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Design methods for offshore wind turbines at exposed sites

Objective



Objectives
Although a number of pilot offshore wind farms have been constructed in rather sheltered waters in Denmark, the Netherlands and Sweden, the full exploitation of the huge offshore wind energy resource in the EU will require the use of more exposed sites in locations such as the North Sea. The use of such sites brings the challenge of designing safe but cost-effective wind turbines and support structures in the face of a potentially hostile combination of wind and wave loading. The aim of this project is to develop the understanding needed for this challenge to be faced with confidence. This aim will be met through the achievement of the following objectives:
- to install a measurement system at the Blyth Harbour offshore wind farm capable of detailed measurements of the wind, waves and currents as well as the loading and response of one of the two wind turbines at the site.
- To use the measurement system for a period of 12 months to establish a database of environmental and structural load measurements. The database will contain wind, wave and current measurements to fully characterise the the environmental conditions at Blyth Harbour, and structural measurements to characterise the dynamic loading of the rotor, drive train, tower and monopile foundation of the offshore wind turbine. - To analyse the database of environmental and structural measurements in order to derive a thorough understanding of the aerodynamic and hydrodynamic loads and their influence on the dynamic response of the offshore wind turbine and its support structure.
- to use the Database of measurements to enable validation and Enhancement of state-of-the-art-methods for computer modelling and design analysis of offshore wind turbines.
- to undertake parametric analyses for investigation of the complex relationships between component fatigue and extreme loading, the design characteristics of an offshore wind turbine and its support stucture, and the site wind, wave, current and sea bed conditions.
- to investigate the robustness of design calculations for offshore wind turbines with respect to variations in the environmental conditions, wind turbine and support structure design concept and methods of analysis.
- to provide a critical appraisal of present design procedures and the Germanischer Lloyd certification rules for offshore wind turbines and to recommend changes where appropriate.
- to catalogue the key design requirements of offshore wind turbines for sites where the environmental conditions are severe.

Technical approach
The project will be undertaken by a partnership of organisations, each with a major interest in offshore wind energy and each offering different expertise and a different perspective on the problems involved. The partnership comprises Garrad Hassan and Partners (UK), Delft University of Technology (NL), Germanischer Lloyd (DE), NEG Micon (DK), Border Wind (UK), and PowerGen (UK).

The project will involve the first set of detailed structural measurements on an offshore wind turbine at an exposed site where the sea conditions are severe. The measurements will be carried out on one of the two NEG Micon 2000kW machines to be installed in the North Sea at Blyth Harbour in north east England. Sea conditions at this site are considerably more hostile than those in the Baltic Sea or the Dutch Ijsselmeer, the locations of the only offshore wind farms to be built to date. The measurements, undertaken over a period of a year, will allow a thorough characterisation of the environmental conditions at the site, the dynamic behaviour of the wind turbine and its support structure, and the combined aerodynamic and hydrodynamic loading of the major structural components. Following analysis of the database of measurements and its use for validation and enhancement of state-of-the-art design tools capable of modelling offshore wind turbines, computational studies will be carried out in order to identify the key design requirements for such machines installed at exposed sites. The project will also involve a thorough review of the current Germanischer Lloyd certification rules for offshore wind turbines, the only such rules in existence.
Recommendations for revisions to these certification rules will be made where this is appropriate.

Expected achievements and exploitation
It is expected that the work carried out in this project will lead to a much improved understanding of wind turbines located at exposed offshore sites.
This improved understanding will be exploited through the use of enhanced design tools and certification rules for offshore wind turbines. In addition, a key deliverable of the project will be a catalogue of those design charcateristsics of an offshore wind turbine and its support structure, which are necessary to ensure safe, reliable and cost-effective offshore wind farms. The exploitation of this knowledge will reduce the technical and financial risks associated with offshore wind energy.

Funding Scheme

CSC - Cost-sharing contracts
Leaflet | Map data © OpenStreetMap contributors, Credit: EC-GISCO, © EuroGeographics for the administrative boundaries

Coordinator

GARRAD HASSAN AND PARTNERS LTD
Address
Saint Vincent Works, Silverthorne Lane
BS2 0QD Bristol
United Kingdom

Participants (6)

Border Wind Limited
United Kingdom
Address

NE46 3PU Hexham, Northumberland
DELFT UNIVERSITY OF TECHNOLOGY
Netherlands
Address
1,Stevinweg 1
2628 CN Delft
GERMANISCHER LLOYD WINDENERGIE GMBH
Germany
Address
Johannisbollwerk 6-8
Hamburg
NEG MICON A/S
Denmark
Address
21,Alsvej 21
8900 Randers
POWERGEN RENEWABLES DEVELOPMENT LIMITED
United Kingdom
Address
Westwood Business Park
CV4 8LG Coventry
Vestas Wind Systems A/S
Denmark
Address
27,Smed Hansens Vej
6940 Lem