Background: Solar energy is broadly utilized in various applications, including solar thermal collectors (STCs), heating, desalination, etc. The SCs are employed to convert solar energy into thermal one. Utilizing nanofluids (NFs) and phase change materials (PCMs) can improve the performance of STCs by enhancing the rate of heat transfer. Methods: The present review paper describes NFs and PCMs, explains STCs, and provides different advances in these subjects. The influences of NFs and PCMs on the performance of STCs are examined. In addition, energy, exergy, economic, and environmental considerations are evaluated, and finally, current challenges and future directions are discussed. Significant findings: It was observed that the use of NF and PCM leads to a significant improvement of the energy and exergy functions of STCs. Also, Also, it was found that a limited number of studies have been done on the performance of NF-based STCs from an economic and environmental point of views, and all of them have reported the positive effect of NFs on the performance of these systems. Moreover, it was revealed that the employment of NFs in the STCs depends on their long-term stability and preparation costs. Therefore, more laboratory investigations are required to characterize thermophysical properties of NFs.
