Darrieus wind turbine

The Darrieus rotor is a wind turbine for wind turbines with vertical rotation axis ( VAWT, vertical axis wind turbine ), and in contrast to the Persian windmill, a quick runner. It was invented by the Frenchman Georges Darrieus and patented in the USA in 1931. In classical form, the rotor blades on the upper and lower ends of the shaft are mounted, and extend arcuately outwards. According to the principle of a catenary shaped, causing the centrifugal force in them only tensile stresses, no bending moments.

Evolution by means of examples

• The Canadian company DAF Indal developed around 1980 different Darrieus turbines with capacities of up to about 250 kW. Plants 4 and 40 kW rated power served as a water pump. Grid-connected systems with rated power 50 kW and 500 were tested in the SCE test center in Palm Springs and in the St. Lawrence Gulf. The larger model, Indal 6400, performed by Paraschivoiu (2002) as commercially. The number of installation is not known.
• From 1974 to 1985, the U.S. Department of Energy DOE promoted the development of Darrieus technology Sandia National Laboratories ( Location Albuquerque, New Mexico) with 28 million U.S. dollars. The company was founded in 1982 FloWind (USA ) acquired the rights to a developed there 17 -m rotor and brought him under the name "300 Darrieus " for the market. The plant, with its 42 m high rotor was 170 and 340 copies in the Altamont Pass and Tehachapi wind farms the most commercially successful of the design with the vertical axis. While the producer indicated 300 kW rated power, led the California Energy Commission, the 510 plants with a total installed capacity of 94 MW (184 kW per system ). During 1995 no wind turbine with a vertical axis was more in Europe in commercial operation, these plants had in California a share of 6% of installed capacity. FloWind planned the replacement of the two-bladed rotors made of aluminum by three-bladed rotors made ​​of fiberglass, but went bankrupt in 1997. The rotors have been replaced by machines with horizontal axis under the repowering.
• East of the town of Martigny, Valais Canton, 1987, a rotor was built, which is sporadically operated together with a biogas engine. The rotor has a diameter of 19 meters, a height of 28 meters and comes to a total mass of 8 tons. The speeds are indicated by 33 and 50 per minute. The asynchronous generator running at 110 kW and 160 kW of power at 1000 or 1500 rpm.

• In Cap-Chat Canadian Éole was built in 1987, one from the floor 110 m high plant with a Darrieus rotor of 64 m diameter and 96 m height and a generator with 3.8 MW rated power. In a total of 19,000 operating hours 12 GWh of electricity was generated (1/6 of the nominal power, 158 W / m² rotor area ), but ' wear ' - the lower rotor bearing was not up to the load. In addition to the weight and vibration contributed to the tension of the six 200 meter long, slanted down guy ropes. In 1992, the rotor was badly damaged in a storm and the plant finally shut down then.

• In the test field of the EVS, today EnBW, at Herold Instead a two-leaf plant Flender AG was established in 1989. It has a diameter of 15 m, a mast height of 25 m and an installed capacity of about 55 kW at 11.5 m / s Rated wind speed. The average wind speed at the height of the location of the rotor center is only 4.1 m / s Therefore, and due to the low power coefficient of Vertikalachsanlage the annual yield was only about 24,500 kWh, corresponding to an average power of only 2.8 kW.
• Especially in England, the U.S. and Germany was trying to develop the H- type of plant commercially viable. For example, until the early 1990s, systems were developed with directly integrated into the rotor structure gearless generator as with the German manufacturer Enercon of Heidelberg engine. From this type of five one - megawatt plants were on the test field next to the wind farm west coast in the Kaiser- Wilhelm- polder. Since the generator as in the 750 -kW Lagerwey machine was similarly very loudly, the rotors had to be turned off at night. Thus, the energy yield was halved, so the equipment had to be dismantled.

