2014 IES Street and Area Lighting Conference
September 14-17, 2014 | Nashville, TN
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This article compares daylight simulation results generated with two simulation programs, Autodesk® 3ds Max® Design 2009 and Daysim 3.0 to indoor illuminance measurements in a sidelit space. The sidelit space was in a single location configured with five fenestration and glazing options operated under a variety of sky conditions. The measurements form a set of ‘daylighting test cases’ that were recently developed to evaluate the simulation capabilities and limitations of different daylight simulation programs. Both 3ds Max Design and Daysim were given external direct and diffuse irradiances as simulation input, from which the programs predicted indoor illuminances on a grid of upward facing work plane sensors and downward facing ceiling sensors.
The comparison of both programs with measurements demonstrated that 3ds Max Design simulated indoor illuminances for the daylighting test cases with reliability comparable to Daysim. Most mean bias errors and root mean square errors were in the range of those reported in earlier validation studies: both programs succeeded in reproducing measurements for a sidelit space with and without a lightshelf. While 3ds Max Design consistently underestimated the incoming light flux going through a translucent panel, Daysim results were lower than measurements for the internal venetian blind test case. The results suggest that the accuracy of both programs is sufficient for typical daylighting design investigations of spaces with complexity comparable to the five daylighting test cases.
The illumination performance of surgical luminaires is quantified by performance indicators defined in an international standard (IEC 2000).The remaining maximum illuminance in relevant situations, the light field size, and the spectral characteristics are performance indicators used by hospitals as input for luminaire opting processes. Industry however focuses on illuminance when communicating with health care professionals. The aim of this study is to evaluate whether these standards are sufficient to describe luminaire performance, especially for modern LED lighting technology. Illuminance distribution and spectrum measurements were performed on 5 different state-of-the-art (LED) surgical luminaires. The results showed that changing situations not only changed the maximum illuminance but also changed the light field sizes and shapes, introducing substantial differences between luminaires. Moreover, colored cast shadows and light colour variations across the light field were observed for 3 luminaires using differently colored LEDs. Both the changing light field sizes and shapes, and the cast shadows and light color variations for LED luminaires are not covered by the current standard. The standard should therefore be extended to incorporate these aspects, especially for such a high-end application as surgical lighting.
A paired comparison experiment was performed to study the effects of spatial frequency and position on discomfort glare. The experiment required the subject to choose which of two stimuli, when presented together, caused more discomfort (termed the “choice” data), and then also rate how much more discomforting the one is than the other (termed the “magnitude” data). A rating scale experiment was also performed.
The UNL Glare Apparatus was designed and built with considerable flexibility so that a number of different types of glare experiments can be performed, with different types and sizes of stimuli. This paper describes its capabilities, its first use, as well as potential improvements.
The UNL Glare Apparatus was designed to systematically vary the four primary factors which affect discomfort glare, including source luminance, source size, source position, and background luminance. It was also designed to have considerable flexibility to research many additional independent and dependent variables. The theatrical lighting fixtures used in the apparatus caused a significant problem for scientific research: the output from the fixture did not produce a uniform illuminance on the target. A “uniformity” filter was created to produce uniform illuminance on the stimulus. This paper describes the non-uniform illuminance problem and the creation of a “uniformity” filter to correct the problem.