Performance analysis and design optimization of a direct-absorption parabolic-trough solar collector with concentric nanofluid partitions

Due to its advantage in solar energy absorption, plasmonic nanofluid has been intensively studied to improve the thermal efficiency for solar energy harvest. On the basis of extensive studies of the optical properties of the nanofluids and their applications on direct absorption solar collectors (DASCs) in the temperature regime, researchers have started working on the application of nanofluids to direct absorption parabolic trough solar collectors (DAPTSCs) for mid-to high-temperature harvest. In this study, DAPTSCs with different concentric partitions have been proposed and studied to enhance their solar thermal conversion. The partition varies from one single tube to two and three concentric tubes, with each partition containing a nanofluid with a certain absorption coefficient. Furthermore, systematic optimization has been conducted for a DAPTSC with two nanofluid partitions. A deep neural network was used for building a surrogate model for the DAPTSC and the genetic algorithm was applied for optimization. The analysis showed that a low-temperature outer layer is necessary to avoid thermal losses. Trade-off needs to be made considering the structure complexity, the nanoparticle concentration, and the thermal efficiency of the DAPTSC.