Luminaire Dirt Depreciation (LDD): Field Data from Several Exterior Lighting Projects

ABSTRACT

Luminaire dirt depreciation (LDD) data were evaluated for seven luminaires from three different project sites in Philadelphia, Pennsylvania, Minneapolis, Minnesota, and Yuma, Arizona. In each case, the luminaires were removed from the installation, carefully packaged and transported to a photometric testing laboratory, and then tested in the “as-is” or dirty condition, cleaned, and retested. In terms of light output, the results showed that the IES RP-36-15 method for estimating LDD was applicable to the light emitting diode (LED) luminaires evaluated. General claims of lower levels of dirt deprecation (or higher LDD values) for LED luminaires than for luminaires using conventional light sources were not supported by the test data for the LED luminaires in these three projects. Though the overall measured lumen depreciation due to accumulated dirt closely matched IES estimates for LDD, the data indicated that the accumulated dirt on the luminaires dramatically altered the luminous intensity distribution of the luminaires, with reductions in intensity of more than 25% at peak angles. These effects on luminous intensity distribution are not accounted for in IES LDD estimates.

KEYWORDS:

• LED sources and systems
• luminaires
• maintenance
• optics and luminaire design
• roadway lighting

Disclosure statement

The authors report no conflicts of interest.

Notes

1. For a detailed history of IES LDD procedures, see Levin et al. (2002), Davis and Partridge (2005), and IESNA (2016).

Additional information

Funding

The original reports on the three projects, the additional analyses of the long-term LDD data, and the preparation of this article were supported by the U.S. Department of Energy’s Solid-State Lighting Program, under contract DE-AC05-76RL01830, and the Office of Energy Efficiency and Renewable Energy.