Optical Modeling of a Cylindrical-Hemispherical Receiver for Parabolic Dish Concentrator

Abstract

Among all sub-systems ofa solar thermal energy system, thereceiverplays a major role while getting the heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy being collected by the receiver, which ismainlycharacterised by the optical parameters likefocal length, aperture diameter, surface absorptivity and slope error. In this paper,the optical analysis of a cylindrical-hemispherical type receiver coupled with a3m diameter parabolic dish concentrator has been discussed. The studyhas been carried out using SolTracesoftware by varying the parameters likereceiver aperture diameter (Da) ranging from 0.125 to 0.162 m, surface error of the concentrator from 1.7453 to 34.907mrad and also surface absorptivity (α) from 75% to 95%for different receiver distances(H) ranging from 1.7 to 1.95m. From the simulation results, it is observed that the optical efficiency is maximum when the receiver distance is 1.85m for receiver aperture diameter of 0.150 m for the given system. Increase in the slope errors from 1.7453 to 17.453 mrad decreases the average optical efficiency by almost 50% for all receiver diameters.It is alsonoticed that uniform heat flux distribution can be achieved when the position of the receiver is maintained at H = 1.85 m from the concentrator for the given receiver diameterand surface absorptivity of the receiver of 0.150 m and 95% respectively.The simulated results of heat flux intensity on the receiver surface are then compared and validated by the experimental results available in literature. The simulatedoptical efficiency of the presentreceiver is also found to be 8% higher when it is compared with a conventional cylindrical receiver having similardimensions.