Since 2000, the U.S. Department of Energy has invested with industry partners in research and development of solid-state lighting (SSL)—including both light-emitting diode (LED) and organic light emitting diode (OLED) technologies. Why such concentrated attention on SSL?
The answer is simple: because of SSL's rapid ongoing improvements and superior energy-saving potential. It is estimated that switching to SSL could reduce national lighting energy use by 75 percent in 2035, saving 5.1 quadrillion Btus—nearly equal to the total annual energy consumed by 45 million U.S. homes. DOE is not alone in recognizing the importance of that kind of savings; Congress recognizes it too, which is why the Energy Policy Act of 2005 mandates DOE to accelerate SSL technology.
The efficacy of LED light sources has already surpassed that of incandescent, halogen, high-intensity discharge, and linear fluorescent lamps, and will continue to improve. By 2020, LED luminaires will be capable of luminaire efficacies approaching 170 lm/W, more than twice that of a typical fluorescent fixture. The top 20% of indoor LED troffers listed on DOE's LED Lighting Facts database (indicated by the white band in the graph above) achieve an average of 131 lm/W, with a range of 124–168 lm/W lm/W.
Keeping a Foot on the Accelerator
Efficacies of 250-350 lm/W are seen as achievable and offer benefits beyond the enormous energy savings. The DOE white paper LED Efficacy: What America Stands to Gain outlines additional benefits, including:
- Scientific and technological advances that extend beyond lighting
- Better LED products that deliver improved lighting quality as well as enhanced services
- Lower first costs for LED lighting products, which in turn will encourage change-out of existing stock to more efficient devices
- Stronger positioning of domestic LED manufacturers who produce high value, high brightness LEDs.
Continued innovation and breakthroughs in materials, processes, product designs, control systems, and manufacturing are still needed to realize the technology’s full potential. Going forward, R&D priorities will also include breakthrough improvements to lifetime, color quality and consistency, and lighting system performance, as well as value-added features that increase the competitiveness of SSL products. In addition, R&D will target flexible production, testing, and monitoring technologies that will position the United States for sustained growth and leadership in SSL engineering and manufacturing.
In addition to energy savings, SSL presents a huge opportunity to improve the performance and value of lighting through enhanced controllability, new functionality, application-specific lighting performance, novel form factors, and targeted improved wellbeing and productivity.
LED sources are inherently dimmable and instantaneously controllable, and they can be readily integrated with sensor and control systems, thus enabling further energy savings through the use of occupancy sensing, daylight harvesting, and local control of light levels.
LEDs are at the heart of the recent push toward smart, connected, intelligent, and adaptive lighting. New functionality within the lighting system can add value by providing optimal lighting for the occupants and the tasks being performed through real-time controls, programmed sensor-driven responses, or learning algorithms. The high-speed modulation capability of semiconductor light sources has introduced new opportunities and features, such as indoor positioning capabilities.
LED technology offers the prospect of full color control over the light spectrum, and will enable precise control over the delivery of light to reduce glare, reduce stray light, and optimize useful light. It affords new levels of control to create new lighting opportunities in areas as diverse as horticulture and human health.
A Comprehensive Program
The DOE SSL program has been deeply involved in SSL R&D for over a decade, establishing both leadership and trust. DOE challenges industry with aggressive reach goals for efficacy and performance, and monitors emerging products to identify and characterize performance issues that prompt progressive R&D.
Modest yet highly strategic investments by DOE have helped to make the United States the epicenter of SSL innovation. DOE has spurred the lighting industry to achieve rapid improvements in efficacy, cost, and value-added features by investing in competitively selected cost-shared R&D projects that reduce the risks of early stage technology development. At the same time, DOE conducts foundational research, laboratory testing, and field evaluations to expand our knowledge base and inform technology development.
With annual workshops as well as periodic stakeholder roundtables, DOE's solid-state lighting program is open and participatory and coordinates with many lighting and standards-setting groups, such as the Illuminating Engineering Society of North America, the International Association of Lighting Designers, the National Electrical Manufacturers Association, the American National Standards Institute, and the National Institute of Standards and Technology. It's also highly transparent, publishing numerous reports and roadmaps that are posted online at this website.