Research progress on secondary concentrator for linear Fresnel reflector

As the most abundant renew energy resource, solar energy has aroused the interest of scientists all over the world. In order to increase its efficient use, collectors maximizing sun power density are developed. According to concentration type, the solar collector system consists mainly of the linear Fresnel reflector (LFR), the parabolic trough collector (PTC), the solar power tower and the parabolic dish collector. LFR has attracted much attention because of its simple construction, low wind loads and optimal utilization of land area. The molten salt can be used as the heat transfer fluid when the fixed secondary concentrator is combined with the high temperature evacuated tube, which makes the system has great potential in reducing the cost of power generation. In this paper, the development of traditional compound parabolic concentrator (CPC) and new secondary concentrator is reviewed. Approaches of leaving a gap between secondary concentrator and receiver and the choice of the half-acceptance angle of the CPC are analyzed. The advantages and disadvantages of new secondary concentrators are summarized. The practical application of secondary concentrator is discussed, and the future research directions of secondary concentrator are prospected. The analysis result shows that for the approaches of leaving the gap, the gap loss of involute starting point moving forward is small and easy to process. Geometric optical efficiency and aperture width of the CPC should be considered for the choice of the half-acceptance angle. The efficiency of the new secondary concentrator based on the adaptive method is close to that of the CPC. When a higher flux intensity or a medium to high circumferential flux intensity homogeneity is required, the CPC is the best choice. © 2020, Science Press. All right reserved.