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Dragonfly Wind Generator

Wind Generator plans and kits by Bill Cornelius
About Dragonfly
Theory
Specifications
Using your own Alternator or Generator (Power Chart)
Field Switch
Maintenance
Parts list
Troubleshooting Guide
Testimonials

Note: This design is developed from plans published by the USDA in 1939. Typical use supplies 12 v. fluorescent light, radio, and laptop for a cabin. Please let me know what you think!

Dragonfly Theory

  • Designed for people who operate and maintain their own system. Dragonfly philosophy recognizes that nothing manmade lasts forever, but planned obsolescence is unethical. Therefore, the Dragonfly is designed to last as long as the user has intrest. It has locally available spare parts, few critical tolerances, and the maintenance technology is uncomplicated. Components are adaptable to the supply: off the shelf hardware, lumber, and almost any make of alternator or generator.

  • Included with plans are directions for construction, wiring, trouble-shooting, towers, battery maintenance, site selection (wind appraisal without an anemometer), some sources of inexpensive materials, and instructions for blade making and balancing (though I also sell blades and kit blades). Blades are twist taper cut from 2x4 lumber.

  • Watts per dollar, Dragonflies are one of the most "efficient" wind generators on the market, though one could expect that initial low cost might be offset by higher maintenance, this is not necessarily true, and depends on the local environment. I personally know of one that was 4+ years old, near the coast, and still working fine after 2 years without maintainance or inspection.

  • A topic that was inconceivable in 1939, but at which Dragonfly absolutely excels, is the carbon footprint. Since Dragonfly uses material that is either renewable or has already been used (consumed?), it has little or no footprint of it's own, their manufacture doesn't produce extra Co2, (unless you use power tools) and in fact helps to reduce any existing carbon debt of the materials used.

  • There's been a lot of advancement in wind generator design since 1939, and so that Dragonfly isn't misrepresented as the pinnacle of technology (an understandable mistake), these are some admitted flaws:
    • A belt drive (or anything but direct drive) wastes about 10% of the energy produced by the blades, ditto for the extra bearings required.
    • The efficiency of car alternators, though cheap and available, could be better.
    Some suggested solutions are here (buy one w/ direct drive & better output) or here (make your own using wood)

  • The most common problem with small wind generators is location, it really helps to have a lot of wind. This link describes testing your site for potential without hiring a pro or investing in expensive equipment.

Self-Feathering

The feathering mechanism consists of a horizontal hinge which allows the blade, axle, and alternator to tip back as a unit to spill high winds over the top. It is held in operating position by its' own weight and a coil pull-spring. Units that I sometimes make are guaranteed to survive winds to 80 mph, when the blade is properly balanced, and the field is loaded. Manual shutdown for stronger wind can be accomplished from the ground. The blade, bearings and drive pulley rotate as one unit about a fixed axle. The v-belt drive pulley is available in several sizes from heating and air-conditioning stores, and may be easily interchanged to obtain the best power ratio.

Specifications

Frame Material: wood, metal brackets.
Net Weight: 50 lbs.
Blade Diameter: 9 feet.
Blade Material: wood, stainless steel.
Blade Weight: 10 lbs.
Minimum windspeed: 10 mph.
Maximum output: 700 watts at 45 mph with Chrysler alternator and a 10 inch drive pulley.



Using your own Alternator or Generator

Any alternator will work, but those with higher rated output means more wind is necessary to overcome the draw of its' large field, so big alternators won't produce in milder winds. Generators and lower rated alternators loose the power advantage of storms, (which occur to a greater or lesser extent about every 2 weeks worldwide), but take better advantage of wind below 10 MPH. Some desirable characteristics are:
Rated Power Output: 400 to 800 watts.
RPM Output Range: between 200 and 1,000. Alternators starting around 450 rpm.

The alternators exposure to the elements is not a problem unless the unit is used in a marine environment. Otherwise there is nothing at the top of the tower that won't be found under the hood of a car, except sunlight which may affect the wiring insulation.

If the unit IS in a marine or other harsh environment, marine alternators are available with enclosed brushes, bearings and a corrosion resistant finish. Electrical terminals can be coated with protective caulking or shellac.

Field Switch

There are two kinds of automatic field switches shown in the Dragonfly plans, either will do: one is a momentary switch that requires occasional cleaning, this switch is normally on and is turned off by the weight of the feathering mechanism at rest in still air. The other is an enclosed mercury switch (good to 32 degrees below zero, needs no cleaning or attention after initial adjustment) which is clamped to the side of the feathering mechanism. The blade is designed to have a high RPM which will create a vacuum behind it to instigate feathering. When the RPMs are sufficient to produce electricity, the blade has already begun to feather slightly. As it tips back, the mercury switch tilts, or the momentary switch closes, to turn the field on.

Maintenance plan A:

Check list in order of probability, depending on climate, 2 to 4 times a year:
1): loose nuts, or fatigue at wire terminals. Too much loose stuff means the blade's out of balance. See manual for balancing.
2): belt tension.
3): check for wear or dirty turntable brushes.
4): loose or dry blade bearings (grit in bearings or unbalanced blade). Zerks require grease gun, should be greased regularly.
5): tight feathering hinge (need oil?)
6): check wood parts for rot, warp, or splitting.

Maintenance plan B: Wait till it stops working, then fix it. This actually is practical, but risks complications like: parts falling off, drained battery, or working in the rain.

Testimonials

The following customer responses testify to the simplicity of design and construction of the Dragonfly wind generator as well as its durability and the ease with which it can be modified to local materials and conditions.

...The plans are already here. ...they are of very high value to me and will save countless hours and money by preventing various mistakes. Thank you for offering those plans to people. Internet became a strange place where quality information becomes harder and harder to get- your site is an exception.

M. Z, Westland, MI

... I really like your design and feathering mechanism. Around Thanksgiving the mill went through an 8 hour storm with winds 50 to 60 mph with one recorded gust of 78 mph and held together.

N.S., Ferndale, WA

...also the other (Dragonfly) worked very well with a permanent magnet generator which I borrowed from a friend...

P.A.W., Kingman, AZ

..We would like to try another machine at a second location...

B.B., Glendora, N.J.

...instead of the mercury switch, I have a centrifugal switch from a Coleman furnace that turns it (a Chrysler alternator) on at about the time it is going fast enough to charge...

J.C., Kingman AZ

We presently (1982) have 20 wind students on-site on our Energy Education Center working with a Dragonfly wind generator that is on campus...

P.E., Red Wing, MN

... the prop blades were very nice and the plans were good... the Dragonfly has proven to be very practical and has been through the worst weather here in more than 100 years. I just had to write you to tell you I am very satisfied with the whole project. Thru rain snow, sleet, hail, sub-zero and winds to 60 MPH plus. It turned 2 days and nights thru a snowstorm and in the morning the prop hub looked like a giant sunflower made of ice and snow...