Comparison of sky luminance maps with instantaneous all-sky images

Conference · Tue Mar 01 04:00:00 EST 1988

OSTI ID:6828337

LeBaron, B A; Michalsky, J J; Larsen, N R

Daylighting designers and modelers require more information than can be provided by measures of the the total illuminance arriving at a surface. A knowledge of the luminance spatial distribution is critical to predicting interior penetration and reflection. A qualitative comparison of contour maps, generated from a series of point measurements around the sky dome, and concurrent instantaneous all-sky photographs is made for clear, overcast, and partly cloudy conditions. It is shown that a discrete set of all-sky measurements, requiring 3 minutes to complete, are adequate to qualitatively capture the structure in the luminance distribution, even under rapidly changing cloud conditions. The models examined, performed reasonably well for the clear and overcast sky when conditions were symmetric and stable, but were unsatisfactory for the anisotropy exhibited under partly cloudy skys. The comparisons suggest that scanning instruments can quantify the essential features of a luminance distribution for conditions of high anisotropy.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6828337
• Report Number(s): PNL-SA-15722; CONF-880615-6; ON: DE88014752
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140100 -- Solar Energy-- Resources & Availability
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320107* -- Energy Conservation
Consumption
& Utilization-- Building Systems-- (1987-)
BRIGHTNESS
CLOUD COVER
COMPARATIVE EVALUATIONS
DISTRIBUTION
MATHEMATICAL MODELS
OPTICAL PROPERTIES
PHOTOGRAPHY
PHYSICAL PROPERTIES
SKY
SPATIAL DISTRIBUTION