Heliostat structural optimization: A study of wind load effects with CFD-FEM methods

In solar power tower plants, heliostat mirrors reflect the sunlight onto the receiver. The mirrors are supported by the facet structure and when it is deformed, the mirror quality is affected (the sunlight is reflected with less accuracy). For this reason, the facet heliostat stiffness has a direct impact on the final plant efficiency. In order to optimize heliostat facet design and thus reduce costs in solar power tower plants, this work proposes a numerical study of facet deformations due to wind and gravity loads. Calculating those deformations via numerical models helps to improve the facet structure that supports the mirror and, thus, achieve an accurate performance. The mainobjective of the simulations proposed here is to obtain high opticalperformance maintaining material costs. Computational Fluid Dynamic (CFD) numerical methods are utilized to calculate the pressure loads due to wind velocity on heliostat surface. In a second step a Finite Element Analysis (FEA) is carried out taking into account those wind loads and the gravity force. CFD-FEA methods allow calculating root mean square error of surface rotations (RMS-error) due to wind and gravity force. This study shows that an improvement in optical quality in the facet structure could be achieved; while still maintaining the material needed in the facet structure