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Wind Energy

November 16, 2020
Paul Gipe

Giant Giromill Loses Blade at Grevenbroich Test Site

Swiss VAWT Vertical Sky 32 lost one of its three rotor arms and blade Sunday 15 November at the Grevenbroich test site according to German media. The prototype turbine was installed at the test site west of Cologne, Germany in September.

Previously, Patrick Richter, the Swiss designer, had installed one version in his native country. His firm, Agile Wind Power, has been developing the 750 kW turbine for the past decade with support from the Swiss energy department, the Swiss climate foundation, Audi, and the European Union.

The H-configuration VAWT at Grevenbroich was 32 meters in diameter and each straight blade was 54 meters long, giving the machine 1,730 m² of swept area.

The swept area of the Sky 32 is equivalent to a conventional wind turbine 47 meters in diameter. Conventional wind turbines in this size class are typically rated at 500 kW or less. The trend in the industry is to increase the swept area relative to the power rating. However, VAWTs--of any configuration--are notorious for high power ratings because they are more reliant on stall than modern conventional wind turbines that use full-span pitch control.

Vertical Sky 32 is one of if not the largest H-configuration or giromill wind turbines ever built. It is twice the size of Robert McAlpine's Musgrove derived VAWT 850 built in 1990. And Sky 32 is bigger than the last French effort, Nenuphar 1, which went belly up after Areva and French state-owned utility Électricité de France abandoned the project in 2018. It is also slightly bigger than the three-blade, fixed pitch, H-rotor built by Stahlprodukt in Poland in 2017.

Large VAWT development had virtually ceased until a brief revival in the mid 2000s by the French and Poles. The Swiss project is an unusual outlier. Vertical Sky 32 employs three articulating sets of two blades attached at a single rotor cross arm. Previous articulating, straight-bladed H-configuration rotors used two sets of cross arms. The blades on the Robert McAlpine turbines did not articulate. They were fixed in pitch.

For more on giromills and VAWTs in general, see A historical review of vertical axis wind turbines rated 100 kW and above. For an excellent video of the turbine rotating with details of the blades, cross arms, and nacelle, see The world largest vertical axis wind turbine starts first test run, and you can read Bernd Riebe's report on the turbine at The world largest vertical axis wind turbine starts first test run.


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