Review of Fluids used for Parabolic Trough Solar Collector Receivers

Parabolic Trough Solar Collectors (PTCs) are among the most mature and widely implemented Concentrating Solar Power technologies for electricity generation and industrial thermal applications. These systems use parabolic reflectors to focus solar radiation onto a receiver tube, where a heat transfer fluid (HTF) absorbs and transports thermal energy. The thermo-physical properties, thermal stability, and operating temperature range of the HTF significantly influence system efficiency. Various HTFs, including synthetic oils, molten salts, water/steam, and nanofluids, have been investigated to enhance thermal performance and reduce losses. This review presents the working principles of PTCs, selection criteria for HTFs, heat transfer enhancement techniques, and recent technological advancements. Thermal loss mechanisms, receiver design improvements, and integration of thermal energy storage systems are also discussed. Furthermore, emerging modeling approaches such as Artificial Neural Networks and Adaptive Neuro-Fuzzy Inference Systems are highlighted for performance prediction and optimization. The study identifies key challenges including experimental validation, advanced fluid development, and heat loss characterization. The findings contribute to the development of efficient, reliable, and sustainable solar thermal systems.