A state-of-the-art review and bibliometric analysis on the sizing optimization of off-grid hybrid renewable energy systems

The development of off-grid hybrid renewable energy systems (HRESs) is essential to rural electrification and global decarbonization. Based on 299 journal papers in the recent five years, this work conducts a state-of-the-art qualitative review and quantitative bibliometric analysis on the sizing optimization of off-grid HRESs. An overview of system configurations, energy management strategies, performance evaluation indicators, and sizing methodologies are presented, and bibliometric analysis is conducted to reveal the overall scope and mainstream of this research field. Finally, promising future works are summarized on the basis of current research gaps. The results of bibliometric analysis indicate that: (1) solar photovoltaic and batteries are the most common energy source and energy storage respectively, and wind-photovoltaic-battery-diesel is the most popular system configuration; (2) most researchers apply rule-based energy management strategies rather than optimized strategies, owing to their advantages of simple implementation and fast computation; (3) 97.99% of articles considers economic indicators in the sizing optimization model, and techno-economic feasibility is the essential research foundation at the planning stage; (4) meta-heuristic algorithms and the HOMER software tool are the two most popular sizing methodologies for off-grid HRESs. In future works, hybrid energy storage systems, deep reinforcement learning-based energy management strategy, sustainability and resilience indicators, as well as distributionally robust optimization-based sizing methodologies are promising research directions. Overall, the presented overviews and outlooks can provide holistic theoretical knowledge about sizing optimization research for practitioners, thus promoting the academic progress and practical implementation of off-grid HRESs.