Darrieus rotor

from Wikipedia, the free encyclopedia
Darrieus rotor from Martigny (canton Valais), built in 1987, Center de recherche et d'enseignement en energie et techniques municipales

The Darrieus rotor is a wind turbine for wind turbines with a vertical axis of rotation ( VAWT , vertical axis wind turbine ). In contrast to historical models such as the Chinese windmill ( folding wing rotor ), it is a fast runner. The rotor was invented by the French Georges Jean Marie Darrieus . His name is not mentioned in the original French patent from 1925. This is only the case in the American of 1931. In the classic form, the rotor blades are attached to the upper and lower end of the shaft and protrude outward in an arched manner. Shaped according to the principle of a chain line , the centrifugal force only causes tensile stress in them, not bending moments .

Mode of operation and aerodynamic design

  • Inflow and forces on a two-vane rotor (principle)

  • Combination with a Savonius rotor (start-up)

  • Flow and forces when a wing rotates (qualitative)

Forces are exerted on the surfaces of a stationary rotor by the fluid (air) flowing at speed vs. The force Fd, which is always perpendicular to the direction of flow, is the dynamic lift . This force can be broken down vectorially into the force Fl acting on the rotor bearing and the driving force Fa acting in the circumferential direction (tangentially). With a stationary rotor with two blades, the oppositely directed forces Fa and -Fa result. The torques Fa ∙ a and -Fa ∙ a compensate each other. The rotor does not turn.

So Darrieus rotors do not start by themselves. You need to be turned on. In the case of small systems, this can be done manually; in the case of larger systems, it can be done with a motor (usually electric motors). A simple solution to the start-up problem is the combination of a Darrieus rotor with a Savonius rotor . The latter starts up by itself.

If the rotor is set in rotation, each surface is approached differently. Here vr is the vectorial superposition of wind flow vs and head wind vu. The resulting currents generate different forces (both in terms of direction and amount) on the surfaces during a rotor revolution. The force components Fa in the tangential direction cause torques that maintain the rotation so that energy can be extracted. The torque M = Fa ∙ a generated during one revolution is not constant, but fluctuates because of the varying resulting flow vr.

The dynamic lift Fd is greater, the greater the effective angle of attack α between the tangentially oriented surface and the resulting flow direction ( lift coefficient ). However, this only applies up to α ≈ 15 ° (stall at larger angles). A drag force Fw arises in the direction of movement of the blades, which is also dependent on the angle of attack α ( drag coefficient ). So that the rotor can emit energy, the driving forces Fa acting during one rotation must outweigh the drag forces. Fa can also assume negative values ​​in certain areas of the rotation during one revolution, ie have a braking effect. Furthermore, centrifugal forces Fz act on the blades during rotation . The bearing load on the rotor results from the signed sum of the forces Fl and Fz.

Darrieus rotors are built with two to four surfaces that have a streamlined profile ( NACA ) to reduce drag (in the tangential direction) . The surfaces are normally inclined tangentially, but can also be arranged at a certain angle to the tangential direction.

Attempts to swivel the surfaces in a suitable way during rotation (model: Voith-Schneider drive ) have so far not been crowned with success. Even before Darrieus, swivel-wing propellers were considered (see Fig. 1 in his patent) and also built (e.g. folding-wing windmills ). In contrast, Darrieus wanted to create a turbine without swivel blades that did not have to be turned into the wind. That is the basic idea behind the concept outlined in the patent. Ernst Schneider recognized the great potential of the swivel vane principle for ship propulsion .

Darrieus rotors are so-called high-speed rotors, ie the amount of the peripheral speed vu must be greater than the speed of the fluid flow vs. Otherwise, the resulting flow can hardly be used. The ratio of vu to vs is characterized by the high speed number. High speed numbers from 3 to 5 are typical. The speed control of the Darrieus rotor is problematic. For example, when the wind speed is high, the peripheral speed of the rotor also increases in accordance with the high speed number. If the speed is braked in such a case (e.g. for reasons of stability), the resulting flow changes in an unfavorable way. The usable torque is reduced.

