FINDING: A light source need not emit energy at every visible wavelength in order to achieve high color quality (see Figure 1.9). An understanding of the spectral power distribution’s effects on luminous efficacy and the color properties of a light source will enable SSL developers to optimize energy efficiency while maintaining good color quality.
FINDING: While it is difficult to discern the contribution of public policies on the adoption of energy efficient products, it is likely that a sizable fraction of the decrease in per capita energy consumption may be attributable to such policies, judging from a study of changes in energy consumption in California. However, the actual impact of any specific policy instrument is difficult to disentangle as is the impact on any one type of household energy use.
FINDING: Improvements in energy efficiency of lighting products have been brought about by a combination of legislation, regulation, RD&D funding, consensus standards, industry programs and initiatives, incentive programs, and market forces.
RECOMMENDATION 2-1: The Department of Energy should develop a study to quantify the relative impact of different policy interventions on the benefits of adopting efficient lighting.
FINDING: DOE has done an impressive job in leveraging a relatively small level of funding to play a leading role nationally and internationally in stimulating the development of SSL.
FINDING: In recent years, DOE has recently expanded its portfolio to include R&D into manufacturing projects, largely at the direction of Congress in the FY2009 ARRA funding and the FY2012 appropriations bill.
FINDING: The percentage of matching funds from R&D grant recipients was 18 percent for FY2011 funds. Ten years ago, for FY1999 to FY2001, it had been roughly 40 percent. It has declined in the past few years, particularly in the Product Development category.
RECOMMENDATION 2-2: The Department of Energy’s solid-state lighting program should be maintained and, if possible, increased.
RECOMMENDATION 2-3a: The Department of Energy should seek to obtain 50 percent cost-sharing for manufacturing research and development projects, as was done with the projects funded by the American Recovery and Reinvestment Act.
RECOMMENDATION 2-3b: As part of the next mandated study of the Department of Energy Solid State Lighting program in 2015, an external review should be conducted to provide recommendations on the relative proportions of funding that should be dedicated to core technology, product development, and manufacturing projects, and what the targeted level of matching funding should be in each of these three funding categories.
FINDING: DOE’s waiver of Bayh-Dole for projects funded by the SSL R&D program is discouraging some universities and small companies from participating in the program.
RECOMMENDATION 2-4: The Department of Energy should consider ending its waiver of Bayh-Dole for SSL funding.
FINDING: A technology-neutral specification for lighting would “raise the bar” for energy efficiency without putting the government in the position of picking and choosing which technologies should be included in ENERGY STAR®. Rather, those technologies that meet the specified criteria (e.g., luminous efficacy, color temperature, color rendering) would qualify for ENERGY STAR® labeling.
RECOMMENDATION 2-5: The Environmental Protection Agency should develop technology-neutral specifications for lighting that are based on performance rather than the type of lamp to provide the most objective and evenhanded standards for energy efficiency.
FINDING: The ENERGY STAR® program provides useful information to residential consumers on energy efficient lighting products. While the ENERGY STAR® program also has a commercial and industrial segment, that program focuses on overall building efficiency rather than the certification and labeling of individual products (with the exception of luminaires in commercial buildings subject to federal procurement). Many other government and industry organizations address lighting product standards for the commercial sector.
FINDING: The EISA 2007 requirements for phasing out inefficient lighting have sparked significant resistance by some legislators, states, and citizens in advance of the implementations of the requirements.
FINDING: Given the currently available lighting technologies, LPD allowances for commercial buildings have reached their practical lower limits, according to lighting professionals. In the long term, SSL may permit LPD allowances in building codes to be reduced further.
FINDING: Minimum building energy standards and model codes are steadily improving. Nevertheless, their adoption, as well as uniform and effective enforcement of adopted energy codes, would result in significant energy savings.
FINDING: Model energy codes for residential buildings only address the efficacy of light sources, not their number or their use. The approach taken by the California residential energy code may be more likely to improve energy efficiency.
FINDING: Non-regulatory incentive programs may play an important role in the adoption of energy efficient lighting technologies.
RECOMMENDATION 2-6: The Department of Energy, in consultation with the Department of the Treasury, should conduct a study to determine the effectiveness and impacts of incentive program designs in fostering adoption of efficient lighting technologies.
FINDING: Other countries are following similar regulatory pathways as the United States in phasing out incandescent lamps, although at different schedules and with some delays.
