Optical design of an aspherical cylinder-type reflecting solar concentrator

• A part of the aspherical cylinder's inner wall is used as a concentrating mirror.
• The relationship between direction vectors of reflected Sunbeams and aspheric coefficients.
• The particular set of aspheric coefficients obtained with particle swarm optimization algorithm.
• The Sunbeams can be focused on a very narrow line segment parallel to the cylindrical busbar.
• The aspheric cylindrical concentrating mirror has a light compression ratio of 285 to 1.

In this paper a highly efficient solar concentrating mirror is presented. A part of the aspherical cylinder's inner wall defined by a set of specific coefficients a2, a4, a6, a8, a10, a12, a14, a16 and C is used as reflective surfaces of concentrating mirror. Based on the particular aspherical equation and the optical law of reflection, the relationship between the direction vectors of the sunlight beams reflected from the cylindrical inner wall and the coefficients of an aspherical equation, a2, a4, a6, a8, a10, a12, a14, a16 and C has been derived. By optimizing these coefficients, the Sunbeams incident on the aspherical cylinder's inner wall can be focused on a very narrow line segment parallel to the cylindrical busbar and form a linear focus (focal line). The particular set of coefficients associated with the particular aspherical equation is obtained by using particle swarm optimization algorithm. The focusing effect of the solar concentrating mirror with respect to the particular set of coefficients is demonstrated by using computer simulations and the experiment. The theoretical results show that this solar concentrating mirror has a light compression ratio of about 285 to 1. The linear spot can be used as a strong light source or a high temperature heat source.