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Optical Design & Engineering

LEDs not so green?

SPIE Newsroom
7 September 2010

Solid-state lighting pioneers long have held that replacing inefficient incandescent light bulbs with more efficient solid-state lighting such as LEDs would lower electrical usage worldwide. But, in a paper published recently in the Journal of Physics D, leading LED researchers from Sandia National Laboratories argue for a shift in that view.

Jeffrey Tsao at SPIE Optics+Photonics"Presented with the availability of cheaper light, humans may use more of it, as has happened over recent centuries with remarkable consistency following other lighting innovations," says Sandia lead researcher Jeff Tsao, who also discussed the topic in his plenary talk at SPIE Optics+Photonics in August. "That is, rather than functioning as an instrument of decreased energy use, LEDs may be instead the next step in increasing human productivity and quality of life."

The assumption that energy production for lighting will decline as the efficiency of lighting increases is contraindicated by data starting with the year A.D. 1700 that shows light use has remained a constant fraction of per capita gross domestic product as humanity moved from candle to oil to gas to electrical lighting.

Thus the societal response to more efficient light production has been a preference to enjoy more light, rather than saving money and energy by keeping the amount of light produced a constant.

"Over the past three centuries, according to well-accepted studies from a range of sources, the world has spent about 0.72 percent of the world's per capita gross domestic product on artificial lighting," Tsao says.

"This is so for England in 1700, in the underdeveloped world not on the grid and in the developed world using the most advanced lighting technologies. There may be little reason to expect a different future response from our species."

Far from an example of light gluttony, Tsao says, by increasing the amount of lit work space and bright time, individuals would enjoy the desirable outcome of increasing their creativity and the productivity of their society.

Other authors of the paper, "Solid-state lighting: an energy-economics perspective," are Jerry Simmons, Randy Creighton, and Mike Coltrin of Sandia Labs, and Harry Saunders of Decision Processes Inc., of Danville, Calif.

The work was supported by Sandia's Solid-State Lighting Science Energy Frontier Research Center, funded by the U.S. Department of Energy's Office of Basic Energy Sciences.

The journal paper is open access for a month at http://iopscience.iop.org/0022-3727/43/35/354001.

In a symposium-wide plenary talk at SPIE Optics+Photonics, Tsao noted several effects on the use and perception of illumination that will come into play as a result of the digital nature of solid-state lighting: the ability to light only where and as much as is needed for a particular task, smart systems that turn on and off as people enter and leave a space, and inexpensive systems that can provide lighting in developing regions.

Tsao also predicted that solid-state lighting will surpass compact fluorescent lighting in efficiency by 2012.

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