DOE releases update on LED-based lighting in harsh outdoor environment

The US Department of Energy (DOE) has released the third in a series of Gateway reports on a trial installation of LED-based luminaires in a harsh desert environment near Yuma, AZ. The continued research confirms that dirt is the major cause of unanticipated levels of lumen depreciation and in changes in the beam distribution at the outdoor solid-state lighting (SSL) project.

The DOE released the initial report on the Yuma project back in late 2014 with the outdoor SSL installed along a section of border fence separating the US and Mexico. A major focus of the project was testing LED-based luminaires in the harsh environment with severe temperature swings and high winds and blowing sand. The initial report indicated improved illumination relative to the legacy quartz metal-halide (QMH) lighting along the fence.

Still, even in the early stages of testing the DOE discovered that the lumen output of the outdoor SSL was depreciating faster than expected. Moreover, the light levels near the pole were increasing while levels were decreasing significantly away from the pole. In May of 2015, the DOE issued a second report documenting the continued change in output and pattern and noting that the researchers had yet to fully identify the cause. As we noted in our prior coverage, the DOE had removed two of the luminaires for laboratory analysis and replaced those fixtures with new models that were instrumented with thermal sensors.

The latest report includes an update on the installation after 7000 hours of operation. The average horizontal illuminance has decreased by 25% on the primary border fence and the average vertical illuminance decreased by 34%. Furthermore, the shift in beam pattern continued.

The latest report includes an update on the installation after 7000 hours of operation. The average horizontal illuminance has decreased by 25% on the primary border fence and the average vertical illuminance decreased by 34%. Furthermore, the shift in beam pattern continued.

The DOE, meanwhile, has not reported on the most recently installed luminaires that were instrumented for robust temperature measurements. The researchers have been logging data since September of 2015 and will continue to do so through the summer of 2016.