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.