Mechanism of optical efficiency loss in linear Fresnel solar concentrator systems under in-service loading

ObjectiveLinear Fresnel Reflector (LFR) systems offer advantages such as lower construction costs, simple yet efficient tracking control systems, and straightforward mechanical structures. In recent years, with the continuous advancement and iteration of linear Fresnel concentrating solar power technology, system designs have increasingly trended toward lightweight and simplified configurations to reduce control technology costs. However, such lightweight structures are prone to deformation under wind loads, leading to a significant decline in optical efficiency. Based on finite element analysis theory, this paper presents a precise opto-mechanical modeling method to quantitatively analyze the mechanism of optical performance degradation in LFR systems under service loads (including wind load and self-weight). The study aims to provide a theoretical foundation for structural optimization and heliostat field layout.MethodsThis paper proposes an integrated optomechanical modeling method that combines Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA), and ray tracing. First, a fluid-structure interaction simulation is conducted using ANSYS Workbench to obtain the deformed grid nodal coordinates of the LFR system under wind load. Subsequently, the deformed mirror surfaces are discretized into triangular planar elements (Fig.2), and their nodal coordinates are extracted (Fig.5). Based on this deformation data, the optical geometric model is reconstructed in SolidWorks and imported into TracePro for ray tracing analysis. The validity of the model is verified by comparing it with data from conventional literature (Fig.12). Finally, by comparing the ray paths, the flux density distribution on the receiver tube (Fig.18), and the optical efficiency between the undeformed (Fig.15) and deformed (Fig.16) states, the impact of wind load on the optical efficiency of the LFR system is quantified. The validity of the model is further confirmed through comparison with data from conventional literature (Fig.12).Results and DiscussionsThe comparative validation results of the optical model show that the flux density distribution on the receiver tube simulated by the method proposed in this paper exhibits strong agreement with the experimental results from the literature (Fig.12), confirming the feasibility of using planar elements to discretize curved mirror surfaces for optical analysis. A case study under a wind speed of 12 m/s reveals that, compared to the condition with gravity only, wind load leads to an approximately 8.4% decrease in the overall optical efficiency of the linear Fresnel reflector system. Analysis of the flux density distribution (Figs.17-18) further indicates that the impact of structural deformation on optical performance exhibits significant spatial non-uniformity: the flux distribution on the receiver tube corresponding to the mirror column in the a-direction—which is farthest from the drive unit and has the weakest support stiffness—shows the most severe distortion (Fig.18(a)). This is characterized by a significant reduction in flux density at the bottom and the appearance of local high-flux zones on both sides. In contrast, the performance degradation of the mirror column in the d-direction, which is closer to the drive unit, is relatively less pronounced.ConclusionsThis study successfully established an integrated opto-mechanical model for linear Fresnel reflector (LFR) systems, enabling accurate calculation of their optical performance under service loads. The results indicate that wind loads cause significant mirror surface deformation, leading to a notable decline in optical efficiency (8.4% in the investigated case) and generating a highly non-uniform flux distribution on the receiver tube, with the most significant decrease in energy flux density observed at the bottom section of the tube. The degradation of optical performance exhibits a clear spatial dependence, being most severe for mirror assemblies with weaker support stiffness and located farther from the drive mechanism. The proposed methodology and related findings provide valuable technical support and theoretical guidance for the wind-resistant structural design and optical optimization of LFR systems.