Thermal Management of Outdoor LED Lighting Systems and Streetlights—Variation of Ambient Cooling Conditions

Abstract

Optimized cooling design of outdoor LED luminaires, and other outdoor electronics, is not possible without better knowledge of ambient cooling conditions and their variation. Temperatures and wind speeds have a significant effect on heat transfer between the enclosure surfaces and their surroundings. In the case of LEDs, where optical characteristics, reliability, and lifetime depend strongly on temperature, information on not only the worst case, but also on average operating conditions is needed. 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, respectively. Variation of local average and maximum night time temperatures is found to be significant from a thermal management point of view. 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.