Vertical Wind Turbines

Wind Energy

Vertical axis wind turbines

VAWT

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft running vertically. Key advantages of this arrangement are that the generator and/or gearbox can be placed at the bottom, near the ground, so the tower does not need to support it, and that the turbine does not need to be pointed into the wind. Drawbacks are usually pulsating torque that can be produced during each revolution and drag created when the blade rotates into the wind. It is also difficult to mount vertical-axis turbines on towers, meaning they must operate in the often slower, more turbulent air flow near the ground, resulting in lower energy extraction efficiency.

Since a tower produces turbulence behind it, the turbine is usually pointed upwind of the tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted up a small amount.

| 01.01.2009 | Read more | Print |

Darrius turbine

"Eggbeater" turbines. Invented by Georges Darrieus, this kind of turbines have good efficiency, but produce large torque ripple and cyclic stress on the tower, which contributes to poor reliability. Also, they generally require some external power source, or an additional Savonius rotor, to start turning, because the starting torque is very low. The torque ripple is reduced by using 3 or more blades which results in a higher solidity for the rotor. Solidity is measured by blade area over the rotor area. Newer Darrieus type turbines are not held up by guy wires but have an external superstructure connected to the top bearing.

Gorlov helical turbine

Essentially a darrieus turbine in a helical configuration. Patented in 2001. It solves most of the problems of the Darrieus rotor. It is self-starting, has lower torque ripple, low vibration and noise, and low cyclic stress. High reliability is expected from tested or matured designs. At least two wind turbine products are on the market as of 2007, including the Turby wind turbine and the Quietrevolution wind turbine. Most importantly, the GHT is an excellent turbine for zero-head hydropower, and appears to be a much needed ecologically benign and affordable solution for micro-hydropower. It is up to 35% efficient, which is competitive with the most efficient VAWT's.

Giromill

A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety have variable pitch to reduce the torque pulsation and are self-starting. The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a lower blade speed ratio; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades may be used.

Savonius turbine

These are drag-type devices with two or more scoops are used in anemometers, the Flettner vents, commonly seen on bus and van roofs, and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops. They sometimes have long helical scoops to give a smooth torque. The Banesh rotor and especially the Rahai rotor improve efficiency with blades shaped to produce significant lift as well as drag. A new variety uses sails that can open or close with changes in wind speed.

Vertical axis turbine

VAWT

This turbine is self starting, turning at low wind speeds, around 1.5 m/s generating power at 3.5 m/s. It take wind from any direction.

Vertical axis turbine

VAWT

Small wind vertical turbine generates power to large office complexes or industrial parks.

Bluenergy

BSWT - wind solar

BSWT turbine is based on sailing engineering. The wind rotor is rotated by two spiral-formed vanes. For best performance, these vanes are covered in solar cells, so that sun and wind produce electricity as one element. The BSWT produces little or no noise.