L Prize Lumen Maintenance Testing Update
Since winning the 60W lamp category of the L Prize in August 2011, the Philips-submitted entry has been undergoing continued lumen maintenance testing. In July, the Department of Energy (DOE) issued the latest report for the lamp, which surpassed the 25,000-hour mark in April. Two hundred lamps samples are operated continuously in an environment of 45 C and tested for relative lumen and chromaticity maintenance on a lumen maintenance test apparatus.
According to the DOE’s press statement, the light output of the winning entry has not altered significantly during the testing period, and the samples are operating at “greater than 100 percent of average initial output.” The competition only required a minimum of 70 percent lumen maintenance at the 25,000 hour benchmark.
Another important finding during testing has been that the color remains stable. Measured against the International Commission on Illumination (CIE) 1976 color diagram, chromaticity change was less than 0.002 after 25,000 hours. This is well within the competition’s stated tolerance of 0.004 at 7,000 hours of operation.
The latest report is one of the first “opportunities to confirm actual performance of a high-quality LED product at 25,000 hours.” For more details about the L Prize testing process, go to lightingprize.org.
DOE Fact Sheets
As LEDs and solid-state lighting systems continue to migrate into lighting and luminaire development, questions have arisen regarding the safety of LED lighting in relation to the human eye. To respond to these queries, the DOE has issued a SSL Technology fact sheet titled Optical Safety of LEDs.
The principal optical safety concern in association with LEDs has to do with what is referred to as the “blue light hazard.” Too much exposure to light in the violet and blue ranges of the light spectrum can result in photochemical damage to the eye’s retina. The new fact sheet indicates that white light LEDs do not pose “any more of a blue light hazard than other types of general-purpose light sources at the same color temperature.” The fact sheet along with others on LED basics, applications, and performance characteristics, can be referenced for free at ssl.energy.gov/factsheets.html.
DOE SSL Outdoor and Roadway Lighting Focus
One area in which solid-state lighting has made great strides is in the realm of outdoor and roadway lighting. High light-output along with maintenance and cost savings are some of the contributing factors that have made outdoor and roadway lighting such an appealing application-base for LEDs. To that end, the DOE has completed several case studies through its Gateway program and product testing through the CALiPER program for this lighting category.
Kansas City, Mo., and Washington, D.C., served as the two locations for the DOE’s most recent Gateway reports. The Kansas City project tested nine different LED luminaires that were first installed in February 2011 as part of a replacement program for existing high-pressure sodium (HPS) fixtures. The Washington, D.C., project looked at parking garage lighting and used a parking facility at the U.S. Department of Labor headquarters as the test location. Existing HPS luminaires were replaced with LED fixtures. Gateway reports can be found at ssl.energy.gov/gatewaydemos_results.html.
The DOE’s Municipal Solid-State Street Lighting Consortium has released Version 1.0 of its Model Specification for Adaptive Control and Remote Monitoring of LED Roadway Luminaires. This document has been created to aid cities and utilities in their switch to LED streetlight systems to reduce energy and maintenance costs. An “estimated 26.5 million streetlights in the U.S. consume as much electricity each year as 1.9 million households, and generate greenhouse gas emissions equal to that produced by 2.6 million cars,” said the report. The model specification, which has already been subject to a public review process, will be revised in future to reflect market changes. To download the model specification, visit ssl.energy.gov/control-specification.html.