FINDING: Disposal of mercury-containing CFL lamps and perceived health impacts are causing concern by some citizens and states. Federal legislators and other actors promoting CFL lamps failed to adequately anticipate these perceived risks and concerns.
RECOMMENDATION 2-7: Policy makers should anticipate real or perceived environmental, health, and safety issues associated with solid-state lighting technologies and prepare to address such concerns proactively.
FINDING: The experience with CFLs provides a number of lessons for SSL, including the following: (1) the quality, reliability, and price of initial products will be a critical factor in the success and consumer uptake of the product; (2) market introduction and penetration take time; (3) manufacturers and others should take care not to over promise; (4) consumer education is critical; and (5) ENERGY STAR® and other credible performance standards can play important roles in raising quality and confidence.
FINDING: LEDs and OLEDs are complementary lighting sources that can together offer a wide range of lighting solutions. OLEDs can provide large-area diffuse lighting, while, in the same venue, LEDs form intense point sources, useful for spot illumination and downlighting. The committee finds value in supporting rapid developments in both technologies, because they both represent large possible markets, new applications, and tremendous energy savings.
FINDING: LED and OLED efficiency and performance are still limited by fundamental materials issues. Improvements in efficiency at the device and materials level, as targeted by the Department of Energy (DOE) SSL roadmap, will have a “lever effect”—influencing the design, performance, and cost of the luminaires. Therefore, improvements in efficiency and performance of the entire SSL system are linked to further fundamental investigations in core technology on emitter materials.
FINDING: Current LED dies used in SSL lighting suffer from inhomogeneities in the light output, color, and operating voltage that necessitate “binning” (hence testing) of dies from a single wafer. This variability severely constrains the yield of the manufacturing process and raises the cost of the technology. These inhomogeneities are in turn related to fundamental materials and materials growth issues.
RECOMMENDATION 3-1: The Department of Energy should continue to make investments in LED core technology, aimed at increasing yields, and in fundamental emitter research to increase efficacy, including improvements in the controlled growth and performance of the emitter material. DOE should carefully consider the range and depth of funding in its portfolio of investments in these areas, given the existing technological challenges, in order to determine how the targeted goals of device performance can indeed be met.
FINDING: Efficient operation of LEDs depends on a number of critical factors related to materials defects, structure, and strain. Such factors not only limit device efficiencies, but also lead to thermal and current droop; all have a major impact on the cost and performance of LED lighting.
FINDING: The color output of LEDs is extremely sensitive to the control of materials composition and thicknesses of the LED structure, which in turn are influenced by the control of the MOCVD growth process.
FINDING: A number of approaches have successfully been used to achieve and modulate color rendition for LED lighting. Phosphor-converted and color-mixed LEDs show promise but face different challenges. The ultimate choice of approach will depend on a multiplicity of issues regarding sensitivity of color control, efficiency, reliability, manufacturability, and cost.
RECOMMENDATION 3-2: The Department of Energy has provided excellent guidance in its roadmap targets for both phosphor-converted and color-mixed light-emitting diodes. Core investment in these technologies should be continued, with consideration for promising new technologies (e.g., quantum dot layers replacing phosphors).
FINDING: Production-scale MOCVD growth of LEDs is a complex process. The uniformity and yield of the structures grown (and hence of the optical performance of the LEDs) is strongly and negatively affected by small variations in the MOCVD growth process. The thermal and lattice mismatch between substrate and overlayer exacerbates the sensitivity of the growth process. Further difficulties of growth control are anticipated with use of substrates with increased diameter.
RECOMMENDATION 3-3: The Department of Energy should fund research to develop instrumentation for in situ monitoring and dynamic control of the metal organic chemical vapor deposition growth process.
FINDING: Significant improvements in LED efficiency, yield, and reliability are possible by using GaN substrates and latticed-matched epitaxial growth processes. Currently, there are no viable techniques for producing high-quality, low-cost GaN substrates. While realization of low-cost GaN substrates is not assured, the potential payoff of this research is immense.
RECOMMENDATION 3-4: The Department of Energy should make a long-term investment in the development and deployment of gallium nitride substrates.
FINDING: LED efficiency and performance is still limited by materials issues. Improvements in efficiency at the device level, as targeted by the DOE SSL roadmap, will have a “lever effect,” influencing design, performance, and cost of the luminaires. Improvements in efficiency and performance are linked to further fundamental investigations in core technology on emitter materials.
RECOMMENDATION 3-5: The Department of Energy should continue to make investments in light-emitting diode core technology and fundamental emitter research. Its portfolio of investments in these areas should be extensive enough to ensure that the targeted goals of device performance can indeed be met.
