Darrieus wind turbine
Buoyancy vertical omnidirectional turbine. Buoyancy means that revolves thanks to the difference in pressure between the two sides of the driving blades. Vertical indicates the deposit of its rotational axis perpendicular to the surface, what is the omni-directional. Catches then the energy of the wind from any direction without the need to first make a perpendicular against the wind.
The name has acquired a turbine, after its inventor George Jean Marie Darrieus, the French engineer aeronautics (field of study concerned with the construction of flying machines), which came out from a knowledge of the characteristics of the wing of the plane and applied them to the lift drive Darrieus turbine.
Principle
The blade profile of the wings (teardrop shaped) operates the wind. The difference in path length, which must overflowing air to pass around the inner and outer sides of the blades, causing a vacuum on the inner side of the blade. This creates a force in the picture a green color, which forces the turbine to spin.
This applies to shovel apparent to the direction of the wind. The scoop on the flip side, the opposite is true, i.e.. Vacuum is formed on the outer side of the blades.
The faster Darrieusova turbine rotates around its axis, the more lift is generated, so the speed of rotation has an impact on the performance of the turbine. Therefore, up to a certain value, when the effectiveness begins to decline see the chart.
For the generation of lift on the blades need to turbine was spinning. Therefore, it is also Darrieus turbine itself heavily gaining momentum, until it reaches the speed necessary to the extraction of wind energy.
For quick commissioning of the turbines to the working speed is often spinning an external source of rotary motion. It is in practice solves either the engine, which gives the turbine to spin, or used a combination of resistance of the turbine (vertical omni-directional, or Savonius turbine) with Darrieus on a one axis.
Resistive turbine so as to ensure the rotation of the Darrieus at lower wind speeds, with a whole has so far produced. Once it will increase the speed of the wind, the Darrieus is in the rotation and can immediately start to exploit the wind.
To build up the turbine to spin also uses a tilting of the blades. This in itself makes the design even more complex.
A very specific idea is the use of the Magnus effect as in the following video:
Darrieus turbine is applicable for small to medium-sized power installation. (Although there are projects of large marine and offshore installation, which must be in the rotation to indicate the engine.)
The design of the turbine is demanding on accuracy, because any nesymetrie and eccentricity causes the vibration of the structure. These lead to rapid wear and structural damage to individual parts of the turbine. Susceptibility to damage is also a common cause of preference for other types of turbines.
To limit the negative effects of vibration, attention is directed on the solution of the shape and spacing of the blades. Therefore, it is also possible to meet with many of the sometimes crazy shapes of structures.
Another direction of research interests is the number of blades.
And last but not least, attention is directed to the profile of the blades in order to increase the efficiency of the turbine.
Pros
Performance is better than all the resistance of the turbine.
It is omnidirectional, so does not waste time when changing the direction of the wind.
Risks and limitations
- Needs support for spin the engine or the auxiliary resistive turbine.
- Prone to vibration, which can damage the structure and the related lower the life of the equipment.
Conclusion:
Darrieus turbine is suitable for home use. For the handyman, however, will be challenging to produce a fully functional machine, which will be after long years of trouble-free. Many experienced builders after the first big snowstorm collects the debris of the turbine on the neighbor's land.
At the same time, it is necessary to remind, that Darrieus turbine works at low wind speed and the designer actually solves two turbine – resistance and Darrieus.
In conditions of the CZECH republic in the volatility of the wind and in the often rugged terrain is difficult to find the perfect space for the construction of this turbine.
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