BACKGROUND: A team of different types of scientists at Rensselaer Polytechnic Institute has developed a radical new solar energy technology that promises to collect and distribute solar energy more efficiently. Rows, or stacks, of pivoting lenses incorporated into a glass building facade track the movement of the sun across the sky, focusing its rays onto high-tech solar cells. The new system uses high-tech solar-concentrator technology and advanced materials. The full-size prototype will be incorporated into a new building at The Center of Excellence in Syracuse, New York
HOW IT WORKS: The key breakthrough is the miniaturized concentrator solar cell, which uses a lens with concentric grooves to focus collected light. Even though it is only the size of a postage stamp -- compared to the usual solar collector area that spans 4 x 4 feet -- the cell is much more efficient in collecting and reusing solar energy. The lens focuses incoming sunlight onto the solar cell. Microchannels at the base of the module transfer energy in the form of heat and light to wires contained inside. Each vertical stack of lenses rolls and tilts like a track blind, keeping the surface of the lenses faced to incoming sunlight as the sun changes position in the sky throughout the day. Incorporating these new cells into arrays could make solar energy an option that is competitive with other energy sources, reducing our dependency on fossil fuels.
ABOUT SOLAR CELLS: The solar cells on calculators and satellites are photovoltaic cells or modules: groups of cells electrically connected and packaged together. Photovoltaics convert sunlight directly into electricity. Photovoltaic cells are made of semiconductor materials like silicon. When light strikes the cell, a certain portion of the light is absorbed by the semiconductor material. The energy of the absorbed light knocks electrons in the semiconductor material loose, allowing them to flow freely. Photovoltaic cells also all have one or more electric fields that act to force the freed electrons to flow in a certain direction. This flow of electrons is a current. By placing metal contacts on the top and bottom of the photovoltaic cell, the current can be drawn off to be used. For example, the current can power a calculator. However, conventional photovoltaic panels made from silicon to provide electricity are expensive, and thus not cost-competitive with electricity from the power grid.