• In the Antarctic research station in 1991 was the first German Georg von Neumayer an H - rotor with 20 kW rated power, 10 m diameter, three wings with 5.6 m height of wings and a gearless ring generator in the framework of a joint research project of the Alfred Wegener Institute for Polar and marine Research ( Bremerhaven ), Bremerhaven University of Germanischer Lloyd ( Hamburg) and manufactured by Heidelberg taken motor GmbH ( Starnberg ) with funding from the Federal Minister for Research and Technology in operation. The development was carried out since 1989 in close collaboration between four research partners under the project leadership of Friedrich Zastrow ( Hochschule Bremerhaven ). The plant was founded in 1990 for one year tested on the test field of Germanischer Lloyd in Kaiser- Wilhelm -Koog and modified ( interpretation of data: max. Wind speed 68 m / s, minimum ambient temperature -55 ° C). The wind turbine supplied as January 1991, both the old and later (from January 1993), the second Georg von Neumayer research station with a portion of the electrical energy (about 6 %), which is needed for heating and other operating the research station. The theoretically calculated CP, max of 0.38 in the design tip speed ratio λ = 2.2 could be determined by measurements to 0.31 at λ = 2.3. 18 years as the system ran virtually trouble -free and supplied approximately 36,000 kWh annually at an average wind speed of 9.5 m / s The next station was a wind turbine without Darrieus rotor.
• The company " Quiet Revolution " founded with venture capital RWE Innogy in 2005 developed a 5 kW system ( " qr5 " ) with dreiblättrigem 13.6 - m ² -helix H- rotor for the market. By 2010, more than 100 plants have been built, mainly in the UK. After the " Microgeneration Certification Scheme " certification at the beginning of the production capacity is exhausted in 2011 with another 105 plants, 30 of them. Inventory for the RWE Innogy At the 2012 Olympics seven plants have been installed at Portland Marina and commissioned the production of 400 units.
• Ishpeming, Michigan, a classic three-blade Darrieus rotor was mounted 26 m diameter and 27 m height in June 2010. With a rated capacity of 200 kW, it shall provide annually 500-750 MWh to the immediately adjacent six-story senior living facility that he just dominated at the 18 -meter lattice mast. The project is the first of its kind for the companies involved and was funded with 620,000 U.S. dollars from the U.S. DOE. Concerns about the safety of seniors delay the control mode.
• Also 200 kW rated power, but at a more convenient location on Sweden's west coast, has a taken into operation in April 2011, three-blade H- rotor of 26 m diameter, 24 m blade length and 40 m hub height. In the twelve -sided tower of laminated wood shaft for a gearless permanent-magnet generator runs. A total of four plants will supply a single inverter. Manufacturer is the Swedish company Vertical Wind, a spin-off of the University of Uppsala. Clients are E.ON and the local utility Falkenberg Energy. The pilot project is also funded by the Swedish Energy Agency, the equivalent of 1 million euros.

Mode of action and aerodynamic design

The results from the rotational movement relative wind, which always makes the rotor blades from the front to the true wind, which constantly circulates from the perspective of a rotor blade superimposed. In sum, they constitute the animation in the blue drawn flow of the profile. In the workspace (see polar ) air force ( red arrow) now affects nearly perpendicular to the oncoming flow, so that a component of this force in the direction of movement as propulsion is effective ( green bar). The vertical line shows the range of variation of the AC load, which requires only the construction and does no work.

Due to the outstanding ever-changing incident flow optimized asymmetric profiles can not be used for a given angle of attack. Deviations from the symmetrical shape and tangential orientation of the profile usually used cause only marginal improvements because positive effects negative at a place of outstanding face elsewhere. Remedy would bring a dynamic adjustment of the blade angle during rotation. Experiments in this direction have so far been unsuccessful.

The suboptimal in many parts of the circumference angle of attack decreases the tunneling in two ways: First, the amount of lift decreases, on the other hand whose direction is unfavorable, see animation. As compensation, the leaf area is increased, usually by increasing the tread depth, rarely by more leaves. But this causes an increase of air resistance.

