In a recent update from Jim Brodrick, Solid-State Lighting Manager for the U.S. Department of Energy, he outlined why, when it comes to LED lighting, it’s important to develop an approach to lifetime projection that takes into account catastrophic failure, lumen depreciation, and color shift all together.
With LED lighting, Brodrick explained that end of life is determined by whichever occurs first: catastrophic failure, unacceptable lumen depreciation, or unacceptable color shift. The latter two parameters are not absolute, but depend on the application. While LED lighting is less prone to shifts in color than are other lighting technologies, the long lifetimes of LED lighting products, which can last well beyond 50,000 hours, can make such changes more pronounced. In addition, the end of life for LED luminaires can be less evident than for conventional lighting, because changes in light output and/or color may be gradual.
To address the challenge of developing accurate lifetime claims, DOE, together with the Next Generation Lighting Industry Alliance, formed an industry working group, the LED Systems Reliability Consortium (LSRC). The LSRC has published three editions of LED Luminaire Lifetime: Recommendations for Testing and Reporting, focusing primarily on lumen depreciation and catastrophic failure. Those reports concluded that numerous subsystems and components in a luminaire, in addition to the LEDs, introduce potential failure modes. A new LSRC report, LED Luminaire Reliability: Impact of Color Shift, focuses on chromaticity. The purpose of the new report is not to define limits for specific applications, but rather to enable a better understanding of how and why color shifts, and how that impacts reliability. For more information, read the new report.