Lighting-on-Demand: Balancing Occupant Needs and Energy Savings

Lighting on demand (LOD) is a high-resolution energy-efficient lighting control technique that dynamically adjusts the lights in a space according to its occupancy. It controls the lights in the space individually such that the area that receives a higher light level is determined by the location of the occupant(s) and, in some cases, by their tasks. In our LOD system, the controls adjust the individual lights above and around the occupant to track him or her while traversing a circulation space. We developed three scenarios with different combinations of light levels in the occupancy and background areas. We built a test bed, developed an occupancy algorithm, and conducted a usability test to demonstrate the acceptability of the LOD system to people walking in the circulation space by asking them to evaluate the conditions they experienced and measuring their walking time. Our test results suggest that in the case of individual occupants walking in a circulation space, the LOD concept is generally acceptable, but there are limits to the dimming potential both for the occupancy area and the background area. Satisfaction seems to be more strongly related to the occupancy area, but walking speed depends on the background level toward which one walks.