More efficient and environmentally-friendly LED designs will allow designers, businesses, and consumers to illuminate locations both indoors and out more economically, will improve recyclability, and will cut waste. Such designs could even make more expensive multiple LED units attractive to new lighting markets, as they last longer and have become easier and cheaper to repair.
Giulio Antonutto, Lighting Associate with architectural consultancy Arup1 at an industry conference this year at Bath University, UK2 described several LED-based solid-state-lighting (SSL) problems that remain unsolved. “We need to achieve a more aesthetic, even distribution of light so that the viewer does not see point sources,” he said.
“Furthermore, as ever, we need more efficient electrical-optical conversion and improved recyclability of the materials and components that go into LEDs and luminaires. The problems of temperature management and color rendering persist.” Antonutto predicted that if this last problem can be solved, the whole face of the urban-lit environment could be changed.
Arup’s own survey of 15 key lighting designers revealed current development priorities for LED-based lighting: quality of light, including color rendering and temperature; evenness of light distribution; output; cutting associated costs; temperature management; and ease of maintenance, presumably last in line because SSL units of the future are forecast to last much longer – maybe forever.
One indication of the scale and potential of energy efficiency improvement through greater deployment of LED lighting was recently given in a statement3 issued by Jim Haworth, CEO of US LED developer Lighting Science Group, regarding the US Government’s consideration to pass the Better Use of Light Bulbs Act, (H.R. 2417). "Energy efficiency is the most powerful and cost-effective tool for achieving a sustainable future. Improvements in energy efficiency can reduce the need for investment in energy infrastructure, cut fuel costs, increase competitiveness, improve consumer welfare, and significantly reduce greenhouse gas emissions.
"Lighting is the low-hanging fruit in reducing energy consumption: it accounts for 19 percent of the world's energy use — and in the United States, 22 percent; public and commercial buildings represent 60 percent of the power used for lighting, as up to 80 percent of offices are lit by outdated and inefficient systems; and lighting accounts for 15 percent of household electricity use. Lighting Science Group and other companies are producing lighting products today that deliver on the promise of ultra-efficient and long lasting LED technology and we are saving consumers, businesses, and governments significant amounts of money."
This article describes some of the recent major developments by many of the key LED developers, which are trying to boost electrical-optical conversion efficiency while reducing the environmental impact of their products.
OSRAM Opto Semiconductors
Powerful, efficient long-life light sources are important for lighting systems that are in operation round the clock, such as those used in industrial environments, as well as architecture, entertainment, commercial horticulture, and signage. The latest chip developments make the new generation of OSRAM Opto Semiconductors’ OSLON SSL LEDs attractive as light sources. They offer high efficiency and good thermal stability, combined with a low thermal resistance of 7°K/W.
OSLON SSL LEDs give up to 20 percent more output than their predecessors and offer improved thermal stability, particularly in Hyper red (660 nm). Energy-demanding applications are therefore much more efficient. Supporting this boost in performance are OSRAM’s latest developments in indium-gallium-aluminum-phosphide chip technology (InGaAlP).
Figure 1: OSRAM OS’s OSLON SSL LEDs deliver 20 percent higher output than previous models and offer improved thermal stability, particularly in “Hyper red” (660 nm).
Depending on the wavelength (in the range 590 - 660 nm), these LEDs achieve performance improvements of up to 20 percent, such as attained by the Hyper red version (660 nm). With a brightness of 400 mW at an operating current of 400 mA, this LED converts 46 percent of current into light. At its optimal operating current of 350 mA, it achieves an output of 355 mW, equivalent to a conversion rate of 49 percent. These LEDs also have a long operating life. At a current of 700 mA and a temperature of 80°C, a unit will last more than 100,000 hours.
With their compact package size of just 3 x 3 mm and choice of beam angles (80° and 150°), the OSLON SSL LEDs are suitable for clustering, so high brightness can be achieved on a small footprint.
Cree has launched its 21st Century Lamp – an LED light bulb, which the company says redefines what is possible with high-performance LED lighting. The lamp delivers more than 1,300 lm at 152 lumens per watt (lm/W). Announced in August 2011, this prototype bulb exceeds the standard demanded by the US Department of Energy for the 21st Century Lamp, the third category in its L PrizeSM competition.
