Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Francesco Grasso (1) F P Ozlem Ceyhan (1) Stefanos Kalentiridis (2)
(1) ECN, Petten, The Netherlands (2) TU Delft, Delft, The Netherlands
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Ozlem Ceyhan Yilmaz is a research engineer and aerodynamicist in ECN-Wind Unit who's speciality is very large rotor designs of the future. She is originally an aerospace engineer with a masters degree from METU, Ankara. She worked in aircraft design projects for 5 years. Afterwards she moved to ECN and is working on the rotor aerodynamics and designs for the last 6 years. She is currently coordinating a task about high Reynolds numbers wind tunnel test in EU project: Avatar. In these tests a blade section of 10MW reference turbine is tested on its actual conditions.
Loads and structural challenges of wind turbine rotor concepts for future offshore wind farm applications
According to a recent study of the European Environment Agency, the technical potential of offshore wind energy in the EU was estimated to 30000 TWh/year. Compared to the electricity consumption estimated by the European Commission of about 4400 TWh in 2030, it appears that offshore wind energy offers a huge potential. The UPWIND project demonstrated that the development of large wind turbines is technically feasible, but not cost-effective when this is done by merely up scaling a given technology. Innovative concepts are needed to obtain lightweight-high-performance rotors able to bring down the cost of energy of future offshore wind farms.
The present work is focused on developing several new rotor concepts and showing their advantages on wind turbine and wind farm performance. In the INNWIND.EU project a 10MW reference wind turbine (RWT) has been created. Starting from this geometry, six alternatives have been designed and compared, aiming to reduce the loads of the turbine while keeping high performance in terms of annual energy production. The focus is given mainly to the rotors with reduced wind-power density from 400W/m2 to 300W/m2, including low solidity blades since they offer very good potentialities for lightweight rotors.
Main body of abstract
The present work focuses on the development of new rotor concepts. In particular, on the challenges connected to structural aspects and loads. It is based on previous investigation done at ECN that was concentrated on aerodynamics and performance.
The present work is intended to be a deeper investigation about those concepts. In this way, the actual value of the new rotor concepts can be assessed, comparing them to the 10MW RWT in terms of cost of energy.
To reach this goal, a novel engineering procedure has been developed at ECN to obtain the structural properties of the rotor concepts. Such procedure makes possible to have realistic values for the structural rotor properties without a detailed internal blade design. As effect, a large number of rotor variants can be investigated in a short time and with low computational efforts.
A selection of representative extreme and fatigue load cases has been used to calculate the behavior of the rotor concepts. Focus6 software has been used in this study.
The preliminary results are promising. Together with the results already obtained about the wind turbine and wind farm performance, they offer a complete overview of the value of such rotor concepts. In fact, some of the solutions show good performance improvements together with satisfactory structural response. In some cases, the tip deflection was too large so it required additional mass and they resulted in more expensive solutions. From the design point of view, the present study highlighted special points of attention for future developments.
innovative rotor design is a key point to develop 10MW+ very large offshore machines that are also cost effective. Several concepts have been developed, ranging from pure upscaling to low solidity. Most of them showed increase energy production and maximum axial force reduction. However, the present work adds value to those initial results. This is because the structural integrity and load response plays a crucial role to assess the impact on the cost of energy of such designs. From design point of view, the study provides more insight on specific problems affecting some configurations and, implicitly, suggesting ad-hoc solutions.
To make cost effective the development of very large offshore wind turbines, innovative solutions are needed. New rotor concepts play a crucial role in this process. What is the most promising concept? What are the new challenges that the designers should address to obtain optimal performance and low cost of energy? The present study aims to answer these questions proposing new designs and assess their value in terms of performance, structural behavior and so costs.