LEPs: a New Flash on the Horizon

Lighting and Energy Efficiency
Time was when your fancy and the weight of your wallet decided what you chose to do with energy and lighting. Not any more. Energy these days is an expensive thing, both from the monetary point as well as from the environmental angle.

Pursuit of energy efficiency is not merely fashionable, but it has assumed the proportions of an essential survival strategy for Homo sapiens on Planet Earth. Hectic campaigns till recently called for the banishment of the ubiquitous incandescent light bulb -- an acknowledged energy guzzler-- and its replacement with a more efficient 'avatar', the CFL (Compact Fluorescent Lamp). In the meantime, questions of environmental concern and energy savings have dimmed the prospects of the CFL, which, like its bigger brother, contains the dangerous pollutant Mercury.

Into this background, LED (Light Emitting Diode) lamps have emerged as a viable alternative. Of late LEDs have been occupying centre stage, having taken a giant leap from its role as the humble indicator lamp on the front panels of electronic equipment to powerful and bright flood-lights illuminating the public spaces and buildings of our cities. The versatile and energy efficient LED is now more or less the de facto choice for lighting.

A Challenger in the Arena

Now a new contender has thrown a challenge to the LED and its claim to the energy efficiency crown. The new technology is actually an 'old timer' into whom new life has been breathed by the boffins at the nanotechnology labs of Wake Forest University, North Carolina, USA. Dr David Carroll, director of the Centre for Nanotechnology and Molecular Materials of the University, has announced the breakthrough with his LEP (Light Emitting Polymer) lamp.

The new LEP lamp is based on Field-induced Polymer Electroluminescence (FIPEL) technology. Polymer electro-luminescence, as mentioned earlier, is rather 'old' technology that involves applying electricity through a conductive polymer to produce light. But this had remained a lab curiosity at best till now as the light emission was rather low--not enough to offer any competition to traditional lights. The Wake Forest researches led by Dr Carroll have worked some magic to make them more efficient. They doped the polymer with multi-walled carbon nanotubes (MWNTs), which drove up the luminance about five times. The device in its final practical form consists of three layers of mouldable polymer 'laced with' carbon nanotube material, with dielectric layers sandwiched in between. When driven by an alternating current (AC), the LEP produces pure white light, with virtually the colour temperature of clear sunlight, in which the eyes see best. According to the inventors, "...they produce a color and quality of light that can match the solar spectrum perfectly”.

This indeed is breakthrough technology, and something that could very well eclipse the future prospects of LEDs (to say nothing of CFLs!). The inventors, though secretive about their plans, point out that this is stable and proven technology on the verge of commercial realization. Dr Carroll has one lamp in his lab that has been working for nearly ten years, and it has been estimated that FIPEL lights can have a service life of 20,000 to 50,000 hours. The University is currently working with an industry partner (rumoured to be CeeLite Technologies, who apparently hold the world-wide licences for the technology) to begin production of the LEP lamps this year itself.

The Bright Duellists
What fires the enthusiasm of the inventors is the clear superiority of the FIPEL technology when compared directly with the CFL and the current favourite, the LED.

The CFL, as we know, is a 'mini' version of the conventional fluorescent tube, the traditional 'choke' (inductor) being replaced with an electronic high-voltage circuit. The fluorescent lamps, because of their flickering light output, is tiring to the eyes, and another irritation is the 50 Hz hum they often produce. They are still made of fragile glass tubes and they have a coating of fluorescent chemicals inside. The greatest danger to the environment, however, comes from the mercury that they contain, which is a hazardous pollutant. The high-voltage driving circuits also contain components and chemicals that are not easy to dispose of as e-waste. Above all, their cost/life factor too is not advantageous.

Longer service life and greater environment friendliness made the LEDs beat the CFLs. Further, they needed no high voltages and they contained no mercury. Over the past few years, great strides were made in the field of LED lighting and today we have capable LED replacements for almost all types of lamps. Yes, LED lamps are "hot" in a world looking for energy efficient alternatives. But they are "hot", unfortunately, in more ways. The fact is high-luminance LED lamps create a lot of heat, necessitating effective cooling/heat-sinking mechanisms. This is not a mere inconvenience, this is energy wastage. Another drawback was the bluish-white light emission of bright LEDs, which was 'tamed by' many innovative techniques, to get a near enough 'natural white' colour temperature. Currently the race is on amongst the leading semiconductor companies like the veteran Philips or the newbie Seoul Semiconductor, to develop a 'universal replacement' for the common ' light bulb'.

All things considered, the LEP has a lot going for it. It scores right away from the environmental angle-- it is all plastic and carbon, a far easier load on the environment as it could be recyclable fully. And their energy conversion efficiency is very high -- virtually the entire energy input gets converted to light, and consequently there is no waste heat. Dr Carroll sums up the LEP's benefits thus: "... we've found a way of creating light rather than heat. Our devices contain no mercury, they contain no caustic chemicals, and they don't break as they are not made of glass". Another great plus for the lamp designer is the versatility the technology offers -- the plastic 'light panels' can be moulded in any shape or size. This means the applications for LEPs would be much wider than as a replacement for the humble light bulbs, CFLs or LEDs. Surely with such mammoth world-wide demand, prices are likely to tumble to affordable or even 'cheap' levels.

At this point in time, the LEP looks like a technology breakthrough whose time has finally come.

(All pics courtesy: The Wake Forest Uty site.)

To learn more, trawl:
http://media.news.wfu.edu/experts/david-carroll/
http://users.wfu.edu/carroldl/Lighting_Display.html

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