A simple way to learn more about building wind turbine generators is to use a bottle dynamo or Sturmey-Archer Dynohub as your alternator rather than building your own. While bottle dynamo generators are useful, they suffer from large friction losses and do not generate much power, therefore the Dynohub is of more interest. It generates power at a much lower RPM (60 RPM to generate 6V / 3W) than a bottle dynamo which is useful for a practical wind turbine.
What is a Dynohub
The Sturmey Archer Dynohub is a heavy over-sized hub that fits onto a bicycle and generates AC electricity with no moving parts of mechanical frictional losses. As the wheel of the bicycle turns, a ring-shaped 20-pole magnet revolves around a fixed coil attacted to the wheel axle. Used in its traditional sense the Dynohub had a tendency to burn through bulbs when the cyclist raced down a hill since the voltage generated increased with the speed of rotation of the wheels.
Making a Dynohub Wind Turbine
Converting a Dynohub into a wind turbine generator is simply a matter of bolting on three suitable turbine blades. We recommend that you make your own PVC wind turbine blades since they are very cheap and easy to make.
You will need to make the turbine blades at least 3 feet long (and ideally 4 feet long) since the Dynohub needs a good bit of torque to get it spinning. Blades any longer than 4 feet will turn the generator more slowly and put extra stress on the hub bearings.
Using a Dynohub Wind Turbine as a Battery Charger
As stated above, the electricity generated by a Dynohub is alternative current (AC). If you intend to connect your Dynohub wind turbine to a small incandescent light bulb you will have no problems – if the wind is strong enough to turn the turbine, the bulb will glow. If you intend to connect it to an LED then there will be some flickering since the LED will only light when the current flows in the correct direction. If however you intend to use your Dynohub as a battery charger you will need to rectify the AC electricity output into direct current (DC) using a suitable bridge rectifier.
Pictured above is a W1005 1.5A 50V Bridge Rectifier perfect for use with a Dynohub wind turbine generator. We have these rectifiers for sale in our REUK Shop together with 35A Bridge Rectifiers (from £1.79) which are suitable for larger wind turbine generators.
A Smoothing capacitor should also be used to smooth the output from the bridge rectifiers if it is to be used to directly power an LED to prevent it from flickering on and off repeatedly. Suitable 16V 1,000uF capacitors are also available in the REUK Shop.
Buy a Dynohub Now
It is virtually impossible to find a Dynohub in the shops today – rather than a cycling shop you’re better off looking in an antique shop! However they can occasionally be picked up on eBay in various conditions and ages from £15-£30 including postage, or found in scrap yards or on old bicycles.
Modern Alternatives to Sturmey Archer Dynohubs
If you are having a lot of difficulty obtaining a Sturmey Archer Dynohub then have a look for one of these alternative Dynamo Hubs for Wind Turbines.
Useful Dynohub Wind Turbine Links
Here is a website which demonstrates the use of a 6Volt / 5Watt Dynohub clone in a working wind turbine generator: GotWind.org