In the picture, the conditions during the rotation of a wing are shown qualitatively for a high speed number 5. It can be seen that the maximum of the driving force is at 0 ° or 180 °. The resulting driving torque Mr becomes negative at 90 ° and 270 °, since there is no driving force, but the drag force Fw ( flow resistance ) acts. With a two-vane rotor, the torque always passes through negative values ​​during one revolution. This is not the case with the three-winged aircraft.

Flow (blue) and force (red) with propulsion component (green) on a blade of a Darrieus rotor, shown in the resting system of the blade. The profile (shown in gray) is type NACA 0015 , the high-speed speed is 4, the air resistance is neglected. The lift is assumed to be dependent on the square of the speed and linear on the angle.

In the accompanying animation, the dependence of the lift on the effective angle of attack and the speed is taken into account. The wind resulting from the turning movement, which always hits the rotor blades from the front (solid black arrow), is superimposed on the true wind, which from the perspective of a rotor blade is constantly revolving (rotating black arrow). In total , they form the flow towards the profile (blue). In its working area (see polar ) the air force (red) now acts almost perpendicular to the flow, so that a component of this force acts as propulsion in the direction of movement (green). The vertical line shows the range of variation of the alternating load, which only stresses the construction but does no work.

Due to the constantly changing flow in circulation, asymmetrical profiles optimized for a certain angle of flow can not be used. Deviations from the mostly used symmetrical shape and the tangential alignment of the profile cause only marginal improvements, because positive effects at one point of the circuit are offset by negative effects at another. A dynamic adjustment of the blade angle during rotation would help. Experiments in this direction have so far not been successful.

The angle of attack, which is suboptimal over large parts of the circumference, reduces propulsion in two ways: on the one hand, the amount of lift decreases, on the other hand, its direction becomes less favorable, see animation. To compensate for this, the leaf area is enlarged, usually by increasing the profile depth, more rarely by more leaves. But this causes an increase in air resistance.

The maximum angle of attack, which from the stall sets in, depends on the profile thickness and determines the optimum tip speed of the rotor. This is in the range of only three to six, one reason for a further increase in the leaf area. The increased rotor mass and the performance curve, which is narrower compared to classic rotors, reduce the yield in turbulent wind conditions.

With the classic Darrieus rotor, the blades of which are shaped like a jump rope, the airflow decreases in the area close to the axis and the fluctuation amplitude of the direction of flow increases. More advanced constructions use thicker, less stall-sensitive profiles and greater profile depths.

construction

  • The very long blades of the classic Darrieus rotor are prone to vibrations. A resonant excitation of the complicated eigenmodes of the rotor by the aerodynamic alternating load including their harmonics is avoided as far as possible. This also applies to the guy ropes - the six 200 m long ropes of the Éole are each supported by lattice masts.
  • Extruded aluminum profiles , which can be manufactured inexpensively, were used as rotor blades . This still applies to H rotors, but aluminum is not sufficiently resistant to alternating loads for the elongated blades of the whisk Darrieus.
  • Since the Darrieus rotor has a vertical axis, its function is independent of the wind direction, so that there is no need for a generator pod that tracks the wind . However, this also eliminates the option of turning the rotor out of the wind in a storm, which is otherwise often used in small wind turbines. The larger blade area has a negative effect here because the entire structure from the rotor to the tower to the foundation has to be designed to be correspondingly more stable.
  • While modern wind turbines are regulated in the nominal power range by adjusting the blade angle and finally shut down, systems with Darrieus rotors are stall-regulated . In order to be able to safely avoid “running through” the system - the safety regulations require a possibility to do this independent of the mechanical brake - the generator of systems with Darrieus rotors is oversized. In this regard, the relatively low high-speed speed of Darrieus rotors is unfavorable, especially for large systems with their already low speed, because it increases the torque to be applied by the generator or the gearbox, which is directly reflected in the costs. Due to the dimensioning of the generator, it follows that the nominal power of a Darrieus rotor cannot be directly compared with that of other types of wind turbine.
  • Depending on the design (classic Darrieus or H rotor), the generator and possibly the gearbox are close to the ground, which makes installation and maintenance easier.
  • Performance coefficients of 30 to a maximum of 40%, based on the projected rotor area, can be achieved with the Darrieus rotor. Conventional rotors with a horizontal axis of rotation achieve over 50%.

