Buildings and Cities
LED Lighting (Commercial)
The origin of LEDs (light emitting diodes) dates back to the 1874 invention of the diode—a crystal semiconductor. Under certain conditions, diodes emit light. In 1994, three Japanese scientists invented high-brightness LED bulbs, for which they were awarded the Nobel Prize in Physics in 2014.
LEDs work like solar panels in reverse, converting electrons to photons instead of the other way around. They use 90 percent less energy than incandescent bulbs for the same amount of light, and half as much as compact fluorescents, without toxic mercury. On top of that, an LED bulb will last much longer than either other type.
Lighting accounts for 15 percent of global electricity use. LEDs transfer 80 percent of their energy use into creating light—rather than heat, like older technologies—and reduce electricity consumption and air-conditioning loads accordingly. LED streetlights can save up to 70 percent of energy and significantly reduce maintenance costs.
The question about LEDs is not whether they will become the standard in lighting fixtures; it’s when. The price (per watt equivalent) is two to three times higher than incandescents or flourescents, but falling rapidly. Virtually any bulb currently in use can be replaced by LEDs.
diodes emit light…observed in 1907: Zheludev, Nikolay. “The Life and Times of the LED—a 100-year History.” Nature Photonics 1, no. 4: 189-192; Schubert, E. Fred. 2014. Light-emitting Diodes. Cambridge: Cambridge University Press, 2007.
1960s…commercial applications: Zheludev, Nikolay, “Life and Times”; Schubert, E. Fred. Light-emitting Diodes. Cambridge: Cambridge University Press, 2014.
Nobel Prize in Physics in 2014: Overbye, Dennis. “American and 2 Japanese Physicists Share Nobel for Work on LED Lights.” New York Times. October 7, 2014.
LED [vs.] incandescent [vs.] compact fluorescent: Pimputkar, Siddha, James S. Speck, Steven P. DenBaars, and Shuji Nakamura. “Prospects for LED Lighting.” Nature Photonics 3, no. 4 (2009): 180-182. 2009.
80 percent of…energy use [for] creating light: Pimputkar et al, “Prospects.”
kerosene lamps…emissions: Lam, Nicholas L., Yanju Chen, Cheryl Weyant, Chandra Venkataraman, Pankaj Sadavarte, Michael A. Johnson, Kirk R. Smith et al. “Household Light Makes Global Heat: High Black Carbon Emissions from Kerosene Wick Lamps.” Environmental Science & Technology 46, no. 24 (2012): 13531-13538; Meaker, Morgan. “The Developing World Faces a Silent Killer. Could a $1 Solar Light Help?” The Guardian. March 1, 2016.
“A sixth of humanity…[vs.] the electrified world”: Mills, Evan. “Can Technology Free Developing Countries from Light Poverty?” The Guardian. July 30, 2015.
India…1 million solar lighting systems: REN21. Renewables 2016 Global Status Report, Paris: REN21 Secretariat, 2016.
lighting…global electricity use: Neslen, Arthur. “Plan for 10 Billion Ultra-Efficient LEDs Lights Up Paris Climate Summit.” The Guardian, December 7, 2015.