An important part of a facility’s integrated security measures — parking lot lighting — doesn’t get discussed as much as it should be.
Nevertheless, it deserves a facilities manager’s attention on three fronts: Security, energy savings and uniformity (more consistency in illumination across surfaces) in performance.
A recent study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute demonstrates how these factors converge to provide improvements at a savings to facilities managers.
Researchers conducted a systems analysis, human factors study and field demonstration to discover the relationship between user acceptance, luminance and uniformity. The goal: To gauge and compare the performance of high-intensity discharge (HID) lighting fixtures versus LEDs in parking lots to generate more uniform beam patterns.
The study was a live test of a luminaire system application efficacy (LSAE) metric developed by the LRC’s Alliance for Solid-State Illumination Systems and Technologies in 2009.
This metric allows building designers and facilities managers to choose the best lighting at the right uniformity levels on parking lot surfaces while saving on energy.
“With the LSAE metric, we wondered if there was a possible tradeoff between illuminance and uniformity,” says Dr. Nadarajah Narendran, the LRC’s director of research and principal investigator of the study in a press release.
“In other words, if the lighting is evenly distributed across the whole parking lot, could we lower the total light level to save energy and still have people feel safe and secure?”
First, scientists invited users and guests the grade two kinds of uniformity — standard (10:1 ratio) and improved (3:1 ratio) — on its Troy, N.Y., parking lot at six different light levels.
Improved lighting delivered with better uniformity was the popular choice. In fact, participants gave lower scores when surfaces were lit at higher standard light levels.
Then, researchers did a performance analysis that compared a number of commercial parking lot lighting fixtures with a custom LED prototype designed for improved uniformity.
Overall, LEDs offered better uniformity than the larger HID fixtures, plus at a savings of as much as 75 percent, says Dr. Narendran.
For assistance with parking lot lighting at your facility, contact Vanguard Resources.