Techno-economic sizing of off-grid hybrid renewable energy system for rural electrification in Sri Lanka

Off-grid hybrid renewable-energy-based power systems for rural electrification have become an attractive solution for areas where grid electricity is not feasible. Hybrid energy systems use several energy technologies, and the selection of proper technologies with optimum sizing of the selected components has become very important. The objective of this study has been to investigate the optimum configuration of a hybrid system that can supply electricity to a rural community in Sri Lanka. A rural village in Siyambalanduwa (Sri Lanka) comprising approximately 150 households with a resultant daily electricity demand of 270 kWh and a nighttime peak of 25 kW has been studied. This region receives abundant solar irradiation with an average of 5.0 kWh/m2/day. In addition, the annual average wind speed of this region is 6.3 ms−1, which results in a wind power density of 300 W/m2 at 50 m above the ground. The total net present cost of configuration has been calculated for 20 years of the system lifetime to examine the lowest energy cost option. The combination of wind turbines, photovoltaic (PV) system, a battery bank, and a diesel generator has been found to be the optimum hybrid system with the corresponding capacities of 40 kW, 30 kW, 222 kWh, and 25 kW. This system can supply electricity at an approximate levelized cost of 0.3 $/kWh. It has also been found that the optimized system can supply the demand with the change in energy costing no more than 0.1 $/kWh, although the annual average wind speed varies in the range of 4.5-6.3 ms−1. Consequently, the influence of changes in the annual average solar irradiation ranging from 4.0 to 5.5 kWh/m2/day on energy cost has been found to be negligible. The energy cost of the project has also been analyzed, considering the off-grid operation of hybrid systems for the first 10 years and the grid-connected operation for the next 10 years. The hybrid system has been found to be economically viable whether it was operated off-grid or connected to the grid.