Press Release

Fraunhofer Institute for Wind Energy and Energy System Technology

Fraunhofer IWES is testing 83.5m Rotor Blade Prototype

World’s Largest Rotorblade on the Test Stand

A huge cargo ship passed through the double lock-gates in Bremerhaven with only one piece of cargo on board: the longest rotor blade in the world, made in Denmark, was heading for the rotor blade testing facility at the Fraunhofer IWES. In the next few months, researchers at the institute will be testing whether the prototype’s design can withstand the extreme and long term loads of a 25 year turbine life-time. The test facility, opened in 2011, is the only one in the world capable of testing blades of this length.

The XXL rotor blade prototype, manufactured by the Danish company SSP Technology, sets new standards. A turbine consisting of these rotor blades attains a diameter of 171m and can therefore produce more full load hours. When in service, the highest demands are made on materials as rotor blades are subject to million-fold load changes through alterations in wind speed and direction. The further developed testing methods at the Fraunhofer IWES ensure that reliable statements can be made concerning durability, according to the requirements of IEC standards 61400-23, within just a few months.

Trends towards increased rotor diameters
If the results of the on-going tests in Bremerhaven are convincing series manufacture can begin. This could mean that by the year 2013, in Korea, these rotor blades will be turning on prototypes of innovative 7 MW offshore turbines. At present, there is only one testing facility in the world which can carry out tests of this magnitude. Owing to fast-growing rotor blade lengths the 11 million euros investment in a testing facility for very large blades, especially in the offshore area, has proven strategically important and correct.

Falko Bürkner, Technical Head of Department Testing Laboratories at the IWES explains, “We are glad that we decided, six years ago, to build such a large test stand and that we were supported by the state of Bremen, the Federal Ministry for the Environment and the European Union, even though at that time we had not reckoned that there would be blades with a length of 80m as early as 2012.”

As testing times are increasing, due to the lower natural frequency of very long blades, manufacturers must secure test capacities as early as possible. The test hall has been operating to capacity since its opening. Other, larger blades can also be tested at the Fraunhofer IWES. However, for these tests, the blade tips, not generally a critical area in the construction of rotor blades, must be clipped.