FINDING: A number of promising approaches have been developed to increase outcoupling efficiency.
RECOMMENDATION 3-6: The Department of Energy should focus on efforts that result in significant light outcoupling enhancements for OLED that are low-cost to implement and are independent of both wavelength and viewing angle.
FINDING: OLEDs show a decrease in efficiency as the current is increased. This results in a reduction in efficiency at high brightness.
RECOMMENDATION 3-7: The Department of Energy should support research to understand the fundamental nature of efficiency droop at high currents in organic lightemitting diodes and to seek means to mitigate this effect through materials and device architectural designs.
FINDING: The lifetime of OLEDs is very sensitive to extrinsic factors such as exposure to air and moisture. The low-cost fabrication of large area OLED lighting sources requires a high degree of fabrication competency that can ensure package hermiticity along the entire large package periphery and scavenge excess water and oxygen that might have been enclosed during the package manufacture.
RECOMMENDATION 3-8: To create a highly environmentally robust organic light-emitting diode (OLED) lighting technology, the Department of Energy should invest in materials and packaging technologies that make OLEDs resistant to degradation over their long operational lifetimes.
In particular, important areas for investment include finding low-cost means to eliminate glass as a primary package constituent, devising molecules and device architectures that are resistant to degradation on exposure to atmosphere, and developing sealing technologies that are fast, precise, and robust to bending.
FINDING: OLEDs are area light sources, and their rise in temperature, even at the highest drive currents (and hence brightness), is minimal. This is a major distinction from LEDs, which are intense point light sources and, hence, operate at high temperatures that require extensive heat sinking and care in their installation. Nevertheless, OLED operational lifetime is very sensitive to temperature increases. As the room temperature rises, the OLED lifetime can be expected to be noticeably decreased.
RECOMMENDATION 3-9: The Department of Energy should support the pursuit of material sets and device architectures that would increase the useful operational lifetimes of high-intensity white organic light-emitting diodes.
FINDING: This is potentially the single most important metric to meet in OLED lighting. It requires simplification of device structure, use of ultralow-cost substrates such as metal foils, development of replacements for costly transparent anodes (current technology is indium tin oxide), low-cost encapsulation technologies, and so on. Also, investment in equipment infrastructure is essential for the success of low-cost, manufacturable products. In-line vacuum deposition sources, roll-to-roll processes on flexible substrates, ultrahigh-speed organic vapor phase deposition, and in situ encapsulation techniques will all require substantial infrastructure development.
RECOMMENDATION 3-10: The Department of Energy should aggressively fund the development of all possible routes leading to significant (100×) cost reduction in organic light-emitting diode lighting sources.
FINDING: Extending the lifetime of blue phosphorescent OLEDs is a primary area where investment will have substantial payoff. It involves a combination of advances in the development of new materials, device architectures, encapsulation, and contact technologies, as well as a fundamental advance in the understanding of degradation processes. Interactions between the phosphor and the conductive host will have an influence on mitigating efficiency droop, or the de-excitation of the molecules in the OLED. The mechanisms for thermally induced degradation also require clarification. Encapsulation compatible with flexible, lightweight substrates is also an important area of development.
RECOMMENDATION 3-11: Given the interactions between the phosphor and the conductive host molecules, the Department of Energy should direct studies for determining what chemical structural combinations lead to the most robust materials sets. Fundamental studies of the degradation mechanisms should be carried out both at room and elevated temperatures. Research on understanding contact and ambient degradation routes and their minimization should also be supported.
FINDING: Increased outcoupling remains the single most beneficial route to increasing device efficiency from the current 100 lm/W to nearly three times that value. Methods to achieve this should be inherently very low cost and deployable over very large areas, even in the context of roll-to-roll manufacture. The outcoupling technology should have the additional attributes of being wavelength and intensity independent, and the light source should exhibit no color shifts as the viewing angle is varied from normal to highly oblique. Clearly, a viable outcoupling technology should not otherwise impact or degrade OLED performance.
FINDING: While the majority of LED products in the marketplace have better luminous efficacy than traditional lighting technologies, for many of them, other quality factors, such as useful life, color appearance and rendering properties, beam distribution, flicker, and noise, may be inferior to traditional lighting products. Even though the optimistic view is that energy has been saved by using SSL technologies, if other factors such as system life, lamp to lamp color variation, glare, flicker, and dimming, do not meet user expectations, they could slow down market adoption of SSL technologies.
