Residential Wind Power

Home wind power under product name of Utility-scale is an important and growing part of the US energy portfolio. Farms ranging in size from dozens to hundreds of turbines can produce in excess of 60 megawatts of power. Plans for gigawatts power are being proposed all over the globe, and new wind farms are regularly being proposed that outstrip one another to be the largest in their respective locations, or in the world. At the far end of the scale, the largest size wind turbines at (413 feet), and are estimated to be capable of producing 20,000,000 kilowatt hours of electricity annually (enough to power as many as 5000 European homes). The power generated by a turbine increases exponentially as it gets larger, new turbines will continue to grow in size.

Home wind power with small-scale turbines is perhaps a more exciting realm of development. The standard, propeller style turbine is well established, and there are many suppliers for this kind of generator in a range of sizes. In 2009, Home power magazine had a roundup of more than a dozen small wind turbines ranging from 8 feet to 56 feet in diameter (the latter of which is far larger than even a large, inefficient household would need for their power requirements)
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You may recall Residential Wind Power running an article on a unique wind turbine last year.  The Single Blade wind turbine has evolved even further and has taken the Horizontal Axis Wind Turbine to a new level.  The guys have launched a new web site and have provided Residential Wind Power with some fresh snaps of the beauty which you can find more of at the end of the post.

The home scale single blade wind turbine previously introduced on this site continues to make good progress in the South Pacific. Powerhouse Wind, based in Dunedin, New Zealand are using a new take with clever electronics to bring the single blade concept to the domestic wind market. A single blade has the appealing benefit of being the most minimal way to sweep a given area. Combined with the electronic innovations, it also creates the opportunity to design a machine that can sense wind strength and react to gusts to improve energy capture from the variable winds typical of a house site.
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As you will probably recall, classical water wheels let the water arrive at a right angle (perpendicular) to the rotational axis (shaft) of the water wheel. Among the Vertical wind turbines the Vertical axis wind turbines (VAWTs as some people call them) are a bit like water wheels in that sense. (Some vertical axis turbine types could actually work with a horizontal axis as well, but they would hardly be able to beat the efficiency of a propeller-type turbine).

The only vertical wind turbine which has ever been manufactured commercially at any volume is the Darrieus machine, named after the French engineer Georges Darrieus who patented the design in 1931.The Darrieus machine is characterized by its C-shaped rotor blades which make it look a bit like an eggbeater. It is normally built with two or three blades.

The basic theoretical advantages of a vertical axis machine are:
1) You may place the generator, gearbox etc. on the ground, and you may not need a tower for the machine.
2) You do not need a yaw mechanism to turn the rotor against the wind.
The basic disadvantages are:
1) Wind speeds are very low close to ground level, so although you may save a tower, your wind speeds will be very low on the lower part of your rotor.
2) The overall efficiency of the vertical axis machines is not impressive.
3) The machine is not self-starting (e.g. a Darrieus machine will need a “push” before it starts. This is only a minor inconvenience for a grid connected turbine, however, since you may use the generator as a motor drawing current from the grid to start the machine).
4) The machine may need guy wires to hold it up, but guy wires are impractical in heavily farmed areas.
5) Replacing the main bearing for the rotor necessitates removing the rotor on both a horizontal and a vertical axis machine. In the case of the latter, it means tearing the whole machine down. (That is why EOLE 4 in the picture is standing idle).

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