▎ 摘　　要

Owing to the obvious advantages of direct solar collectors, considerable research has been continuously conducted for improving the efficiency of solar energy storage. Due to the instability in the solar energy reaching the Earth and the uneven distribution of solar irradiation during the day and night, it is difficult to continuously output the heat source. In order to further improve collection system performance, we have proposed a direct absorption solar collector, which uses graphene oxide (GO) nanosheets and titanium nitride (TiN) nanoparticles mixed with heat transfer oil as the working fluids, and uses a ternary mixed molten salt (44% Ca(NO3)(2), 12% NaNO3, and 44% KNO3) as the heat storage core. Moreover, this new kind of collector has been experimentally investigated, and its solar thermal performance is studied with different proportion of GO to TiN in the nanofluids. The experimental results show that the maximum thermal energy can be stored in the collector is nearly 526.96 J, and the energy retention rate can reach 51.7%. Moreover, the solar thermal efficiency of this collector is up to 56.5%. In addition, the mechanism of heat storage is also studied in detail. This study provides a practical avenue for improving the application potential solar collector, which can effectively promote the heat storage for medium temperature of the collector subjected to incident irradiation. (C) 2021 Elsevier B.V. All rights reserved.