In the future, most wind turbines will not stand alone in a field, but together with other wind turbines as part of large wind farms on land or at sea. If yield and durability are to be perfect, the location of each wind turbine must be planned carefully. The Risø-led EU project TOPFARM provides the tools for a more rational design of wind farms.
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Image: The flow field behind two wind turbines (symbolised by a vertical black line) One wind turbine is placed in the wake of another wind turbine. The orange color indicates high speed, while green and blue colours symbolise low speed. The shelter effect behind both wind turbines is obvious.
The 9 participants in TOPFARM
Risø National Laboratory for Sustainable Energy, DTU (Project Manager)
DTU Mechanical Engineering
DONG Energy
Vestas
Universidad Politécnica de Madrid
Cambridge Environmental Research Consultants ltd.
Garrad Hassan and Partners ltd.
Germanischer Lloyd Industrial Services GmbH
Teknikgruppen AB
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When you place several wind turbines together, they will have an impact on each other, and they will not experience the same wind load.
When the wind is blowing on a wind turbine at the edge of a wind farm, it pulls a certain amount of energy out of the wind, so that the flow field behind it changes. The air then loses speed and the turbulence in the wake of the turbine increases.
This means that the next wind turbine in the series produces less power, while experiencing a heavier load. The turbulent air affects the turbine from all directions, and nothing can endure these changing loads in the long run, just think of how you can break a piece of metal by bending it back and forth for a while. The wind farms designed today is based on a simplified power production optimization, and the load dimension is not part of the optimization. The EU project TOPFARM, coordinated by Risø DTU, addresses this problem. The goal is - by the end of 2010 – to have a useful optimization tool which takes into account production as well as load aspects for wind turbines in wind farms.
All this should lead to a more rational design of future wind farms.
Wind farms in theory and practice
The TOPFARM project is divided into six Workpackages, dealing with various aspects of the theoretical basis of calculation.
To verify the theoretical basis, a full-scale test has been performed on a wind turbine in Tjæreborg Enge near Esbjerg. The flow field was measured behind the turbine, using laser technique.
The project is to result in a toolbox consisting of models for the wakes, energy production, load, costs and control strategies. Together these models will form a completely new optimization tool that can be used to improve operation of existing wind farms and to plan new, efficient wind farms.
In order to complete the project, the new basis of calculation will be used to re-design two existing wind farms - one in England and one in Denmark (Middelgrunden).
Conference with 50 presentations
In October 2009 Risø DTU and Universidad Politécnica de Madrid organized a colloquium within the framework of Euromech (European Mechanics Society) with the theme "Wind Turbine Wakes". The colloquium is part of the TOPFARM project. There were 10 sessions during 3 days with topics about how wind turbines in wind farms impact each other.
Click here to read a summary of the 50 presentations
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