Offshore wind power is becoming a mainstay of the energy transition in Germany. However, the potential cannot yet be fully exploited worldwide. This is because offshore wind turbines can currently only be installed in the seabed at an economically justifiable cost at maximum water depths of 50 metres. This limits the number of suitable marine areas. To expand the possibilities of regenerative energy production, EnBW is researching new offshore technology together with the North German engineering company aerodyn, in which wind turbines float on the water surface. The prototype of the floating wind turbine Nezzy² (scale 1:10) will be first tested in a flooded gravel pit near Bremerhaven and then in the Baltic Sea in wind and wave conditions. If the tests are successful, the model is to be tested at full-scale with another partner in China.
Floating wind turbine compared to conventional offshore wind turbines (Monopiles Jackets, Flaoting, from left to right) Floating Technology
The Nezzy² floating wind turbine consists of two wind turbines, supported by a floating, semi-submersible foundation in the shape of a horizontal "Y". The wind current automatically aligns the floating foundation, which is connected to anchors on the seabed by six lines. The two wind turbines are supported by two towers which are placed at an angle in the centre of the foundation. They are connected to each other and to the foundation by tensioning cables. The 1:10 scale model is almost 20 meters tall up to the tip of the blade, and has a draught of about 1.5 metres. The prototype is being tested in two different rotor variants with two and three rotor blades.
Nezzy² in the flooded gravel pit
EnBW and the North German engineering company aerodyn engineering are jointly testing a new offshore technology of floating wind turbines. The prototype of such a turbine at a scale of 1:10 was installed in a flooded gravel pit in Hymendorf between Bremerhaven and Cuxhaven. Due to the lack of waves and currents here, it was possible to examine the yawing of Nezzy² in isolation. The two-month tests of the joint research project were successful. The Nezzy² floating plant is now being tested under realistic conditions in the Baltic Sea.
Nezzy² in a floating water pit in Hymendorf near Bremerhaven (Photo: Jan Oelker / EnBW / aerodyn)
EnBW and aerodyn test floating wind turbine (Photo: Jan Oelker/EnBW/aerodyn)
Installation of the Nezzy² prototype in the flooded gravel pit (Photo: Jan Oelker/EnBW/aerodyn)
Novel offshore technology tested in a flooded gravel pit (Photo: Jan Oelker/EnBW/aerodyn)
Nezzy²: The floating wind turbine
Nezzy² in the Baltic Sea
The model of the floating wind turbine Nezzy² was successfully tested in a flooded gravel pit near Bremerhaven. The prototype of the new offshore technology is now being installed in the Bay of Greifswald in the Baltic Sea. In the new two-month test, EnBW and the north German engineering company aerodyn are investigating how the floating turbine at a scale of 1:10 behaves in wind and wave conditions. If the tests in the Baltic Sea also go well, the full-size floating turbine is to prove itself in China at the end of 2021 or the beginning of 2022.
Nezzy² has been built up and lies on the quay in Vierow harbour (Photo: Jan Oelker / EnBW / aerodyn).
Nezzy² is launched with a large crane in Vierow harbour (Photo: Jan Oelker / EnBW / aerodyn).
Nezzy² has just plunged into the water at the quay in Vierow harbour, but is still hanging on the crane (Photo: Jan Oelker / EnBW / aerodyn).
The prototype of the floating wind turbine Nezzy² on a scale of 1:10 is being prepared for the test (Photo: Jan Oelker / EnBW / aerodyn).
Nezzy² successfully proves itself
The floating wind turbine has successfully passed the two-month test in the Baltic Sea. With 180 sensors in 30 different measurements it was tested how Nezzy² behaves when exposed to different wind directions and speeds, wave heights and directions. Nezzy² even withstood a storm tide in mid-October. Scaled up to the later true size of Nezzy², the wave and wind conditions were equivalent to a category four to five hurricane with waves reaching heights of up to 30 metres. Even under these extreme weather conditions, Nezzy² remained stable in the water.
The tests have shown that the prototype is now ready to be tested in the sea on a full-size scale. The 1:10 scale model has now been dismantled and the recorded data will be further evaluated. The findings will then be incorporated in the design of the 1:1 scale model, which is set to be tested in China at the end of 2021 or start of 2022.