H Darrieus rotor

H-Darrieus-Rotor in Dülmen-Rorup
Darrieus helix rotor

While the curved blades of the classic Darrieus rotor converge at the top and bottom with the rotor axis, the H-Darrieus rotor consists of straight blades on support arms, arranged parallel to the axis of rotation. The design with two or more vertical leaves and a horizontal support arm is reminiscent of the letter "H", hence the name.

Spirally curved blades on an H-Rotor-Darrieus model have a more even torque and do not require any starting aid, as long as an iron-free generator winding (low starting torque, no cogging torque of the magnets) is used.

These designs avoid some of the disadvantages of the classic curved Darrieus rotor listed above:

  • All areas of a sheet move at the same speed, with the same angle of attack.
  • Bracing downwards from the effective area is possible.
  • Less material used with a higher performance coefficient for the same effective area.

The wind power plant (WKA) shown shows the only large plant of this type still in existence in Rorup . The WKA was previously in the test field at Kaiser-Wilhelm-Koog on the North Sea. The special feature of this variant is that not only the upper area of ​​the wind turbine rotates, but the entire system (rotor blade area, tower and the rotor of the generator at ground level). A smaller, similar wind turbine from the test series is still owned by the operator. However, this has not been rebuilt.

A blade angle adjustment guided by the wind direction ( giromill ) can improve start-up behavior and efficiency. The principle has been known since the early 1970s. The higher level of efficiency and better start-up behavior are countered by the cost-effectiveness and the higher construction costs. In the range of up to 10 kW nominal power, commercial systems that work with a wind direction-controlled blade adjustment are advertised. It is not known whether or in what number such systems are in operation.

Use in the water

Recently, concepts have also been developed to use the Darrieus rotor in an underwater ocean or river current.

