Jan 292012

SunCentral’s goal is to have its sunlight collectors built right into the prefabricated panels

English: Gathering storm over Wetherlam with r...

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For those of us who spend most of our days under the alien glow of the artificial light that illuminates most large buildings, a brighter future may be at hand.

Technology being commercialized in British Columbia aims to transform building interiors — providing practical, affordable illumination by harnessing the natural light of the sun. It’s light that will be brighter, more attractive, less expensive and more sustainable than electric light, according to Tony Formby.

Mr. Formby is president of SunCentral Inc., a company developing technology based on breakthroughs made by University of British Columbia physics professor Lorne Whitehead. That technology uses computerized collector panels located on the sun-facing exterior walls of buildings to gather and concentrate sunlight, which is transported and dispersed inside the building by special light guides.

Dr. Whitehead, who holds more than 100 patents, first began dreaming about piping sunlight into buildings in 1978 when he was a graduate student working in a windowless laboratory. His interest in the quality of light had been piqued by a stint helping out with theatre lighting, and he recalls thinking, “Wouldn’t it be great if it were practical to bring sunlight indoors?”

He soon found out why that had never been done. “The problem was,” he says, “that we didn’t have efficient light guides. … You have to channel or guide the light to get it inside in a practical way.”

Because light travels very efficiently through air, the basic idea of any light guide is quite simple, says Dr. Whitehead: “Take any pipe and mirror the inside surface, and if light goes in one end, it kind of has to come out the other because it reflects.” However, nothing’s perfect, he adds, and in the case of a hollow light guide, the snag is the loss of light that occurs with each reflection.

A typical household mirror reflects about 90 per cent of the light that strikes it, and in 1978 Dr. Whitehead couldn’t find anything more reflective he could practicably use in a light pipe. And that wasn’t good enough. “If you have 10-per-cent loss and if you have 100 reflections, essentially nothing gets to the far end,” he points out.

By 1981 Dr. Whitehead had invented the prism light guide, the world’s first efficient way of piping light. It featured a thin plastic sheet lined with prisms. The inside of the sheet was smooth; on the outside, 90-degree prisms in a saw-tooth pattern ran the length of the film.

The prismatic film is made of transparent polymer – no reflective coating is necessary because the prisms reflect light of certain angles due to an optical phenomenon called total internal reflection. “The pattern of right-angle prisms on the outside of the film turns out to be an extremely efficient reflector of light rays,” says Dr. Whitehead.

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