Research On The Hot Bending Process Of The Deflection Surface Concentrator

In the industrialization of solar thermal power generation, cost problem is an important factor that hinders its development. As for parabolic trough collectors that used for solar thermal power generation, it is urgent to develop a kind of concentrator with low cost and a good performance. Deflection surface concentrator as a higher order cylinder collector that has been developed shows great potential. In this paper, hot-bending control and mirror shape optimization of this concentrator were studied.Firstly, based on the molding process of the deflection surface concentrator on a hollow mold, the tolerance of factors including mould manufacturing error, glass geometry size effect and hot-bending arch height error that affected the hot-bending mirror shape error were analyzed. Through the analysis we found that a two-dimensional deformation caused by glass width and the maximum deflection control error have bigger influence on deflection mirror shape, which are key controlling factors to ensure high quality mirror shape.Secondly, in terms of hot bending surface type control, we established a dynamic equation of mirror shape during the hot-bending process and analyzed the factors influencing the hot-bending speed. Overall considering the influence of thermal inertia deformation and thermal spring-back deformation on the final hot-bending mirror type, we predicted the annealing point, and completed the control of the hot-bending arch high with the help of hot-bending indicating amplifier. The two-dimensional mirror shape in glass width direction was controlled through the cooperative use of limit beam and indicating amplifier. Experimental tests showed that the error can be controlled within 1mm, effectively reducing the mirror group design and installation debugging difficulty. Thirdly, as for the problem that deflection surface concentrator’high tailor percentage, concentrated load and bending moment were put forward to optimize the mirror shape. And the focusing characteristics of the two kinds of optimized mirror shape were analyzed through Tracepro software. Compared with the deflection surface concentrator with uniformly distributed load, the focal spot width of the optimized one can be reduced by more than10%, and circumferential energy flow density distribution was more concentrated, Reducing the tracking support structure stiffness and precision.At last, on the basis of design parameters at the early stage, the optimized mirrors were used to constitute the mirror arrays through angle and position change of mirrors. It can be found that the focal spot width has been reduced from 63 mm to 55 mm.