Solar Power Goes Underground

Using what they call the world's first 3-D solar panel system, scientists at Georgia Tech have created photovoltaic cells that work underground.

Like the idea of free and clean solar power but hate the thought of ugly, black panels covering the roof of your home? Help is on the way.

Scientists in Georgia and New Jersey are taking solar panels off the roofs of homes and cars, and moving them into basements and walls. The new panels could unobtrusively provide solar power while simultaneously protecting the delicate photovoltaics.

"No one wants to buy a big, nice, fancy car with a huge solar panel on the roof," said Zhong Wang, a scientist at Georgia Tech designing what he calls the world's first 3-D solar panel system.

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Instead of using traditional solar panels, the Georgia Tech scientists will capture sunlight and turn it into electricity using fiber optics cables coated with zinc oxide, the same white compound lifeguards slather on their noses.

The fiber optic cables, each one two to three times the width of a human hair, would be installed on the roof of a house, car or any other structure.

Only the very tip of the cables would be exposed to the outside environment.

Light enters the tip of the fiber and travels to the end. The light is absorbed and turned into electrical energy along the way.

Once the light reaches the end of the fiber, it actually bounces back, giving the zinc oxide another chance to absorb any light missed during the first pass.

The fibers can be cut to any length depending on the needs of the user. A 10-centimeter (four-inch) fiber would conservatively generate about 0.5 volts.

Powering a 10-watt light bulb would require about 10,000 fibers, each about 10 centimeters (four inches) long. That might sound like a lot of fibers, but it's about the same size as a small handful of human hair.

Although the fibers are small, they aren't particularly efficient. Right now, they convert about 3.3 percent of all the light that enters them into electricity. Some silicon-based solar cells can absorb 30 percent of light.

Wang thinks that further work could get his number up to 8 percent.

Efficiency can take a backseat to ease of production, however. Conventional solar cells with the highest efficiencies are generally expensive to produce, require temperatures of several hundred degrees, and can damaged relatively easily by rocks or hail.

Fiber optic photovoltaics, on the other hand, are easy to produce. A solution of zinc oxide is heated to about 70 degrees Celsius (158 degrees Fahrenheit), about the same temperature as a cup of coffee. The cables are then dipped into the zinc oxide and allowed to dry.

Expose one end of the fiber to light and attach some wiring, and the electricity will start to flow.

Wang isn't the only person who hopes to rid rooftops of conspicuous solar panels. Raymond Saluccio is the CEO of New Jersey based EarthSure, a company that recently announced its own plan to route light, be it from the sun or incandescent light bulbs, using fiber optic cables connected to underground solar panels.

Known as SubSolar, the plan could generate solar power 24 hours a day, seven days a week in hospitals or office buildings where the lights are always on.

"We don't even have to put the fiber optics on a roof," said Saluccio "We can put our fiber optics cables in the lawn, on a tree, even indoors."

Instead of generating power on the surface of the fiber optic cable, the light would travel to submarine-shaped capsules buried several feet underground.

Homes could be powered by six-foot-long systems, while businesses would need a pod up to 20 feet long and 10 feet in diameter.

"Putting the panels underground we can make them out of cheaper materials because they don't have to stand up to heat, cold, rain, hail, or sleet," said Saluccio.

Until EarthSure can raise more funds to develop a prototype device or Wang creates a start up company to produce and market, concealed solar panels will remain out of reach for most consumers.