Energy, Exergy, Environmental, and Economic Assessment of Solar Agricultural Dryers: Bibliometric Trends, Technological Niches, and Evidence Gaps

Abstract

This study maps research on energy, exergy, environmental, and economic assessment of solar agricultural drying systems using 145 Scopus-indexed documents published from 2003 to 2025. A broad search returned 917 records; addition of an explicit 4E/LCA block reduced the set to 155, and title-and-abstract screening retained 145 documents. The bibliometric corpus comprises 127 core and 18 contextual records. Full-counting analysis of author keywords retained 33 terms at a minimum occurrence of three, producing 178 links and a network density of 0.337. Of the 127 core records, 87 addressed energy, 105 exergy, 52 environmental performance, and 51 economics; only 23 integrated all four dimensions and 10 explicitly applied life cycle assessment. Energy–exergy was the strongest pair-wise overlap (Jaccard = 0.587), followed by environment–economics (0.471). Indirect and mixed-mode configurations showed broader multi-dimensional coverage than direct or greenhouse configurations, while thermal storage/phase-change materials and PV/PVT were the most frequent integration niches. The field has expanded rapidly since 2020 but remains geographically concentrated and methodologically uneven. The evidence therefore supports partial convergence toward 4E assessment rather than a mature or dominant integrated paradigm.