A, Optimization of Hydro-Solar-Biogas Hybrid Systems for Off-Grid Rural Electrification: A Review With Focus on Developing Countries.

Abstract

Access to reliable, affordable, and sustainable electricity remains a major challenge for many rural communities in developing countries. Although governments continue to expand national power grids, a large number of rural settlements are still either unconnected or experience frequent power outages due to inadequate infrastructure, transmission losses, and poor system maintenance. This persistent energy gap constrains socioeconomic development, restricts access to quality healthcare and education, and contributes to increased rural–urban migration. Hybrid Renewable Energy Systems (HRES), particularly those integrating hydro, solar, and biogas resources, present a viable solution for decentralized and off-grid electricity supply that aligns well with the resource conditions of many rural areas. However, designing and operating these hybrid systems involves significant technical complexity. Challenges related to optimal system sizing, energy scheduling, and operational control under fluctuating demand and intermittent renewable resource availability remain critical. Without effective management, these systems may suffer from reduced efficiency, higher costs, or unreliable power supply. This review presents a comprehensive evaluation of optimization techniques applied to fully renewable hydro–solar–biogas hybrid energy systems. It synthesizes existing literature on optimization algorithms, performance assessment metrics, and practical implementation challenges, with the aim of providing useful insights for researchers, system designers, and policymakers.