Lateral translation micro-tracking of planar micro-optic solar concentrator

Abstract

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.

Thin-film micro-concentrator solar cells

“…Insolight has recently demonstrated this concept for pre-industrial modules, achieving peak 29% electrical efficiency. Another approach based on lateral displacement of two stages of planoconvex lenses designed using the simultaneous multiple surface (SMS) algorithm can theoretically achieve 500X with ±24°acceptance using a polar single-axis tracker [86][87][88][89]. Related to this concept, planar micro-tracking concepts use concentrator lenses to focus light on some micro coupling features that scatter or reflect light into a waveguide, which direct light towards the edges where the receiver cells are located.…”

Tailored free-form optics with movement to integrate tracking in concentrating photovoltaics

“…1. Reduce the external tracking effort in favour of a compact installation, for example [9][10][11][12][13][14] 2. Fine-tune the tracking functionality allowing coarse external solar tracking [15] Furthermore, it is of course possible to combine both functionalities to reduce the external tracking effort and to allow coarse remaining external solar tracking at the same time.…”

“…This symmetry follows immediately from the later introduced Eqs. (9) and (10). The linear systems of equations for the correspondent Taylor series coefficients have null vectors as only possible solutions and are therefore discarded in the Taylor series.…”

Beam-steering array optics designs with the SMS method

“…Recently lateral moving CPV optics has also been investigated to find a possible way to reduce the tracking system's cost. Justin [3] has studied a light-guide type micro-structured optics to achieve sun tracking and collect its energy with edge mounted solar cells. Sweatt [4] designed two horizontally movable lens arrays to concentrate sun light onto an array of solar cells.…”