Analysis Of Modal And Static Optimization On Heliostat

Heliostat plays an important part in the tower solar power system. It worksoutside the door months and years. For the environment around it is very complex andchangeable. Therefore, the structure is easily damaged by the dynamic load (windload). The accurate modal parameter identification is a basic work of the structuraldynamic analysis. At the same time, the cost of the heliostat is so high that itsconstruction cost accounts for approximately60%of the total, which enormouseconomic benefits could be brought by optimizating it. Considering the above twoaspects, the following reseach and analysis were done in this paper.Firstly, the APDL of the ANSYS software was written and3D finite elementmodel was established. Then the first15modes of the five conditions, which the yawangle respectively is0°,30°,45°,60°and90°, were extracted. Natural frequency, modeshape, partic factor of mode shape and mass were given. Some analysis was donefrom the perspective of the wind load and mode shape characteristics.Secondly, modal test was respectively done on the upper supporting structure andcolumn of the heliostat. Six modes of the former four conditions and three modes ofthe last condition were obotained by modal synthesis. Modal test result shows thatstructural damping is small that the maximum is2.74%. Compared with the finiteelement analysis (FEA) result, Corresponding shapes of FEA could be found toconcide with the modal test. The maximum relative error of frequency is16.74%.Therefore, the results of FEA and modal test are found to be in good agreement. Itproves that the finite element modal is reasonable.Then, static analysis was done under the effect of weight and wind load. Theresult shows that wind-induced dynamic response (deformation and stress) of theexisting heliostat is far less than the allowable value. Therefore, much work ofoptimization could be done to reduce material consumption.Finally, the plane and space truss’s rod sizes were looked as the designparameters, displacement and stress as the constraints. Uniform Design Method wasadopted to approximately optimize a heliostat under effect of wind load. And thenapproximation functions between objective (displacement, stress and consumption ofsteel) and parameters were obtained. At last, the thesis gives the rod specifications atdifferent conditions. Compared with the existing structure, the optimized structure saves the steel up to13.8%. The whole process is simple and reliable. The method canbe promoted in solving similar problems and extend the further application in variousfields.