Detection and Acceptance of Demand-Responsive Lighting in Offices with and without Daylight

Abstract

Participants (N ϭ 33) in an office laboratory were exposed to an initial baseline electric lighting level of 400 lx on the desktop. The electric lighting was dimmed smoothly over 10 seconds. During the dim, and for 30 seconds afterwards, the participant performed a computer-based proofreading task. The participants indicated if they had noticed the change, and whether the lighting conditions were acceptable. This was repeated over multiple trials, with dimming from 0 to 80 percent, and with or without daylight. The level of dimming not noticed by occupants was 20 percent with no daylight, 40 percent with relatively low prevailing daylight, and 60 percent with high prevailing daylight (or, alternatively, an amount which represents 20 percent of total light level). The level of dimming that resulted in conditions that were still acceptable was 40 percent with no or low daylight, and 80 percent with high prevailing daylight. These results may be used to develop guidelines for using lighting in demand response actions. They suggest that dimming lights can contribute large electricity demand reductions during periods of grid stress without major inconvenience to occupants.

Assessment of Commercial Building Lighting as a Frequency Regulation Resource

“…Half of participants detected a 15% change and accepted a 20%-30% reduction [22] • Occupants noticed a 20% change without any daylight, a 40%-60% change with daylight, and an 80% change with strong daylight [23].…”

Energy Saving Potential for Integrated Daylighting and Electric Lighting Design via User-Driven Solutions: A Literature Review

“…In integrated design, daylight works as a mediating factor in the perception of light fading. A study by Newsham et al (2008) surveyed 39 individuals who underwent 42 different trials in private daylit mock-up offices, while performing computer-based tasks under various daylight conditions. The electric lighting was set to full output at the start of the trial, and then dimmed down to the target of 400 lux.…”

“…The study confirmed that a reduction of 20% illuminance -provided, in this case, by a mix of daylight and electric lighting -is unlikely to be noticed. However, with high daylight provision, this 20% actually corresponds to up to 60% of dimming down of electric lighting (Newsham et al, 2008).…”

“… Energy savings can be fostered by dimming electric light, provided that the speed and range of variation is appropriately regulated (Newsham et al, 2008). Shading automation may be limited to opening shading devices at the end of the day to maximize daylight, since users usually maintain the default setting.…”

Dimming strategies for open office lighting: User experience and acceptance

“…Newsham et al performed a follow-up study that did include daylight. 8 In the experiment, they dimmed lighting down from the baseline of 400 lx with 0%, 20%, 40%, 60% and 80%, all in 10 seconds. They showed that in situations with no daylight, the artificial lighting can be dimmed down by 20% without occupants noticing the change and dimmed down by 40% to still be perceived as acceptable.…”