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From spring 2015, wind turbine nacelles with up to 8 megawatts of electrical capacity can be tested at a stretch in Germany´s first test rig.
© Fraunhofer IWES
Test rig for wind turbine nacelles
Projektinfo 15/2014
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Fast-track testing of nacelles

In Bremerhaven, a test rig is being developed that can test complete wind turbine nacelles in the multi-megawatt class. Unprecedented: a load transmission system mechanically simulates the wind loads occurring in the field. The researchers are investigating the electrical components using a simulated electricity grid. Laboratory tests are also providing information on how wind turbine concepts can be improved. With these properties, the test rig has the world’s most powerful grid simulation system.

The increasingly large wind turbines and new turbine designs need to prove their reliability and efficiency – even under challenging operating conditions. In particular, lightning strikes, extreme loads but also fatigue and wear of the components are ubiquitous risks. At higher altitudes, greater wind speeds are an additional burden on the ever-larger towers.
According to a reliability study on variable-speed wind turbines as part of the EU’s RELIAWIND project, the most common faults occur in the electrical system and the mechanical drive train. The technical reliability of the large-volume and extremely heavy nacelles for wind turbines – to which the components mostly belong – largely determines the overall availability in the grid. This is why accelerated and realistic testing procedures are becoming increasingly important. Manufacturers previously had to build a prototype for each new turbine – which is a very time-consuming and expensive procedure. Using accelerated test procedures on a nacelle test rig enables the prototype testing phase to be considerably shortened.

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For this purpose, the Fraunhofer Institute for Wind Energy and Energy System Technology IWES in Bremerhaven has developed a test centre, the Dynamic Nacelle Testing Laboratory (DyNaLab). The heart of the DyNaLab is a nacelle test rig where, from spring 2015, primarily gearless nacelles with up to 8 megawatts of electrical capacity, including both prototypes and serial production nacelles, can be tested for onshore and offshore applications. In the laboratory, field tests can be mimicked under realistic conditions. The nacelle test rig is supplemented with other testing facilities for the main components of wind turbines such as converters, generators, bearings and main shafts. “The tests on the test rig help to increase the reliability of the wind turbines – especially offshore. In addition, the loads acting on the drive train can be reduced by new control strategies,” says DyNaLab project manager Martin Pilas in explaining the benefits for manufacturers and operators of wind turbines. The tests enable a reduction of the tower head mass, improved operational management and control, an increase in the grid availability and shorter production lead times thanks to the accelerated certification.

Eliminating weak points early on

The investigations using the nacelle test rig contribute to a better understanding of the wind turbines. The simulation of specific operating cases enables weaknesses to be identified and countermeasures to be developed, which makes them more reliable. Potential flaws can already be corrected during the construction before the first prototype is erected in the field. This shortens the commissioning phase, which in turn leads to a quicker market introduction. Before a nacelle can be tested, a detailed testing campaign is drawn up, which also includes the safety concept. Here, for example, load limits or abortion criteria are set and the respective adapters are designed. A nacelle test can take between three and twelve months in accordance with customer wishes. This means that a maximum of two to four nacelles a year can be tested on the test rig.

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Addresses

Project management
Fraunhofer IWES

Links

 Video zum DyNaLab
Video on the nacelle testing in the DyNaLab

EU-Projekt RELIAWIND
Final report on the EU’s RELIAWIND project

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