Solid-state lighting, the LED in particular, has advanced to become a promising light source because of its ability to save energy and money, reduce environmental pollutants, and provide custom, quality lighting. This advancement could not have been achieved without industry collaboration. This year, the Lighting Research Center at Rensselaer is celebrating the 10th anniversary of the Alliance for Solid-State Illumination Systems and Technologies (ASSIST).
Since 2002, the Alliance for Solid-State Illumination Systems and Technologies (ASSIST)
has brought together a global group of lighting manufacturers, academia, public benefit organizations, and government to become an international resource for research, education, and demonstration of solid-state lighting. In the last decade, those with a stake in LED lighting have committed their time and resources to ASSIST because of the group’s focus on tackling industry issues and concerns; the collaborative model employed in which members meet to formulate questions and guide research; and the benefits from drawing on the LRC’s holistic knowledge of lighting. On behalf of ASSIST, LRC researchers conduct the alliance’s selected research and educational projects.
ASSIST members include Acuity Brands Lighting, Amerlux Global Lighting Solutions, Bridgelux, Cirrus Logic, Cooper Industries, Cree, Dow Corning, Federal Aviation Administration, GE Lighting Solutions, Industrial Technology Research Institute (ITRI), Intematix Corp., LG Electronics, LG Innotek, Lighting Science Group, Lite‐On, New York State Energy Research and Development Authority, OSRAM Sylvania/OSRAM Opto Semiconductors, Philips Lighting, POSCO LED, Sharp Laboratories of America, Seoul Semiconductor, Toshiba, United States Environmental Protection Agency, WAC Lighting, and WattStopper.
Nadarajah Narendran, professor, LRC director of research, and the director of the Solid-State Lighting program, said he appreciates the active support of ASSIST members and looks forward to continued success in the future.
“Going forward, ASSIST intends to maintain its collaborative approach to overcoming market transformation barriers,” said Narendran. “This will include knowledge creation and dissemination, demonstrating the value of solid-state lighting systems that create better lighting and more convenience, and new metrics to quantify this value. ASSIST will also continue to support test procedure harmonization around the world, and outreach education and support.”
In its first 10 years, ASSIST has made critical contributions to the development of LED lighting, including developing definitions and test methods that have informed the standards-setting process; demonstrating applications where LED lighting shows better performance and value; creating innovative concepts for using LEDs; and educating those with an interest in this next-generation technology.
Research to Inform Industry Practice, Overcome Market Barriers
Ten years ago, no standards and few definitions existed for LED light sources and lighting systems. Early claims promised LED lighting products to last 100,000 hours. The problem with this claim was it simply wasn’t true under realistic conditions. A single, bare LED might last that long, but once integrated into a lighting system, the LRC showed that LED life could be far less. The light output also could be considered too dim to be useful after a short period, thus shortening the system’s “useful” life. Long‐term life‐testing research led to the understanding that heat negatively affects LED life, and that there are many ways in which LEDs might be exposed to high heat. In turn, this led to research to develop methods of estimating the junction temperature of LEDs.
In 2005, ASSIST published the first document in the ASSIST recommends series, a definition for the end of LED useful life and a recommended test method for estimating LED life for general lighting. ASSIST recommends: LED Life for General Lighting became the basis for IES LM‐80, the Illuminating Engineering Society’s approved method for measuring the lumen maintenance of LED light sources, published in 2008.
Since developing the ASSIST life‐test method, on behalf of ASSIST the LRC has continued to investigate life issues and develop test methods for LED drivers and LED light engines (ASSIST’s test method for LED engines is the basis for the recently released IES LM‐82 standard). Further studies have explored how the application environment impacts performance, leading to ASSIST’s application‐based test methods for under‐cabinet lighting, directional and downlighting, which consider the impact of temperature in the typical operating environment. In turn, the application concept led to further ASSIST research to develop metrics that quantify the performance, or “application efficacy,” of luminaires; that is, how well they direct light and meet typical lighting requirements, rather than just how much light is emitted per watt. ASSIST’s application efficacy metrics for parking lot and roadway lighting, as well as an online calculator that incorporates these metrics, can be used by lighting specifiers to compare luminaires before purchase. (For details, see http://www.lrc.rpi.edu/programs/solidstate/outdoorTools.asp
ASSIST has also taken on other human factors-based technology research interests, including visual efficacy during nighttime conditions, light source flicker, discomfort glare, color rendering, and light source color appearance. This work brought the development of improved metrics for ensuring the best color rendering, calculation methods for estimating flicker and glare, and findings for white light source color preference.
