Buildings and Cities
LED Lighting (Household)
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. By transferring most of their energy use into creating light—rather than heat, like older technologies—LEDs reduce electricity consumption and air-conditioning loads.
The price (per watt equivalent) for LEDs is two to three times higher than incandescents or floursescents, but falling rapidly. And an LED bulb will last much longer than either other type. Still, upfront cost remains an obstacle for household adoption.
When the sun sets, more than a billion people live in the dark. Low energy use means LEDs can be powered with small solar cells. Solar-LED lights can replace expensive kerosene lamps and their noxious fumes and emissions, while addressing the problem of light poverty.
Technical summaries for each solution will be available May 1, 2017.