Design and Optimization of Ellipsoidal Windows for Concentrated Solar Irradiation

Abstract

This work presents a numerical study on transmission performance of ellipsoidal windows used in receivers under concentrated solar irradiation. The Monte Carlo ray tracing method is used to analyze the transmission of concentrated solar radiation through an ellipsoidal window. The effects of concentrator shape error (1–3 mrad) and geometry parameters of the window, including window height (30–60 mm), radius of concave region (20–55 mm), and shape factor (0–100 mm), on the transmittance are examined. It is found that the transmittance increases with the increase of shape factor and window height and the decrease of the slope error of the concentrator. The dependence of the transmittance on the radius of the concave region is nonmonotonic. To maximize window transmittance, a single-variable nonlinear optimizer is used to optimize the concave region radius. The results indicate that the transmittance can be increased by 1.7% at most by increasing the shape factor, within the parameter range. Only if the window height is greater than a certain critical value, could the transmittance of the ellipsoidal window be significantly higher than that of plane window. The critical value increases with the increasing slope error and decreasing shape factor, varying from 20 to 40 mm. The transmittance of the ellipsoidal window with optimal parameter can range up to 98.9%, which is 7.82% higher than that of flat window. The conclusions drawn from the present study could be useful for the design and application of ellipsoidal windows to reduce reflection losses of windowed receiver.