Improving the performance of a 2-stage large aperture parabolic trough solar concentrator using a secondary reflector designed by adaptive method

• Published in: Renewable energy 2020-06, Vol.152, p.23-33
• Main Authors: Gong, Jing-hu, Wang, Jun, Lund, Peter D., Hu, En-yi, Xu, Zhi-cheng, Liu, Guang-peng, Li, Guo-shuai
• Format: Article
• Language: English
• Subjects: Adaptive method; Optical efficiency; Parabolic trough concentrator; Secondary reflector; Thermal efficiency
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2020.01.019

In this study, the efficiency of a large aperture 2-stage parabolic trough concentrator (PTC) is improved using an innovative design method for the secondary reflector (SR). The design method is based on an adaptive approach in which the SR is step-wise optimized to maximally reflect back to the absorber tube (AT) the part of solar radiation reflected by the primary reflector (PR) but not captured by the AT. The adaptive design method results in a SR design which consists of several parabolas with different focal lengths, each having a focus which lies in the focus of the PR. This ensures that the originally unabsorbed solar radiation will now hit the surface of AT. The optical efficiency of the PTC could be increased by 5.2% and thermal efficiency by 4.9%, respectively, compared to a case without optimized SR. In addition, the uniformity of the solar radiation flux on the AT’s outer wall could be doubled, its temperature was more even. The new adaptive design approach of the SR could help to better optimize PTC systems. •New design approach for secondary mirror in parabolic trough concentrator.•Adaptive method to design secondary mirror.•Step-wise optimization to maximally reflect radiation to absorber.•Optical and thermal efficiency of concentrator increased by 5.2% and 4.9%.