LEDs are a Bright Idea Whose Time Has Come

The day the Nobel committee began announcing its 2014 winners earlier this week, National Geographic published a list of Nobel should-have-beens. Dan Vergano’s contribution—Thomas Edison for the lightbulb—proved prescient. One day later, a Nobel for physics was finally awarded for the lightbulb. Unfortunately for the Wizard of Menlo Park, it didn’t go to Edison. The winners were Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura for their work on blue light-emitting diodes, or LEDs.

LEDs represent a huge increase in the efficiency of lighting.
Credit: John Loo/OnEarth Magazine

Edison was still a genius, and his inventions did change the world, but he’s not exactly an environmental hero. Only about 2 percent of the energy that flows through the filament of an incandescent bulb actually generates light. Edison’s invention is a much better heater than a light source.

LEDs are a dramatic improvement. The most cutting edge claim to be 15 times more efficient than the incandescent bulb and four times more efficient than compact fluorescents (the squiggly ones), which now appear to be little more than a transitional technology. On a global scale, the energy savings from a worldwide switch to LEDs could be massive. In 1997, when incandescent bulbs still ruled the night, Evan Mills of Lawrence Berkeley National Laboratory estimated that lighting resulted in the emission of 1,775 million metric tons of carbon dioxide equivalents. If, at that moment, we could have immediately replaced all of the world’s incandescent bulbs with LEDs, the greenhouse gas savings would have been like taking 300 million cars off the road.

In real life, the changeover from incandescent to compact fluorescent to LED bulbs has had a less dramatic impact, for a variety of reasons. The most depressing candidate is known as the “rebound effect,” as Brad Plumer points out at Vox. The theory goes that when lighting (or any technology) becomes more efficient, it gets cheaper. When something gets cheaper, people use more of it. The rebound effect, however, is a hotly disputed phenomenon. Physicist David Goldstein and his colleagues at NRDC (which publishes OnEarth) argue that the rebound effect is at best negligible on a societal scale. Their data shows that people use only a tiny fraction of their energy savings to buy more lighting (or heating or refrigeration or whatever the more efficient technology may be). “Policies and consumer preferences are steadily pushing in the opposite direction—saving more energy, not less,” Goldstein writes.

Another challenge with LEDs, known as droop, has troubled physicists for years. As you increase the current flowing through an LED, the efficiency plummets from 300 lumens per watt of power down below 100 lumens, which isn’t much better than a compact fluorescent bulb (which costs a small fraction of the LED’s current price tag). A few people, including recently minted Nobel laureate Nakamura, have proposed explanations for what causes droop, but no one is entirely certain. Once physicists find the answer, it will still take engineers years to design a solution. Until then, producing bright light with low amounts of energy requires lots and lots of small LEDs stacked together, which is a problem from both a cost and an engineering standpoint.

Approximately 19 percent of the world’s population lacks access to electricity. LEDs could eventually offer a cheap, low-carbon light.
Credit: Tony Webster/OnEarth Magazine

Fortunately, the LED light may play a role in training the scientist who will eventually solve this problem. Approximately 19 percent of the world’s population lacks access to electricity, and there are surely many geniuses among them. The LED’s tiny energy demands make it possible for off-grid communities to store enough solar power in low-cost batteries (see “India Calling”) to provide light after sunset.

Why does that matter? My father-in-law grew up in a small village in India. When the sun went down, he had to stop studying, because his family couldn’t provide enough light to read. He still managed to earn a Ph.D. in chemical engineering, but I often wonder how many kids like him were held back by darkness — an absurd obstacle to academic achievement in the modern world. Maybe one day the Nobel Prize will go to a child who can thank today’s winners for all those late nights spent studying under their creation.

This article is provided by NRDC’s OnEarth magazine, a Climate Central content partner, and appears online at onearth.org

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