|February 08, 2012|
Switch off the lights, here comes the sun
|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.
But it wasn't until the first part of this century that the availability of sophisticated electronic equipment, and the movement to reduce energy consumption, inspired Dr. Whitehead to refocus on lighting buildings with sunlight. This time, his research was energized by a conceptual breakthrough.
Previously, thinking about routing sunlight had a vertical focus: collecting it on the roof and channelling it downward. The obstacle was that the shafts necessary to transport the light claimed valuable floor space. The breakthrough came when Dr. Whitehead began to focus on devising compact collectors that could be placed on the side of the building and pipe the light inside.
"It was exciting when we did the calculation of all the benefits that came from this revolutionary approach, and we found that this was a design that could be cost-effective just in terms of the energy savings," recalls Dr. Whitehead.
In short order, his lab created collector panels incorporating an array of flat mirrors that moved in unison to track the sun and redirect its rays toward the building. The rays were then concentrated by two parabolic lenses and set upon their journey down the light guides.
The first collector panels designed in Dr. Whitehead's lab were as wide as a dining room table. By doing away with mirrors and replacing them with an array of small lenses, SunCentral, which was incorporated in 2008 to bring Dr. Whitehead's new technology to market, was able to shrink the panels to about the width of a large paperback (15 centimetres). By using proprietary acrylic lenses of its own design, SunCentral hopes to make the panels even thinner.
SunCentral's goal is to have its sunlight collectors built right into the prefabricated panels now used to clad many buildings. "We hope to be able to sell to curtain wall makers. These are the people that build the high-tech skins of buildings, which are made in factories now and shipped out to the site," says Mr. Formby, who took over as SunCentral's president in 2010.
SunCentral is gearing up for commercial production beginning in 2013. Having already installed working examples of the technology at a handful of demonstration sites, including a building at the British Columbia Institute of Technology -- SunCentral will later this year install its most current technology at the Oregon Sustainability Centre in Portland, which is being built to the highest level of LEED standards.
SunCentral is currently doing its best to spread its message to architects and builders about the energy efficiency of its product and the benefits of natural light.
On its website, SunCentral declares a bold vision: that in the near future most major commercial buildings around the world will be lit by sunlight whenever the sun shines. The coming months, as SunCentral tweaks its product, sets its selling prices and prepares to take orders, will go a long way to determining the soundness of that vision.