Application of hybrid nanofluids in a novel combined photovoltaic/thermal and solar collector system.

• A novel combined PVT and ST system is developed. • Different kinds of hybrid nanofluids for improving system performance are studied. • The SiC/Gr hybrid nanofluid has the best performance compared to others. • In the combined system, ST produces more entropy generation compared to PVT. Because of the low outflow temperature of the conventional photovoltaic thermal systems and lack of electrical production of the solar thermal collectors, a novel combined system is proposed to solve the two mentioned drawbacks. This novel system is achieved by connecting a photovoltaic thermal unit to a solar thermal collector in series. To increase the overall performance of this novel combined system, different hybrid nanofluids include (1) multiwall carbon nanotube-aluminum oxide (2) multiwall carbon nanotube-silicon carbide (3) graphene-aluminum oxide, and (4) graphene-silicon carbide are compared. The investigation is performed based on the three-dimensional simulation, and the Eulerian-Eulerian model is selected for the simulation of hybrid nanofluids. To estimate the performance of this novel combined system, the first and second laws of thermodynamics are used. Moreover, the share of entropy generation in all components of the system is calculated. The results indicate that the multiwall carbon-silicon carbide hybrid nanofluid with the average electrical and thermal energy efficiency of 13.85% and 56.55%, respectively, has the best performance compared to other fluids. Furthermore, in the combined system, different components of the solar collector produce more entropy generation than the components of the photovoltaic thermal module. [ABSTRACT FROM AUTHOR]