How to Build a Homemade Windmill With an Alternator

Build a homemade windmill from an alternator as a step towards self-sufficiency. Generate power to charge car batteries without having to pay for extra electricity. People often use these windmills in remote locations where hooking up to "the grid" may be a little too expensive.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Measuring tape
• Alternator (with disk attached)
• 1/4 inch nuts, bolts and washers
• Drill with 1/4 carbide drill bit
• 5 inch diameter, 25 inch length of PVC pipe
• Skill saw
• 600 grit sand paper
• Plastic pop bottle
• 1 foot by 6 inch length of cutting board (plastic)
• Hot glue gun (with glue)
• Zip tie
• (Optional) diverter, rectifier, ceramic heating element and water heater

1. Obtain an alternator of the type that is used in older vehicles (without electronics built into it). Make sure it is the kind of alternator that has the metal disk/face attached to the front of it. This is where the blades will be bolted down. The alternator can be bought 'used' but if it is bought new it will last longer. Buy 1/4 inch bolts, nuts and washers that fit with them. Also buy a section of PVC pipe that is 25 inches long and 5 inches in diameter.

2. Look at the plate that comes on the end of the alternator. There will be four screw holes on it. Drill them out so that the 1/4 inch bolts fit through them. Drill holes halfway between these holes and the central axle, making sure not to get so close to the axle that the bolts will get in the way of the pivoting face of the alternator.

3. Cut the pipe in half the long way down (on opposite sides of the pipe) while making sure the cut edge is as straight as possible. Take half of the pipe and measure 1/4 of the way from one edge at one end and 1/4 of the way from the opposite edge at the other end of the pipe. Use a piece of tape to make a diagonal line from one of these measurements to the other. Then use a skill saw to cut as straight a line as possible from one mark to the other mark near the opposite corner.

4. Drill bolt holes that will fit the blades onto the alternator at the wide end of the pipe cuttings. The blade should be positioned radial to the central axle. Do any further trimming on the edges of the blades using a joiner or plane if desired to reduce vibration. Sharpen the leading edge (the straight edge of the blades) by sanding with 600 grit sand paper. The blades are already contoured from the natural curve in the pipe.

5. Bolt the blade on by inserting the bolts from the back to the front so that the bolts stick out the front and don't catch on anything. Make sure that there are washers on either side of the bolts as they pierce the holes in the blades that were made earlier. Tighten the nuts on the bolts by hand, being careful not to crack the PVC blades.

6. Use plastic from a pop bottle and zip ties to cover the housing so that the alternator is protected from water. First cut the plastic sheets from the water bottle and then use zip ties to secure the plastic around the alternator.

7. Cut a 1 foot by 6 inch length of cutting board. Hold the board the long way and trace the pattern that you will cut. At one end, draw a line 2 inches (1/3 of the way) from one of the edges and draw this line for 6 inches. At this point, let the line taper out to the far edge at a rate of 2 inches to the side per inch forward. When you are done, the board should look like half of a paddle with the dividing line straight down the middle. Attach the "handle" of the paddle with the dividing line against the housing of the generator with some hot glue and then zip tie the handle onto the generator.

Tips & Warnings

• You can also use the alternator method with vertical axis windmills. Make sure that if you are using a generator to charge batteries, you use a rectifier (to keep the batteries from turning the alternator like a motor). Use a diverter to siphon off electricity once the battery is charged to prevent overcharging the batteries and ruining them. Some people have the diverter go to a ceramic heating element that they use to heat water in a water heater.
• This generator should be fine for medium wind locations but if the wind gets too furious, a braking mechanism should be applied or the generator should be temporarily taken out of service. If the generator is left up, there is a chance that the wind can get fast enough to tear the blades apart and throw them outwards as dangerous projectiles. Please see the resources for an example of this problem on a professional-sized wind generator.

Resources

• Man Makes Electricity For Home: Blog
• Making Blades:
• Too Fast (Blades Desintegrate): Video
• Environmental Controversies of Wind Energy