Abstract

A multiple film based daylight control system for window has been developed to maintain the illuminance level at task plane. The developed system consists of three films with a visual transmittivity (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 changes in light intensity with the help of photosensor placed on the ceiling and facing the task plane and accordingly adjusts the film-position as well as the control voltage of dimmable CFL to maintain the task plane illuminance within a tolerance of-10%,+ 20% of setpoint. Optimized use of solar illuminance saves energy used for the task lighting for the period from 8: 00 to 19: 00, which was found to be about 70%. The paper describes the design, implementation of the proposed system and the preliminary results for task light illuminance and energy savings achieved in laboratory setup.