Hybrid Renewable Energy Systems (HRES) for Off-Grid Rural Electrification: A Comprehensive Review of Components, Optimisation, and Real-World Applications

Background: Hybrid Renewable Energy Systems (HRES) are considered an attractive option for rural electrification in off-grid areas, where solar, wind and biomass/micro-hydro resources can be integrated with storage technologies to improve the reliability and lessen dependence on diesel. With the rapidly evolving optimisation techniques, energy management schemes and the methodologies of developing smart microgrids, it requires a fresh review of these topics. Objectives: This review investigates acceptable technical, economic, environmental and policy pathways of HRES; discusses successes and barriers encountered in the past; suggests a better operation regimen to meet next-generation rural microgrids. Method: A systematic literature search was performed using predefined keywords in hybrid systems, rural electrification, energy storage and optimisation. The study selection process was conducted according to PRISMA-compliant protocols and included studies published from 2020 to 2025. The selection criteria were multi-source HRES with quantitative performance information. Exclusion criteria removed single-source systems and studies lacking technical indicators. Comparative analysis considered reliability metrics, levelized cost of energy, renewable penetration, emission reduction, and control strategies. Findings: Recent studies show a 30–40%increase in reliability, 10–25% less expensive and 40–60% emission reduction relative to diesel ones. Primary bottlenecks are due to high up-front costs of capital, battery degradation and high dependence on the financing environment, as well as climate sensitivity. Innovative concepts such as AI-based control, hybrid battery–hydrogen storage, and IoT-enabled monitoring facilitate the optimisation of overall system performance. Significance: This review presents more insight into self-adaptive HRES with Digital Twin technology, which fills in the gap of previous reviews by focusing on life-cycle optimal operation, climate resilient HRES, predictive maintenance and community-centric operation and offers novel understandings to scalable rural electrification. Keywords: Hybrid Renewable Energy Systems, Off-Grid Electrification, Digital Twin, Optimisation, Rural Energy Access