The maximum angle of attack, which begin in the stall is dependent on the thickness profile and determines the optimal tip speed ratio of the rotor. This is in the range of three to six, one reason for a further increase in the leaf area. The increased rotor mass and narrower compared to classical rotors power curve lower in turbulent wind conditions the yield.

In the classical Darrieus rotor, whose leaves are shaped like a jump rope, takes in the region near the axis of the airstream and the amplitude of the fluctuation of inflow to. Advanced designs use there thicker, less stall- sensitive profiles and greater tread depths.

Construction

• The very long in the classical Darrieus rotor blades are prone to vibrations. A resonant excitation of the complex eigenmodes of the rotor by the aerodynamic load changes, including their harmonics is avoided whenever possible. This also applies to the guy ropes - the six 200 m long ropes of Éole are to each supported by pylons.
• As the rotor blades of extruded profiles were used in aluminum, which can be manufactured economically. For the H- rotors still, for the elongated leaves of the whisk - Darrieus is aluminum but not sufficient change overload.
• Since the Darrieus rotor has a vertical axis, its function is independent of the wind direction, so that it can be dispensed with the wind tracking generator nacelle. However, this also eliminates the otherwise with small wind turbines like used option to turn the rotor out of the wind during a storm. Here, the larger leaf surface has a negative effect because the entire structure must be designed from the rotor on the tower to the foundation in accordance stable.
• While modern wind turbines in the range of rated power are controlled by blade pitch control and eventually shut down plants with Darrieus rotor stall- regulated. In order to reliably prevent a "runaway " of the system can - the call for an independent safety of the mechanical brake way to do this - the generator of systems with Darrieus rotor is oversized. In this respect, the relatively low tip speed ratio of Darrieus rotors, especially for large systems with their already low speed unfavorable because so that applied by the generator or the transmission torque increases, which is directly reflected in the cost. Due to the dimensions of the generator follows that the power rating of a Darrieus rotor can not be directly compared with that of other types of wind turbines.
• The generator and possibly the transmission are depending on design ( classical Darrieus or H- rotor ) at ground level, which facilitates the maintenance and replacement of components.
• Power coefficients of 30 to a maximum of 40 % can be achieved at the Darrieus rotor. This is in contrast to conventional rotors with horizontal rotation axis, reaching over 50%.

H- Darrieus rotor

While the curved sheets of classical Darrieus rotor run together up and down with the rotor axis, consists of the H- Darrieus rotor of straight, arranged parallel to the axis of rotation leaves on support arms. The design with two or more upright leaves and a horizontal support arm resembles the letter "H", hence the name.

Spiraling curved leaves on a H -rotor Darrieus model have a more uniform torque and require no traction, while a coreless generator with low internal resistance and no detent of the magnets used.

Avoiding these types some of the above-mentioned disadvantages of the classic curved Darrieus rotor:

• All areas of a blade moving at the same speed, with a uniform angle of attack.
• A bracing from the effective area down and out is possible.
• Reduced material use at higher power coefficient for the same effective area.

The wind turbine pictured (WKA ) shows the only existing large-scale plant of this design in Rorup. The WKA was formerly in the experimental field at the Kaiser- Wilhelm- enclosed land on the North Sea. The special feature of this variant is that not only the upper portion of the WKA turns, but the entire system (rotor blade area, tower and at the floor level of the rotor of the generator). A smaller, similar WKA of the test series is still in the possession of the operator. This has, however, never rebuilt.

A wind direction guided blade angle adjustment ( giromill ) can improve the starting performance and efficiency. The principle is known since the early 1970s. The higher efficiency and better starting behavior is determining the cost-effectiveness against the higher construction costs. In the range up to 10 kW nominal power are commercial systems that work with a wind direction guided blade adjustment advertised. Whether or in what number of such plants are in operation, is not known.

Use in water

In more recent times, concepts have been developed to take advantage of the Darrieus rotor in a sea or river flow under water.