2014 IES Street and Area Lighting Conference
September 14-17, 2014 | Nashville, TN
Click here for more information >
Advanced Energy Design Guides: Free Download >
Two experiments on the use, effects, and potential energy efficiency of office task lighting were conducted. Participants worked under ambient lighting provided by recessed parabolic luminaires, augmented with task lighting in some cases. Participants were allowed to adjust the level of ambient illuminance. The presence of task lighting did not lower the preferred ambient levels. Apparently, the use of task lighting does not save energy under preferred illuminance conditions.
Visual performance of a visual search task was compared for lighting systems with two different amounts of 100 Hz component modulation: 3 and 32 percent. Though participants could not visually discriminate between the two conditions, their visual performance was higher for the low modulation condition.
A simple and accurate general model for describing the flux attenuation with distance in a general light guide is described. The model has only two free parameters, and therefore measurement of decay at just two positions along the guide allows quite accurate prediction of flux at other distances. This prediction algorithm is expected to be helpful in illuminating engineering designs using light conduits.
Photometric data are reported for a sample of high-intensity discharge low-beam headlamps for model year 2004 vehicles in the U.S., and for the corresponding tungsten-halogen low-beam headlamps manufactured for use on the same vehicles. The technological and photometric trends for low-beam headlighting in the U.S. from 1997 to 2004 are analyzed. The results is that from 1997 to 2004 there was a general photometric improvement of both tungsten-halogen and HID low beams, and the photometric performance of the current HID low beams is superior to that of the current tungsten-halogen low beams.
The relative merits of the various light sources available for roadway lighting are evaluated economically. Certain sources have particular benefits, but the economics of using sources other than High Pressure Sodium have not been clear. The cost issues related to lamp type are reported. Initial costs are addressed on a total cost per mile basis, influenced by pole spacing. Operating costs include power and maintenance costs. All are evaluated and summarized on the basis of meeting identical IESNA performance recommendations.
Algebraic expressions of high accuracy that predict the tabulated values of CIE Standard Observers and Stockman Cone Fundamentals are reported. The algebraic models are linear combinations of Gaussian functions. The concise mathematical expression of these important curves appreciably simplifies computational applications in illuminating engineering.