1. Department of Energy Conversion and Storage; Technical University of Denmark (DTU); Risø Campus, Frederiksborgvej 399 DK-4000 Roskilde Denmark
2. Facultat de Fısica; Departament d'Estructura i Constituents de la Materia; Universitat de Barcelona; Diagonal 647 E-08028 Barcelona Catalonia Spain
3. Department of Wind Energy; Technical University of Denmark (DTU); Risø Campus, Frederiksborgvej 399 DK-4000 Roskilde Denmark