The U.S. Department of Energy has released a follow-up GATEWAY report on LED system performance at the Yuma (Arizona) Sector Border Patrol Area. Six LED luminaires – installed on three poles as part of a trial installation detailed in a prior GATEWAY report – continue to be monitored, with illuminance measurements recorded initially in February 2014 and again in September 2014 at about 2500 hours of operation and in March 2015 at about 5000 hours of operation.
 
Among the findings, measured data at the project site after nominally 2500 hours and 5000 hours indicate that the illuminances are changing more rapidly than anticipated. The distribution of illuminance also changed, with values nearest to the pole increasing while the values decreased farther away from the pole, and the greatest decreases were at the points farthest from the pole. The average horizontal illuminance decreased by 18% near the primary fence and vertical illuminance decreased by 25% on the primary fence. These changes in the illuminances delivered by the lighting system occurred after 2500 hours of operation, and persisted after 5000 hours of operation. There was no measured shift in the color of the light.
 
The Yuma site is an extreme environment: high ambient temperatures and direct solar radiation heat up the luminaires throughout the day, and at sunset the LED luminaires turn on and generate internal heat. A full understanding of the causes for the observed changes depends on understanding the effects of the ambient thermal conditions on the internal operation of the luminaire. DOE researchers are exploring plans for thermal simulations of the luminaire, as well as removal of one or more of the luminaires from the site for detailed laboratory analysis, and also plan to collect additional data from the site to more fully assess possible effects from dirt accumulation and other site-specific effects.
 
The full report and an accompanying brief are available on the GATEWAY Outdoor Projects webpage.