## Abstract

A two-axis tracking scheme designed for <250x concentration realized by a single-axis mechanical tracker and a translation stage is discussed. The translation stage is used for adjusting positions for seasonal sun movement. It has two-dimensional x-y tracking instead of horizontal movement x-only. This tracking method is compatible with planar waveguide solar concentrators. A prototype system with 50x concentration shows >75% optical efficiency throughout the year in simulation and >65% efficiency experimentally. This efficiency can be further improved by the use of anti-reflection layers and a larger waveguide refractive index.

© 2014 Optical Society of America

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### Equations (6)

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(1)
$${\theta}_{1}={\delta}_{i}-\mathrm{arc}\mathrm{tan}\left[\frac{1}{2\left(f/D\right)}\right]<\theta <{\theta}_{2}={\delta}_{i}+\mathrm{arc}\mathrm{tan}\left[\frac{1}{2\left(f/D\right)}\right],$$
(2)
$${\overrightarrow{k}}_{i}=k\left[\begin{array}{ccc}\mathrm{cos}{\delta}_{i}& -\mathrm{sin}{\delta}_{i}& 0\\ \mathrm{sin}{\delta}_{i}& \mathrm{cos}{\delta}_{i}& 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{c}\mathrm{sin}\gamma \mathrm{cos}\Omega \\ \mathrm{cos}\gamma \\ \mathrm{sin}\gamma \mathrm{sin}\Omega \end{array}\right]\triangleq \left({k}_{x},{k}_{y},{k}_{z}\right).$$
(3)
$${\psi}_{i}=\mathrm{arc}\mathrm{cos}\left({k}_{y}\mathrm{cos}\beta +{k}_{z}\mathrm{sin}\beta \right)>{\theta}_{cc}=\mathrm{arc}\mathrm{sin}\left(1/{n}_{w}\right).$$
(4)
$${\overrightarrow{k}}_{\text{r}}=\left({k}_{x},{k}_{y}\mathrm{cos}2\beta +{k}_{z}\mathrm{sin}2\beta ,{k}_{y}\mathrm{sin}2\beta -{k}_{z}\mathrm{cos}2\beta \right)\triangleq \left({k}_{x0},{k}_{y0},{k}_{z0}\right).$$
(5)
$$\text{x-axis}:{\psi}_{sw}=\left|\mathrm{arc}\mathrm{cos}\frac{{k}_{x}}{k}\right|\ge {\theta}_{cside}=\mathrm{arc}\mathrm{sin}\left(\frac{1}{{n}_{w}}\right),$$
(6)
$$\text{y-axis}:{\psi}_{sub}=\left|\mathrm{arc}\mathrm{cos}\frac{{k}_{y}}{k}\right|\ge {\theta}_{csub}=\mathrm{arc}\mathrm{sin}\left(\frac{{n}_{s}}{{n}_{w}}\right),$$