High-concentration solar-power optics require precise two-axis tracking. The planar micro-optic solar concentrator uses a lenslet array over a planar waveguide with small reflective facets at the focal point of each lenslet to couple incident light into the waveguide. The concentrator can use conventional tracking, tilting the entire assembly, but the system geometry also allows tracking by small lateral translation of the lenslet relative to the waveguide. Here, we experimentally demonstrate such microtracking with the existing concentrator optics and present optimized optical designs for systems with higher efficiency and angle range.

Planar micro-optic concentrators are passive optical structures which combine a lens array with faceted microstructures to couple sunlight into a planar slab waveguide. Guided rays propagate within the slab to edge-mounted photovoltaic cells. This paper provides analysis and preliminary experiments describing modifications and additions to the geometry which increase concentration ratios along both the vertical and orthogonal waveguide axes. We present simulated results for a 900x concentrator with 85% optical efficiency, measured results for small-scale experimental systems and briefly discuss implementations using low-cost fabrication on continuous planar waveguides.

Étendue limits angular acceptance of high-concentration photovoltaic systems and imposes precise two-axis mechanical tracking. We show how a planar micro-optic solar concentrator incorporating a waveguide cladding with a nonlinear optical response to sunlight can reduce mechanical tracking requirements. Optical system designs quantify the required response: a large, slow, and localized increase in index of refraction. We describe one candidate materials system: a suspension of high-index particles in a low-index fluid combined with a localized space-charge field to increase particle density and average index. Preliminary experiments demonstrate an index change of aqueous polystyrene nanoparticles in response to a low voltage signal and imply larger responses with optimized nanofluidic materials.

High-concentration photo-voltaic systems focus incident sunlight by hundreds of times by combining focusing lenses with accurate, dual-axis solar tracking. Conventional systems mount large optical arrays on expensive tracking pedestals to maintain normal incidence throughout the day. A recently proposed micro-optic solar concentrator utilizes a twodimensional lens array focusing into a planar slab waveguide. Localized mirrors fabricated on the waveguide surface reflect focused sunlight into guided modes which propagate towards an edge-mounted photovoltaic cell. This geometry enables a new method of solar tracking by laterally translating the waveguide with respect to the lens array to capture off-axis illumination. Using short focal length lenses, translations on the order of millimeters can efficiently collect 70° full-angle incident fields. This allows for either one or two-axis tracking systems where the small physical motion is contained within the physical footprint of a fixed solar panel. Here, we experimentally demonstrate lateral micro tracking for off-axis light collection using table-mounted components. We also present a novel tracking frame based on de-centered cams and describe a lens configuration optimized for off-axis coupling.

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