Optimization on a cylindrical Fresnel lens and its validation in a medium-temperature solar steam generation system

Abstract

This paper presents an optimization on cylindrical Fresnel lens and validates it by using a medium-temperature solar steam generation system. The optimal transmittance condition of prism is used for designing the edge-prism of cylindrical Fresnel lens. A method that used for estimating Fresnel lens' real transmittance is given, by which the real transmittance is figured as 81.6%. Finally, a 20 m2 area solar concentrator is set up as heat source for steam generator. Experimental test is carried out under two operating gauge pressures of 0.2 MPa and 0.5 MPa. The results show that the average collection efficiency of concentrator is about 0.48 and 0.44, correspondingly under gauge pressures of 0.2 MPa and 0.5 MPa. The experimental data is fitted as a linear relationship, in which the intercept efficiency is about 63%. Finally, a comparison with traditional solar steam generation system is undertaken, including structure, concentration performance and price. Cylindrical Fresnel lens system has relatively higher collection efficiency, easy-tracking and cost-effective etc. While the stable working time is about 4.5 h, which is shorter than parabolic trough concentrator's 6.2 h. Thus, enhancing its stable working time will be one of the research priorities in the future.