The Hottel-Whiller-Bliss characteristics of particular comparable examples of asymmetric and symmetric compound parabolic concentrating solar energy collectors are presented. It is shown that over the relevant range of operating conditions at an optimum absorber configuration an asymmetric inverted flat absorber compound parabolic concentrating collector has a solar conversion efficiency 10%-15% greater than a comparable tubular absorber symmetric compound parabolic concentrating collector.
Kothdiwala, A. F., Eames, P. C., Norton, B., & Zacharopoulos, A. (1999). Comparison between inverted absorber asymmetric and symmetric tubular-absorbercompound parabolic concentrating solar collectors. Renewable Energy, 18, 277-281. https://doi.org/10.1016/S0960-1481(98)00786-1