Stepwise multi-objective optimization for high-concentration and uniform four-dish solar concentrators

The advancement of solar-thermal concentrators requires architectures that combine high flux density, uniform focal distribution, and structural simplicity. However, multi-dish systems often suffer from coupled trade-offs among concentration, spot uniformity, and geometric stability, which can limit thermal efficiency and increase hot-spot risk in high-temperature applications. This study targets this coupled-design challenge by enabling a controllable and robust focal spot in a modular multi-dish architecture. This study presents a four-dish off-axis conjugate concentrator optimized through a global optimization framework that integrates ray-tracing simulations with a unified objective function. The objective is to achieve high effective concentration while simultaneously improving flux uniformity and spot geometry under practical alignment/manufacturing uncertainties. The framework adopts a staged dynamic-weighting strategy to achieve a smooth transition from "energy concentration" to "focal spot quality". Unlike traditional approaches that vary numerous complex structural parameters, the proposed design constrains the optimization space to radial and axial displacement, focal length, and receiver dimensions, thereby simplifying assembly requirements while still enabling high-dimensional exploration of optical behavior. Optimization results demonstrate coordinated improvements across all metrics: the concentrator sustains C95 above the design threshold (Cthreshold= 600), increases spot uniformity from 0.38 to 0.53, reduces RMS radius to 38 mm, and lowers the shape factor to 0.25, yielding a compact and geometrically stable focal spot. Outdoor validation confirmed these findings: under 35 °C and 620 W/m2, the prototype reached 783 °C within 4 s and achieved C95≈ 742, exhibited uniform, repeatable heat maps with strong tolerance to disturbances. These results contribute a four-dish off-axis conjugate architecture that suppresses off-axis aberration-induced spot degradation, and a staged, unified optimization framework that explicitly balances concentration–uniformity–spot geometry with experimental validation, providing a practical pathway toward deployable high-flux multi-dish concentrators.