Light piping performance enhancement using a deflecting sheet

Abstract

This paper presents results of laboratory measurements of illuminance for various angle configurations of a deflecting sheet coupled to a mirror light pipe (MLP). The target of the work is to assess whether the performance of a light pipe can be enhanced throughout the year with a deflecting sheet at zero azimuth on the inlet of the duct and altering, on a monthly basis, the angle the sheet forms with respect to the pipe’s axis. The results indicate the performance achievement giving the optimum angle of the sheet to maximize the output for every month of the year. A large enhancement is obtained for low elevations during the winter months, this increase enables the MLP to be useful for longer periods, but in the meanwhile the measurements show a small output reduction in the summer months and a considerable reduction under diffuse light. The work sets the basis, in the authors’ opinion, for a system that could be proposed to the market in the form of a simple and affordable mechanical device (eg, using a mechanism similar to a blind) mounted on a light pipe in which the customer could adjust the deflecting sheet throughout the year.