Combining ideas from both fields might be the answer.
Canada's SunCentral is in the midst of testing a solar lighting system that it says can reduce lighting and cooling loads in buildings while making offices more pleasant places to work. The system revolves around concentrators. In a nutshell, a set of mirrors in a weatherproof container on the outside of a building concentrate sunlight and focus it onto a lens, similar to how mirrors and lenses concentrate light onto solar cells in concentrating PV arrays.
Once the light passes through the lens, it is then shuttled into ducts about the size and shape of fluorescent lighting fixtures. By cutting apertures into the duct, daylight can be streamed into offices and reach rooms deep inside a building. The duct, in fact, can be a fluorescent fixture, so that when the sunlight dims, the fluorescent lights slowly go up.
The system relies on a 10x concentrator. "If you don't have concentrated sunlight, you've got different trade-offs," said Lorne Whitehead, the head of the board of directors and the NSERC/3M Industrial Research Chair in Structured Surface Physics at the University of British Columbia, during a meeting at the Emerging Technologies Summit that took place last week in Sacramento. "Unconcentrated sunlight won't be economical. And if you get beyond 10x, it may not be safe."
The company has inserted ten collectors, which deliver 60,000 lumens each, on a building at the British Columbia Institute of Technology. (A typical incandescent puts out 800 lumens.) It has reduced the need for electric lights by 340 minutes on average on a sunny day and 267 on a cloudier day. More trials are on the way. See the picture? That's the BCIT trial. The small boxes on top of the building hold the concentrating mirrors and lenses.
One of the key elements of the system is that it doesn't rely on fiber optic cables. Other companies have tried to pipe sunlight into buildings with fiber optics. The cables, though, can limit the amount of light that can be shuttled into a particular space. It can also distort the color of the light. Big ducts make more sense. (Editor's note: we know of another company in stealth thinking along the lines of big ducts. More on that company later.)
Fiber optic cables can be used for short hops, i.e., to pipe light into a closet or store room, but SunCentral will rely on big ducts for the long haul.
Sunlight is free, he noted, but "it takes money in the form of precision optics."
In a sunny place like Arizona, it might take five years to recover the cost of the retrofit through lower cooling and light bills. In a more standard climate, it might take a decade. While sunlight can be warm, the system ejects some of the heat before it enters the building. The lower demand for electric lights in a building then help lowers the demand for air conditioning. Of course, the system can be installed along with other energy efficiency measures to help spread the cost. (Lighting, heating, air conditioning and ventilation account for about two-thirds of the power consumed in buildings.)
But the system provides benefits beyond economics. Sunlight is attractive light. Have you ever noticed how bad you look in gas station bathrooms or other places with cheap fluorescents? It's not you -- it's the light source. Better lighting can lead to increased retail sales and a more pleasant office environment.