A study of daylight-responsive photosensor control in five daylighted classrooms

This study analyzes the performance of daylight-responsive photosensor control in five different daylighted classrooms using advanced, computer modeling (Radiance). The daylight configurations considered, include windows, lightshelves, clerestories and skylights. The electric lighting systems include both direct and indirect lighting systems. Different photosensor positions and field-of-view were applied to determine their impact on a system's ability to properly track the daylight levels within each space. For each daylighted classroom condition, correlation coefficients were computed and graphical evaluations were conducted to assess the ability of different photosensor configurations to track the daylight levels at the critical work plane point within the spaces. The findings show that full-field, cosine sensors work quite well since they help to minimize problems associated with high window luminances and direct sunlight patches within a space. Cutoff distributions, which are required for ceiling-mounted photosensors employed with indirect lighting systems, also provide very good correlation, provided they are positioned a proper distance from the window to minimize the direct contribution from daylight sources. Energy analysis of different dimmed lighting zone control schemes illustrate the daylight savings that could be achieved in each of these spaces. The results of this study provide important information on the design and layout of photosensor controlled lighting systems.