1. Department of Renewable Energies, University of Applied Forest Sciences Rottenburg, Schadenweilerhof, 72108 Rottenburg, Germany
2. State Institute of Agricultural Engineering and Bioenergy, University of Hohenheim, Garbenstr. 9, 70599 Stuttgart, Germany
3. Tropics and Subtropics Group, Institute of Agricultural Engineering, University of Hohenheim, Garbenstr. 9, 70599 Stuttgart, Germany