Has anyone got a simple doable windcharger set of plans?

-- mitch hearn (moopups@citlink.net), December 11, 2001

Answers

When I designed my own windmill (built from three 55 gallon drums and $50 hardware) I intentionally designed it for low rpm, high torque and light weight. Rather than use a mechanical drive to increase the rpm's for the generator, I looked at the alternator to see why it needs the high speed. Basically, the rotor of the alternator has to move in the magnetic field of the field coils to generate a current.

But the alternator can't tell the difference between a steady magnetic field -fast rotor combination and a changing magnetic field -slow rotor. So I simply built a control circuit that pulses the field coils of the alternator. I can also increase the voltage to the field coil allowing a standard automotive alternator to produce power at any rpm and to produce up to 10 kw at high wind speed.

If you stall the wind turbine, it produces no power and if you let it run free, you don't generate power either. Between the stall speed and free running, there is a bell shaped curve that describes the amount of power that can be generated. By adding a microprocessor chip to the pulse controller, I can program the system to produce the maximum power at any speed. You don't even have to feather the prop of propellor type windmills because the controller can be use to prevent overspeeding.

-- Paul Clint (smithja@sisna.com), January 24, 2002.

There is a phenomenon in physics known as the electret effect by which the surface between a conductor and a dialectric can be endowed with a permanent electric field. This field has the same effect on static electricity that a magnetic field has on iron filings.

A treated piece of insulated wire strung out in the wind will act as a Van Degraff high voltage generator. In some conditions, a 400 foot length of wire can generate 10 kilowatts and even on a bright sunny day with a breeze of 3-4 mph, it will average 1 kilowatt.

The static electricity generated can be used to charge a battery using nothing but a spark plug, a coil and a capacitor

-- Paul Clint (smithja@sisna.com), January 24, 2002.

Mitch, would you have an old-style manual lawn mower? I think the internal gearing of the wheels might be suitable for a wind charger utilizing a car alternator.

-- john hill (john@cnd.co.nz), December 27, 2001.

I think a small car battery is about 35 ampere hours so for a four hour charge you would need something like 8 amps.

There have never been plans for any of the systems I built but I will describe two successful ones.

The first was used by a scientific expedition to Campbel Island which is south of NZ and in a very windy part of the world. That one used a permanent magnet DC motor from an old mainframe computer's tape drive system. That was a pretty hefty motor, I guess the physical size would be about a quart or maybe a little bigger. The motor was rated at 48volts and 4 amps. The motor was mounted horizontally on a pivot with a short shaft through a solidly mounted ball bearing, the shaft was coupled to the motor through a piece of reinforced rubber hose such as used in car heater systems. We used a plastic multi bladed fan from a building air conditioning system, it was about 20 inches in diameter. The hardest part was to make a swivel to conduct the power away when the system turned into wind. I fabricated simple brass slip rings around the outside of a piece of plastic sanitation pipe slipped over the steel water pipe the system swiveled on. That system was very successful and although the motor was only rated at 4 amps when it was connected to a 12volt battery it easily delivered 8 to 10 amps but of course at only about 16 volts.

The second system was a 'brute force' job. We erected two wooden posts about 8 feet high and joined them with a pair of 4x2s top and bottom. This frame supported a simple turbine made from one 44gallon and one 12 gallon oil drums, (sorry those are 'imperial' measures and I guess the US equivalent would be about 50 and 15 gallons respectivley).

Each drum was opened out and the two halves welded to a length of 3 inch steam pipe. The big drum was inside the frame and the smaller drum was mounted above the frame and at 90 degrees to the lower turbine.

The lower end of the steam pipe axle had a flange welded to it which coupled to the wheel flange of an old Toyota back axle.

The axle has the half shaft removed from one side and we set that end of the housing in concrete in the ground. The spider gears were welded up so they could not turn.

The axle passes up between the upper 4x2s and through a hole in a 1/4 plate. We mounted three old ball races around the axle to give it the necessary support.

The turbines do not spin very fast but there is a lot of torque, the action of the differential gears spin the pinion shaft at a good speed though and with a 12 inch pulley there is a good speed to the 60 amp alternator. Under normal conditions this contraption produced a reliable 15 amps or so.

Unfortunately I sold the smaller unit some couple of years ago and the larger is on a farm that has since been sold so I don't have any current (excuse the pun) information on either.

-- john hill (john@cnd.co.nz), December 17, 2001.

I need something capable of covering the phantom load losses of a 10 unit 12 volt system and or charging a car battery to full in a 3 or 4 hour period. My main goal is simplicity with low cost, low maintance, self protecting unit.

-- mitch hearn (moopups@citlink.net), December 13, 2001.

Hi mitch, what scale do you have in mind? A few watts to keep a single 12v car type battery charged for emergency use? Enough to run the house? Or something really grunty to run an aluminium smelter?

I have made a couple of the smaller ones no problem.

-- john hill (john@cnd.co.nz), December 13, 2001.