Hybrid Energy System for Rural Electrification in Sri Lanka: Design Study

Abstract

Off-grid hybrid renewable energy based power system for rural electrification has become an attractive solution for areas where grid electricity is not feasible. Depending on the availability of the resources, single energy source or a combination of several sources, including an energy storage system is used in an off-grid hybrid energy system. As there can be several candidates, the optimum sizing of the components against resource potential, cost and reliability is a vital issue. This chapter presents a study of optimum sizing of a renewable sources based off-grid hybrid energy system that is designed for electrifying a rural community in the Siyambalanduwa area in Sri Lanka. The community consists of approximately 150 households with a daily electricity demand about 270 kWh and night time peak of 25 kW. This region receives abundant of solar irradiation with an average of 5.0 kWh/m2/day. The annual average wind speed of this region is 6.3 ms-1 which results in wind power density of 300 W/m2 at a height of 50 m above the ground. The total net present cost of a configuration is calculated for 20 years of system’s lifetime to examine the lowest energy cost option. It is found that the combination of wind turbines, PV system, a battery bank and a diesel generator made the optimum hybrid system having capacities wind—40 kW, PV—30 kW, battery bank—222 kWh and the diesel generator—25 kW. This system can supply electricity at an approximate levelized cost of 0.3 $/kWh. It can supply the demand without change in energy cost more than 0.1 $/kWh even though the annual average wind speed varies in the range of 4.5–6.3 ms-1. Consequently, influence on energy cost for changes in annual average solar irradiation in the range of 4.0–5.5 kWh/m2/day has been found to be negligible. The energy cost analysis of the project has also been made considering off grid operation of hybrid systems for first 10 years and grid connected operation for next 10 years. It is found that the hybrid system is economically viable whether it is operated in off-grid or grid connected mode.