EVENTS, ADVANCES, AND NEWS
■ BY JEFF ECKERT
PHOTO COUR TES Y OF DONNA COVENEY, MI T.
■ Organic solar concentrators that
collect and focus different colors of
sunlight may soon be integrated into
cost-efficient power systems.
The idea of harnessing concentrated
sunlight is not a new concept —
far older than our childhood pastime
of frying ants with a magnifying glass.
According to legend, Archimedes used
polished bronze shields as mirrors
during the siege of Syracuse, circa
214 BC, in an attempt to repel the
invaders. Unfortunately, it didn’t work
all that well, as the city eventually
fell, and Archimedes was slain by a
Roman soldier. Likewise, modern
attempts to harness daylight have
met with limited success, particularly
for generating electricity.
PHOTO COURTESY OF IBM.
Focused sunlight is nice for drying
fish and even powering steam engines,
but the associated heat has about the
same effect on semiconductors as it
has on ants. In the 1970s, scientists
experimented with dye-impregnated
plastic sheets that were designed to
capture photons on the flat surface
and channel them toward the edges,
thus concentrating the energy while
avoiding the heat problem. But the
dyes weren’t stable enough, and the
photons tended to be reabsorbed
by the plastic.
In July, however, some MIT
engineers announced a new twist on
this long-abandoned technology. The
new method uses dye-coated glass
to collect and channel the photons
toward an array of solar cells mounted
along the edges. It seems that using
thin, concentrated layers of dyes on
glass works better than filling plastic
with lower concentrations, and the
materials are cheaper.
One proponent has predicted
that we could be as little as three
years away from a commercial product
that allows a building to draw energy
from tinted windows and roof-mounted
panels. The hitch seems to be that
they have yet to develop dyes that
can endure the 20 to 30 years of
exposure required for a viable product.
Coming at it from another direction,
IBM earlier this year announced a
breakthrough in concentrator
photovoltaics (CPV) in which a large
lens focused a record-setting 230W
(equivalent to 2,300 suns) onto a
one sq cm solar cell. That energy was
then converted into 70W of usable
electrical power, which represents
about five times the power density
developed in typical solar farms.
The trick was overcoming the
■ IBM’s breakthrough concentrator
photovoltaic cells could bring more
watts at lower cost.
aforementioned heat issue, which
they accomplished using a “liquid
metal” thermal cooling system
originally developed for the
The system uses a thin layer of a
gallium/indium compound sandwiched
between the cell and a copper cooling
plate. The layer transfers heat so
efficiently that the temperature of the
chip is reduced from 1,600 to 85°C.
If the company can overcome the
usual challenges in moving “from lab
to fab,” the result could be a system
that cuts the number of photovoltaic
cells and related components by
90 percent, achieving similar cost
The camera-in-a-pill concept has
been around for several years,
by which doctors drop a miniature
still camera down your throat, take
snapshots of your innards, and transmit
gooey Kodak moments to an external
receiver. This is pretty useful for
locating hemorrhages and cysts in
your intestines, but the gutcams —
weighing about 5 g —tend to drop
through your esophagus and down to
the lower stomach wall too quickly to
gather much information. As a result,
patients who need a detailed
■ This pill camera can be magnetically
steered to provide more detailed
esophageal and stomach analysis.
PHOTO COUR TES Y OF FRAUNHOFER INSTI TUTE
FOR BIOMEDICAL ENGINEERING.