Solar thermal energy harnesses sunlight to produce thermal energy for industrial, residential, and commercial applications. Central to this technology are solar thermal collectors (STC), where heat‐carrying fluid is employed to distribute collected solar thermal energy to its point of use. Over the past three decades, nanofluids (NFs) (fluids containing nanoparticles) have significantly impacted material science and engineering, enhancing the cumulative functionality of solar collectors (SCs). Recently, a direct absorption solar collector (DASC) incorporating has been introduced to surpass the limitations of conventional SCs. The deployment of mono and hybrid NFs, incorporating nanoparticles like plasmonic, carbon‐based materials, etc., as thermal media in DASCs represents a prominent focus in current research. This review analyses the implications of various mono and hybrid NFs, nanoparticle concentrations, and other factors on the performance of DASCs, drawing on contemporary literature. It highlights the advantages of hybrid NFs as opposed to mono NFs and explores their applicability in DASCs. The review presents key findings from existing research, noting both the benefits and limitations of using NFs in DASCs. Additionally, the study addresses long‐term challenges associated with NF application in DASCs. It offers future research directions and recommendations to enhance DASC thermal effectiveness.
Dhanola et al. (2026) studied this question.