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LEUKOS - The journal of the Illuminating Engineering Society of North America
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The Journal of the Illuminating Engineering Society of North America    Volume 3     Number 4     April 2007

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Editorial:

ALLIANCES AND ALLEGIANCES: THE MODEL LIGHTING ORDINANCE

Articles:

DAYLIGHTING OF ATTIC ROOMS BY DORMERS

JITKA MOHELNIKOVA

Dormers have found wide applications in the design of new buildings and also in the renovation of under-roof spaces in existing buildings. Comfort and illuminance for visual activity in attic rooms illuminated by dormers depends mainly on the dormer dimensions and its position with respect of the utilization area of the room. This article evaluates selected types of dormers for daylighting of attic rooms. The evaluation of daylighting from dormers in the administrative part of the university building was carried out using computer simulations and illuminance measurements. The daylighting studies were completed for separated dormers compared with the alternative design solution of one continuous dormer with the same glazed area. Results from computer simulations give information about illuminance level and daylight distribution in the whole area of the investigated rooms. Daylighting simulations for the dormer were compared with alternative design solution with skylights.

EFFICIENT DUAL-FUNCTION SOLAR/ELECTRIC LIGHT GUIDE TO ENABLE COST-EFFECTIVE CORE DAYLIGHTING

ALEXANDER ROSEMANN, GUTHRIE COX, ALLEN UPWARD, PETER FRIEDEL, MICHELE MOSSMAN, LORNE WHITEHEAD

As a component of our cost-effective core daylighting research program, we have developed a hollow light guide that can be used to distribute sunlight collected by a heliostat device, and can also operate as an efficient fluorescent light fixture when the sunlight is insufficient to illuminate the workspace. This dual-function prism light guide structure has a cross-section that is similar to standard commercial fluorescent light fixtures, but with an increased depth in order to pipe the sunlight. The bottom surface of the guide is lined with a thin polycarbonate film having prismatic surface features, while the top and sides are lined with a highly-reflective multilayer optical film having a luminous reflectance greater than 98 percent. The angular constraints of the concentrated sunlight, combined with the high reflectance of the surfaces, enable the sunlight to be efficiently transported within the guide along a distance of greater than 10 m. The guide can also illuminate the room using electric sources, since the light from the lamps strikes the prismatic bottom surface at angles for which it is an efficient transmitter. Photometric characterization of the new dual-function guide has been performed, resulting in illuminance levels, uniformity, and efficiency values well within recommended standards. The dual-function design approach has yielded a daylighting system that can be cost-effectively incorporated into standard office building construction.

REPLACING FUEL BASED LIGHTING WITH LIGHT EMITTING DIODES IN DEVELOPING COUNTRIES: ENERGY AND LIGHTING IN RURAL NEPALI HOMES

PRAMOD BHUSAL ALEX ZAHND, MARJUKKA ELOHOLMA, LIISA HALONEN

More than one quarter of the world’s population, who does not have access to electric light, live in the developing countries. Nepal is one of these countries, where the people in the remote rural areas have to rely on fuel based lighting to bring minimal lighting services in their homes. This paper reviews the quality of lighting, energy and health issues due to the use of fuel based lighting in rural Nepali villages. Recommendations are given on the amount of light needed as the first time electric lighting services in those remote places. The measurement results show that LED technology can bring necessary light in these rural homes with least energy use and it is the potential technology to replace fuel based lighting in a sustainable way. Replacing fuel based lighting by white LEDs can also contribute to the overall development of the underprivileged and underdeveloped communities by helping to improve the health, education, and life expectancy of the people as well as income generation.

RECENT CHANGES IN HEADLAMP ILLUMINATION DIRECTED TOWARD TRAFFIC SIGNS

MICHAEL SIVAK, BRANDON SCHOETTLE, AND MICHAEL J. FLANNAGAN

This study examined the differences in sign light between 1997 tungsten-halogen and 2004 high-intensity discharge (HID) low-beam headlamps manufactured for use on U.S. vehicles. The results indicate that the HIDs tended to deliver less light above the horizontal straight ahead and to the left of the vertical, and less light to the right of the vertical above about 1.5° up. The consequences of the changed beam pattern were analyzed in detail for three typical sign locations: center overhead, right shoulder, and left shoulder. The most frequent geometric conditions were modeled: a straight road, and very large-radius left and right curves, all with no vertical curvature. Viewing distances between 50 m and 300 m were considered The results imply that with current HID low beams, sign retroreflectivity would need to be increased to maintain the effectiveness that a given sign had a decade ago with tungsten-halogen low beams. This applies to overhead signs on straight roads and on very large-radius left and right curves, and to right and left shoulder-mounted signs on straight roads and on very large-radius left curves.

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