At present, rotor blade prototypes are tested by moving them separately both in and perpendicular to the direction of the wind in order to obtain infor- mation about how their material behaves over their 20-year service life more rapidly – this is a major simplification of how loads actually occur simultane- ously in the field. As part of the “Future rotor blade concept” research project, scientists at Fraunhofer IWES are developing new methods that provide signif- icantly more realistic data and allow a load-appropriate design to be produced. The Federal Ministry for Economic Affairs and Energy and the Federal State of Bremen intend to invest € 10 million to further develop methodological exper- tise and an innovative test infrastructure in Bremerhaven.
Better safe than sorry: Since, in reality, only one rotor blade will undergo the complete blade testing procedure right through to certification, the calculative safety factors selected are not necessarily those leading to optimum costs, but rather those which can cope with the operational loads with certainty. A higher number of tests that can be realized at reasonable cost allow the safety margins to be reduced, which, in turn, means a more economical design for the rotor blades.
This is the starting point for the rotor blade experts at Fraunhofer IWES. Separating a blade into segments for testing – e.g. root segment and rotor blade tip – has two ad- vantages: Tests become possible at higher frequencies and with a more accurate load profile. The tests are rendered even more accurate when individual sections with a critically high load and greater material thickness or strong curvatures, for example, are investigated separately. This innovative approach not only produces more informative results, but also reduces the testing times by a calculated 30%, which means a notice- able cost saving.
