Nanofluid-based cooling of photovoltaic systems: A systematic review of performance claims, modeling assumptions, and deployment readiness

Nanofluid-based cooling has attracted significant attention for improving the thermal management and electrical performance of photovoltaic (PV) and photovoltaic/thermal (PVT) systems. However, the practical reliability of many reported efficiency gains remains unclear due to simplified modeling assumptions, inconsistent validation practices, limited hydraulic analysis, and insufficient stability assessment. This systematic review critically analyzed 55 peer-reviewed studies published between 2014 and 2024 using the PRISMA framework. The review combined bibliometric, content-based, and critical analyses to evaluate nanofluid types, operating conditions, modeling approaches, validation methods, hydraulic penalties, and deployment-related considerations. Aluminum oxide (Al₂O₃) was the most widely studied nanofluid, while binary and ternary nanofluids showed growing research interest. The findings revealed that performance improvements were influenced more strongly by cooling geometry and operating conditions than by nanofluid composition alone. Approximately 91% of studies adopted single-phase homogeneous models, only 29.1% quantitatively assessed hydraulic penalties, and formal long-term stability evaluation was rarely performed. In addition, outdoor validation under realistic climatic conditions remained limited. Overall, the review highlights a clear gap between reported laboratory-scale performance improvements and deployment-ready evidence, emphasizing the need for more realistic modeling, standardized validation, hydraulic-energy balance assessment, and long-term stability evaluation in future nanofluid PV/PVT research.