Today, the spotlight beams down brighter than ever on LEDs to provide more energy-efficient, lower-cost illumination. Underscoring that urgency, the International Energy Agency says that lighting accounts for about 19% of global electricity production, and about two-thirds of current lighting is based on older energy-wasting technologies developed before 1970.
To that end, U.S. Congressional legislation to ban the sale of 100-W incandescent light bulbs has gone into effect this year, with other lower-wattage versions to follow. Moreover, many European and Asian countries have already enacted initiatives to do the same. Even though there’s some pressure to delay certain aspects of this legislation, several LED lighting groups and manufacturers have indicated they intend to follow the law, regardless of what happens in the U.S. Congress.
Present LED costs are too high to make a significant impact right now, but they’re making greater inroads into a wider array of outdoor and indoor applications. Evidence is clear as more cities, states, governments, and businesses switch to LED lighting, and consumers adopt LEDs for indoor illumination and decorative lighting.
Transparency Market Research Co. forecasts that the global LED market is estimated to reach $18.2 billion by 2016 for the period 2011 to 2016, growing at a compound annual growth rate (CAGR) of 14.9%. The study notes that the residential market represents a 40% share (the largest) of the overall lighting market.
A study conducted by market research firm Yole Développement shows that when the cumulative cost of ownership is considered, a standard A19 warm white LED bulb with 800 lumens and no maintenance cost becomes significantly less expensive than other light sources in residential applications (Fig. 1).
Focus On Better Manufacturing, Packaging
According to Paula Doe, a contractor at SEMI and Yole Développement, today’s LED bulb costs about $40, which is still too high to compete with incandescent and compact fluorescent bulbs. This has led LED makers to shift focus from increasing efficacy levels (which are reaching practical limits) to manufacturing efficiency for better mass-market penetration. They’re also working to improve packaging to achieve even higher efficacies where possible. She figures that if cost drops to about $10, the LED’s longer life and lower energy use would make it a compelling choice for consumers.
That said, LED bulb prices have been dropping about 20% annually, a trend most experts believe will continue for high-brightness LEDs. Driving this trend is the move to larger wafer sizes, from 50-mm diameter sapphire wafers to 300-mm silicon wafers that are used to create high-volume silicon ICs.
The manufacturing process for LEDs—metal organic chemical-vapor deposition (MOCVD)—is quite different than that for silicon ICs. The process produces thin films of compound semiconductors, as typically used in LEDs, through chemical reactions on the surface of the LED substrate. The reactions occur at temperatures above 800°F and at pressures up to approximately 100 kPa in the absence of oxygen.
Of course, one way to wring out costs is to further automate the manufacturing process. However, LED makers attempting to automate must face the fact that few standards exist for carrier and equipment interfaces on LED fab equipment. As a result, it becomes tough to implement any kind of material-handling automation, because each fab is liable to handle wafers with slightly different hardware.
To overcome these and other obstacles, the SEMI North American HB LED Standards Committee was established to help set form factors for widely used manufacturing equipment. Observers say this could result in greater use of robotic wafer handling, automated glove boxes, inter-bay automation, and standard mechanical interfaces (SMIFs). Since LED wafers aren’t as big as the 300-mm wafers used for ICs, the material-handling equipment involved needn’t be as heavy.
LED experts and consultants have demonstrated that commercially available 60-W-equivalent LED bulbs relatively cost about $50/kilolumen, down significantly from a year or two ago. They project that figure to drop to the $2 to $3 range in a couple of years and to $1 by 2020. Much of this cost reduction will likely be attributed to economical packaging, improved optics, better thermal/mechanical components, driver electronics, and a more automated assembly process (Fig. 2).
OSRAM Opto Semiconductors recently introduced the Olson Square 3- by 3-mm LED for lighting applications. It envelopes the LED chip in a reflective package to increase system efficiency, redirecting light from the side and back of the LED chip to the front (Fig. 3). Light reflected back to the LED within a system (e.g., from a diffuser) can be recycled in this way.
The device comes in various versions and color temperatures, and it’s operable at different currents. Featuring a thermal resistance of 3.8 to 4.0 K/W, it suits outdoor, office, and retrofit lighting applications. For example, at a color temperature of 300K, it provides a warm white light and high color stability over a wide viewing angle of 120° with a color-rendering index (CRI) of 80.
The Olson Square LED is currently being used in a street-lighting project in Beijing, China. Specifically, the project involves luminaires, developed by HBTechnology Cast Group, that integrate OSRAM’s 1-W-class Olson LEDs. Beijing’s hope is that these 120-W and 180-W fixtures, which are replacing 250-W and 400-W sodium vapor lamps, will realize 50% energy savings. The 80° beam angle, the 3- by 3-mm size, and the color rendering of the Olson LEDs simplify their installation in the present luminaire system.
China, in fact, is one country that’s taking the lead in LED lighting applications under its “10 Cities 10,000 Lights” program. It’s spearheading the use of energy-efficient solid-state lighting in streets, tunnels, subway and light-rail installations, and parks. The program is being funded by the China Ministry of Science and Technology.
At last September’s Designing with LEDs Workshop in Boston, Mass., a panel of experts emphasized the importance of developing market-ready LEDs that are not only intelligent, but also easy and inexpensive to use.
“The consumer market is really about coolness and convenience,” says Eric Holland, vice president of engineering at the Lighting Science Group (LSG). “When we talk about the average consumer and what it’s going to take to get massive LED adoption, it has to be as simple as replacing a light bulb and offering alternatives in which consumers don’t have to change out their switches.”
