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HullWindmill.jpg

[Photo from Connors934 on Flickr]

For this final installment of our Make: Green series, we look at a promising technology for generating electricity: wind turbines. A wind turbine consists of a propeller, a generator, and either an inverter or storage system. The propeller is essentially two or more airfoils attached to a hub. When the wind blows across the surfaces of the blade, it creates areas of low and high pressure, and this difference causes a change in movement. As the turbine turns, a generator attached to the hub on the prop turns a coil in a magnetic field. Moving magnets cause electricity to move through the wires of the generator, which moves through the circuit towards the electronics that regulate either the battery storage system or the inverter for grid-tied systems.

OtherPower, the cutting edge of low technology, is a great resource for information on wind energy and turbine building. They’ve been building and testing wind-harnessing systems for years, and recently published a book HowmeBrew Wind Power, to help people learn how to generate their own wind power.

If you want to roll your own wind-powered electricity, definitely check out the great resources at The Workshop, which has all kinds of useful documentation of experiments and ideas. Their energy pages are especially good. I like this one on experimenting with the blades from box fans.


Hull, Massachusetts, is one of the leaders in municipal wind power in the United States. The town has a long history of generating power from the wind that blows across the nearby waters. Volunteers in the town operate the Hull Wind website, archiving and distributing information about wind power generation.

turbulence Making electricity out of thin air

[Image from The Back Shed]

If you have some spare stepper motors in your junk/parts pile, you might want to check out some of the stepper motor based generators. The Back Shed has a neat project idea that uses steppers to convert the wind energy to electricity.

There is a lot of energy in the wind. Power is the cube of speed, so a 40kmh wind has eight times the power of a 20kmh wind. As an example: a perfectly efficient windmill may produce 200 watts of power in a 20kmh breeze, 800 watts in a 40kmh wind, and 6400 watts in a 80kmh storm gust.

But what sort of windmills are we talking about? First up a few simple rules about windmills. Windmills behave in a way very similar to your average car engine. They have a power and torque curve, with different speeds for maximum power or torque. For electrical power generation, ideally, you need to operate your windmill in its peak power output.

  1. More blades = less speed, less power, but more torque, perfect for pumping water.
  2. Less blades = more speed.
  3. Larger propeller diameter = less speed, but more power.

Shawn Frayne, author of one of the chapters in the Engineering the Future high school engineering text, developed a really clever way of generating electricity from the wind: the wind belt. Jason Striegel wrote about it here a few years ago. The video above points out some of the amazing possibilities.


You may also want to check out the other articles in our Make: Green series:

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