Optimal Sizing of Micro-Grid: A Case Study of Kelawlo

Abstract

Access to reliable and cost-effective electricity is crucial for socio-economic development, yet rural off-grid communities face significant challenges in obtaining electricity due to the high cost and technical difficulties of extending the national grid. Hybrid micro-grid systems, which integrate multiple renewable energy sources, offer a sustainable alternative for decentralized electrification. This study aims to design and optimize a stand-alone micro-grid system to meet the energy demand of Kelawlo, a rural community in northwestern Tigray, Ethiopia, while minimizing costs and environmental impacts. HOMER Pro was employed as the optimization tool to determine the most cost-effective micro-grid configuration. The optimal sizing process involved estimating the electricity demand of the community based on previous studies and commonly used appliances. Solar and wind resource data for Kelawlo (latitude 14.2864, longitude 37.9611) were obtained from NASA Power, and wind speed at 10 meters was extrapolated to the wind turbine hub height using the wind shear power law. Micro-grid components, including photovoltaic (PV) modules, wind turbines, batteries, and converters, were selected and modeled, with their associated costs incorporated into the Homer Pro optimization process. Four scenarios were analyzed to determine the most suitable solution for the selected site: (1) diesel generator-only system, (2) PVbattery micro-grid system, (3) PV-wind-battery hybrid micro-grid system, and (4) PV-wind-diesel generator-battery hybrid micro-grid system. The scenarios were evaluated based on Net Present Cost (NPC), Levelized Cost of Energy (LCOE), renewable fraction, and capacity shortage. Scenario three, the PV-wind-battery hybrid micro-grid configuration, was identified as the optimal solution for the Kelawlo community, with an NPC of $505,707 and an LCOE of $0.126/kWh. This optimal system achieved a 100% renewable fraction with an allowable capacity shortage. It was determined that the PV system contributes 73% (277,937 kWh/year) of the total electricity production, while the wind turbines account for the remaining 27% (102,555 kWh/year). This study provides valuable insights into designing optimal hybrid micro-grid systems for rural electrification, contributing to sustainable energy development and reduced reliance on traditional energy sources.