Line-focus solar concentration 10 times higher than the 2D thermodynamic limit

Abstract

Line-focus solar concentrators have traditionally been limited by the 2D concentration limit due to the continuous translational symmetry in these systems. This limit is orders of magnitude lower than the 3D limit, severely limiting the achievable concentration ratio compared to point-focus systems. We propose a design principle for line-focus solar concentrators that bypasses this 2D limit, while maintaining a trough-like configuration and only requiring single-axis external solar tracking. This is achieved by combining the concept of étendue squeezing with the concept of tracking integration. To demonstrate the principle, we present a design example that achieves a simulated average yearly efficiency of 80% at a geometric concentration of 335x under light with a ±9mrad angular distribution and horizontal single-axis external tracking. We also show how the same design principle can achieve a line-focus with 1563x geometric concentration at 90% efficiency if design constraints are relaxed by foregoing tracking-integration and assuming two-axis external solar tracking. This design principle opens up the design space for high-concentration line-focus solar concentrators, and may contribute to a reconsideration of the trade-off between concentration and acceptance angle in such systems.