2014 IES Street and Area Lighting Conference
September 14-17, 2014 | Nashville, TN
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A field study was conducted in a deep-plan office building equipped with suspended direct-indirect luminaires located centrally in cubicle workstations. In order to reduce lighting energy use, the luminaires employed integral occupancy sensors and light sensors (daylight harvesting), as well as individual dimming control accessed through occupants' computer screens. Data were collected from 86 workstations over a year to examine the energy savings and power reduction attributable to the controls, and how the controls were used. An awareness campaign that used e-mail reminders to encourage the occupants to use the individual control feature of the lighting system was also conducted. Results indicate that the lighting system generated substantial energy savings and peak power reductions compared to a conventional fluorescent lighting system installed on a neighboring floor. The installed lighting power was 42% lower than that of the conventional system. The three controls combined saved 42 to 47% in lighting energy use compared to the same lights used at full power during work-hours; this translated into overall savings of 67 to 69% compared to the conventional lighting system. If the three lighting controls systems had been installed separately, occupancy sensors would have saved, on average, 35% if used alone, light sensors (daylight harvesting) 20%, and individual dimming 11%. The light sensor savings were, as expected, higher in perimeter workstations, and would have matched the performance of the occupancy sensors with some modifications to the control parameters. The average daily peak power demand for lighting was also reduced by a similar amount, which resulted in an average effective lighting power density of only 3 W/m2. Although not detailed in this paper, surveys indicated that the studied lighting system was also associated with higher occupant satisfaction. This was likely due to the individual dimming control, although use of this control beyond an initial preferred setting was rare.
A method for simulating the effects of visual adaptation using image processing techniques was developed, and then tested for accuracy in predicting the reductions in visual performance that occur with adaptation. The simulation process entailed transforming digital photographs of realistic exterior scenes into the spatial frequency domain, filtering the transformed data using contrast sensitivity functions for different adaptation levels, transforming the filtered data back into the luminance domain, and producing a new digital image of the scene. Two experiments were conducted that compared performance on a realistic visual detection task when the subjects were adapted to different luminances, to performance on the same task when subjects' adaptation level was held constant while they viewed the simulated adaptation effects. Results showed that the simulations produced decreases in performance in the same direction as actual adaptation effects, but the effects were of smaller magnitude. A third experiment was conducted to better quantify the differences between the simulated and actual adaptation conditions; this experiment utilized a standardized visual test target, the United States Air Force (USAF) 1951 test pattern.
Ballast-integrated compact fluorescent lamps are widely used for replacing incandescent lamps as energy saving alternative light sources. In spite of their high efficacies, the luminous run-up characteristics of the lamps covered with outer globes are slow and rather unsatisfactory, especially within a second or two. The luminous run-up characteristic of these lamps should be divided into two stages: the luminous flux at starting and luminous increase for several minutes. The former is related to the mercury vapor pressure change in the discharge tube during off-period; the latter is related to the mercury diffusion along the discharge path after starting. In this paper, we focus on the mercury vapor pressure in the discharge tubes that have main and auxiliary amalgam. It is found that the mercury vapor pressure during off-period is determined not only by the auxiliary amalgam composition but also the main amalgam one and the distance of its site from the discharge space. The luminous run-up characteristic is much more improved by using bismuth-tin main amalgam dosed in the end of long extended thin tube connected to the discharge tube with gold-plated auxiliary amalgam flags.
Color is becoming a key issue in many e-commerce products. This made it necessary to develop a color course easily accessible from the Internet or distributed on CD-ROM. This article describes the advantages of the electronic approach – compared to class-room demonstrations – to bring the fundamentals of colorimetry to the student with the help of demonstrations.