FINDING: LED efficacy strongly leverages cost, physical size, and weight of SSL luminaires.
RECOMMENDATION 4-1: The Department of Energy should place a high priority on research directed at increasing the efficacy of LEDs.
FINDING: OLEDs are typically low-intensity, large-area lighting sources. However, numerous applications require more intense, specular lighting as afforded by LEDs. The lifetime of OLEDs are negatively impacted by high currents used to generate high brightness.
RECOMMENDATION 4-2: The Department of Energy should invest in research that can lead to small area but highintensity lighting systems with organic light-emitting diode for use in directional illumination applications.
FINDING: Because of the large number of different ways to construct an LED lamp, industry has recognized the need for some levels of standardization and has organized to develop such standards.
FINDING: OLEDs are still in their infancy. While the driver electronics may have many similarities to that of LEDs, there are some essential differences in their operating performance because of the large capacitive load presented by OLEDs.
FINDING: LED replacements for incandescent lamps may not work with all existing control infrastructure, especially dimmers.
RECOMMENDATION 4-3: Industry should develop standards for LED drivers and future generations of lighting controls that will ensure that all LEDs that are designated “dimmable” work well with all new dimmers in the future. In the meantime, SSL products should indicate on their labels that they may not function correctly with presently installed controls.
FINDING: Additional standards or revisions to standards are needed to resolve unknowns that will otherwise be left to consumers and other lighting decision makers to resolve, specifically test procedures and/or de-rating factors that account for higher temperature environments, where performance may vary from LM-79 data, and alternatives to LM-80 that can predict whole product life more accurately. In the case of the latter, research is under way to develop test procedures to predict whole product life more accurately.
RECOMMENDATION 4-4: (a) Manufacturers should publish data for photometric quantities and life per industry standards and de-rating factors for use in typical applications. (b) IESNA should develop a test procedure to predict whole product life more accurately. (c) ANSI should revise the color binning standard to ensure imperceptible color differences between two adjacent light sources.
FINDING: There are existing standards for THD and PF for electronic ballasts for linear fluorescent lamps, but at present there are no such residential standards for LED drivers that are external to the lamp. Standards for low-wattage, integrally ballasted CFLs with medium screw-bases in residential applications allow low PF and high THD.
RECOMMENDATION 4-5: For external solid-state lighting drivers in general, industry should adopt the same total harmonic distortion and power factor standards that are in place for electronic ballasts for linear fluorescent lamps. Industry should revisit the standards for low-wattage medium screw-base lamps to determine their impact on power quality before applying them for light-emitting diode lamps, and these standards should match those for commercial and industrial applications.
FINDING: The power requirements and flexible physical configurations of SSL make attractive the concept of a new dc building lighting infrastructure.
RECOMMENDATION 4-6: The SSL industry should collaborate with other industries such as building materials and construction to explore the challenges and potential benefits of developing and adopting standards for a new dc electrical infrastructure.
FINDING: Replacing incandescent or fluorescent lamps with LED lamps provides an opportunity to greatly reduce power load and increase lamp life. They can also turn on instantly and are able to dim. The market for these lamps will only expand as the light and color quality improve and the costs are reduced.
FINDING: The best LED applications take advantage of the directional light put out by LEDs, such as downlights, wall washers, and grazing and accent lighting.
FINDING: Omni-directional LED lamps are not as efficient as linear fluorescent lamps. In order to become a viable replacement alternative for linear fluorescent lamps, SSL products need to improve efficacy, become more omni-directional, and reduce initial cost in order to compete with fluorescent lamps.
FINDING: SSL must have power quality standards to mitigate against high THD, low PF, and repetitive peak current issues.
FINDING: New dimmers must be able to operate LED luminaires and lamps smoothly without perceptible flicker and should be available to dim from 100 percent power to 1 percent power.
FINDING: Industrial applications of SSL products will require higher light output for ambient lighting because of their use in high ceiling applications.
FINDING: Discomfort or disability glare can be an issue with directional LED luminaires. Luminaires must be designed so as not to increase glare potential compared to their HID counterparts.
FINDING: LED white light products produce light in spectral regions that may create environmental and health concerns. These concerns should be recognized in the design and application of LED luminaires.
FINDING: Exterior lighting is a prime candidate for early adoption of SSL because of the lower lighting levels required in such applications and the optical control, long life, and dimmability characteristics of SSL.
