Daylighting Dynamic Control by Smart Window with Grating Optical Filter

Abstract

A smart window with a novel grating optical filter is proposed, which supplies dynamic daily and annual control of window transmission without the use of blinds and similar devices. The filter attenuates direct solar radiation, letting in diffused and reflected radiation, thus creating more comfortable conditions for daylighting, insolation, and sun protection in rooms. A method for calculating the grating filter is changed and numerical modelling is conducted to show the capabilities of the new method of dynamic control of transmission. The optimal geometric parameters of the filter for a single-glazed smart window at a given azimuth of the window orientation are determined. The hourly values of the light transmittance of the filter during daylighting hours are calculated for the 15th day of each month from April to September, and the theoretical angular characteristics of the transmission of the filter, corrected for reflection and absorption, are constructed. The average monthly values of the theoretical and corrected light transmittance of a smart window are obtained, based on the results of calculations every hour compared to the time of day when the azimuths of the Sun and the window are equal. It is shown that the smart window with the built-in grating optical filter provides the minimum transmission at a given time of the day, taking into account the azimuth of the window, the geographic coordinates of the building, the seasonal and daily distribution of the solar radiation intensity on the calculated day of the year, and in the rest of the time, with the most demanded protection from solar radiation, the filter functions within acceptable limits. It is stated that the smart window with the built-in optical filter is most suitable for rooms with a long stay of people during daylight hours that is for office, educational, industrial, etc. rooms, in order to provide comfortable daylighting and the required insolation and thermal conditions during working hours.