Vertical rotor (wind turbine)

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Hybrid of Darrieus and Savonius turbine

A vertical rotor (also V ertical ( a chs) w ind t urbine , -windrad or Rotor called short VAWT , English V ertical A xis W ind T urbine ) is a type of wind turbine , in which the axis vertical ( perpendicular ) stands.

In such turbines, the rotary motion is normally independent of the wind direction ; so you do not need any wind direction tracking . Such a wind direction-independent turbine is therefore also called a panemone (from the Greek pan = "everyone" or "all"; anemos = "wind").

For historical reasons, the designation horizontal (wheel) windmill is common for windmills with a vertical axis , whereby the indication of direction "horizontal" does not refer to the position of the axis, but to that of the wheel plane (cf. horizontal wheel water mill ).

Current state of development

The Swiss company Agile Wind Power has developed a vertical turbine with real-time rotor blade pitch control. This should make it possible to optimally adapt the rotor blades to the wind direction at lightning speed and thus achieve a better degree of efficiency than with the previous models. In the meantime, the company has also set up a branch in Germany at Lemwerder Airport to start manufacturing rotors there. In addition, a lattice mast for a first prototype has already been erected on the Grevenbroich wind test field . This is to be continued with further assembly after the winter break in 2019/2020. Then the test run for certification should begin.

history

Horizontal windmills are among the oldest known mills because of their simple and robust construction. Long before today's windmills with a horizontal axis, they were used by the Chinese (see also folding-wing rotor ), the Persians and other advanced cultures. It was not until the Middle Ages that the design with a horizontal axis of rotation and blades made of wood and / or cloth was established in the New World.

  • Persian windmill (model in the Deutsches Museum)

  • Chinese windmill

From the middle of the 19th century, engineers and technicians worked on the development of so-called "wind motors", i. H. advanced windmills as machine drives for pumping stations and for generating electricity . Work was carried out on both wind turbines with a horizontal axis (such as the Westernmill ) and further developments with a vertical axis:

  • Horizontal windmill with folding blades (1880)

  • Vertical axis windmill as a drive for a pumping station (Paasloo, Netherlands, 1899)

  • Wind engine by James Blyth (1905)

  • Wind engine as drive for a sawmill (Leipzig, 1907)

Types

Resistance runner

  • How a Savonius rotor works

  • Twisted Savonius rotor (helix shape)

Resistance runners mainly use the flow resistance of the wings. Due to the dynamic pressure , by slowing down the wind flow on the windward arises page (to the wind) of the wing, a force acts on the surface of the wing, which wing by Lee presses (away from the wind). The force is greatest when the wing is standing still, it decreases the faster the wing turns. The high-speed number lambda is always less than one; Resistance runners are therefore downright slow runners. The theoretically achievable performance coefficients are around a maximum of 0.2 - the practically achievable even significantly lower.

Types

Buoyancy runner

  • Darrieus rotor in "whisk" shape

  • Darrieus rotor in "H" shape, three-bladed

  • Darrieus rotor in "helix shape", three blades

Lift runners use the dynamic lift effect of a wing . The flow around the profiled wing creates a suction (negative pressure) on the front side of the wing and a slight overpressure on the back. The pressure difference creates a force on the wing. This force reaches its maximum when the wing is in motion; the optimal speed depends on the wind speed and the wing profile. The high speed number lambda is greater than one, up to about fifteen; performance coefficients of up to 0.5 are achieved. However, the more powerful the rotor is in the upper speed range, the lower the starting torque at standstill; large lift runners without wing adjustment therefore need an auxiliary motor to start.

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

Hybrid forms

Hybrid forms aim to combine the advantages of drag and lift runners at different wind speeds. The high torque of the resistance rotor acts in the lower speed range, so that no starter motor is required. The high torque of the lift rotor acts in the upper speed range. Hybrid forms can be used more flexibly, but do not achieve such high performance coefficients and thus performances as pure lift rotors.

Advantages and disadvantages, areas of application

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

Advantages:

  • No wind direction tracking necessary
  • simple and robust construction
  • insensitive to changing winds (strength and direction)
  • The generator and gearbox can be easily accessible near the ground

Disadvantage:

  • low performance coefficients, especially with resistance rotors
  • pulsating torque (can be reduced by twisting the rotor → helix shape)
  • low wind speed near the ground
  • An auxiliary motor may be required as a starting aid for lift runners
  • powerful lift runners tend to vibrate on the wings
  • cannot be turned out of the wind to protect against storms

Areas of application:
Due to the disadvantages, in particular the low output, vertical axes have not established themselves for large-scale use for power generation. Horizontal axes are used almost exclusively here today.

