2014 IES Street and Area Lighting Conference
September 14-17, 2014 | Nashville, TN
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Results of modeling, experiments, and simulation of transmission of beam and diffuse daylight through straight circular light pipes with and without bends are presented. An analytic method is used in the development of an algorithm for tracing light rays that enter, are reflected from interior pipe surfaces, and eventually transmit from a pipe. Each bend section is modeled as a torus. For short straight pipes, the transmitted collimated rays at the exit ports form interesting geometrical patterns. Results from calculation of transmission of beam and diffuse daylight through straight pipes with and without bends match well with results from experiments. The paper also compares results from calculation of transmitted daylight illuminance when measured luminance of 145 standard sky zones are used to form entering rays, and when generated luminance of the same sky zones are used. The method presented is theoretical but lends itself to practical application.
Abstract—This paper analyzes the illuminance uniformity of 30 outdoor sports fields at various points in their service lives. The study was limited to the fields that employ 1500 W metal halide lamps with a rated life of 3000 hours. The sample was comprised of 12 soccer fields, 14 baseball fields, and 4 softball fields, all of which are owned and maintained by municipal parks and recreation departments. Five uniformity indices were computed for both measured illuminance and initial design calculations: maximum to minimum ratio (Max:Min), maximum to average ratio (Max:Ave), average to minimum ratio (Ave:Min), coefficient of variation (CV), and uniformity gradient (UG). Measured uniformity was rarely as good as the uniformity predicted by the design calculations. The uniformity of the baseball and softball fields was better with hours-of-use, with infields and outfields exhibiting similar trends. Max:Min, UG, and CV indices, as well as the illuminance of the transition area between infield and outfield, are suggested as key evaluation parameters. Group vs. spot lamp replacement, as-built vs. as-designed, dirt accumulation, and outgassing are factors that contribute to sports lighting uniformity.
X-ray computer tomography gained increasing interest last years, when it became affordable not only for medical applications. The diagnostic opportunities provided by X-ray computer tomography in end-of-life investigation of HID lamps are presented here. Limitations of this technique are discussed.
We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed.
SAE Recommended Practice J852 and ECE Regulations 119 and 48 for cornering lamps were compared. Photometric points described in each specification were then compared to naturalistic low-speed turn trajectories produced by 87 drivers. Future locations of a vehicle engaged in a turn were calculated based on the vehicle’s momentary position and speed, and the calculated time required to bring a vehicle to a complete stop. The angular offset and distance separating current and future positions were compiled to produce a map of useful preview positions—that is, positions relative to the current position of the vehicle that are far enough away to allow a driver to successfully stop if an object is first seen there. The distribution of preview positions shows strong concentrations between 30 and 35 degrees to the right or left of the current direction of travel. Geometric characteristics of this distribution were then compared to the geometry implied by the photometric minimum points indicated in the two specifications. Implications for path illumination during turns were discussed.