Figure 2: Cree’s 21st Century Lamp is an LED light bulb that delivers more than 1,300 lm at 152 lumens per watt.
Neal Hunter, Cree co-founder, commented, “Not long ago, fixture efficacy of more than 100 lm/W was impossible, but we are now shipping fixtures at 110 lm/W. If fully deployed, LED lighting at 150 lm/W could lead to a 16.5 percent reduction in the electric-energy consumption of the United States alone.”
LED lighting at this level of performance is enabled by advances in design across all components from lighting-class LEDs, optical elements, and drivers through to power supplies. Optimizing each element has been critical in achieving the new lamp. As an efficiency comparison, a traditional 75 W incandescent light bulb produces 1,100 lm at only 14.6 lm/W. Independent testing by OnSpeX laboratory has confirmed that the Cree lamp delivers more than 1,330 lm and consumes only 8.7 W, a greater than tenfold improvement in efficiency.
Lighting Science Group Corp.
A partnership between LED manufacturer Lighting Science Group and Dixon Technologies, an electronics technology company based in Noida, India, could lead to a reduction in the price of LEDs. The companies unveiled their first joint product, an omnidirectional 60 W-equivalent A19 LED bulb priced below $15. Lighting Science Group is expected to release the bulb to the international market in 2012.
Atul Lall, deputy managing director of Dixon Technology, said, “With 800 million incandescent light bulbs and 300 million CFLs sold in India each year, the market is ready for these highly efficient, long-lasting, and nontoxic products. Conventional incandescent bulbs use 60 billion units of electricity each year, 7 percent of India's total. Lighting Science Group’s Definity lamps could save over 70 percent of that."
The Definity bulb uses 85 percent less electricity than a conventional incandescent source. When compared to CFLs, the bulb saves 35 percent more energy, and contains no toxic mercury.
Figure 3: LSGC’s Glimpse LED lighting unit, which adapts to most 5 in and 6 in recessed downlight cans, cuts energy usage by up to 80 percent while giving an operating life up to 25 times that of traditional incandescent sources.
Lighting Science Group’s Glimpse LED-based downlight bulb offers an improved thermal design that reduces the amount of raw materials needed for assembly. Jim Haworth, CEO, commented, "The Glimpse ranks among the greenest LED fixtures on the market today. In effect, we have pioneered a product that not only consumes fewer initial resources, but because Glimpse is fully recyclable and free of toxic hazards including mercury, it also generates virtually no waste."
The Glimpse's low profile form factor adapts to most 5 and 6 in. recessed downlight cans, and transforms them into high performance LED fixtures, enabling both a reduction of energy usage of up to 80 percent and a life up to 25 times longer than traditional incandescent sources.
LED manufacturer Bridgelux was named in the annual Global Cleantech 100 list4, which recognizes the leading companies in areas such as water and waste, renewable energy, and energy efficiency that are forecast to make “a significant market impact” over the next five to ten years. Bridgelux CEO Bill Watkins commented, “This honor validates our ongoing efforts to provide smart, energy-efficient solid state lighting solutions. We continue to invest in the advancement of solid state lighting with our breakthrough in GaN-on-Silicon technology, while we continue to deliver leading GaN-on-Sapphire array solutions.”
Sheeraz Haji, Cleantech Group CEO, noted, “The Global Cleantech 100 list is a leading resource in the clean technology sector. Stakeholders, including members of the corporate community, investors, and regulators, watch the Global Cleantech 100 list closely to gauge which sectors look most promising and which companies are poised for growth.”
40 W replacement market ‘worth billions’
Bridgelux has also announced an expansion of its portfolio of solid-state light sources to address the requirements of the $1 billion 20 to 40 W lamp replacement market with the introduction of the Micro SM4. This source delivers high flux density in a smaller footprint, making it suitable for applications where discrete LEDs are preferred.
Figure 4: With the launch of its Micro SM4 LED, Bridgelux is targeting the estimated $1 billion 20 - 40 W lamp replacement market.
The Micro SM4 dramatically reduces the component count, cost, complexity, and size of lighting systems, enabling a cost-effective, high performance LED solution for diffuse and directional lighting, such as 20 to 40 W incandescent, 20 to 35 W halogen, B10-style (candelabra), and low wattage compact fluorescent lamp replacements.
