New LED Technology Could Reduce Light Pollution

Peter Suciu for — Your Universe Online

Until the advent of the electric light, cities were not exactly welcoming places after nightfall. Today, street lights make it easier to see the way after the sun goes down, but this is one of the major contributors to light pollution that washes out the night sky.

It has gotten so bad the International Dark-Sky Association held weeklong festivities earlier this month, which was designed to promote ways to help put a dent in light pollution.

Beyond that the night sky is washed out, worse still is the fact the typical incandescent light bulb has changed little since it was invented more than 130 years ago, and is notoriously inefficient. However, researchers from Taiwan and Mexico have reportedly developed a new lighting system for street lights that harnesses LEDs and ensuresthe light only shines where needed, sparing the surrounding homes and even the evening sky from unwanted illumination.

The team reported their findings in the latest issue of the Optical Society´s (OSA) open-access journal Optics Express.

LEDs offer advantages not only in the fact the lighting is more efficient, with less energy lost to unwanted heat, but also in the fact they are more adaptable to different street light lamp designs. This makes it ideal for a variety of street and road uses, where they can provide uniform illumination with high energy efficiency.

The new LED lights won´t just be limited to use on street lights either, as NPD DisplaySearch recently noted demand for LED lighting is growing rapidly thanks to significant expansion in manufacturing capacity, falling prices, environmental concerns and government incentives. The research firm´s LED Light Market and Forecast Report predicts LED lighting applications will double the market from 16 million units in 2012 to a forecasted 33 million in 2013, and could triple by 2016.

“LEDs are playing a leading role in the lighting industry, driven primarily by government incentive policies and consumer demand for more efficient light sources with advanced technologies such as wireless and color control,” said Steven Sher, analyst, NPD DisplaySearch. “This increased demand will manifest over the next three years, as consumers look to replace their traditional light bulbs with more efficient LED lighting options.”

New, efficient lighting methods could thus be used to help make roads safer.

The Taiwanese-led study, which was conducted at the National Central University, found a new design that could be used for different illumination requests while maintaining high efficiency. This could involve a three-part lighting fixture, where clusters of LEDS, fitted with a special lens — called a Total Internal Reflection (TIR) lens, focuses the light so the rays are parallel to one another instead of intersecting. This process is called collimation. These lenses are then mounted inside a reflecting cavity, which can “recycle” the light to ensure that as much of it as possible is used to illuminate the ground below. Finally, the light passes through a diffuser or filter to cut down on unwanted glare.

“A general LED street light could reduce power consumption by 40 to 60 percent,” said Ching-Cherng Sun, co-author of the research.

Sun added increased efficiency of the proposed design would likely save an additional ten to 50 percent of the energy, while the module would be simple to fabricate since it comprises just four parts, including a commonly used type of LED bulb.

To date, the team has tested the design´s performance by analyzing how little the beam would spread as it hit its target–a road or sidewalk ten meters or more away from the source of the light, and found in addition to being more efficient, light pollution was also significantly reduced.

Sun´s team will reportedly finish a prototype of the design in the next three to six months. This will be followed by practical installations of the new street lamp as early as next year.

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