LSG supplies the Home Depot chain of stores with a 40-W-equivalent LED, part of the EcoSmart lighting products line, for $9.97. By this summer, LSG expects a 60-W version, at a cost of less than $15, to possess the same efficiency as Philips’ L Prize bulb.
Last year, the L Prize, formally known as the U.S. Department of Energy’s (DoE) $10 million Bright Tomorrow Lighting Prize, was awarded to Philips Lighting North America. Philips won by meeting a slew of DoE requirements: an output of at least 900 lumens (as much light as a 60-W incandescent bulb), power consumption under 10 W (much less than an incandescent bulb), and a lifetime of 25,000 hours (approximately 25 times as long as that of an incandescent bulb).
Philips Lighting has been at the forefront in calling for expanded use of LED lighting, a call that has resonated worldwide. Philips believes that LED lighting has reached a tripping point, whereby it can now be used in general high-quality lighting for nearly all applications.
At last year’s United Nations Climate Change conference in Durban, South Africa, the company advocated a worldwide switch to LED lighting. Harry Verhaar, senior director for energy and climate change at Philips Lighting, challenged the world’s governments and businesses to make a rapid switch to highly energy-efficient LED lighting.
“LED lighting offers both dramatic savings in energy use and maintenance costs, while at the same time enhancing the feeling of safety, security, and comfort of people on the streets and public spaces, in buildings, and at home,” Verhaar said. He made these comments at the conference’s Climate World Summit, a high-level side event convening representatives from the public and private sector.
Novel LED Bulbs
The wait is on for LED light bulbs with a single-digit price. For example, a 40-W-equivalent LED bulb with a decent hue retails for about $20, and higher wattages cost even more. Still, there are applications where the benefits of LEDs cancel out their higher price.
LEDnovation Inc. has released what it calls the most efficient 60-W-equivalent omni-directional A19 LED lamp, the LEDH-A19-60-1-27D-IO (Fig. 4). The first in a series of EnhanceLite omnidirectional lamps, it offers an 810-lumen output at a 2700K color temperature, delivering energy-saving light that suits applications like table lamps, wall sconces, hanging pendants, ceiling lamps, and other luminaires and fixtures.
Cree introduced what it says is the first high-brightness, 20° tilted-view angle LED optimized for elevated outdoor video screens. The Screen Master C45MT and C45 LEDs are the two brightest LEDs in the company’s high-brightness P2 oval LED family. The former delivers the brightest peak intensity at a 20° angle, and the latter at a 0° angle.
Cree’s XLamp MT-G LEDs are optimized for 35-W to 50-W halogen MR-16 retrofit bulbs and other accent, track, display, and down lighting applications. The multi-die LEDs target high-output (560 lumens at 1.1 A at 85°C and 1525 lumens at 4 A at 85°C for warm white 3000K temperatures), small form-factor (9- by 9-mm footprint) lighting applications. Featuring the company’s EasyWhite technology to deliver consistent color in a small high-efficiency package, the MT-G LEDs are binned and tested at 85°C to simplify luminaire calculations.
Last fall, Cree launched the TEMPO (Thermal Electrical Mechanical Photometric Optical) tool with design and evaluation services to accelerate LED product development (Fig. 5). The latest addition to TEMPO includes new thermal simulation and advanced photometric testing.
Taiwan-based Epistar Lab has announced what it says is the highest-efficacy, high-voltage LED warm white lamp chipset at 216 lumens/W. The company achieved this efficacy at an operating current of 5 mA with a CRI of 87 and a color-corrected temperature of 2700K.
Not to be outdone, a low-cost “World Bulb” from LSG offers a 35% better total cost of ownership than compact fluorescent lamps (CFLs), the company says. The omnidirectional, 60-W-equivalent A19 bulb was selected as a 2012 International Best of Innovations Design and Engineering Awards Honoree at this year’s International CES.
Unique LED Lighting Apps
Outdoor usage of LEDs isn’t tough to spot, as they’re being used to light up parking lots, streets, bridges, tunnels, stadiums and arenas, walkways, building facades, and other public facilities. They’re also making their way into indoor offices, restaurants, malls, and transportation stations, among other locations.
On a more grand scale, Philips has provided LED lighting for the Hardbrücke Bridge in the center of Zurich, Switzerland (Fig. 6). Reportedly the largest LED installation in the country, the 2.3-km bridge’s underside is lit with 1750 LEDline2 luminaires, which require 25 kW for 1654 hours a year, or 41,000 kWh/year.
Last year, officials at the Mercedes-Benz Superdome in New Orleans, La., flipped on the switch to illuminate the Louisiana Landmark with a state-of-the-art Martin Professional LED lighting show (Fig. 7). Overall, the display included approximately 288 Martin Professional Exterior 410 lighting fixtures (luminaires).
The LEDs can reproduce every color of the rainbow on all of the stadium’s 96 concave aluminum panels that ring the building’s exterior. The bright, compact luminaires used pre-mixed LEDs and RGBW color mixing, part of the Exterior 400 Range of outdoor LED wash lights that includes color calibration for more uniform color projection.
Due to their multi-color capabilities, LEDs can generate some intriguing lighting conditions. For example, researchers at the Germany-based Fraunhofer Institute of Industrial Engineering teamed up with fixture manufacturer LeiDs GmbH to create ceiling tiles that give the look of overhead sky clouds.
Each 50- by 50-cm tile contains 288 RGB and white LEDs mounted on a board. A white diffuser film is attached 30 cm beneath the LEDs to ensure that each LED isn’t seen as an individual point of light. The main focus of the project was to simulate natural lighting conditions on a cloudy day.