Study, Design And Modeling Of A PV-Powered DC-Home With Optimizedstorage Appliance For Rural Electrification: The Case Of Tullo Gudo Island, Ethiopia

Abstract

Energy storage will be important to overcome the intermittency and changeability of renewable energy sources. Due to the rapidly changing nature of the weather, renewable energy harvesters – e.g. photovoltaic cells, energy storage systems (ESS) needed to balance energy demand from renewable energy supply. This research optimally sizes the energy storage systems based on days of autonomy. As the number of days of autonomy increases, the size of battery increases, and the battery should be large enough to store sufficient energy to operate the appliances at night and cloudy days, which is costly. This research focuses on the study, design, and modeling of storage optimization for solar-powered DC home appliances for rural electrification system. A hypothetical house assumed to have several household appliances is modeled in detail. Finally, the optimization of storage system is studied for PV-powered DC home with the aim of rural electrification application using HOMER pro software, the model of DC load is modeled, and the converter voltage controller is modeled and simulated by MATLAB/Simulink software. The DC bus system is 130V for 4.801kW household load sample. Constant load voltage is maintained using PID controller coupled with buck convertor irrespective of variation of load and irradiance. In order to determine the optimal days for battery autonomy (energy storage), five different conditions are discussed to determine the optimal day based on their cost of energy (COE) in $/kWh and net present cost (NPC) in $. The cost of energy for condition I (when days of autonomy’s are two), condition II (when days of autonomy’s are three), condition III (when days of autonomy’s are four), condition IV (when days of autonomy’s are five), and condition V (when days of autonomy’s are six) are $0.689/kWh, $0.912/kWh, $1.16/kWh, $1.4/kWh, and $1.64/kWh; their net present costs are $46,290, $ 61,291, $77,861, $94,223, and $110,540 respectively. Two autonomy days is determined as the optimal time for the battery (energy storage) for the particular rural electrification site (Tullu Gudo Island) with minimum net present costs (NPC) of $46,291 and cost of energy (COE) of $0.689/kWh.