Breakthrough for Harnessing Light Winds?

October 12, 2008 – Vol.13 No.30

BREAKTHROUGH FOR HARNESSING LIGHT WINDS?

Wind turbines, large and small, have what’s called a cut-in speed, the velocity at which the wind must blow to get the turbine blades spinning and generating electricity. Looking at the long slender blades of a turbine you’d think that the slightest breeze would make them turn. This is not the case, however. There are prohibiting factors that prevent this from happening.

First, there’s the mass of the blades themselves. The longer they are the heavier they get and considerable energy from the wind is needed to get them moving to overcome inertia.

Then there’s the internal workings of the electric generator, or dynamo, itself. As the rotor within the electric generator is turned by the blowing wind moving the turbine blades it passes through a magnetic field where there’s a magnetic resistance. The force of the wind on the blades must be great enough to apply enough torque on the rotor to pass it though that magnetic field. If the wind speed isn’t great enough the generator won’t budge. At cut-in speed the wind is strong enough to both overcome inertia and push the rotor in the generator past the hump of magnetic resistance.

It’s remarkable that a breeze that would barely tussle your hair could turn a big megawatt class turbine at all. but it does. Turbine makers try to harness low wind speeds by making the blades ever longer that will grab more air and thus apply sufficient torque, that twisting motion, on the shaft of the generator.

But, what if an electric generator, at least at start up, had no magnetic resistance to turning at all? What if the rotor within the generator just spun freely, at least at low RPMs (revolutions per minute)? Wouldn’t wind turbines be able to generate at lower wind speeds thus harness greater portion of available wind resources to generate more electricity?

Axial Vector Energy Corporation says it has developed what it calls the Axial flux generator, or AFG, that, at startup, spins freely. The company describes the AFG as this:

“The main advantage of Axial flux generators (AFGs) over conventional radial flux generators is the high power density. This compact size makes them ideal for generators in windmills. AFGs require zero torque at startup, so a control module could have the windmill spin until a desired speed to energize the AFG. If the speed drops below the set point, the AFG is de-energized and the speed increases. In this way, a windmill could produce energy in very light wind. This simple advantage opens many doors for the windmill producers as it makes areas with low wind velocity, previously thought uneconomical, now capable of being used to produce energy.”

It seems likely that there are more regions with low wind resources on the planet than those with strong wind. Even in areas with good wind resources the wind might not blow consistently all day. But if regions with only marginal wind resources could be tapped for wind energy and areas with good wind resources tapped for a longer period of the day then there would certainly be a breakthrough for wind energy, globally. We’ll see what happens with this technology.

Axial Vector plans to introduce and demonstrate the advantages of its Axial flux generator for use in wind turbines at the Friedland Equities Global Investment Forum on Monday, October 27 at the Burj Al Arab Hotel in Dubai.

Links:

Axial Vector Energy Corporation
http://www.axialvectorenergy.com