Determination Of The Optimum Hybrid Renewable Energy System For Powering The School Of Engineering, University Of Nairobi

Abstract

Off-the-grid and on-the-grid hybrid renewable energy systems have become effective solutions to providing reliable, affordable and environmentally protected electricity for the rural communities where extension of the conventional grid is not feasible and institutions where the cost of electricity is relatively high. The goal of this research project was to determine the optimum hybrid renewable energy system that can supply reliable and affordable power to the School of Engineering, University of Nairobi. The load profile of the site was determined using Power and Energy Logger (PEL) and data analysis was done using DataView software. The total power demand and consumption of the establishment were found to be 84.59kW and 1172kWh/day respectively while scaled average of 144.62kW and 1200kWh/day were simulated and optimized. In addition, the wind speed scaled average measured at 50m height, the mean global horizontal solar scaled average radiation and the temperature scaled average were found for this site as 4.76m/s and 5.93kWh/m2/day and 19.90C respectively. Grid/wind turbine/photovoltaic/diesel generator/battery bank/converter was simulated and optimized in HOMER Pro Microgrid Analysis Tool with the total net present cost calculated for 25 years in order to find the lowest cost of energy for the optimal system. The optimum hybrid system has been found to be Grid/Photovoltaic/Diesel generator system. This system gives COE of Ksh 7.89, NPC of ksh 69,512,100.00, Initial capital cost of ksh 30,264,100.00, renewable fraction of 71.6%, simple payback period of 6.15years, discounted payback period of 7.76years, present worth of Ksh 12,819,300.00, annual worth of ksh 965,700.00, excess electricity generation of 2.48% etc. The system proves to have reduced the power being purchased from the grid from 100% to 23% approximately (90kW to 20kW). 9 sensitivity cases were used for sensitivity analysis and the result gave the same configuration except in cases where the sizes and prices of some components were changed. v The study had put into perspective the Feed-in-Tariff policy in Kenya which would allow excess electricity generated by the system to be sold back to the national grid through the PPA policy.