L-Prize; Bright Tomorrow Lighting Prizes

Lab Testing for Philips Entry

All L Prize entries go through an extensive laboratory testing process to ensure that winning products meet the competition's stringent requirements in areas including exceptional efficacy, long life, form factor, and suitability for mass manufacturing. A Technical Review Committee (TRC) reviewed all reports, test results, findings, and documentation for the Philips entry, and determined that it met the requirements.

Short-Term Testing

In Spring 2010, the Philips 60W replacement entry completed the first stage of the evaluation process: photometric testing. More than 200 samples of the product were subjected to LM-79 procedures measuring luminous flux, intensity distribution, correlated color temperature and chromaticity, color rendering index, and power factor. Instrumentation used in the testing included an integrating sphere and goniophotometer. Testing was conducted at two CALiPER-qualified labs: Independent Testing Laboratories, Inc., in Boulder, Colorado, and OnSpeX/CSA International in Atlanta.

L Prize Requirement Philips Result
(average for 200 units)*
Luminous flux (lumens, lm) > 900 lm 910 lm
Wattage (W) ≤ 10 W 9.7 W
Efficacy (lm/W) > 90 lm/W 93.4 lm/W
Correlated color temperature (CCT) 2700-3000 K 2727 K
Color rendering index (CRI) > 90 93

*NOTE: TRC approval was based on a complete analysis of the distribution of values for each parameter, not just the average values.

High-temperature test bed Photo

Long-term testing of the L Prize entry was conducted
in a specially designed high-temperature test bed.

Long-Term Testing

In June 2010, the next stage of evaluation began: long-term lumen maintenance testing. The 200 samples were sent to Pacific Northwest National Laboratory to be tested in a new high-temperature testing apparatus specifically designed for the L Prize competition and built with assistance from Orb Optronix. The test bed was maintained at 45°C to simulate actual operating conditions and the lamps were operated continuously through the 25,000 hour mark, to take advantage of the first public opportunity to confirm actual performance of a high-quality LED lighting product. A movable integrating sphere (light measurement device) took spectral measurements on each lamp every 100 hours for the first 3,000 hours of operation, and every 168 hours (weekly) thereafter. Data for the first 7,000 hours of operation were used to predict lumen maintenance of the lamps at 25,000 hours. With 95 percent confidence, lumen maintenance was predicted to be 97.1 percent* at 25,000 hours, which significantly exceeds the 70 percent L Prize requirement. At 25,000 hours of testing, the actual lumen maintenance was 100%, and chromaticity change remained less than .002. A selection of 31 of those lamps passed the 50,000-hour point of continuous operation in August 2016. Their average lumen maintenance after 50,182 hours was 93.0%, with no failures, and the average chromaticity change was 0.002. These results show that well-designed LED integral lamps can operate very reliably over long periods of time, with excellent lumen and chromaticity maintenance, and validate the methods being used for predicting performance.

Read the updated report on lumen maintenance testing of the Philips 60W L Prize entry.

Predicted vs. Actual Results at 25,000 Hours L Prize Requirement Predicted Philips Result
(95% confidence, 200 units)
Actual Results
Lumen maintenance at 25,000 hours 70% 97.1% 100%
Color maintenance (change in color point as measured on the CIE 1976 (u',v') diagram) <0.004 0.0006 <0.002

*Projected lumen maintenance was originally reported as 99.3%. Subsequently, an error in the projection calculations was discovered, and the correct figure is 97.1%.

Photo of CFL and Philips L Prize lamp stress testing

Philips L Prize entry lamps were subjected to multi-level stress testing alongside benchmark CFLs.

Stress Testing

Independent stress testing was conducted by Intertek Laboratories using a proprietary method called Failure Mode Verification Testing (FMVT). This stress testing consisted of a simultaneous combination of electrical, thermal, vibration, and humidity stresses which were increased over 14 stress levels. Tests were benchmarked against good-quality, commonly available 60W replacement compact fluorescent (CFL) lamps. Throughout the testing, photometric performance was conducted to assess any changes in performance as well as failures.

During 10 levels of increasing stressors, including extreme maximum and minimum temperatures, vibration, high and low voltage, high humidity, and various electric waveform distortions, two-thirds of the CFLs included in the tests failed, but none of the Philips L Prize lamps failed. The remaining CFLs failed upon additional incremental stressing, while the Philips L Prize lamps continued to operate.

Read the report on stress testing of the Philips 60W L Prize entry.

Learn more about solid-state lighting at the U.S. Department of Energy Solid-State Lighting Web site

Last Updated: November 1, 2016
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