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Looking at the Brightness of the Future of LED Lighting

2009/06/05 | By Steve Chuang

C.L. Wu, chairman of the TLFEA
C.L. Wu, chairman of the TLFEA
With lighting burning around 20% of the total electricity consumed globally, LED (light emitting diode), due to smaller size, energy efficiency, longer lifespan and quicker activation than traditional lighting sources, is regarded as the answer to future lighting needs of the 21st century, especially with the growing awareness of the importance of environmental protection.

The lighting industry generally agrees that LED lighting holds immense potential to replace traditional counterparts in the next decade. With global warming threats looming in the background, LED lighting has a bright future for it can be installed literally flat on surfaces, does not shatter like incandescent bulbs, nor pose mercury contaminants as with fluorescents. So featuring low thermal resistance, high luminosity and reliability, LED lighting has been the focus of R&D in recent years, and looks to become a daily lighting source in the future.

Despite well-publicized efforts by many nations, lighting makers and advocates have not been able to sizably increase the market shares of LED lighting, evidenced by relatively few LED lamps available at retailers. Makers optimistically predict that 1W or higher super-bright LEDs are expected to grow at 14% annual compound growth rate in the following years, but so far less than 10% of typical lighting are LED powered. After years of development, LEDs are mainly used for nighttime advertising, auto lamps and traffic lights, with its focus being turned to larger-sized displays indoors and out, but not as mainstream lighting for indoors or outdoors. The costs and prices of LEDs are some 20-times higher than for conventional lighting, as well as the luminous efficiency of white LEDs being only 40-50lm /W are the reasons cited as the hindrances to their becoming more popular. And that LEDs are rarely used in traditional commercial lighting is an issue that needs to be addressed.

Many Challenges

Many obstacles stand in the way for white LEDs to widely replace fluorescent lamps, which are mostly used in office lighting, especially the high-efficiency, super-thin T5 fluorescent tubes. The T5s boast luminous efficiency of 100Lm/W, color rendering of Ra85, 91% light output after 10,000 hours of use, and diameter of only 16mm. Coupled with minimized pollution via using solid mercury alloy, T5s now pose less environmental hazards. Also white LEDs will not likely achieve similar luminous efficiency as T5s in the near future, as well as featuring relatively narrow projection angles, hence unable to illuminate spacious settings.

Instead of significantly boosting the use of LEDs, widely advocated policies to ban or replace incandescent bulbs have directly benefited energy-saving bulbs, such as compact fluorescent lamps (CFL). In Taiwan alone, the sales of energy-saving bulbs increased 20-30% annually during January to July 2008. With incandescent bulbs to be completely banned in most developed countries, the demand for energy-saving bulbs due to replacement worldwide will peak in two to three years. Such rising demand will not be met without raising the production of energy-saving bulbs accordingly.

Intermediate Product

An intermediate product, one between traditional halogen and LED lighting, for spotlighting has been developed: Major lighting makers have used ceramics to build the ceramic metal halide (CMH) lamp, which features good color rendering of Ra80-90, stable color temperature, is 4-times as durable as halogen lamps, with low-wattage CMHs burning only half the electricity. Coupled with electronic ballasts, CMHs are not only good lights but also energy efficient.

A study of a furniture chain store in Taiwan shows that replacing 2,700 units of 50W halogen lamps with 1,500 units of 20W CMH lamps saves 118KW per hour. Coupled with the added saving in air conditioning due to reduced heat output from less lighting, a single store saves NT$2.3 million (US$68,886 at US$1: NT$33.4) in power consumption, cutting carbon dioxide emissions by 250 metric tons a year to help lessen global warming.

Outlooks

Currently typical LED applications are 80% concentrated in cellphone, automotive, consumer appliance and other displays. Such trend may not change despite the optimism of the Optoelectronics Industry Development Association in Washington, DC, which predicts the luminous efficiency of white LEDs to rise to 150lm/W by 2012, with rapid price reductions to widely popularize such lighting. Also Japan aims to entirely replace fluorescent lamps with white LED lamps nationwide by 2012. Although the R&D of LED lighting has clearly progressed since 2000, but a single LED still has only 5W of maximum efficiency, coupled with 35-40 Lm/W of luminous efficiency for white LEDs, so for such lighting source to be truly practical remains questionable.

LEDs are undoubtedly the best energy-saving lighting solution. But self-delusional mindsets of lighting makers and governments, as well as technical challenges, may blind consumers, preventing them to weigh the issue of marketability.

White LED lamps still leave much to be desired in terms of color temperature. Exceeding 6,000K, white LEDs cannot compete against even incandescent and fluorescent lamps, especially for applications calling for mood-creation as in restaurants, hotels and homes, where fluorescent lamps with color temperature lower than 3,000K are often needed.

Excessively pale color temperatures of white LED lamps also make such products less marketable for residential lighting in temperate zones, for consumers there generally prefer softer lighting to create comfortable, warm atmosphere in homes. In short, white LED's low luminous efficiency and excessive brightness, which has to be toned down with lens or diffuser, make such lighting less desirable in color rendering and hence less marketable in some locations.

Ultimate Goal

Developing practical LED lighting may not be as difficult as building LED lamps that are rated good products after being used by consumers, which should be the ultimate goal for lighting makers. In other words, lighting makers have to firmly grasp the characteristics and needs of LED lighting applications to turn LEDs into practical, competitive lighting products. The reason that LEDs have yet to become ubiquitous indoor lights is that R&D people lack in-depth understanding of lighting applications, still trying to replace original forms of lighting, when they should be developing LED lighting as a new source by looking at its characteristics and human vision.

As such, more work awaits to be done to study and properly position the suitability and role of LED lighting, as well as integrate the resources of LED makers and lighting designers. The current focuses on LED lighting development seem properly aimed, tapping the inherent properties of such light source as brightness and fast activation, with LEDs mostly used in traffic signals, advertising displays, marquees, emergency lights etc.

The lighting industry in the 21st century will undergo further systems integration. The top-three lighting makers have been taking over smaller peers in Asia and Eastern Europe to expand markets, as well as horizontally integrating electronic ballast makers to set up systematic lighting businesses, hence enhancing competitiveness.

Against the backdrop of Taiwanese makers of traditional lighting having migrated offshore, developing high-tech, value-added LED lighting is the way for Taiwan-based makers to build global market shares in the future.