Recent advances in thermal performance improvement of parabolic trough solar collectors using magnetic nanofluids and supercritical carbon dioxide fluid

Among various available types of sustainable energy sources, the role of solar energy is vital due to its safety and low cost. Multiple rigs have been designed to use solar energy to generate steam, where the parabolic trough solar collector (PTSC) is a prominent example. Numerous numerical and experimental studies have been conducted to date to improve the thermal effectiveness of PTSCs. These studies include using hybrid nanofluids, insert types, magnetic nanofluids and supercritical carbon dioxide. The current paper provides a review of these studies, including an in-depth discussion section, an account of remaining challenges, and suggestions for future directions. The study shows that twisted tape and helical screws inserts provide optimal performance for PTSCs. Moreover, the articles reveal the average particle diameter for magnetic nanofluid to be 20 nm. Furthermore, inlet temperature, supercritical carbon dioxide, volumetric concentration and preparation methods are also shown to considerably affect the thermal performance of PTSCs. Additionally, detailed future recommendations are provided to pinpoint important research gaps and possible paths for enhancing thermal and techno-economic performance of PTSCs.