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Measurements on and modelling of offshore windfarms


The three main objectives of the project are 1) To complement the existing base of windfarm data by gathering information on wind speed deficit, turbulence and structural loads at the Vindeby offshore windfarm and one wind turbine on the Finnish island Sottunga, 2) To investigate the structure of single and multiple wakes under the ideal homogeneous, lowambient turbulence conditions found offshore, and thus be able to model wake behaviour more correctly, and 3) To be able to characterize turbulence and shear in the incoming flow as a function of upstream turbine separation to be utilized in the design phase for calculation of loads on wind turbines to be located offshore.
In terms of manpower and cost the data collection and data analysis at Vindeby will dominate the present project. The tasks of gathering data from the Vindeby Windfarm, pre-processing and extended data processing will be undertaken by Risi with the support of ELKRAFT. Data collection at Sottunga will be undertaken by FMI. Flow modelling will be carried out by UPM, Ris and FMI with UPM in the leading role. The task of outlining load cases will to some extent be shared by all parties.

The project is centered on the measurements on two of 11 450 kW Bonus wind turbines placed approx. 2 km offshore the Danish island of Lolland, the Vindeby Windfarm being the first of its kind in the world. In parallel to the measurements modelling of the atmospheric flow inside the windfarm will be performed. The anticipated project tasks have been divided into 4 subtasks: A) data collection and pre-processing of data, B) extended data analysis, C) flow modelling and load cases, and special analysis regarding D) power performance. The project will produce important information on the flow characteristics in offshore windfarms, including structural loads on the wind turbines as well as additional experimental evidence on the power performance of windfarms. It is expected that the experimental evidence at the end of the project period will be sufficient, with an appropriate mix of parameters such as turbine spacing, surface roughness and terrain complexity, to produce guidelines for the design of wind turbines placed in near-coastal offshore environments.

Funding Scheme

CSC - Cost-sharing contracts


Risø National Laboratory
399,Frederiksborgvej 399
4000 Roskilde

Participants (4)

Bonus Energy A/S
7330 Brande
5,Lautruphoej, 7
2750 Ballerup
Finnish Meteorological Institute
24,Vuorikatu 24
00100 Helsinki
Universidad Politécnica de Madrid
2,José Gutiérrez Abascal
28006 Madrid