Development history based on examples

  • The Canadian company DAF Indal developed various Darrieus systems in the power range up to around 250 kW around 1980  . Systems with a nominal output of 4 and 40 kW served as water pumps. Grid-connected systems with a nominal output of 50 and 500 kW were tested in the SCE test center near Palm Springs and in the Gulf of St. Lawrence . The larger model, Indal 6400, is listed as commercial by Paraschivoiu (2002). The number of installations is unknown.
  • From 1974 to 1985, the US Department of Energy, DOE, funded the development of Darrieus technology at Sandia National Laboratories (Albuquerque, New Mexico site) with US $ 28 million. FloWind (USA), founded in 1982, acquired the rights to a 17 m rotor developed there and brought it to market maturity under the name "300 Darrieus". With 170 and 340 units respectively in the Altamont Pass and Tehachapi wind farms, the turbine with its 42 m high rotor was the most commercially successful of the vertical axis design. While the manufacturer stated a nominal output of 300 kW, the Californian Energy Commission managed the 510 systems with a total of 94 MW installed capacity (184 kW per system). While in 1995 there was no longer any vertical-axis wind power plant in commercial operation in Europe, in California these plants still accounted for 6% of the installed capacity. FloWind planned to replace the two-bladed aluminum rotors with three-bladed fiberglass rotors, but went bankrupt in 1997. The rotors were replaced by systems with a horizontal axis as part of repowering .
  • A rotor was installed east of the city of Martigny in the canton of Valais in 1987, which is operated sporadically together with a biogas engine. The rotor has a diameter of 19 meters, a height of 28 meters and a total mass of 8 tons. The speeds are given as 33 and 50 per minute. The asynchronous generator runs with 110 kW and 160 kW power at 1000 or 1500 revolutions per minute.
  • In 1987, Eole was built in Cap-Chat, Canada , a 110 m high system measured from the ground with a Darrieus rotor 64 m in diameter and 96 m in height and a generator with a nominal output of 3.8 megawatts. In a total of 19,000 operating hours, 12 GWh of electricity were generated (1/6 of the nominal output, 158 W / m² rotor area), but 'for wear' - the lower rotor bearing was not able to cope with the load. In addition to the weight and vibrations, the tension of the six 200-meter-long guy ropes running diagonally down contributed to this. In 1992 the rotor was badly damaged in a storm and the turbine was finally shut down.
Dornier vertical axis at Heroldstatt
  • In 1989 , in the test field of EVS, today EnBW , near Heroldstatt , a two-wing system was built by the Dornier works and the Flender shipyard . It has a diameter of 15 m, a mast height of 25 m and an installed output of around 55 kW at a nominal wind speed of 11.5 m / s. The mean wind speed of the location at the height of the rotor center is only 4.1 m / s. Therefore, and because of the low power coefficient of the vertical axis system, the annual yield was only around 24,500 kWh, corresponding to an average output of only 2.8 kW. The plant was finally shut down in 2000 after frequent repairs to all parts of the plant.
  • Darrieus H rotors in the West Coast wind farm
    In England , the USA and Germany in particular , attempts were made to develop the H-plant type so that it could be used commercially. For example, until the beginning of the 1990s, the German manufacturer Heidelberg-Motors developed systems with a gearless generator integrated directly into the rotor structure, as at Enercon . Five 1-megawatt turbines of this type were on the test field next to the west coast wind energy park in Kaiser-Wilhelm-Koog . Since the generator was very loud, similar to the 750 kW Lagerwey machine, these rotors had to be switched off at night. This halved the energy yield, which is why the plants had to be dismantled.
  • In the Antarctic, an H-rotor with a nominal power of 20 kW, a diameter of 10 m, three blades with a blade height of 5.6 m and a gearless ring generator was developed in the first German Georg von Neumayer research station in 1991 as part of a joint research project of the Alfred Wegener Institute for Polar and Marine Research (Bremerhaven), Bremerhaven University of Applied Sciences, Germanischer Lloyd (Hamburg) and Heidelberg Motor GmbH (Starnberg) started operations with funding from the Federal Minister for Research and Technology. The development has been carried out since 1989 in close cooperation between the four research partners under the project management of Friedrich Zastrow (University of Bremerhaven). In 1990, the system was tested and modified for a year on the test field of Germanischer Lloyd in Kaiser-Wilhelm-Koog (design data: max. Wind speed 68 m / s, lowest ambient temperature −55 ° C). Since January 1991 the wind turbine has supplied both the old and later (from January 1993) the second Georg von Neumayer research station with part of the electrical energy (approx. 6%) required for heating and other operation of the research station. The theoretically calculated C P, max of 0.38 with the design high speed number λ = 2.2 could be determined by measurements to be 0.31 with λ = 2.3. The system ran almost without any problems for 18 years and delivered approx. 36,000 kWh annually at an average wind speed of 9.5 m / s. The successor station received a wind turbine without a Darrieus rotor.
  • Two Darrieus-H-Helix on a measuring container near Neumayer Station, Antarctica
    The company "Quietrevolution", founded in 2005 with venture capital from RWE Innogy , developed a 5 kW system ("qr5") with a three-bladed 13.6 m² Helix-H rotor, ready for the market. Over 150 plants had been built by 2012, mostly in Great Britain and Ireland. For 40,000 pounds each, the Portland Marina adorned itself with seven facilities for the 2012 Olympics , which, however, had to be renewed two years later. Compared to the neat qr5 ( The elegant design of quietrevolution's qr5 turbine is geared towards adding visual appeal to its surroundings ), in March 2013 the company praised the conventional Hy5 wind generator as a more economical solution.
  • In Ishpeming, Michigan , a three-bladed classic Darrieus rotor with a diameter of 26 m and a height of 27 m was assembled in June 2010. With a nominal output of 200 kW, it was supposed to deliver 500 to 750 MWh annually to the immediately adjacent six-story senior citizens' residential complex, which it just towers above on its 18 m lattice mast. The project was the first of its kind for the companies involved and was funded with US $ 620,000 from the US DOE . Concerns about the safety of the elderly prevented regular operations. The system, which had been idle for years, was to be replaced in 2014 by a further developed, smaller model from the same manufacturer.
  • A three-bladed H-rotor with a diameter of 26 m, a blade length of 24 m and a hub height of 40 m, which was commissioned in April 2011, also has a nominal output of 200 kW, albeit at a more favorable location on Sweden's west coast. A shaft to the gearless, permanently excited generator runs in the tensioned, twelve-sided tower made of plywood . The manufacturer was the Swedish company Vertical Wind, a spin-off from Uppsala University. The clients are E.ON and the local utility Falkenberg Energy. The pilot project was also funded by the Swedish Energy Agency with the equivalent of 1 million euros. In the research reports published to date on careful tests below the nominal speed of 33 / min, the system achieves a C P of about 0.3 in moderate winds (between 16 and 21 / min) or in stronger, gusty winds in electrically forced stall (constant 20 / min) an output of 85 kW.
  • A vertical axis wind turbine will be installed in Grevenbroich in 2019 and is scheduled to go into operation in 2020. A special feature is an active and continuous blade adjustment of the rotor. The system is designed for an output of 750 kW and has a rotor diameter of 32 m, rotor blade length 54 m and a height of 105 m. According to the manufacturer AGILE WindPower, the systems can be scaled up to 1.5 MW.

