Application of heliostat in interior sunlight illumination for large buildings

Abstract Heliostat daylighting systems, used to transmit sunlight deep into rooms where natural light cannot reach, are increasingly applied in buildings. A roof-mounted heliostat with an area of 22.95 m 2 was developed in this work to verify the feasibility of high flux and long distance daylighting in large building interior. The developed heliostat system consists of a heliostat, a secondary reflector, and glass windows forming the light path within the building. The problem of gravitational deformation of the steel beams base of the heliostat was solved by a rectification algorithm embedded into the computer program, to realize vertical daylighting. The spectrum and chromaticity of the heliostat daylighting system developed was measured, and the results verify the good visual quality of the interior illumination. The light transmission distance is more than 70 m, and the system can provide a level of 20–80 klux daylighting illuminance in the daytime. An economic analysis was carried out, and data indicates a good cost-effectiveness of the heliostat daylighting system developed. It is hoped that this research will be of some reference value to the design of heliostat daylighting systems in large buildings.