According to a study conducted by the U.S. Department of Energy, lighting accounts for 18% of the energy used by commercial buildings in the U.S., making lighting upgrades with controls a significant opportunity for energy savings. When properly designed, today’s LED technology pairs well with advanced controls. One example of a lighting control strategy typically used in circulation spaces for commercial buildings like offices and schools is occupancy sensing, which automatically turns lights off when spaces are unoccupied and turns lights on when spaces are occupied. Studies show that occupancy sensors—also known as motion sensors—can help reduce electrical lighting energy use ranging from 25% to 50%. The actual savings realized depend on decisions made during the commissioning process of the lighting system, including the desired “low level” light output used during unoccupied periods and the rate at which the system changes its light output from high to low, known as a “ramp rate.”
Despite this, museums and retail stores do not generally accept dynamic dimming of their lighting systems due to the potential for visual disruption and distraction. This limits smart lighting implementation in these applications, which could contribute to deeper energy savings. To determine the ideal ramp rate where occupants will ideally not be disturbed, researchers at UC Davis’ California Lighting Technology Center, in collaboration with the Universidad Autónoma de Guadalajara in Mexico, recently conducted a study with 70 participants. This study focused on exploring the Just Noticeable Difference (JND)—also known as the difference threshold—which is the minimum level of stimulation that a person can detect 50% of the time. Researchers tested perception to changes in light levels with both central and peripheral vision at different dimming ramp rates.
To learn more, read CLTC's research published in IES LD+A November 2023 Research article.