1. Energy Research Centre, Wind Energy, 1755 ZG Petten, The Netherlands
2. Wind Energy Dept., Risø National Laboratory, 4000 Roskilde, Denmark
3. The Robert Gordon University, School of Mechanical and Offshore Engineering, Aberdeen AB10 1FR, Scotland
4. Dept. of Energy and Semiconductor Research EHF, University of Oldenburg, D-26111 Oldenburg, Germany
5. Wolfgang Schlez, Garrad Hassan and Partners Ltd, Bristol BS2 0 QD, UK