Demonstrating Innovative Uses for LEDs
Because of the small, flexible, and durable nature of LEDs, it is possible for LED lighting to be more than just a replacement for traditional light bulbs. ASSIST has worked with various sponsors to demonstrate innovative uses and concepts for LED lighting, as well as applications where LEDs provide value over traditional lighting.
One application where LEDs provide greater value is in the frozen food aisle. Many supermarkets today illuminate their frozen foods with LEDs, which can withstand cold temperatures much better than the traditional fluorescent lighting found in older freezer cases. In 2002, the LRC began studying LED lighting for supermarket freezers in the lab. In 2005, LRC researchers followed up with an in‐store demonstration project and shoppers’ survey, sponsored by ASSIST member NYSERDA along with product support from ASSIST member GELcore (now GE Lighting Solutions). Then in 2008, ASSIST sponsored the development of a test method to evaluate the performance of luminaires designed for freezer display cases. Today, this application is mostly transformed, with new freezers employing LEDs and retrofit LED lighting kits available for existing fluorescent-lighted freezers. (For details, see http://www.lrc.rpi.edu/programs/solidstate/LEDFreezer.asp
In 2004, ASSIST provided seed money to develop and demonstrate a flexible interior infrastructure that could integrate solid‐state lighting with other building materials and systems. Such an infrastructure would allow for rapid reconfigurations of fixed, built‐in lighting, making it as easy to redesign lighting as it is to rearrange furniture. It would also allow for easy upgrade of LED luminaires as they improve in performance. In 2005, LRC researchers designed and built a full‐scale vignette of an executive office at the LRC’s laboratory to showcase a flexible infrastructure and to demonstrate the value in an easily changeable lighting design. In 2009, the California Energy Commission awarded project funding to the LRC to demonstrate this new concept. A prototype 24 volt dc electrical grid system with integrated LED lighting was built by project partner and ASSIST member OSRAM Sylvania and was installed in the walls and ceiling of a conference room at Paramount Pictures in Hollywood, Calif. The project is now under evaluation and is scheduled to be completed in the fall of 2012. (For details, see http://www.lrc.rpi.edu/programs/solidstate/or_adaptableSSL.asp
Over the past decade, the LRC has partnered with ASSIST members, including Boeing and the Federal Aviation Administration (FAA), to conduct research to advance lighting in aviation applications. The LRC has conducted system performance and human factors research to develop specifications for LED-based systems in a variety of applications. For Boeing, the LRC developed specifications for the interior lighting of the Boeing 787 Dreamliner. For the FAA, research findings helped in understanding the performance of taxiway lighting, guard lighting, and remote airfields, and brought new recommendations for light source color and intensity for better visibility to pilots. The findings from these studies are leading to revised FAA regulations that incorporate LED lighting and helping the FAA’s transition to LED-based airfield lighting. (For details, see http://www.lrc.rpi.edu/programs/solidstate/aviation.asp
Education and Training Seminars
Since early on, education has been a major focus of ASSIST. The alliance’s goal has been to help those interested in LED lighting to understand the state-of-the-art technology, thereby increasing the chance for LED’s market success. The LRC was the first to offer an independent, research-based university workshop that elevates participants’ knowledge of LED lighting technology and best practices for application. The biannual LED Lighting Institute along with other institutes for photometry and outdoor lighting, sponsored by ASSIST, as well as international seminars and conferences, have been educating lighting designers, architects, engineers, and other lighting professionals from around the globe for 10 years. Beyond the lighting community, ASSIST has published application guides and LED product selection how-to’s geared toward retail consumers and homeowners. (For details, see http://www.lrc.rpi.edu/programs/solidstate/SSLeducation.asp