With the DualWingGenerator, as part of the Bionic Learning Network, Festo has developed an extraordinary technology platform that uses two pairs of horizontally arranged wings instead of rotor blades to generate power. Thanks to its intelligent control technology, the self-optimizing system can adapt itself to different wind conditions and, in terms of its efficiency, is by no means inferior to conventional small wind power stations. The concept features amazing benefits even at low wind speeds.

Reverse principle of the natural beating of wings

The system’s principle consists of reversing the natural wing-beating principle: while birds generate the necessary power to move forwards in the air by flapping their wings, a stationary system like the DualWingGenerator can take the kinetic energy from the

flow of air. The wind power creates a linear lifting movement here, which is converted into a rotary movement. With the aid of an electric generator, the system turns the energy produced into electricity.

Opposing pairs of wings for optimal power generation

The four wings are arranged on both sides of the central column. The two top and the two bottom wings are each positioned on the same motor-driven rotary axle, which is fitted on a slide. When the wind blows, the two slides move synchronously on the vertical guide in opposing directions: while the top two wings travel upwards, the bottom wings move downwards. The pair of wings on one side forms a functional unit, whose fluid-mechanical properties enable power to be generated in an optimal manner. At the apex, a servomotor turns the wings and they automatically move back towards each other. Their active rotation means the wings are always set so that air flows onto them at the optimal angle. This enables the adaptive system to achieve an optimal energy yield with a very high, scientifically proven effectiveness level. Festo already technically implemented this so-called active torsion in 2011 with the SmartBird.

When developing the artificial silver seagull, the engineers studied how birds actively rotate their wings and thus make the most energy-efficient use of the wind conditions.

From lifting movement to electrical energy

The whole mechanism used to turn the wind power into electrical energy is integrated in the central column on the DualWingGenerator. The column also contains the sensor technology, which helps to optimize the mechanical movement and enable it to be adapted to the wind conditions in an energy-efficient manner.

If air flows towards the system, the central column turns automatically and always directs the wings, made of carbon, at right angles to the oncoming wind. The flow of air thereby acts on the airfoils of the wings, which are lined up at an appropriate angle by the servomotors. This leads to the slides moving up and down on the axle with the wings, which produces the opposing movement of the wings. The movement is synchronized in opposite directions using a timing belt, which transfers the force to two bearing shafts. These rotary movements are rectified by means of free wheels and transferred to the generator using another timing belt. The wind power thus generates firstly kinetic and finally electrical energy.

Whilst the wings are moved by the oncoming wind, the system only has to provide power for the two servomotors and for the CPX control system, which is installed under the central column.

Higher system efficiency due to tandem wings

Using two pair of wings with only one central column allows the wing area to be doubled – with the mechanical layout remaining the same and hence the same friction. This increases the area of wind contact in relation to the mechanism and hence the efficiency of the system.

The opposing tandem wings neutralize the bearing torques from the upwards and downwards motion. In the middle, the wings get so close that a suction effect is created between the airfoils, which enables a higher level of effectiveness. When the wings move toward each other, the air between them speeds up. In turn, this acceleration creates a drop in pressure, which pulls the two airfoils together and thus further increases the energy yield. A video at the Festo site is equally fascinating.

Festo
http://www.festo.com/cms/en_corp/13707.htm

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