LED walkway lighting evaluated in DOE report

April 2, 2008
A report released by the DOE under its Gateway Demonstration Program evaluates a small installation at an FAA site in New Jersey.
LED walkway lighting The U.S. Department of Energy (DOE) has published the final report from the Federal Aviation Administration (FAA) demonstration of LED walkway lighting. This report, prepared by Pacific Northwest National Laboratory (PNNL), provides an overview of project results which include energy savings of more than 25% over existing lighting, improved illuminance uniformity, and positive user feedback.

The study furthermore found that energy savings could be cost-effectively increased to 50% through a slight reduction in the existing lighting levels, while still easily meeting IESNA minimum recommended illumination levels for walkways.

A PDF copy of the FAA demonstration report is available for download on the DOE SSL website on the Gateway Demonstration Program page. The Gateway Program showcases high-performance LED products for general illumination in a variety of commercial and residential applications.

HPS luminaire replaced by... In the project, six LED luminaires from Beta LED were installed to replace six existing high pressure sodium (HPS) luminaires mounted on 14-foot poles on a set of exterior walkways and stairs, situated between a pair of buildings and a parking lot located at the Federal Aviation Administration (FAA) William J. Hughes Technical Center in Atlantic City, New Jersey. Installation of the SSL product occurred in December, 2007.
...LED luminaire In this project, the SSL product demonstrated energy savings of more than 25% while maintaining illuminance levels and improving illuminance uniformity, compared to new high pressure sodium (HPS) lamps installed in the existing luminaires at the site.

As a new technology, LED luminaires cost more to initially purchase than the traditional, commodity-grade HPS light sources. Many factors contribute to the economic performance of LED luminaires in any given installation, so a range of payback scenarios are considered in the report.

The Beta LED product used in this project is modular, consisting of a series of “light bars” that each contain 20 LEDs. Adding (or subtracting) light bars from a given fixture increases (or decreases) both light output and final cost. The fixtures selected for this application used a 3-bar configuration (for a total of 60 LEDs) to produce illuminance levels similar to the existing HPS luminaires.

However, computer simulation has determined that 2-bar (40 LED) luminaires would also easily provide the IESNA recommended minimum level of illumination needed for this particular walkway application (minimum average of 0.5 foot candles), while going to the lower wattage luminaire would significantly reduce the payback period.

In a scenario where the old luminaire has to be replaced with either a new HPS luminaire or an LED luminaire(*), the payback period for LED lighting (including both energy and maintenance costs) is reduced from 7 to 3 years in going from the 3-bar to the 2-bar LED luminaire.

The report says that, in the future, the dramatic pace of improvement underway in both LED chip performance and price can be expected to continue reducing the premium on LED-based products. Both of these factors will lead to further reductions in the payback periods achieved from LED retrofits.

[*The alternative is to consider the cost of fitting a new LED luminaire versus retaining the old HPS luminaire; here the payback period is much longer.]