by John B. Carnett: HOW IT WORKS As the wind turns the wings, magnets in the alternator spin, generating voltage in the wire coils. The current travels through wires to a rectifier, which converts the voltage to DC, and then to a bank of batteries. John B. Carnett

Ed Lenz's house is pretty hard to miss-it's the one with a home-built vertical-axis wind turbine on the roof. A career tinkerer, Lenz put the turbine up there for a test run three years ago, and it's still turning away today, a super-quiet model of efficiency and ingenuity. The "Lenz2" turbine, built primarily from easy-to-find supplies like aluminum, plywood and magnets, can produce about 50 kilowatt-hours of electricity per month with steady wind. Its output-about 10 percent of the total power Lenz uses-is then stored in a battery bank that feeds into his home lines. The slow-turning vertical-axis design is most efficient in gusts of 6 to 20 mph, so it's ideal for relatively low-wind areas like western Michigan, where he lives. You can download plans at windstuffnow.com to build your own Lenz2. It's not a quick weekend project, but once it's up and running, paying the electric bill should be a breeze.

Build a Vertical Wind Turbine

Cost: $300
Time: 3 Days
Easy | | | | |
Hard

1. Construct the wings
   
   Cut teardrop shapes from plywood, connect with four-foot rods, and cover with aluminum.
2. Build the alternator
   
   Glue magnets to two steel discs, tape copper-wire coils to a plywood disc (the "stator"), and slide all three discs over the shaft.
3. Attach the parts
   
   Clamp both ends of the shaft to the rectangular frame. Weld the wings' arms to the bottom disc on the alternator, as well as to a steel disc at the top of the turbine.
4. Mount the frame
   
   Attach cables to the frame arms and stabilize with sandbags.
5. Power the house
   
   Wire the alternator to a rectifier, a device that converts the power from AC to DC, and connect it to the batteries. It takes four to six hours for Lenz's turbine to fully charge his bank of eight batteries.

Another Build: The $30 Open-Source Turbine
Go to velacreations.com to find instructions for off-grid DIY'er Abe Connally's Chispito wind generator, a horizontal-axis-turbine design that more than 200 builders have built and helped perfect. Made entirely of salvaged parts, such as a treadmill motor and recycled sewer pipe, the Chispito can generate 100 watts in a 35mph wind. And if you're able to find all the supplies, you can build it for less than 30 bucks.