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ECN publication
The ICORASS feasibility study
Bulder, B.H.; Hendriks, H.B.; Langen, P.J. van; Lindenburg, C.; Snel, H.; Bauer, P.; Polinder, H.; Rooij, R. van; Subroto, H.; Zaayer, M.B.
Published by: Publication date:
ECN Wind Energy 19-2-2007
ECN report number: Document type:
ECN-E--07-010 ECN publication
Number of pages: Full text:
90 Download PDF  

This is the final report of the joint TU-D/ECN project ICORASS (Integral Composite Offshore Rotor Active Speed Stall control) . This project was performed to investigate the feasibility of a very large offshore wind turbine consisting of integrated components to offer a major improvement in the levelized production costs and reliability of offshore wind energy. The ICORASS concept was originally described as a (very) large robust wind turbine with integrated components. To create a robust wind turbine the idea was to reduce the number of components and integrate functions as far as possible into single components. By increasing the size of the wind turbine the number of wind turbines in the wind farm, of a specific nominal power, will reduce and hence reduce the chance of failure. Another reason for increasing the size of the wind turbine is the lower specific maintenance cost. The project focus was on the wind turbine concept taking into account the interaction with the wind farm design. The technological aspects of the wind turbine that have been investigated are: 1) the aerodynamic rotor design regarding performance, active speed stall controllability and preliminary aeroelastic stability; 2) the generator design and rotor speed control concept; 3) the support structure and nacelle layout including both installation and operation and maintenance concepts. The low speed active stall control option was preferred over the high speed option. No technological barriers were found, although quite a lot of fields were identified for further research. Especially on the aerodynamic stall properties, structural blade layout and controllability should be elaborated before a final decision is made on the viability of the ICORASS concept. From the economical evaluation of the concept it appears that the up scaling from current large scale turbines (3-6MW) towards the intended 10MW for the ICORASS turbine introduces a levelized production cost increase. Although, the active speed stall regulated concept seems to provide a cost reduction with respect to pitch regulated wind turbines due to a decrease in both hardware and maintenance costs. However, the increased fatigue loads may cancel out these beneficial effects.

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