Optical performance of fixed east–west aligned CPCs used in China

In this article, a mathematical procedure is developed to estimate the annual collectible radiation captured by fixed compound parabolic concentrators (CPCs, in short) oriented in east-west direction based on the monthly horizontal radiation. Results show that for fixed east–west aligned symmetric CPCs used over the atmosphere, the optimal acceptance half-angle for maximizing its annual energy collection was 25.97°, the yearly optimal tilt-angle of apertures relative to the horizon was equal to the site latitude, and the maximum annual average optical concentration ratio was uniquely related to the site latitude. For CPCs used in China, the optimal acceptance half-angle were in between 25.3° and 26°, the yearly optimal tilt-angle approached the site latitude with a deviation less than 1°, and the maximum annual average optical concentration ratios ranged from 1.45 to 1.74. Results also indicated that CPCs were more favorable to be used in the areas with higher latitude and abundant solar resources. Effects of tilt-angle and azimuth angle of CPCs on its annual solar gain were also presented.