Net power maximization from a faceted beam-down solar concentrator

The beam-down solar concentrator at the Masdar Institute Solar Platform (Abu Dhabi, United Arab Emirates) is optimally coupled with a final optical element (FOE) to maximize the net power recovered by an upward-facing solar receiver. The FOE is designed as a converging reflective passage of hexagonal cross-section to further concentrate the solar flux onto the solar receiver. We develop efficient ways to optimize the orientation of the tower central reflectors simultaneously with the geometry and size of the FOE. Net power recovered by the receiver and optimized dimensions of the FOE designs are presented as a function of FOE internal surface reflectivity and the height of its inlet with respect to the ground. Setups where the receiver aperture is 3 m above the ground that are optimized simultaneously with an 85%-reflective FOE absorb 20% additional power incoming from the central reflector than equal setups optimized without an FOE. Such optimal FOE designs remain feasible, with inlet-to-outlet lengths below 2 m. The results may be applied to the design of other beam-down projects with planar central reflectors.