A comprehensive systematic review of hybrid energy systems: Addressing challenges and future direction

Hybrid Energy Systems (HES) have emerged as a vital framework for achieving sustainable, efficient, and resilient energy infrastructures by integrating diverse energy sources and storage technologies. This systematic review provides a comprehensive analysis of HES across technical, economic, environmental, reliability, policy, and cyber-physical security dimensions. Persistent challenges—including renewable intermittency, storage degradation, multi-vector integration complexity, governance gaps, and increasing vulnerability to cyber threats—are examined alongside evolving objectives such as minimizing Net Present Cost (NPC), enhancing system reliability, reducing emissions, and maximizing renewable utilization. The review also incorporates a bibliometric analysis using R Studio and VOSviewer to identify research trends, keyword co-occurrences, and thematic evolution within the field. Additionally, the study highlights the growing role of AI and machine learning in forecasting, optimization, and real-time control, as well as the global shift toward multi-objective frameworks that balance cost, sustainability, resilience, and security. Future directions emphasize adaptive policy design, harmonized regulatory frameworks, cyber-secure digitalization, life cycle sustainability assessment, and circular economy integration. By consolidating insights across technological, economic, environmental, and governance dimensions, this study provides a holistic foundation for developing next-generation hybrid energy systems capable of supporting global decarbonization and energy transition goals.