1. Department of Physics, University of Nairobi, Nairobi P.O. Box 30197-00100, Kenya
2. Distributed Energy Team, Jeju Global Research Center, Korea Institute of Energy Research, 200 Haemajihaean-ro, Gujwa-eup, Jeju-si 63357, Republic of Korea
3. Department of Electrical Electronic and Information Engineering, South Eastern Kenya University, Kitui P.O. Box 170-90200, Kenya