shop for motors accordingly.

To be continued...

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