Skew rays in one stage tracking concentrators

A fundamental method is presented to determine whether skew rays can be collected in axisymmetrical concentrators, and techniques of synthesis are developed for the cases in which skew rays are limiting ones. The analysis is restricted to mirrors with a shape close to a parabola or to thin Fresnel lenses. It is found that for full collection of the rays within the cone subtended by the sun with a squared flat Fresnel lens and a squared cell, taking into account chromatic aberration, the upper limit of concentration is 376* that which is achievable with a f/1.35 lens (the aperture diameter must be considered along the diagonal). If the cell is circular, no skew ray limitation is produced, but the concentration is restricted to 309* with a f/1.74 squared lens.