The areas of application for vertical axes, in particular resistance rotors, are predominantly in areas where only a comparatively low power is required and where the advantages, in particular the simple construction and the insensitivity, predominate. Since they can be produced with comparatively simple means, they are often used in self-construction for the home area.

Vertical-axis rotors are mainly used as wind generators for power generation to supply stand-alone networks or systems , to charge batteries or as wind energy heating. Feeding into the public grid is seldom done.

As a mechanical drive, vertical axis rotors are sometimes used, for example, to drive pumping stations for irrigation and drainage. It is also widely used in heating and ventilation technology to strengthen the natural draft through fans with VAWT drives, which are placed on roofs or chimneys.

Also Whirligig -Windspielzeuge and wind-driven kinetic sculptures often have a vertical axis of rotation.

Analogies to water turbines

Although in water turbines (with the exception of a few special applications such as in tidal, ocean current or wave power plants) the direction of the flow is almost more constant and the great argument of directional independence is no longer applicable, cross-flow turbines are also used as water turbines :

  • Classic water wheels , including horizontal wheels , can only be compared with VAWTs to a limited extent, as the flow does not flow through the wheel transversely, but only flows around it on one side tangentially.
  • Ossberger turbine : water flow turbine
  • Gorlov turbine : similar to a twisted H-Darrieus rotor

literature

  • Winfried Halbhuber: Operation of small wind turbines - an overview of the market, technology and profitability . GRIN-Verlag , 2010, ISBN 3-640-58796-0 ( limited preview in Google book search).
  • Robert Gasch : Wind turbines: basics, design, planning and operation . Ed .: Jochen Twele. 8th edition. Springer, 2013, ISBN 3-8348-0693-5 , pp. 17 (in particular Section 2.1 Wind turbines with a vertical axis , pp. 17–19).

Web links

Commons : Vertical-Axis Wind Turbines  - Collection of Images, Videos and Audio Files

Individual evidence

  1. ↑ Note: Strictly speaking, it is a shaft because it transmits torque .
  2. ↑ rp-online
  3. ↑ windtest-nrw
  4. ↑ agile wind power
  5. ↑ a b c d Gasch, 2010 (see literature)
  6. ↑ a b Judith Jäger: Wind turbines. (PDF) Wind energy: physical basis and different types of wind power plants. Lecture. (No longer available online.) Physics Institute of the University of Tübingen, August 23, 2006, archived from the original on June 10, 2007 ; Retrieved August 4, 2011 .
  7. ↑ a b C. Tropea: Wind turbines. (PDF) lecture notes. Technische Universität Darmstadt, Faculty of Mechanical Engineering, Faculty of Fluid Mechanics and Aerodynamics, January 7, 2010, accessed on October 8, 2012 .
  8. ↑ a b c Thomas Emmert: Wind turbines - an overview. (PDF; 93 kB) ProjektE, Faculty of Mechanical Engineering, Technical University of Munich, archived from the original on April 29, 2004 ; Retrieved August 4, 2011 .
  9. ↑ Toni Klemm: Numerical and experimental investigations on fans with high power density . Dissertation at the Faculty of Mechanical Engineering at the University of Karlsruhe. Karlsruhe 2005, Chapter 8.
  10. ↑ Hannes Riegler: HAWT versus VAWT . In: REFOCUS . (July / August), 2003, p. 44–46 (English, full text ( Memento from January 31, 2012 in the Internet Archive ) [PDF]). HAWT versus VAWT ( Memento of the original from January 31, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.victordanilochkin.org
  11. ↑ With the targeted use of wind farms , however, higher outputs per space are possible in research scenarios than with horizontal -axis wind turbines, see John O. Dabiri: Potential order-of-magnitude enhancement of wind farm power density via counter-rotating vertical-axis wind turbine arrays . In: Journal of Renewable and Sustainable Energy . tape 3 , no. 4 , July 1, 2011, p. 043104 , doi : 10.1063 / 1.3608170 , arxiv : 1010.3656 .
  12. ↑ a b c d Halbhuber, 2009 (see literature)
  13. ↑ Note: Since water currents, in contrast to wind currents, are not always directed horizontally, the absolute orientation of the axis is less important here, but rather the relative orientation perpendicular to the direction of flow.