Impacts of collector configurations, absorber plate designs, thermal storage materials and waste heat recovery on performance of solar air heaters: A comprehensive review

Rising global energy demands necessitate efficient solar thermal technologies; however, conventional Solar Air Heaters (SAHs) suffer from inherently limited thermal efficiency and complete operational cessation after sunset. This study aims to systematically evaluate recent SAH advancements and propose a novel, highly efficient synergistic conceptual framework to overcome existing thermal limitations. A comprehensive systematic review of contemporary literature was conducted, critically analyzing geometrical modifications, thermal energy storage (TES), and various performance enhancement strategies. The analysis reveals that utilizing a hybrid geometry integrated with a 45° wavy absorber plate maximizes convective heat transfer. Furthermore, while paraffin wax is identified as a superior Phase Change Material (PCM), its prolonged charging time remains a critical challenge. To resolve this, integrating a waste heat recovery (WHR) system (compressed air unit) for inlet air pre-heating is proposed to drastically accelerate the PCM melting process. The distinct novelty of this article lies in synthesizing these historically fragmented technologies geometry, TES, and WHR into a single pioneering architecture. This integrated approach can reach a cumulative daily thermal efficiency of 87% while ensuring continuous useful energy output well into the evening. Ultimately, this review establishes a new actionable thermoeconomic benchmark for future SAH designs.