1. Department of Power Engineering, Faculty of Mechanical Engineering, University of Žilina, Univerzitna 1, 010 26 Žilina, Slovakia
2. Department of Renewable Energy Sources, Institute of Earth Resources, Technical University of Kosice, Park Komenského 19, 0420 00 Košice, Slovakia
3. Department of Design and Mechanical Elements, Faculty of Mechanical Engineering, University of Žilina, Univerzitna 1, 010 26 Žilina, Slovakia