Hybrid renewable energy systems in rural electrification: A review of design approaches and optimization techniques

The increasing global push for sustainable and inclusive energy access has intensified interest in Hybrid Renewable Energy Systems (HRES), particularly for rural and off-grid communities where conventional grid extension is economically or technically impractical. HRES integrate two or more renewable energy sources commonly solar photovoltaic, wind turbines, and micro-hydropower along with storage and control systems to ensure a continuous, stable, and cost-effective electricity supply. This review provides a comprehensive overview of the renewable energy technologies relevant to rural electrification, detailing their operational principles, energy conversion mechanisms, and hybrid configurations. Special focus is given to system design considerations such as load profiling, resource assessment, and component sizing, which are critical for achieving both technical and economic viability. The paper also explores various optimization techniques, including heuristic algorithms and simulation tools, used to balance competing objectives such as cost, emissions, and system reliability. Recent deployments and case studies from Sub-Saharan Africa and beyond are examined to highlight real-world applications. Finally, the study identifies key implementation challenges and outlines future research directions to support the broader adoption of resilient and decentralized energy solutions.