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• A comprehensive review of the recent nano-based PV cooling systems is conducted. • Separate nano-enhanced PCMs, separate nanofluid-based, and hybrid PV cooling units are discussed. • Governing equations of materials' properties and PV performance are derived. • Detailed systems' description and major results are illustrated. • Research trend is analyzed via VOSviewer software based on Scopus database, and Future prospects are suggested. The environmental pollution and growing energy demand necessitate the development of power generation using renewable energy systems, especially solar photovoltaic (PV) panels. Despite being an eco-friendly and durable power generation technology, PVs demerit for low conversion efficiency (15–20%). In other meaning, a very low amount of the incident irradiance is converted into electricity, whereas the major is absorbed as heat, uplifting the PVs' surface temperature and declining their efficiency and reliability. Therefore, it is crucial to find a proper cooling technique for upgrading PVs' performance. Recently, along with the nanotechnology development, nano-based PV cooling units have been proposed and investigated as the inclusion of nanoparticles enhances the thermal properties of base materials. Herein, in this paper, the conducted efforts to improve the PVs' performance using nano-based cooing systems were reviewed and discussed. The surveyed PVs' cooling methodologies were classified into separate and hybrid systems: nano-enhanced PCMs, nanofluid-based, and hybrid nano-based cooling units. All relevant equations of materials' properties and PV performance were presented. In addition, the research trend of this field was analyzed by conducting a comprehensive bibliometric analysis using VOSviewer software and based on the Scopus database in the period (2006–2020). Besides, comprehensive discussions of proposed and designed systems were conducted, and major findings were summarized. Based on the literature, using hybrid nano-based cooling systems, the surface temperature reduction can reach 16 °C with enhancement in electrical efficiency up to 50% compared to conventional uncooled PV panels. Furthermore, some future work suggestions were given. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) panels, being an eco-friendly technology, have become a crucial source of electricity, satisfying the increasing energy demand and substituting the related shortage occurring in the conventional energy sources. Despite absorbing about 80% of incident radiation, PV cells have low conversion efficiency; hence, a minor portion of the absorbed radiation is gained as electrical power, and the majority is converted into heat increasing the panel temperature. Undesirably, the higher panel temperature, the lower conversion performance, and lesser reliability over the long term occur. Hence, many cooling systems have been designed and investigated, aiming to effectively avoid the excessive temperature rise. This paper aims to review and merge the recent cooling methods investigations on PV, categorizing them according to heat transfer modes: convective cooling (hydro and aero-based cooling with or without extended surfaces), conductive cooling (phase change materials), and radiative cooling. Each category and corresponding works are discussed in detail, and main resulted enhancements, with respect to uncooled PV panels, are presented. In addition, applications of hybrid photovoltaic-thermal systems are clarified with indicating main improvements in their electrical, thermal, and overall efficiencies. It expected that the presented work can provide a new comprehensive taxonomy for cooling techniques applied to photovoltaics. • A deep survey on the state-of-the-art aspects of PV cooling is presented. • A new comprehensive taxonomy for cooling methodologies including nanofluid-based PVT are proposed. • Enhancements of thermo-electric performance of PVT systems are discussed. • Improved convective cooling via extended surfaces is surveyed. • Radiative cooling performance of PV modules, and corresponding applications are reviewed. [ABSTRACT FROM AUTHOR]