The world largest vertical axis wind turbine starts first test run

Wind turbine
The Vertical Sky A32 shortly after construction

The world’s largest vertical wind turbine in the megawatt class is currently located on the world’s largest wind test field at Neurather Höhe near Grevenbroich, Germany. The turbine has been completed and the test run could begin in October. The Swiss company Agile Wind Power has developed the system.
The machine, called “Vertical Sky A32”, has a diameter of 32m, is 105m high and is expected to produce 750kW.

Grevenbroich wind test field, Vertical Sky A32 under construction, in the background the Neurath lignite-fired power plant. Picture from 18.08.2020

In the technology of wind turbines, the horizontal axis with 3 wings, which are guided by the wind, clearly dominates.
Advantages of horizontal axis wind turbines:

  • The towers are relatively tall which allows the blades to face much higher velocity winds in high altitude. In some places, the power output of the wind turbine could increase up to 30% every ten meters in altitude because the wind speed is increased by 20%
  • High efficiency, the blades always move perpendicular to the wind, receiving power through the whole rotation unlike vertical axis wind turbines.


  • High construction and installation costs. Large Machinery is needed.

“Vertical axis wind turbines actually only cause problems”, is what experts say. At least one rotor blade always runs against the wind. The rapid change in the angle of attack causes the blades to stall, resulting in a loss of performance.
Compared to the horizontal-axis wind turbines commonly used today, the verticals deliver about 30% less power. Agile Wind Power has allegedly solved this problem by means of a “real-time rotor blade pitch control”. The active and continuous blade adjustment enables high efficiency at low rotor speeds. The angle of attack to the wind direction is therefore always optimal
This would have successfully met the biggest challenge, namely the dynamic stall of the blades, as the angle of attack changes rapidly.

wind turbine
The vertical axis with the pitch-controlled rotor blades

The company’s website lists the advantages:

The significantly lower noise level and the simple logistics for transport, installation, operation and maintenance ensure a high level of environmental compatibility. This makes it possible to move Vertical Sky® closer to populated areas. Difficult-to-access locations that cannot be served with existing technologies can thus be developed with little effort. This makes Vertical Sky® attractive for decentralised power supply.

Low operating costs ensure a high level of economic efficiency. Lightweight components allow easy transport without major damage to the floor. A Vertical Sky® system requires neither special transport nor special cranes. A convenient self-assembly system protects the resources of man and nature.

The test operation now starting at the Grevenbroich wind test field will show how this new development proves itself in practice. We will report here as soon as the blades rotate in the wind at the beginning of October.

Here is the video of the first test run – still in fixed pitch mode


Bernd Riebe – 19 NOV 2020

The company Agile Wind Power has just issued a press release:

On the evening of Sunday 15 November 2020 – while the commissioning phase was still underway – a rotor arm with the rotor blade attached to it broke off at the plant. Nobody was injured. Apart from damage to the land and the damage to the affected rotor arm and rotor blade, no other third-party damage was recorded.
After the incident became known, the securing of the accident site was ordered. Investigations to determine the cause of the damage were initiated. 

Update 23 NOV 2020

Windturbine Fracture

At the time of the accident, a cold front was moving through, with gusts of 20m/s (Bft 8) measured at nearby weather stations. The broken off rotor arm with wing is about 50m away from the tower.

Wind Turbine Crash

Text, photos, video: Bernd Riebe, 24 NOV 2020

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