Building a Wind Turbine Requires Respect: Wind Energy: Eco20/20

Building a Wind Turbine Requires Respect

If you're a do-it-yourself type of person, who intends to build a wind turbine, be aware that if you are careless, or clueless, about blade balance and vibration issues it will be exceptionally unsafe to take a stab at building a backyard turbine from scratch. In fact, there could be laws in your community against experimenting with some of the more powerful versions of this technology. If, however, you simply want to know a thing or two about the technology, or if you want to build a small experimental device, here is a lexicon of some of the more essential bits and pieces.

Balancing the Blades:

* If you've ever whirled a tent-stake on a string and watched it impale a tin-shed wall when you released it, you might understand the need to respect the possibility that pieces of debris outweighing a hammer-drill could be flung a quarter mile by a disintegrating device standing higher than your roof. The most important word in any builder's vocabulary should be safety.

o If a hefty turbine fails catastrophically because it was built unsafely, it could kill someone. If you are a hobbyist, stick to small devices - or for large devices buy a design-engineered and properly tested build kit.

o The rotor must be perfectly balanced. It takes patience. It takes specific knowledge. Research it - don't wing it.

Generator:

* The generator will normally be a permanent magnet alternator (PMA) with a DC rectifier or a direct-current permanent magnet (DCPM) motor used as a generator. The device should be rated for low revolutions and high voltage so it will generate a good ratio of volts per revolution. It's possible to use a surplus motor.

o When the wind is right, the goal for a backyard turbine is to produce enough power to charge a small rack of 12 volt storage batteries.

o If high winds are endemic to the build-site, a larger turbine may be more suitable, but in un-blustery wind conditions, several smallish generators will more efficiently increase the harvest of power.

o The generator must be covered by a weather-proof nacelle.

Yaw bearing, thrust bearing, rotor & tail:

* A yaw bearing is used at the top of the tower, under the generator mount, to help support the weight of the turbine and provide smooth movement when the device is swiveling.

* A thrust bearing is a secondary bearing that may be needed to help support the rotation around a fixed axis (axial load).

* 'Rotor' is the correct term for the blade assembly. The rotor needs a good lift ratio for spinning faster than the wind.

* A turbine's tail works like the tail of a weather vane, to keep the rotor pointed into the wind.

Blocking diode, slip ring & governing system:

* A blocking diode is a cutoff device. It prevents a motor from reversing the power in an effort to keep turning when there is no wind.

* A slip ring and brushes are used to avoid twisted wires. The brushes move with the device, and make electrical contact with a ring to which the fixed wires are then attached.

* A governing system is a way to prevent the turbine from burning out if the wind gets too strong for it to handle.

Other requirements include a regulating system to prevent over charging; which may include a load device to expend the excess power if the batteries cannot take more charge. An overcharged battery is another dangerous possibility of a poorly designed turbine. Here again, the most vital requirement is a deep respect for safety.

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