1. Department of Heat, Hydraulics and Environmental Engineering, “Angel Kanchev” University of Ruse, 7017 Ruse, Bulgaria
2. Department of Energy Efficiency and Hydrogen Technology, National Research University Moscow Power Engineering Institute, Moscow 111250, Russia
3. Department of Economics and Enterprise Management, Russian University of Cooperation, Kazan 420034, Russia
4. Department of Transport, “Angel Kanchev” University of Ruse, 7017 Ruse, Bulgaria