Vertical axis wind turbine

A vertical rotor (also vertical ( axle ), wind turbine, windmill - called or - runner, VAWT short, English Vertical Axis Wind Turbine ) is a type of wind turbine in which the axis is vertical ( plumb ) position.

The rotation is at such turbine normally independent of the wind direction; So they do not need Yaw. Such wind -directional turbine is therefore also called Panemone (from Greek pan = any or all; anemos = wind).

In wind mills with vertical axis, the term horizontal ( rad) is historical windmill usual, with the indication of direction "horizontal" not here on the position of the axis of the wheel plane but refers ( cf. Horizontalrad water mill).

History

Horizontal windmills are due to its simple and robust design, the oldest known mills. Long before today's conventional wind mills with horizontal axis, they were from the Chinese (Chinese windmill ), the Persians ( Persian windmill ) used and other civilizations. Until the Middle Ages established himself in the New World, the design with horizontal rotation axis and wings made ​​of wood and / or scarf.

Chinese Windmill

From the mid- 19th century working engineers and technicians in the development of so-called " wind engines " that is advanced windmills as machine drive for pumping stations (wind pump) and to generate electricity. This has both on wind turbines with a horizontal axis (such as the Westernmill ), as well as to further developments with vertical axis worked:

• James Blyth ( engineer), from around 1885: Resistance Runner exoskeletal
• Georges Darrieus, from the mid- 1920s (patents in 1927 and 1931): Invention of the Darrieus rotor
• Sigurd Savonius, mid -1920s (patent 1926): Invention of the Savonius rotor

Vertikalachswindmühle as a drive for a pumping station ( Paasloo, The Netherlands, 1899)

Wind engine by James Blyth (1905 )

Winch motor to power a sawmill (Leipzig, 1907)

Types

Resistance runner

Twisted Savonius rotor ( helix form)

Resistance Runner primarily use the drag of the wing. By the dynamic pressure generated by the braking of the wind flow on the windward side ( the wind to ) of the wing, a force acts on the surface of the wing, which pushes the wing downwind ( with the wind path ). The force is greatest when the wing is at a standstill, it is reduced, the faster turns the blades. The tip speed ratio lambda is always less than one; So resistance runners are pronounced slow runners. The theoretically achievable power coefficients are approximately at a maximum of 0.2 - the practically achievable even lower.

• Savonius rotor Helix form ( twisted)

• Persian windmill
• Chinese Windmill ( light hybrid properties, see below)

Upward furling

Darrieus rotor in an "H" shape, a triptych

Darrieus rotor in "Helix - form ", a triptych

Buoyancy runners use the dynamic lift of an airfoil effect. Due to the flow around the profiled wing arises on the wing front suction ( negative pressure) on the back of a slight overpressure. The pressure differential causes a force on the wings. This force reaches its maximum when the wing is in motion; the optimal speed depends on the wind speed and the wing profile. The tip speed ratio lambda is greater than one, up to about fifteen; there are obtained power coefficients of up to 0.5. However, the more powerful the rotor is in the upper speed range, the lower the starting torque at a standstill; therefore large upward furling without wings adjustment need an auxiliary motor to start.

• Darrieus rotor O-shape ( " whisk " shape, classic )
• H-form
• Helix form (" Gyromill " twisted)

Hybrid forms

Hybrid forms have the goal to combine the advantages of drag and lift rotor at different wind speeds. In the lower speed range affects the high torque of the rotor resistance, so no starter motor is required. In the upper speed range, the high torque of the rotor affects buoyancy. Hybrid forms are more flexible, but do not reach such high power coefficients and thus benefits as pure buoyancy runner.

Advantages and disadvantages, areas of

Due to their design, and their physical operating principle Vertikalachser have a number of advantages and disadvantages:

• No Yaw necessary
• Simple and robust construction
• Insensitive to changing winds ( speed and direction )
• Generator and gearbox can be easily arranged to be accessible at ground level

• Low power coefficients, particularly in resistance runner
• Pulsating torque ( can be reduced by twisting the rotor → helix form)
• Low wind speed near the ground
• Possibly an auxiliary engine as starting aid required for buoyancy runners
• Powerful impetus runners tend to oscillate on the wings
• Can not be turned for protection from the wind in a storm

Due to the disadvantages, in particular the low power to Vertikalachser have not enforced for large-scale use for electricity generation. Here today are almost exclusively Horizontalachser used.

The applications for Vertikalachser, especially resistance runners are, mainly in areas where only a comparatively small power is needed, and where the benefits, especially the simple design and the insensitivity, predominate. Since they can be produced by relatively simple means, they are often used in DIY for the home.

As a wind generator to produce electricity Vertikalachsrotoren are predominantly for the supply of isolated networks or systems for charging batteries or wind energy heating used. Rarely feeding into the public grid is made.

As a mechanical drive Vertikalachsrotoren are sometimes used, for example, for driving pumping stations for irrigation and drainage. Also widespread is the use in heating and ventilation technology to enhance the natural train by fan with VAWT drive, which are placed on roofs or chimneys.

Also Whirligig Wind toys and wind-powered kinetic sculptures often have a vertical axis of rotation.

Analogies to water turbines

Although water turbines (up to a few special applications such as in tidal, ocean current or wave power plants ), the flow in their direction is approximately constant, therefore the major argument of the direction of independence, cross-flow turbines are also used as water turbines:

• Traditional water wheels, and horizontal bikes are limited with VAWTs comparable, as the wheel does not flow across, but is only tangentially flows around one side.
• Ossberger turbine: water - flow turbine
• Gorlov turbine: similar to a twisted H- Darrieus rotor