DOE Releases L Prize Lumen Maintenance Report after 18,000 Hours of Testing

The U.S. Department of Energy (DOE) has published a report, Lumen Maintenance Testing of the Philips 60-Watt Replacement Lamp L Prize Entry, after completing 18,000 hours of lumen maintenance testing. Long lifetime is a much-touted potential advantage of solid-state lighting and one of the L Prize competition requirements. The minimum test period defined for the competition was reached in April 2011. Because the L Prize competition has provided an unprecedented opportunity to test some of the pivotal assumptions about LED lighting products, DOE continues to run the lumen maintenance testing of the Philips entry. This enables:

* Collection of independent, high-quality, long-term, statistically valid lumen and chromaticity maintenance data for the L Prize-winning LED replacement lamp product.
* Comparison of long-term data with lumen maintenance predictions based on shorter-term (6,000-hour) lamp aging data and LM-80-08 data for the LED packages used in the integral lamp.

The testing involves running 200 sample lamps continuously in a high-temperature (45°C, 113°F) test bed to simulate actual conditions, with a movable integrating sphere taking spectral measurements on each lamp at regular intervals. Data from the first 7,000 hours of operation showed lumen maintenance predicted with 95 percent confidence to be 97.1 percent at 25,000 hours—a level of performance that significantly exceeds the L Prize lumen maintenance requirement of 70 percent (L70). In July 2012, accumulated run time surpassed 18,000 hours. Using the latest data, key findings include:

* Very little change in light output
* Chromaticity remains well within the L Prize requirements
* Most recent data projects lumen maintenance will be 97.8% at 25,000 hours

The Lumen Maintenance report supplements the Stress Testing report posted in April 2012. To learn more, visit the L Prize Lab Testing webpage, or view the video below.

Craig DiLouie

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