Optical Performance of Bladed Receivers for CSP Systems

Bladed structures offer an approach to improve the efficiency of conventional concentrating solar power (CSP) cylindrical receivers, due to improved light-trapping via the cavity effect, and by allowing more tubes to be compressed into a smaller aperture, enabling the flux on the aperture to be increased without exceeding the peak flux limitation on individual tubes. In this paper, we present an optical model of a hypothetical bladed receiver mounted on the tower of the Sandia National Solar Thermal Test Facility (NSTTF). We examine the impact of receiver geometric parameters including receiver width, receiver height, number of blades, blade depth and blade angle, through analysis using ‘Tracer’, an open-source Python-based Monte Carlo ray tracing library. Validation of Tracer is provided, through comparison with results from other tools. At the optimal configuration, 15 blades with a depth of 4.5 m and angle of 63.9° from the vertical are spaced vertically over a 9.6×9.6 m back wall. In this configuration, the peak flux occurs on the back plane and is considerably lower than a corresponding flat receiver. The design-point receiver optical efficiency increases from 93.8% for a flat receiver to 98.5% for the bladed configuration, and is shown to be robust to sun position changes.