Posted: January 5, 2010

New knowledge about materials to increase wind turbine reliability

(Nanowerk News) Funding has been granted for a new centre at Risø DTU to increase the operating reliability of wind turbines: The Danish Council for Strategic Research’s Programme Commission on Energy and Environment has granted funding of DKK 38.0 million for the establishment of the Danish Centre for Composite Structures and Materials (DCCSM). The new centre will be headed by Senior Scientist Bent F. Sørensen, Materials Research Division at Risø DTU. The project title is ‘Danish Centre for Composite Structures and Materials for Wind Turbines’.
Wind turbine blades are usually made from composite materials such as fibreglass and are designed to last for at least 20 years. During this period, they are exposed to fierce weather conditions, including gale-force winds. At the same time, developments are moving in the direction of larger and more efficient wind turbines, and they are being sited offshore, which makes servicing more expensive and also more of a challenge. This calls for very reliable wind turbines with as few stoppages as possible.
Early damage detection
The structures and components which make up each wind turbine must be able to withstand minor damage without necessarily causing stoppages. It is also important that the wind turbines are fitted with a range of sensors which can detect any damage as early as possible so that parts can be repaired or replaced before the wind turbine suffers a stoppage. This is particularly true of the blades; these are gigantic rotating parts which on the newest wind turbines measure up to 60 metres long.
Wind turbine blades can suffer damage ranging from microscopic cracks to metre-long fractures. They develop from minute defects stemming from the manufacturing process. DCCSM will therefore develop new experimental and calculatory methods covering everything from nanoscale defects to fractures which are several metres long. The idea is to improve our understanding of what makes a nanoscale defect develop into a major fracture which can cause the wind turbine to stop completely. The aim is optimisation at various length scales.
Can a blade safely be left to rotate? Is it worth repairing it or should it be replaced?
The research will involve developing methods for looking at what happens from when the wind turbine blade is on the drawing board until it starts rotating on the finished wind turbine generator far out at sea. The research will look at the materials chosen, the design and manufacture of the wind turbine blade and the detection of damage, and also at model calculations which can predict how blade design may affect the way in which cracks develop.
Armed with such knowledge, manufacturers will be able to design lighter and stronger wind turbine blades with built-in sensors which will continuously monitor any damage to the blade and whether there is a risk of such damage developing into something more serious. Such analyses can also be used to predict the strength of a wind turbine blade which has suffered damage and its remaining useful life. It will provide a valuable basis for making the right decisions.
The greatest scientific challenge concerns the coupling of models at different length scales. The plan is also to use the centre as a unifying force for the strong Danish research environments within composite structures and materials for wind turbines in Denmark, including for example the coordination and launch of future research projects.
Source: Risø DTU