literature

  • Erich Hau: Wind turbines - basics, technology, use, economy. 5th edition. Springer, Berlin - Heidelberg 2014, ISBN 978-3-642-28876-0 . limited preview in Google Book search
  • Ion Paraschivoiu: Wind Turbine Design with Emphasis on Darrieus Concept. Polytechnic Int. Press, Montreal, Canada 2002, ISBN 2-553-00931-3 . (Preview)
  • Robert Gasch , Jochen Twele (Hrsg.): Wind power plants. Basics, design, planning and operation , 8th updated edition, Springer Vieweg, Wiesbaden 2013, ISBN 978-3-8348-2562-9 .
  • Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( limited preview in Google Book Search).
  • Kristian R. Dixon: The Near Wake Structure of a Vertical Axis Wind Turbine. Master's thesis, TU Delft, 2008, download (pdf, 13 MB).

Web links

Commons : Darrieus Wind generators  - Collection of images, videos and audio files

Individual evidence

Attention! With DEPATISnet information, an error message often appears the first time it is clicked. The second time the link works.

  1. ↑ DEPATISnet | Document FR000000604390A. Retrieved December 4, 2017 .
  2. ↑ Patent US1835018 : Turbine having its rotating shaft transverse to the flow of the current. Filed December 8, 1931 , published October 1, 1928 , applicant: Darrieus Georges Jean Marie, inventor: Darrieus Georges Jean Marie. ‌
  3. ↑ Henze, Schröder: Vehicle and wind turbine aerodynamics. RWTH Aachen, accessed on December 4, 2017 .
  4. ↑ PC Klimas, MH Worstell: Effects of Blade Preset Pitch / Offset on Curved-Blade Darrieus Vertical Axis Wind Turbine Performance. Sandia National Laboratories Report, SAND81-1762, 1981, PDF .
  5. ^ Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( p. 173 in the Google book search).
  6. ↑ Lars Åkesson (SP Technical Research Institute of Sweden): Wind Energy Technology Survey for Ferry Free E39 Project , 5/2012, ISSN  0284-5172 .
  7. ^ RN Clark: Design and Initial Performance of a 500-kW Vertical-Axis Wind Turbine. Trans. ASAE 34 (1991) 985–991, PDF ( Memento of the original from October 24, 2011 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 / ddr.nal.usda.gov
  8. ^ DW Lobitz: Dynamic Analysis of Darrieus Vertical Axis Wind Turbine Rotors. Sandia National Laboratories Report, SAND80-2820, 198l, PDF .
  9. ^ TG Carne: Guy Cable Design and Damping for Vertical Axis Wind Turbines. Sandia National Laboratories Report, SAND80-2669,198l, PDF .
  10. ^ Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( p. 172 in the Google book search).
  11. ↑ Desire de Gourieres: Les éoliennes: Théorie, conception et calcul pratique . Editions du Moulin Cadiou, Paris, 2008, ISBN 978-2953004106 , p. 132 (Fig. 109).
  12. ^ Robert V. Brulle: Engineering the Space Age - A Rocket Scientist Remembers (PDF; 4.7 MB), Air University Press, Alabama, 2008.
  13. ↑ Paul Gipe: Wind Energy Comes of Age , Wiley, 1995, limited preview in Google book search.
  14. ↑ Windgate product page. Retrieved August 30, 2012 .
  15. ↑ Schweizer Fernsehen, Einstein , August 27, 2009. (No longer available online.) Archived from the original on February 27, 2014 ; Retrieved August 30, 2012 . 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.srf.ch
  16. ↑ James Glynn, Kirsten Hamilton, Tom McCombes, Malcom MacDonald: Marine Power Project: Vertical Axis Turbine. In: 'Marine Current Resource and Technology Methodology' website. University of Strathclyde, April 30, 2006, accessed June 10, 2019 .
  17. ^ GCK Technology Inc .: The Gorlov Helical Turbine. (No longer available online.) Archived from the original on October 18, 2018 ; accessed on June 10, 2019 .
  18. ^ A b Winds of Change: American Turbine makes 1975 - 1985
