Let there be light, optical cables included

A company called Sunlight Direct is developing a hybrid solar lighting system that distributes daylight into buildings through fiber-optic cabling, even to people not seated near windows.

The notion of maximizing outdoor light inside is common in interior design by using various methods, including skylights and even roof-mounted tubes with mirrors.

But Sunlight Direct is taking a high-tech approach by seeking to create a commercial product from Department of Energy research.

Its hybrid solar lighting system features a 40-inch mirrored dish with a GPS-director monitor to move it during the day and maximize light intake. Once light is collected from a roof and concentrated, it is filtered and then spread through a building through bundles of plastic fiber-optic chords.

About 25 retail outlets and office buildings are testing the company's system, which the company hopes to bring to market early next year.

The selling points are lower electricity bills and the benefits that natural light has on people, whether they are employees or customers, according to the company.

"No longer do you need to be the CEO in the corner office. You can have daylight piped into the office," said Duncan Earl, the company's chief technology officer. "Natural lighting is just the best lighting for humans."

A daylight distribution system can reduce the amount of power consumed during the middle of the day, when demand on the electricity grid is highest. Sunlight Direct estimates that its hybrid solar lighting system can result in saving up to $8,000 per year per unit.

Sunlight Direct is one of a growing number of companies seeking business opportunities while energy prices and concerns over the environment are high.

Another company called Ice Energy, for example, has created a product that was conceived from Department of Energy research.

Its air conditioner, which freezes water at night to cool refrigerant, has become more economically viable because of higher electricity prices and a soaring demand for power worldwide, according to CEO Frank Ramirez.

Happy people buy more
Sunlight Direct's technology, started ten years ago at the Oak Ridge National Laboratory in Oak Ridge, Tenn., originally was conceived with an eye toward energy efficiency, said Earl.

However, Sunlight Direct is finding that the less tangible benefits of natural light on people are also prompting its initial customers to test out the system.

"The original idea and value proposition was purely about energy," said Earl. "What we found in developing it was that (energy) was still a very valid value, but there are all these secondary benefits of natural lighting."

For example, a Wal-mart Stores outlet in Texas and Staples stores in New York and Florida are evaluating whether the Sunlight Direct lighting system will increase sales. Similarly, office buildings are using it to measure potentially positive effects--such as productivity and reduced absenteeism--on employees.

Green-building advocates argue that productivity benefits on people justify any financial premium that constructors must pay in design and materials.

In a 2003 study, Heschong Mahone Group, a building design firm, found significant financial benefits to natural lighting in retail situations and office buildings.

In the retail study, it found that stores lit by diffusing skylights had a strong association with increased sales. It concluded that an optimized day-lighting system could save a retail store 24 cents per square foot per year in energy costs and could increase sales by 66 cents per square foot per year.

The studies, commissioned by the California Energy Commission, found similar patterns in office buildings and schools.

"Both the school and the office studies found strong and consistent correlations between better views and better performance. There is a clear suggestion from this work that window views are important for sustained human performance," according to the report.

Mass market?
But to make potential customers buy its day-lighting system, Sunlight Direct needs to lower the cost of the product, Earl said. The notion of using fiber-optic cables has been around since the 1970s, but cheaper components will help lower system prices, he said.

Right now, the company is trying to fine tune its system and devise a cost-effective manufacturing technique to make it suitable for wide usage.

A breakthrough in the hybrid solar lighting system was the engineers' decision to use plastic, rather than communications-grade, glass fiber-optic cables. Although they are 40 percent cheaper, the plastic cables cannot withstand the same amount of heat as glass cables.

"We ended up burning fibers for two years before we developed a passive cooling system," Earl said.

Researchers developed a way to filter out the infrared light with the use of a secondary mirror which, along with other "engineering tricks," prevents a build-up of intense heat, he said.

If it's a cloudy day, the system can monitor internal light levels and compensate with lamps.

Ultimately, Sunlight Direct would like to harvest that filtered light, which is now just reflected away from a building. The idea is to beam the excess light onto solar photovoltaic panels to generate electricity.

Because the sunlight is concentrated by the dish, the panel should create more electricity than a traditional system, Earl said.

The company, which is expecting to finish its seed financing this year, is also eyeing the possibility of light dishes on people's homes.

"We'd like to go there but for now, because of maintenance, reliability and safety reasons, we're not offering it to home owners," Earl said. "We need to make sure we have all the kinks and maintenance worked out."