2014 IES Street and Area Lighting Conference
September 14-17, 2014 | Nashville, TN
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Optimized cooling design of outdoor LED luminaires is not possible without better knowledge of ambient cooling conditions and their variation. Temperatures and wind speeds effect heat transfer between the enclosure surfaces and their surroundings. Optical characteristics, reliability, and lifetime depend strongly on temperature. This study presents outdoor night time temperature and wind speed data for 50 locations worldwide. Dew point temperatures, precipitation and snowfall data are also discussed. The average night time temperature and wind speed are found to be 12.5 degrees Celsius and 3.1 meters per second. Variation of local average and maximum night time temperatures is found to be significant factor for thermal management. Wind speed is, on average, above zero over 90% of the time, suggesting its effect on convective cooling of outdoor LED luminaires should not be neglected. The data indicates that the design parameters for optimized cooling of outdoor LED luminaires vary significantly between installation locations. In an example simulation presented, over 40% reductions in weight and cooling area are achieved using a location specific approach. The data presented provides information on cooling parameter variation, as well as on the average and worst case night time ambient conditions experienced by outdoor LED luminaires. The information should be taken into consideration in luminaire cooling design, as well as in research on thermal management, reliability, and optical performance of outdoor LED lighting systems.
The analysis of plasma temperatures by self-reversed mercury lines is well established in the diagnostics of HID lamps. In mercury-free HID lamps or mercury containing lamps including a complex fill, however, the analysis of mercury lines could be impossible or difficult because additives may disturb the spectral line shape. This work analyzes the suitability of self-reversed scandium lines for temperature determination using Bartels method. Temperatures obtained by the three scandium lines analyzed here were found to agree very well with results from mercury lines, demonstrating their applicability as a diagnostic tool in multicomponent HID lamps.
The introduction of solid-state lighting and high-power light emitting diodes (LEDs) has initiated a new generation of surgical luminaires. When designing a virtual prototype it would be beneficial to have a cost- and time-effective method to test luminaires for compliance with the European Standard for surgical luminaires, which defines regulatory requirements and performance indicators that are used by hospital managers and surgeons to compare surgical luminaires. Unfortunately, far-field intensities do not allow an evaluation of these luminaires with respect to the standard and near-field ray-data must be used. To validate this near-field approach, we used angular- and spatially-resolved ray-data of a luminaire and modeled a virtual setup that corresponds to the setup used in the European Standard. This paper compares illuminances obtained from simulations and photometric measurements. Good agreement was found: relative differences between simulations and measurements for the central illuminances deviate maximally 0.4 percent (+ 3.2 percent, -0.4 percent), while the maximum difference for the various scenarios amounts to 5.6 percent (˜ 2.2 percent). The technique can be applied to virtual prototypes of surgical luminaires that are composed of optical components such as reflectors and lenses and use spatially- and angular-resolved luminance-data of individual LEDs. This permits a compliance check with the European Standard before assembly, allowing for the more economical and time-effective development of new luminaires that maintain the quality requirements.
Two LED streetlighting luminaires were installed in the city of Al-Ain, United Arab Emirates, one of the hottest regions in the world. The street was closed to traffic and illuminance measurements were taken daily every 10 minutes for 300 days including the summer of 2010. Temperature and relative humidity values were acquired inside the driver compartment of the luminaires and outside of the luminaires. This paper reports the illuminance levels, temperature, and relative humidity data. Illuminance did not change by more than 12 percent throughout the test period. The drop in illuminance was 4.5 percent per 10 degree C for the ambient temperature range of 20 to 40 degrees C.