After six months of measurements, Risø DTU estimates that now only 266 hectares need to be cleared at the future national test centre at Østerild to make space for the wind turbines and ensure the right wind conditions around them.
The new test centre for large wind turbines at Østerild will be located in woodland at Østerild and Hjardemål dune plantations. The trees in the forest strongly affect the wind flow conditions in the area. It is important to a wind turbine test centre that both shear (variation of wind with height) and turbulence (fast wind variations) are within certain limits. If these limits are exceeded the measurements become too uncertain. One of the major issues concerning the Østerild location is how many trees have to be felled in order to establish a test centre of high quality. The report from Risø documents the flow conditions at Østerild based on measurements recently made on the site. On the basis of these measurements and additional modelling, a recommendation has been made in connection with the coming test centre on the distance needed between the turbines and the forest boundary. The work has been done by the Wind Energy Division, Risø DTU in collaboration with a working group consisting of Risø DTU, Siemens Wind Power AS, Vestas Energy Systems AS, the Danish Forest and Nature Agency and the Danish Wind Industry Association. It will not be difficult to meet the national parliament of Denmark’s requirement for not cutting down more than 450 hectares of forest before establishing the coming national test centre for wind turbines at Østerild. The final number will probably be considerably smaller. There might be a need for additional forest clearing to establish new wetlands that can intercept the nitrate released from clearing 266 hectares of forest. But the Danish Forest and Nature Agency’s preliminary assessment is that it is a matter of 50 to 80 hectares at the most. In any case, the total forest area to be cleared will be less than 450 hectares. In collaboration with DMU (the National Environmental Research Institute) it must now be further examined how many wetlands are necessary, where to have them and whether they can be established without clearing the forest.
Peter Hjuler JensenDeputy Head DTU Wind EnergyWind Energy (VEA)
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