Requiring only 4.6 W of power, this LED delivers up to 520 lm in warm white (2700 K, 3000 K) and cool white (5600 K) color temperatures. Minimum 80 and 90 CRI options, with three-step MacAdams Ellipse color selections, will be offered for warm white products.
Avago Technologies has launched three series of high-brightness oval through-hole LEDs designed for electronic signage applications. The design of the HLMP-Lx75, HLMP-Hx74/75 and HLMP-Ax74/75 LEDs reduces the current required to drive displays. The LEDs’ matched RGB radiation pattern maintains consistent light and uniform color mixing from all viewing angles. This combination enables sharper viewing quality with lower power consumption for full-color signage in a wide variety of applications such as billboards, stadium video screens, building video walls, as well as for simpler roadway and commercial signage.
Figure 5: Avago’s HLMP-Lx / Hx / Ax series of LEDs offer cost savings through lower power consumption and reduced maintenance, the company states.
These LEDs offer a typical viewing angle of 40° by 100°, while the HLMP-Ax74/75 LEDs offer 30° by 70°. The wide typical viewing angles and the high luminous intensity of the LEDs deliver optimal performance for outdoor applications. The red AlInGaP LEDs are available at 626 nm dominant wavelength, and the green InGaN and blue InGaN LEDs are available at 530 and 470 nm, respectively. Francis Khor, Avago’s director of marketing, optoelectronics, said, “These efficient and durable LEDs provide superior viewing performance and cost savings through lower power consumption and reduced maintenance.”
Dialight, a developer of LED lighting technology, says its DuroSite LED Low Bay fixture is now listed on the Designlights Consortium’s Solid State Lighting Fixtures Qualified Products List in the Parking Garage Luminaire category. Recognition by the DLC list identifies fixtures as eligible for valuable utility rebate programs with participating DLC utility partners. The Low Bay source features Dialight’s optics design for precision light placement and reduced glare for clear visibility in low-clearance applications.
Figure 6: Dialight’s DuroSite LED Low Bay fixture, which delivers up to 75 lm/W, is an energy efficient source for “low clearance” situations; at least 50 percent savings over typical HID lamps.
The DLC’s Qualified Products List covers SSL luminaires for commercial spaces. It guides program administrators in determining which lighting products meet desired energy efficiency guidelines in categories not addressed by the U.S. Department of Energy’s Energy Star program. Fixtures listed on the DLC’s qualified product list may be eligible for state and utility energy efficiency rebate programs that enhance the overall cost savings.
Toshiba introduces new high luminous flux white LEDS
Toshiba America Electronic Components, Inc., (TAEC) announced in 2011 the addition of a series of compact high luminous flux white LEDs. With specifications ranging from high-efficiency, high-output models to high-color rendering models, these LEDs can be used as light sources for a variety of lighting applications, including replacement lamps, architectural lighting, retail display, commercial/industrial, outdoor and residential lighting. Suitable as a replacement for traditional fluorescent bulbs in general lighting applications, Toshiba's new high-output white LEDs provide one of the industry's highest levels of efficiency at 120 lm/W, are housed in a very thin package (0.65 mm thick, making them suitable for small equipment) and have a long lifespan due to their low thermal resistance. Additionally, a unique packaging structure and wide directional characteristics make these LEDs appropriate for lighting large areas.
- Luminous efficiency up to 120 lm/W. (1-watt type)
- One of the industry's thinnest packages for 1-watt white LEDs
- Package size: length: 3.1 mm; width: 3.8 mm; height: 0.65 mm
- Wide directional characteristics: 130° to 140° (typ.)
- Color variation: 6500 to 3000 K (this chromaticity range is compliant with ANSI C78.377)
Considering the combination of factors that make LED lighting an attractive alternative to traditional sources, whether due to legislation increasingly prohibiting incandescents or consumer resistance to CFL sources, the market potential seems to be great. The LED lighting takeover is market driven and dictated by market economics. Demand is growing, but it appears that it will be at least 2020 before the market reaches saturation. Aesthetic values mean that commoditization is possible at the LED chip but not at the system level. One of the power benefits of the LED revolution – especially considering some of the efficiency improvements described here, could be that by 2020 widespread deployment of SSL could reduce the worldwide need for power plants by at least 500 5.
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