FINDING: Were OLEDs to become commercially viable, they would provide an opportunity to change the form factors of how luminaires are designed with smaller sizes, less material, and fewer physical constraints and offer an ability to change from traditional-looking luminaires to internally lighting surfaces and materials.
FINDING: Replacing existing incandescent lamps with LED lamps in existing luminaires may under certain conditions cause the LED to overheat. Examples include downlights adjacent to insulation or in enclosed luminaires. This is true also of the use of SSL in industrial applications having higher ambient temperatures. LED lamp heat management needs to be addressed for all such applications.
FINDING: Many LED lamps currently available do not have the same light output and color rendering properties as incandescent lamps. SSL products with improved light output that are color consistent from product to product will be needed for the public to readily accept these as replacements for incumbent lighting technologies.
FINDING: There is no standardized method for measuring the lifetime of SSL products.
FINDING: The CRI does not always yield results that predict or evaluate performance well, so manufacturers cannot rely on it to guide product development.
FINDING: To make LED-based luminaires and lamps at high efficacies (notionally those exceeding 150 lumens per watt) at prices lower than fluorescents, technological and manufacturing breakthroughs will be needed.
RECOMMENDATION 6-1: The Department of Energy should concentrate its funding on light-emitting diode core technology and fundamental emitter research that have the potential to lower costs of solid-state lighting products.
FINDING: There are currently no industry-accepted accelerated life tests for SSL products, which slows the development and deployment of new reliable products.
RECOMMENDATION 6-2: The Department of Energy should continue efforts to help develop accelerated life tests for luminaires and LEDs.
FINDING: The labels designed by DOE and FTC for lamp packages help consumers better understand the characteristics of the product they are purchasing, but important information is missing from the labels that would help consumers to better differentiate products and assign value to the products.
RECOMMENDATION 6-3: The Federal Trade Commission should conduct a study in 2014, 2 years after introduction of the label, to determine the effectiveness of the labeling and whether it could be improved by additions and/or changes.
FINDING: The move to new lighting is changing the entire vernacular used for lighting. It is going to be critical to label products in a clear way and educate retailers, consumers, lighting designers, and contractors on the opportunities and challenges with these new lighting technologies. To this end, EISA 2007 authorized $10 million a year to advance public awareness, but this money has not been appropriated.
RECOMMENDATION 6-4: The Department of Energy and lamp manufacturers and retailers should work together to ensure that consumers are educated about the characteristics and metrics of the new technology options.
RECOMMENDATION 6-5: The Environmental Protection Agency in conjunction with the Department of Energy should conduct a study to understand the environmental impacts of SSL and to determine potential disposal strategies, if necessary, that should be developed as SSL deployment develops.
FINDING: Without appropriate data on consumer lighting use, it is difficult to establish an appropriate baseline of energy use in lighting and benchmark energy lighting efficiency.
RECOMMENDATION 6-6: The Energy Information Administration should collect data on energy demand for lighting through the Residential Energy Consumption Survey, the Commercial Energy Consumption Survey, and the Manufacturing Energy Consumption Survey. These efforts need to be pursued on a consistent basis and should consider adding questions that would increase the accuracy and usefulness of the data. In addition, detailed lighting market characterization based on nationally representative surveys, such as the 2001 Lighting Market Characterization from the Department of Energy, need to be pursued every 5 years. It would be helpful if these surveys are available before this study is updated in 2015.
FINDING: On a life-cycle basis, warm and cool white LEDs are already cheaper than incandescent lighting and will likely be comparable to that of fluorescent lighting technologies in the near future. For applications where the daily usage is larger than 10h/day, cool white LEDs have now a similar consumer cost to CFLs or T12.
FINDING: As discussed in this chapter and in previous chapters, demonstration, outreach, and public and industry education programs are important for widespread adoption of SSL products and can help to avoid the problems encountered during the introduction of CFLs.
RECOMMENDATION 6-7: The Department of Energy should take a leadership role, in partnership with the states and industry, to examine and clearly identify opportunities for demonstration, outreach, and education so that its activities in support of SSL deployment are most valuable.
FINDING: Government agencies that manage building assets can play a larger role in helping the deployment of energy efficient SSL.
RECOMMENDATION 6-8: The Office of Management and Budget should develop criteria for determining life-cycle costs and for including social costs in evaluating energy purchases and incorporating this methodology into agency procurements.
RECOMMENDATION 6-9: Government and industry should continue to provide support in a cooperative and comprehensive manner to upstream, midstream, and downstream market actors and should support market activities evenly.