First demonstration of a novel 2D-waveguiding solar concentrator

Abstract

The first experimental demonstration results will be presented for a novel, two-dimensional waveguiding solar concentrator consisting of a primary concentrator (a microlens array) and a secondary concentrator (tapered multimode waveguides). The microlens array collects the incident sun light and focuses it onto a turning mirror. The turning mirror couples the light into a tapered multimode waveguide, which alleviates connection, cooling and uniformity issues associated with conventional solar concentrating systems. Therefore, a large area of light can be efficiently concentrated to a small waveguide cross-section and guided to an array of co-located photovoltaic cells with high optical efficiency. To achieve the maximum coupling efficiency of the light to the waveguide, the design of the turning mirror and waveguides are optimized to avoid any inherent decoupling loss in the subsequent waveguide propagation. Experimental results indicate that a 38 mm diameter lens with a multimode waveguide that is 3 mm x 3 mm x 10 cm, using only total internal reflection surfaces, can achieve 126x concentration with 62.8% optical efficiency. We will present details on the experimental device characterization. A critical requirement for this design is maintaining low waveguide propagation losses, which as we demonstrate can be less than 0.1 dB/cm. Considering 100% TIR coupling and the use of antireflection layers, the theoretical efficiency limit for this particular system is ~88%.