Multiple Film Based Daylight Control System

A multiple film based daylight control system for window has been developed to maintain theilluminance level at task plane. The developed system consists of three films with a visualtransmittivity (Tvis) range of 0.159 - 0.015 and a 2x55W dimmable compact fluorescent lamp(CFL) fixture. The system works on the principle of feedback control, which records the changesin light intensity with the help of photosensor placed on the ceiling and facing the task plane andaccordingly adjusts the film-position as well as the control voltage of dimmable CFL to maintainthe task plane illuminance within a tolerance of -10%, +20% of setpoint. Optimized use of solarilluminance saves energy used for the task lighting for the period from 8:00 to 19:00, which wasfound to be about 70%. The paper describes the design, implementation of the proposed systemand the preliminary results for task light illuminance and energy savings achieved in laboratorysetup.