Friday, 15 May 2009

Advanced experiment is to make wind turbines more efficient and quiet

Tjæreborg Enge, 10 kilometres south of Esbjerg, is going to set the framework for some of the most advanced wind turbine experiments ever seen. A blade from one of the wind turbines in Tjæreborg Enge is removed and replaced with a test blade that has advanced measuring equipment. The measurements on the new test blade begin in May and aim at making the wind turbines of the future more efficient and quiet.

The experiments are going to provide an accurate picture of how the wind acts around a cross-section of a wind turbine blade. These air currents can be calculated and the calculations can be used for designing new blade profiles. Unfortunately the calculation models are not quite accurate, so a piece of the newly designed blade will have to be tested inside a wind tunnel. But these measurements are not entirely accurate either. For in the wind tunnel the blade is standing still during the measurements, while the blade rotates in real life, just as the atmospheric wind is different than the flow inside a wind tunnel. Moreover, the blade is elastic and therefore it moves. All these uncertainties will become significantly smaller because of the new experiments.

LM Glasfiber has produced the blade
The advanced test blade has been produced by LM Glasfiber. Seen from outside it looks like the blades that are already attached to the wind turbine. However, it carries measuring devices. More than 300 measurement points will be read 30 to 100 times per second and some of them up to 50,000 times per second. The only visible thing on the blade is 4 small pipes, pointing out from the front edge of the blade. They measure the wind which hits the blade on the place where the blade has a number of small holes (1 mm in diameter) making it possible to measure the pressure distribution on the blade.

The measurements will take 3-4 months starting in May 2009, after the test blade has been attached to the wind turbine. The measurements will be made in series lasting 3-4 days. When there are no ongoing measurements on the turbine, it will stand still or rotate quite slowly in order to protect the instruments. There will be no measurements during rainy or humid weather, as it may cause damage to the instruments.

Noise measurements
In periods noise measurements are carried out on the wind turbine, as the test programme also includes basic conditions concerning noise from wind turbines.

Finally, a few times laser beams will be used to measure the wind conditions. The laser system is a so-called LIDAR instrument, which is able to measure the wind speed at a point far from the instrument by means of a thin laser beam. This means that when placed on the ground the instrument can make measurements high above where the blades are rotating. A LIDAR throws a beam into the air and is not of any danger to humans or animals in the area.

Cooperation among Vestas, Siemens, LM, DONG Energy and Risø DTU
The research project ”Experimental rotor- and profile aerodynamics on MW wind turbines” is supported by the Danish energy research programme EFP-2007. The major Danish industries within wind energy take part in this project and support it financially. Participants in the project are Risø DTU, Vestas, Siemens, LM and DONG

Source: RISO

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