  19. ^ Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( pp. 85-87 in Google Book Search).
  20. ^ Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( p. 170 in the Google book search).
  21. ^ Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( p. 172 in the Google book search).
  22. ↑ Alan Jaroslovsky: Memorandum of Decision Re: Ownership of Windmills. (No longer available online.) United States Bankruptcy Court - Northern District of California, April 23, 1999, archived from the original on December 31, 2010 ; Retrieved September 19, 2011 . 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.canb.uscourts.gov
  23. ↑ a b Dörner: Darrieus rotor
  24. ^ Paul Gipe: Wind energy comes of age . Wiley, 1995, ISBN 0-471-10924-X ( p. 104 in the Google book search).
  25. ↑ a b according to the display boards on the plant, seen in a video by Peder Tee: Darrieus Windkraftanlage Heroldstatt . YouTube, August 26, 2016.
  26. ^ Dörner: Wind energy projects in Baden-Württemberg
  27. ^ G. Heidelberg et al .: Vertical Axis Wind Turbine with Integrated Magnetic Generator. 1990, in: H. Kohnen, J Texeira (Ed.): Proceedings of the Fourth Symposium on Antarctic Logistics and Operations. Sao Paulo, Brasil, 16 to 18 July 1991, pp. 72-82.
  28. ^ Geosciences Volume 12, December 1993, Verlag Ernst & Sohn, pp. 419, 420.
  29. ^ F. Zastrow: Wind energy. Lecture at the Hochschule Bremerhaven, Bremerhaven, 2006. Calculation and measurement
  30. ↑ Homepage of Quiet Revolution uk & ireland market ( memento of the original from March 25, 2015 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. 2012. @1@ 2Template: Webachiv / IABot / quietrevolution.com
  31. ↑ treehugger.com: Vertical Axis Turbine Maker Builds on Olympic Success .
  32. ^ Company blog
  33. ↑ Quietrevolution: Hy5 turbine set to change the landscape of small wind in rural areas  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , Press release, March 8, 2013.@1@ 2Template: Dead Link / www.quietrevolution.com  
  34. ↑ MTI Energy Management: Photo report on production and construction ( Memento from October 6, 2011 in the Internet Archive ) (web archive)
  35. ↑ Gang Rapids Business Journal: Grant helps MAREC tenant ( Memento of October 16, 2011 in the Internet Archive ) (October 25, 2010, web archive)
  36. ↑ Upper Michigans Source: Wind turbine spins briefly in Ishpeming ( Memento from April 20, 2014 in the Internet Archive ) (June 10, 2011, web archive)
  37. ↑ Zach Jay: No date for wind turbine replacement; Ishpeming facility hasn't generated anything but anger, controversy . The Mining Journal, September 18, 2014.
  38. ↑ Further information was found in a presentation by the manufacturer ( Memento from December 1, 2011 in the Internet Archive )
  39. ↑ technepolis group: Evaluation of the research ( Memento of the original from October 24, 2011 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. (Feb. 2009; PDF; 932 kB) @1@ 2Template: Webachiv / IABot / www.technopolis-group.com
  40. ↑ Swedish Energy Agency : Cleantech Opportunities 2009  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 3.0 MB)@1@ 2Template: dead link / webbshop.cm.se  
  41. ↑ Sandra Eriksson et al .: Tip speed ratio control of a 200 kW VAWT with synchronous generator and variable DC voltage . Energy Science & Engineering 1, 2013, doi : 10.1002 / ese3.23 .
  42. ^ Jon Kjellin et al .: Electric Control Substituting Pitch Control for Large Wind Turbines . Journal of Wind Energy, 2013 doi : 10.1155 / 2013/342061 .
  43. ↑ Manufacturer blog on the structure
  44. ↑ Technology - Vertical Sky. Retrieved November 20, 2019 .