Validation of the Spatial Brightness Estimation Formula in Offices With Windows

Abstract

In recent years daylight harvesting has been one of the promising systems to reduce lighting energy consumptions. Usually in this system the lighting environment is taken into consideration by securing the horizontal surface illuminance on the desktop using photosensors on the ceiling, however, it has become clear in some studies that the quality of the lighting environment does not always link with the desktop illuminance, and luminance distribution at the occupant's eye or vertical illuminances are more important for evaluating the lighting qualities. Therefore, in this research, we aim to develop a new method for daylight harvesting systems by measuring ceiling and window luminance using simple photosensors. The goal of this system is to secure appropriate spatial brightness in the office space and to improve energy efficiency performance at the same time. In this paper simple formulae for estimating spatial brightness in offices with windows were obtained.

Reproduction of the spatial brightness on a high-luminance large screen display

“…However, these models can be utilized mainly for the lighting environment with electric luminaires, and the prediction of spatial brightness under daylighting still needs to be discussed 12 . It is sometimes difficult to evaluate the spatial brightness of the lighting environment with daylighting which changes by the second 11 . Therefore, the evaluation method of spatial brightness using still images, which can always present the same lighting environment, may help to elucidate the mechanism of the spatial brightness.…”

Development of Daylighting Control Method for Ensuring Spatial Brightness in Office Space

“…Fig 16. Relationship between estimation value and evaluation value of spatial brightness in the small office at the windowfacing seat with no classification…”