Hi all,
I am no expert of wind energy, it makes sense to produce energy from wind if it has a medium speed of 4,6 meteres per second.

Which is the wind turbine that start to run with the weak wind?

Regards

Mario Calvi

mariocalvi@hotmail.com

Hello Mr. Calvi,

That is a great question because many wind turbine manufactures claim to have wind turbines that perform wonderfully in low wind conditions. In regards to your question about wind turbines that perform well in low wind speeds one must remember that the energy that is contained in the wind is a function of the wind velocity cubed. Wind machines that promise superior performance in low wind speeds are still limited by Betz's Limit, which states that only 59.3% of the energy contained in the wind can be captured. The best designed rotors can only capture a little above 40% of the energy in the wind. This makes doing proper wind resource assessment for your site essential before investing in a wind turbine because even with the best equipment you can only extract so much of the power that is in the wind. For more information about wind resource assessment check out Windustry's Wind Prospecting web page. It contains how to manuals and links to great resources about performing a proper wind resource assessment for a site.

Windustry page on Wind Prospecting

Please let us know if you have any more questions about wind energy.

Thanks,

Generally wind turbines require a class 4 wind to be profitable, though rising energy costs are impacting that formula. However, there is a possible solution for people located in class 2 to class 3 areas. The Wind Accelerator Dome can accelerate the wind by as much as 30%. An acceleration of 17% will raise a class 2 wind to a class 4 wind. The DOE in Pa has a write up on the Wind Accelerator Dome in a site they operate.

Basically the dome is a relatively inexpensive structure that you would use (barn, greenhouse, school gymnasium, etc). The domes come in different sizes, shapes, functions and costs. But, once you have the dome, the space above it becomes an ideal location for a wind turbine.

Stuart

This is sort of a trick question. There are turbines that run at a high efficency in slow winds due the airfoils that are used in the props, and there are turbines that are designed themselfs for low winds. For the latter, I am speaking of turbines with a larger than average set of blades, as compared to the generator size of a usual turbine. Just like Mr. Antonich showed, there is only a certant amount of power in lower wind speeds, and the only real way to increase the power that is taken into the gennerator is to increase the blade diameter/swept area. As for improving the airfoils used, it is mostly common knowlage in the wind turbine industry that blade efficencys are basically at there max, and that is why they are spending most of there development money on building larger turbines, instead of more aerodynamicially efficent designs. The majority of the airfoil work is focused on making turbines quieter, not more powerfull.

I like to invite you to take a look at

http://greengower.blogspot.com/

-There will be a link for DOY Wind Rotor. Where you can harest wind engery to most you can I do not claim it is 100 times the yield compare to the same height turbine. But you can experiment yourselves. (a 16'D x 8'L will have enough 100% energy to furnish a sizable home used).

- There is also a short study of how much money in term of energy resource that you have on your land. (all you need is then mean go harvest them).

Vertical turbines generally have a higher "cut in" wind speed, i.e. the speed required to start rotating. There is a vertical turbine called the Windspire that has a "cut in" speed of 8 mph. So, if your wind is usually below that speed, then there is no point.