First with offshore MW prototypes

Bonus is the first Danish wind company to erect a megawatt prototype turbine destined for the offshore market, though it is the last to go public with its plans for multi megawatt technology. The other four Danish wind companies released their plans in the autumn (Windpower Monthly, October 1998). But Bonus beat them to the starting line when it installed a Bonus 2 MW prototype, with a 70 metre rotor and 60 metre hub height, at the wind test field of Deutsches Windenergie-Institute (DEWI) near Wilhelmshaven in Germany. The machine was due to start turning last month.

According to Bonus technical director Henrik Stiesdal, the design is a further development of the company's 600 kW and 1 MW turbines. The 33.8 metre blades are from LM and the gearbox by Flender, the largest developed by the company for a wind turbine. Stiesdal says several prototypes will be tested along with a zero-series before the 2 MW is on the market.

The Wilhelmshaven prototype is owned and operated by Projekt-WinVest, a subsidiary of the Oldenburg planning office. The machine is to be tested for about two years before being marketed for offshore installations, says AN Windenergie of Bremen, a German affiliate of Bonus. DEWI will carry out the testing and measuring of noise emissions and output.

The choice of Germany as the testing ground for the 2 MW was not made voluntarily, says Stiesdal to Danish newspaper The Engineer. It proved impossible to find a site in Denmark which was not opposed by the authorities -- a problem facing other Danish wind companies as well.

A second new Bonus design is also being tested not far from the DEWI test field. An AN Bonus 1.3 MW with a rotor diameter of 62 metres, developed from the 1 MW machine with its 54 metre rotor diameter, was installed in December by Oldenburg-based LUV Windenergie. It is owned and operated by a subsidiary of the developer, LUV WEA-Memershausen. The machine and LM blades were supplied from Denmark while the tower was built in Germany.