 Copper Increases
Efficiency of Solar Cells
Shell Solar has used copper to design an environmentally
friendly, solar-energy product that will provide power to the
people of the 21st Century.
Shell Solar is the world's leading manufacturer in the Photovoltaic
industry. Working with the assistance of experts from several
countries, Shell is trying to use sunlight, along with another
resource that is in abundant supply: copper, to power the future.
Shell Solar set about testing the capabilities of a new thin-film
photovoltaic module that is created by applying a fine film of
copper indium diselenide (CIS) to a glass backing - producing
a semi-conductor. When the semi-conductor is exposed to sunlight,
it actively converts sunlight into electricity - at a cost up
to 10 times less than the crystalline silicon based cells now
on the market.
This record setting one-foot by four-foot module was developed
in collaboration with U.S. Government's National Renewable Energy
Laboratory (NREL). Record breaking efficiencies of more than
12 percent have been confirmed for this new thin-film module
- Shell Solar ST40 large-area copper indium diselenide (CIS)
photovoltaic (PV) product. Shell has also begun research and
development on a new module that combines amorphous silicon with
CIS to create a double-layered thin-film that has a conversion
efficiency of 15.6 percent. Amorphous silicon, which powers small
solar devices, makes up more than 30 percent of all the photovoltaic
power generated in the world. But this material also has a flaw
that causes it to lose efficiency upon exposure. Layering this
material with CIS might help eliminate this efficiency flaw.
This double layering is also being tried with a variety of other
materials to achieve higher performance at a lower cost.
"The increased efficiencies in solar technology brings
us one step closer to the goal of developing this renewable energy
resource for practical use in our everyday lives," said
Energy Secretary Bill Richardson.
The joint effort between the DOE and Shell Solar marks a partnership
that is working to supply energy for the future while keeping
an eye on environmental concerns. After testing at the NREL Outdoor
Test Facility in Golden, Colorado, the array's efficiency has
proved to be 40 percent above the closest thin-film contender,
while all modules surpassed the 10 percent DOE year 2000 goal
for commercial CIS modules.
"This is an important research milestone and a stunning
achievement," James Rannels, Acting Director, Office of
PV and Wind Technology, DOE, said.
While Shell Solar produces a large product line of solar modules,
the ST40 is for higher power applications. Other Shell modules
are ideally suited for low power battery-charging applications,
such as in emergency telephones or telemetry systems, but higher
power modules like the copper indium diselenide modules can be
used in large grid-connected systems. This CIS technology can
be applied in applications where options were formerly limited
to crystalline silicon. The efficiency of these CIS modules has
opened doors to a variety of new uses. For instance, the matte-black
CIS solar module distinctive appearance makes it visually striking
in architectural applications, opening up new possibilities for
architects and designers of PV systems that are incorporated
into building facades.
The production of these new photovoltaic cells will provide
a cost-effective product that will make solar power cost effective
for many new applications. In these times of political instability,
there are stable supplies of energy readily available from the
sun. This goal can only be achieved by transferring the technology
from the lab to the factory for mass production - causing the
cost of solar energy to be greatly reduced and opening the door
for anyone to use this technology in the 21st century.
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