In addition to solar energy, wind energy also plays an important role in the implementation of the energy transition. Wind turbines are by no means new, but have been used for many years. In the meantime, the first generation of wind turbines is being replaced by newer turbines with improved rated power through extensive repowering measures. This alone is significantly increasing the share of wind energy in the electricity mix.
Wind turbines from the 1990s had an average rated output of around 0.5 MW. In contrast, new turbines today reach around 2.7 MW.
But the new generations also have old limitations. For example, they can only use wind close to the ground up to a height of 200 metres. By contrast, airborne wind turbines fly much higher. They do not consist of a rigid construction, but look more like oversized stunt kites. Anchored to the ground with tethers, they make circles or figure eights at heights of up to 800 metres. A rope attached to the flying body drives a winch that is connected to the ground.
The first pilot plants generate nominal power of 100 KW, which can supply about 400 households. Several start-ups are working on product maturity for the series production of such flying wind turbines.
While windmills and stunt kites are almost heroic role models for wind power and flying wind systems, Spanish startup Vortex Bladeless drew inspiration for their innovative wind towers without rotor blades from a bridge collapse. After the Tacoma Narrows Bridge collapsed in the USA in 1940, strong winds turned out to be the cause. They had caused the bridge to vibrate, and the vibrations increased until the structure could no longer withstand the energy.
Vortex windmills use the same principle to make a column vibrate. It almost looks like a wind turbine under construction, which is only missing the rotor blades (see photo). But it doesn't need them, because the vibrations and deformations of the column generate electrical voltage without any external moving parts. Even if they are not yet as efficient as modern rotor systems, there are some advantages to their use. Without rotors and gears, they require little maintenance and have a longer service life. In addition, they do not produce audible sound and pose no danger to birds or other animals. The biggest advantage, however, is that they take up less space.
The example of the O-Wind turbine shows that it does not always have to be classic rotors. This spherical turbine is particularly interesting in places where conventional wind turbines have no place: in inner cities. Here there are too many obstacles for large turbines and the wind blows too chaotically. This is exactly what the O-Wind turbine exploits perfectly. Similar to the solar balcony power plants, it can be set up practically anywhere where the wind blows. On a small surface of about 25 centimetres, there is room for vertical and horizontal vents that are larger than the outlet. Thus, even a light wind creates a backwash that drives a turbine and generates electricity.
Although the amount of electricity generated is manageable, such small systems can be used almost anywhere. And in a decentralised power grid, it is ultimately only the total output that is decisive, not how many generation plants it comes from.
Text: Falk Hedemann
Part 1 of our series on innovations in renewable energies is about solar systems: