Streetlights are so bright they can be seen from orbit and even might tell aliens we're here on Earth.
But the lights are misdirected. They often illuminate places that don't need to be illuminated and create light pollution that makes life harder for astronomers and amateur stargazers to see the night sky and can even confuse migratory birds, leading them to crash into buildings.
Light Pollution Blankets Even The Brightest Stars
To solve this problem, Xuan-Hao Lee and Ching-Cherng Sun of the National Central University of Taiwan and Ivan Moreno of the Autonomous University of Zacatecas in Mexico designed a new kind of streetlight, one that shines most of the light on the ground.
The proposed lamp contains light emitting diodes, or LEDs, mounted inside a small housing. Each LED is fitted with a lens and a diffusing layer. The lens shines light in parallel rays, while the housing reflects any spilled light toward the ground. The diffusing layer cuts glare, making the light "softer." The result is a beam of light shaped more like a rectangle, than a cone. The rectangular shape puts more of the light onto the street.
Should We Turn Off The Lights?
By moving more light to the street, the new lamp also saves energy, since fewer of them would be needed to light up a given area, and the number of LEDs needed to get the equivalent amount of light would be smaller. LEDs, while more expensive than conventional bulbs, are also more energy efficient. More of the electrical current that goes into an LED makes light, whereas with ordinary bulbs a lot of the electricity is wasted as heat.
Sun said in a press release that the total energy savings could be big - some 40 to 60 percent over current streetlamps.
Credit: H. Lee et al., Optics Express