Ivan's small wind turbinesWelcome to my site, my name is Ivan Benkovič and I come from Slovakia. I would like to introduce you my small wind turbines. Maybe you will find here some ideas for building your own model. I know there are lot of sites about wind energy and aerodynamic theory on the web nowaday so I will put here mainly pictures with brief description.
The first model I built in June 2004. The most common are lift-based wind turbines look like this.
It's a 3-bladed horizontal axis wind turbine (HAWT) with passive yaw to set direction just toward wind direction (with tail). Three-bladed configuration is the most optimal respecting the starts in low speeds of the wind, efficiency and balance. The rotor is made from plastic, it has about 70 cm in diameter. An old step motor is used like a 2-phase generator. It products a little power, just for a lighting a small bike light with four red LEDs.
2-bladed prop named FloppyTurbine
The second model I built in September 2004 from an old 5.25" floppy disk drive. For more details about assembly click here.
It's also HAWT with passive yaw, but it has only 2 blades. There are cut from one piece of plastic with lenght of 40 cm too. It spins little bit faster than 3-bladed type but it requires stronger wind to start. The layout of coils has been changed to build single-phase AC generator. A stator is fixed on frame of an old fan motor with yaw axis. It produces comparative power with a previous model. Still not enough to light the tungsten bulb.
This is the third model I built in September 2004 too. It's quite different in principle. It's drag-based vertical axis machine or also called a Savonius turbine.
These types of wind turbines don't need a yaw mechanism at the cost of less efficiency (about 15%). It uses drag force of the wind. That's why the rotor wheels slowly - maximal speed is little less than wind speed, but it has a lot of torque of force and the bearing must be very strong at the base. A 2-phase printer step motor is used for generating of electricity. Again, LEDs indicate producing of power from wind. Whole machine is fixed easy to fence-post.
My own design - PVC sheet props
This is very easy to build, also very safe and low-weight turbine, ideal for low wind speed places. The propeller is made from 0.75 mm thick PVC sheet and can be 3 or 4 bladed. Just take the triangle or square PVC sheet, shear and some oddments and prop is ready to fit on the generator. Some pictures with details about these types of turbines are here.
Standard 3-bladed HAWT
This is classic style three bladed windturbine made from an old fan and PVC pipe. I modified fan motor to generate the electricity. Just add a two neodymium magnets from old HDD to make a generator. You can see some details at this link. Whole machine was finished after a few hours. A two white-light LED inside of generator box are flashing when turbine runs. It's beautiful in the night.
2-bladed version (my latest model)
A two bladed prop is little faster than three or more bladed, but it produces more vibrations. There is special circuit inside of generator's cabinet with voltage doubler, current limiter and blinking green and high light blue LED. It is flashing in the dark, people walking the street are wondering about it.
Simple DC to AC inverter
A schematic bellow represents DC
to AC converter for increasing the output voltage. Maximum output power
can be about 200W with the same power rating transformer used. The
output waveform is square (not sine!) so it is good for bulb or fluor
tube as for audio equipment (because of many harmonics that just make
lot of noise and hum).
It consists of square wave oscillator circuit with CMOS hex-inverter 4069, MOSFETs in H-bridge configuration and the output transformer for step-up voltage conversion. Frequency can be set by resistor R, 2k2 makes about 60Hz. Because of high current flowing when oscillator stops, fuse must be put in circuit.
There are many other websites about home-built wind turbines with power of hundred watts and a rotor diameter of 2 metres. Some windmill guys do seminars and workshops to share their experiences in homebrew wind turbines. Also they have a fun and play country music in the evenings. I recommend to see some articles from Hugh Piggot who is father of many homebrew windturbines over the world.
Good luck !