A large number of our site visitors have found our article How I Built a Wind Turbine to be interesting reading and a useful resource. That relatively simple wind turbine was constructed using an Ametek PM motor as its electricity generating alternator.
In this article we will look at a DIY wind turbine generator constructed from scavenged parts with 3.4 metre diameter wooden wind turbine blades and a homemade alternator.
Building a Wind Turbine
This wind turbine was not built following exact plans, instead the information from a selection of books and online resources was pooled and the turbine built accordingly. Of particular use was Hugh Piggot’sbook Windpower Workshop which is essential reading.
Wind Turbine Blades
First the wooden wind turbine blades were carved with an efficient aerofoil section and twist much like a propeller. Three 1.7 metre long blades were hand-carved (following calculations from Windpower Workshop) aiming for a tip speed ratio of 8, and a rotation speed of 450 rpm in a 22mph wind.
The Alternator (Generator)
The generator was designed with a 24 Volt three phase stator (3 coils each phase) and two rotors with twelve 46x36x12mm rectangular shaped NdFeB (Neodymium) magnets each. The hub and rotor assembly was built out of scrap 1995 BMW front strut with a pair of brake discs.
The magnets were first superglued in place on the brake discs, and then cast permanently in resin.
The nine stator coils were wound using a homemade coil winder and reclaimed enamelled magnet wire. To keep the coils tight they were taped and superglued while everything was put together waiting to be cast in resin as per the rotors.
Metalwork
A turbine this size must have a mechanism to prevent it from spinning too quickly in very strong winds. A simple self-furling system was chosen and constructed from scrap parts. This limits the wind turbine output to around 70 Amps (2.2KW) stopping the turbine from going out of control.
The wind turbine tower was constructed from 4″ pipe with a piece of 3″ pipe welded to its base to act as a bearing when the tower is to be raised or lowered. This is in turn fitted to an ‘H’ shape welded from RSJ offcuts to be buried as the base anchor in concrete in the ground.
With everything put together, the completed wind turbine was raised for the first time (using a gin poleand a car to tow everything to vertical). The finished tower is held vertical by three (wire) guy ropes.
The total financial outlay so far was a miserly £350!
Wiring and Controls
On a wind turbine of this size a great deal of care and attention needs to be paid to the wiring, controls, and battery bank. Firstly it is essential to have a suitable dump load to prevent the (expensive) batteries from being overcharged. (Click here for details on wind turbine charge controllers – used to divert energy from the batteries when they are fully charged to the dump load.)
Keeping on with the recycling and reusing ethic, an old 240 Volt fan heater was converted to operate as a three stage 1kW dump load (pictured below with 42 Amps passing through it):
A water heater dump load was also put together to turn excess energy into useful hot water, and a 1.5kW (3kW peak) power inverter purchased to convert the 24VDC from the battery bank into 240 VAC for use in the home.
Relays were wired into the domestic electrical system to automatically switch between (wind charged) battery power and mains electricity to provide a reliable consistent electricity supply. (See our articleSwitch from Inverter to Mains Automatically for more information).
More Information
Many thanks to Richard Blackburn (username diablo on the old It’s Not Easy Being Green forum) for his permission to reproduce some of his excellent photographs here where they have been an inspiration to the many home built wind turbine enthusiasts that visit this site.
Back in 2007 when Richard and his father-in-law put the wind turbine together, Richard planned to purchase a smallholding with space for proper workshops and start selling 3.4m and 5m wind turbine kits. If the kits are of the same quality as his first turbine they will be worth every penny, but unfortunately we have not heard any news over the last years of whether this plan came to fruition.
A detailed photo-journal of the construction of this wind turbine was available on the old INEBG Forum which subsequently changed ownership and became The Green Living Forum when it appears the photo-journal was lost.