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The Sunny Side of Lighting


Researchers are capturing sunshine and bringing it indoors with solar hybrid lighting. By Rabia Mughal


The sun is now shining indoors with the help of a technology that captures sunlight and distributes it within a building.

Researchers at Oak Ridge National Laboratory have developed a four-foot wide solar collector that is mounted atop a building to collect sunlight and focus it into bundles of plastic fiber optics. This light is piped into the building, where hybrid fixtures fitted with diffusion rods spread the light in all directions. One solar collector can power up to 12 hybrid fixtures, producing enough light to illuminate 1,000 square feet. On cloudy days, and after sunset, the fixtures switch to electricity in order to maintain a constant level of lighting.

This hybrid solar lighting (HSL) system can reduce the use of energy for lighting, but also for cooling because it reflects infrared energy and ultraviolet waves, keeping the building cooler and reducing the need for air conditioning. Also, the natural light has several advantages over artificial light. According to Melissa Lapsa, manager of the lab's Solar Technologies Program, studies indicate that natural light “increases retail sales, increases student productivity, and increases worker productivity.”

Sunlight Direct, LLC is currently testing the patented technology at commercial buildings, where lighting is a major portion of the electric bill. With an increase in production and design changes, the developers hope to significantly reduce the price—currently $24,000 per system—within the next year or two. The company will test ten systems within the next year as part of a nationwide demonstration called “Sunlight Inside Initiative.”  Wal-Mart, Aveda Corporation, the Tennessee Valley Authority, and Long Island Power Authority are some of the participants.

Not everyone agrees that HSL is the way to go.

“In my opinion it is unnecessarily complicated, would be very expensive to purchase, [and] difficult to install and maintain,” said Francis Rubinstein, a staff scientist at Lawrence Berkeley National Laboratory in California. The technology relies on transporting light through fibers, which is inefficient because some of the electric energy is lost, reducing the amount of light at the end of the fiber, she said. Rubinstein suggests using skylights instead to illuminate the topmost floors of buildings.

But Lapsa maintains that hybrid solar lighting offers a higher level of flexibility and control than skylights, and expects the price to drop once the technology is mass produced, eventually making the system an affordable complement to skylights.

 

Michael Siminovitch of the University of California Davis said that while he agrees with Rubinstein that the approach is currently prohibitively expensive, that will likely change in the near future.

 

“We are going to see these systems evolve over the next coming years,” said Siminovitch. “The view now is to keep our minds open, assess the evolving technology, and help encourage imaginative solutions.”