By Patricia Daukantas

We in the optics community all know the spiel: Solid-state lighting is better than incandescent lighting because the latter wastes a log of energy as heat. But where might hot light bulbs actually be a good thing?

The answer: in traffic lights that get exposed to a lot of ice and snow. According to news reports that have appeared over the last couple of days, LED-illuminated traffic signals don’t generate enough heat to melt off the ice and snow that get stuck to the signal lenses during a storm. Such a frozen crust can make the lights difficult or impossible for motorists to see.

According to one story datelined Milwaukee (Wisconsin, U.S.A.), public-works authorities in several states are testing out possible methods of keeping LED traffic lights cleaned off: weather shields, special heating units like the ones in airport runway lights, or water-repellent coatings. But mainly, they’re resorting to good old-fashioned manual labor to clear off the ice and snow. (Remember, one of the advantages of LEDs is that they don’t have to be replaced anywhere nearly as often as incandescent bulbs.)

That news article also cites the case of a woman in Oswego, Illinois (U.S.A.), who was killed while making a left turn at an intersection where the signals were mostly covered with snow.

The red, yellow and green lights on most American traffic signals have metal hoods to help drivers see the lights even in bright sunlight. However, those hoods don’t help as much when the snow is blowing horizontally in a blizzard.

By Patricia Daukantas

Another example of the inroads that solid-state lighting is making: the New York Times reports that the star that tops the Rockefeller Center Christmas tree in midtown Manhattan is getting a makeover with LEDs.

The 5-year-old Swarovski crystal star has 12 glass rays and “a million glittery facets,” according to the Times, but the designer wanted to send more light through the rays. So workers retrofitted the star with 720 1-W white LEDs. The stainless-steel framework inside the rays had to be redesigned to accommodate the LEDs and their circuitry.

The Rockefeller Center tree, a decades-old tradition in New York City, will be illuminated this holiday season from Dec. 2 to Jan. 7. The rest of the tree was converted to LED lighting two years ago.

By Patricia Daukantas

U.S. cities are beginning to use solid-state lighting (SSL) to save on electricity and maintenance costs, but they have much further to go, lighting experts told a congressional audience yesterday.

OSA and the U.S. House of Representatives’ Research & Development Caucus organized the Washington, D.C., briefing, at which several lighting experts showed off recent local-government success stories and discussed how to gain more acceptance for the technology.

The U.S. Department of Energy (DOE) has studied the history of compact fluorescent lamps (CFLs) to find out what went wrong in the marketplace with their initial introduction, said James Brodrick, manager of the DOE’s SSL program. He recounted the frequent complaints about the old-style CFLs from 20 years ago (they buzzed, they took a while to light up, they made people look like corpses).

More than 200 manufacturers have signed up for the Lighting Facts program, which is supposed to provide consumers with consistent energy-consumption information for bulbs and bulb replacements according to Brodrick. He also showed off the 90-lumens-per-watt entry for the L Prize technology competition:

LED performance is getting close to the “holy grail” of more than 120 lumens per watt, which would make outdoor and indoor lighting much more attractive, said Mathew Sommers of General Electric Co.’s Lumination division. He reviewed a number of the talking points used to pitch SSL technology to business and municipal customers: glare reduction in product display cases, more uniform coverage of outdoor sites, substantial reduction in maintenance costs (such as bulb replacement) and – oh, yeah – huge savings on energy costs over incandescent lights.

Although a representative from the government of Ann Arbor, Mich. (U.S.A.), couldn’t get to Capitol Hill to talk about that city’s LED lighting program, a representative of Cree Inc. (Durham, N.C., U.S.A.) reviewed several public-sector SSL projects: the parking garage at the Raleigh Convention Center, a street in Chapel Hill, N.C., and a dormitory at North Carolina State University. Deb Lovig, Cree’s LED programs evangelist, passed around the room an LED replacement for the recessed indoor “can light,” which usually takes an incandescent bulb.

Consumers are less interested than governments and other large organizations in return-on-investment arguments, noted OPN contributing editor Alexandre Fong, who moderated the discussion. Also, the U.S. lighting infrastructure, heavily based on screw-in lights that run on alternating rather than direct current, isn’t yet right for LEDs.

“There are four billion sockets out there,” Sommers said. “That’s a lot of sockets to put bulbs in.”

Indeed, bulb manufacturers will probably develop lots of interesting solid-state bulb replacements to fit into those sockets – and to meet the U.S. lighting-energy standards that go into effect in 2012 and become much more stringent in 2020.

A future issue of OPN will include much more coverage of the policy issues surrounding solid-state lighting development and usage. Stay tuned!