Solar collectors for a sustainable future: innovations and energy efficiency trends

Recent modifications in solar air collectors (SACs) have significantly improved performance, expanding their applications in solar energy harvesting and conversion. This review investigates SAC applications in industrial thermal processes, space heating, and drying, with a focus on recent advancements and performance enhancement techniques. Key aspects include absorber plate design, operating conditions, and environmental parameters. Parameters such as collector tilt angle, glazing type, and air mass flow rate are found to critically influence thermal and exergetic performance. Corrugated absorber plates outperform plain ones due to increased turbulence, heat transfer area, and vortex formation. Double glazing reduces radiative and convective losses compared to single glazing. While higher air mass flow rates improve energy efficiency, they also increase pressure drops. Seasonal variations show greater efficiency in summer, attributed to higher solar insolation. The review also covers construction elements i.e. ducts, glazing, absorber plates, and insulation and highlights innovative enhancement methods like artificial roughness, extended surfaces, multi-pass airflow, and advanced geometries such as V-grooves and 3D roughness. Thermo-hydraulic analyses are used to assess energy, exergy, and effective efficiency, helping identify optimal operating conditions. Applications in space heating, agricultural drying, building integration, and solar-assisted conditioning are discussed alongside numerical and theoretical modeling techniques, including the potential for Computational Fluid Dynamics (CFD) to support future system optimization. While the energetic performance of SACs is widely investigated, the review identifies exergy analysis and material aging effects (especially of glazing and coatings) as areas requiring deeper study. Finally, the work emphasizes the broader economic and environmental impacts of SAC deployment. The review concludes by outlining several future research directions, such as CFD-integrated modeling, expert system-based optimization, nano-coating development, and PCM hybridization, aiming to accelerate the adoption of SACs in sustainable energy systems. The review examines absorber plate innovations, including corrugation, artificial roughness, and extended surfaces, revealing substantial improvements in solar air collector heat transfer and overall efficiency. Critical collector parameters—such as tilt angle, mass flow rate, glazing configuration, and duct geometry—are shown to significantly influence thermal, exergy, and effective efficiency of solar air collectors. Enhanced geometries like V-grooves, fins, and baffles boost heat exchange and energy capture but also create higher pressure drops, necessitating careful optimization to balance efficiency and fan power. Economic benefits include reduced energy consumption, short payback periods, increased property values, and job creation, reinforcing the role of solar air collectors in sustainable development. Environmental advantages highlighted are lowered greenhouse gas emissions, improved air quality, sensible land use, and contribution to long-term climate change mitigation and resource conservation. Applications discussed span space heating, industrial processes, and agricultural drying; integration of phase change materials and nanoparticles offers further performance enhancements in varied settings. The review emphasizes the potential of computational fluid dynamics (CFD), expert systems, and nano-coatings for future research, calling for more studies on material aging and two-phase modeling.