Hybrid Solar–Biomass Energy Systems for Rural Agro-Industrial Applications: A Technical and Bibliometric Review

The combination of solar and biomass energy represents a sustainable alternative for thermal generation in rural areas, particularly in agro-industrial processes such as crop drying and food preservation. Hybrid configurations enable continuous operation under variable solar radiation, improving thermal efficiency and reducing fossil fuel dependence. However, the literature on this topic remains limited and fragmented. Therefore, a technical and bibliometric review was conducted to identify research trends, key actors, and knowledge gaps in hybrid solar–biomass systems applied to agricultural and food sectors. The Scopus database was used for the 2005–2025 period, applying the query TITLE-ABS-KEY(("hybrid" W/2 (solar AND biomass)) AND (dryer OR drying OR "process heat") AND (agricultur OR food OR agroindustrial))*. A total of 22 documents published in 21 sources were analyzed, including 15 journal articles, 3 reviews, and 4 conference papers. Results indicate an annual growth rate of 3.5%, an average of 7.18 co-authors per document, and an international collaboration rate of 27.3%, reflecting a small but increasingly connected research community. India leads scientific production (11 papers), followed by Nigeria, Malaysia, and Spain, with major contributions from the Indian Institute of Technology Delhi and the Federal University of Agriculture. Thematic mapping revealed four clusters: (i) biomass–solar drying and food preservation as motor themes; (ii) energy efficiency and food processing as niche technologies; (iii) hybrid systems, renewable energies, and cost effectiveness as basic developing topics; and (iv) temperature, heat transfer, and desiccation as emerging research areas reactivated by advances in modeling, CFD simulation, and intelligent control. Overall, the results highlight a growing focus on the design and optimization of hybrid solar–biomass systems as key enablers of rural energy transition and sustainable agro-industrial development.