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Will LEDs lead to a greener world? Maybe

Photonics Spectra
Nov 2010
Charles T. Troy, Senior Editor, charlie.troy@photonics.com

Conventional wisdom says that replacing the power-hungry incandescent bulb with compact fluorescent bulbs or LEDs that are more efficient will lead to a reduced demand for electric power and the eventual shuttering of polluting power plants, making the world greener.

But scientists at Sandia National Laboratories in Albuquerque, N.M., recently predicted that the increased use of LEDs will not necessarily green the world. The results of their study were published in the Aug. 19, 2010, issue of Journal of Physics D.

“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,” said lead researcher Jeff Tsao. “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.”

Checking the history

Using historical records and a raft of modeling equations, the investigators concluded that artificial light consumes about 0.72 percent of the world’s gross domestic product and an estimated 6.5 percent of the world’s primary energy, as a result of its high energy intensity relative to other goods and services. The increased use of LEDs may, they suggest, not change this.

The reason is similar to that often associated with gasoline. When gasoline hit $4 a gallon a few years ago, drivers stayed close to home and drove less, and the demand for gas declined. When prices came down, drivers took to the road once again, and demand rose. Similarly, as lighting has historically become more efficient and less costly, consumption has increased.

So how does Tsao square his team’s observations with the popular opinion that LEDs mean green?

“Conventional wisdom is that demand for artificial light is near saturation and that more efficient lighting technology, like LEDs, won’t result in increased consumption of light,” he said. “Of course, that wouldn’t necessarily cause power companies to shutter existing power-generation plants, but they probably wouldn’t have to build as many new ones.”

The popular opinion may be correct, Tsao added. “However, it was certainly not correct in the past, for which the empirical evidence is that demand for artificial light was not near saturation but increased both as wealth and lighting efficiency increased,” he said. “Of course, this was not necessarily a bad thing, as the increase in consumption of light was accompanied by an increase in productivity and standard of living for human society.

“If – and I emphasize if, because no one can predict the future – this trend continues to hold in the future, we can anticipate that new uses of light would similarly enable society to be more productive but would not necessarily bring about energy savings.”

By “new uses of light,” he is not necessarily referring to residential lighting in the developed world. “Instead, these new uses could be for outdoor evening lighting in the developed world, or residential and outdoor lighting in the developing world, which uses very little artificial light right now,” he said. “Therefore, there are plenty of opportunities for US homeowners to save energy by switching to higher efficiency lightbulbs – compact fluorescent lamps now and, before long, solid-state lighting lamps.”

Commercial availability

A sure sign of things to come was Home Depot’s announcement this summer of a proprietary brand of LEDs under the name EcoSmart. The line includes the equivalent of a 40-W bulb that retails for $19.97. Offering 429 lm and a 50,000-hour expected lifetime, it is the most affordable bulb of its kind on the market to date. A mere two years ago, a 60-W equivalent cost $90, and a 100-W dimmable bulb went for $360. In addition, the company will offer LED bulbs for use in many types of fixtures, including room lighting, accent lighting, track lighting and outdoor spotlights.

In addition, legislation requires that, by 2012, select forms of incandescent bulbs will no longer be manufactured in the US. By 2014, most incandescent bulbs will be discontinued, and consumers will have to look for energy-efficient options.

Will Tsao’s observations or conventional wisdom prevail? Stay tuned.


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