Future of SSL LED lighting is not dim, but it's flickering

Congresswoman Bachmann, former Republican presidential hopeful, has led a campaign for several years in defense of the historic Tom Edison-style incandescent lightbulb, against government pressure for consumers to adopt new, more energy-efficient lighting solutions.

Michael Poplawski, meanwhile, has led one of the government's teams – at the Pacific Northwest National Laboratory – seeking to solve issues that currently hobble the widespread deployment of LED (Light Emitting Diode) technology, which remains both more expensive and far more efficient than Rep. Bachmann's beloved tungsten-filament vacuum tube.

"Complicated," was the commonest word from Poplawski, senior energy engineer at the Portland, Oregon national lab, as he spoke to a session at the DESIGN West conference here Tuesday. He cited numerous complications in the effective use by consumers of LED lighting, and obstacles to reducing costs for the technology.

One of the points Poplawski stressed was that every LED light is a solid-state (SSL) electronic device, while a lightbulb is just, well, a lightbulb. In a presentation that exceeded its planned duration by some 30 minutes, Poplawski dwelt on four problems that his group is working to resolve: flicker, dimmability, power quality, and lifetime limitations linked to "driver reliability."

Flicker, for example, is not just a relative of the yellow-bellied sapsucker.

Flicker is inherent in every form of electric lighting and it affects everyone differently, according to individual levels of visual sensitivity. "A good chunk of people," said Poplawski, with a measure of awe, "are seeing things (flicker) at upwards of a thousand hertz." Flicker's biggest moment in the limelight occurred in the film, "The Andromeda Strain," when the stroboscopic flashing of a laboratory light caused one of the characters to suffer an epileptic seizure.

Poplawski mentioned the danger of seizures, and added other side-effects of flicker, including headaches, fatigue, blurred vision, eye strain, reduced visual task performance and distraction on the job.

The good news about LED lighting is that it can reduce flicker, especially compared to standard fluorescent lights. The bad news is a determination by researchers that flicker – which is consistent and predictable in current lighting systems – is more "complicated" in SSL. It tends to vary substantially, both in amplitude and frequency, in various LED bulbs.

Among the solutions Poplawski's national lab is exploring is the development of LED solutions with minimal flicker, which requires researchers to identify and measure qualitatively (in terms of human reaction) the presence of flicker. In the end, flicker must be measurable in a way that its level can be reported to consumers in a way they'll understand it.

Among other issues with which Poplawski's team is wrestling is dimmability. Many homes are equipped with dimmers, virtually all of them designed to dim conventional incandescent and fluorescent lights. The difficulties of designing LED bulbs that react to existing dimming technologies required Poplawski 20 minutes to explain. The adaptation is not easy. Poplawski boiled it down to the fact that consumers don't know what will happen when they use their twentieth-century dimmer to soften the glare from a post-millenial high-tech bulb.