Yearly yield of a low-enthalpy parabolic trough solar collector based on nanofluids: a numerical simulation

The adoption of nanofluids in concentrating solar collectors appears to be very promising in order to obtain higher thermal efficiencies. Thus, we present a simulation environment for the evaluation of the yearly yield of a nanofluid-based parabolic trough solar collector (PTC). Four water-based nanofluids at different weight concentrations are investigated: TiO2 (1, 10, 20, 35 wt%), SiO2 (1, 5, 25 wt%), Fe2O3 (5, 10, 20 wt%), and ZnO (1, 5, 10 wt%). The nanofluids were experimentally and numerically studied. The simulation environment was validated by experimental tests conducted on two prototypes of PTC that worked with water as heat transfer fluid. A typical meteorological year for the city of Ancona, Italy, was used to perform the simulation that presents a time-resolution of one hour. A specific arrangement for the PTC, similar to that of one of the considered prototypes, was defined. The mass flow rate and the inlet fluid temperature were fixed to 0.13 kg/s and 60 °C, respectively. Results are presented both in graphical and tabular form: in particular, we provide a direct comparison with water in order to prove the convenience in the adoption of certain concentrations of nanofluids.