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Thinking
big while focusing on small, a solar company and a national energy lab
combined talents to develop a solar power concentrator that generates
electricity at prices competitive with natural gas.
The Amonix 7700 Concentrated Photovoltaic (CPV) Solar Power Generator, developed by Amonix and DOE’s National Renewable Energy Laboratory,
is the size of an IMAX screen but costs much less than comparable
generators, partly because of the efficiency of its small solar cells.
It delivers more “energy per acre” than anything yet available in the
solar energy world. The public-private partnership won a 2010 R&D 100 award.
The
7700 uses acrylic Fresnel lenses to concentrate sunlight up to 500
times its usual intensity and direct it onto 7,560 tiny, highly
efficient multi-junction PV cells.
The
cells, originally developed by NREL scientists, can convert 41.6% of the sunlight that shines on them into usable electricity in a
laboratory setting, a world record. The multi-junction cells on the
Amonix 7700 are achieving 31% efficiency at the module level and
27% at the system level in the field, the highest ever achieved
for an operating CPV concentrator.
A
six-inch square silicon wafer in traditional photovoltaic (PV) panels
produces about 2.5 watts of electricity. That same-sized wafer, cut into
hundreds of square-centimeter cells in the Amonix 7700, each teamed
with a Fresnel lens, produces more than 1,500 watts. It reduces the
required area for cells 500 times.
The
key breakthrough that lifted the 7700 to a 50% greater power
output than previous generations of Amonix generators was the
substitution of the multi-junction cells made of gallium indium arsenide
and gallium phosphide for the more common silicon cells.
A
conundrum was how to use the highly efficient cells without breaking
the bank. Researchers solved that problem by teaming an inexpensive
Fresnel lens—at less than $2 a pop—with each of the 7,560 high
efficiency solar cells that make up one 53-kilowatt 7700 system. The
500-power amplification of the Fresnel lens allowed the solar cells to
be tiny, while
still packing record-setting efficiency.
Solar
energy has found a niche on rooftops, especially of green-minded
homeowners. But if it is to play a major role in the broader electricity
market, it needs to come in at or below the costs of electricity
generated from coal, which is projected to cost from 6 cents to 15 cents
per kilowatt-hour in four years. The 7700’s cost per kilowatt-hour is
expected to be well within those price ranges as production and sales
continue to grow.
The
concentrator also is kinder to the environment than most large systems,
using no water in its operation. Propped up two feet above the land, it
doesn’t hinder the movement of wildlife. “You simply can’t put enough
solar systems on rooftops to achieve the scale and capacity necessary to
generate electricity in the quantities required by utilities and by
society,” said Amonix’s founder and chief technical officer, Vahan
Garboushian. “This is a technology that can meet the terawatt (trillions
of watts) needs of the world for clean electricity.”
