TECH KNOWLEDGEY
EVENTS, ADVANCES, AND NEWS
2010
■ BY JEFF ECKERT
ADVANCED TECHNOLOGY
NEW APPROACH TO SOLAR
We've become pretty much accustomed to the steady flow of ho-hum incremental improvements in solar
technology, but engineers at Stanford University
( www.stanford.edu) claim to have come up with a
process that can more than double the efficiency of solar
cell technology and even make it price competitive with
petroleum. Called photon enhanced thermionic emission
(PETE), it is uniquely able to simultaneously tap into the
sun's light and heat.
Most photovoltaic cells use a silicon semiconducting
material to convert photons into juice, but they use only a
portion of the light spectrum and discard the rest in the
form of heat. Unfortunately, such cells become less
efficient (and physically degraded) at higher temperatures,
so you generally can't boost their output via
concentrating devices such as parabolic dishes. (In 2008,
IBM demonstrated a system that focused 2,300
equivalent suns on a one sq cm cell to generate 70W, but
it required a "liquid metal" cooling system to keep the
temperature in check.) In contrast, a PETE device doesn't
really hit its peak output until it gets past about 200°C
(392°F), so there's no reason why you can't couple one
with a thermal conversion system to double the overall
output. The new photovoltaic is based on coating a
■ A small
PETE device
glows
inside a
vacuum
test
chamber.
different semiconductor material (in this case, gallium
nitride) with a layer of cesium to produce a substance
that can handle the high temperatures. The nice touch is
that, if properly designed, a PETE system can be
retrofitted to existing thermal systems for a relatively
inexpensive conversion. According to Prof. Nick Melosh,
"This is really a conceptual breakthrough, a new energy
conversion process, not just a new material or a slightly
different tweak. It is actually something fundamentally
different about how you can harvest energy." The
materials used in the devices are cheap and readily
available, so we're not talking about something that's
exotic and cost prohibitive. The only apparent catch is
that you probably won't want something sizzling on your
rooftop at temperatures as high as 800°C (1,500°C), so
the devices will probably be exiled to such places as the
Mojave Desert. ▲
US ARMY DEVELOPING SNAKEBOTS
The desktop prototype may not look like much, but the US Army Research Lab ( www.arl.army.mil) is expanding on snakebot technology developed at Carnegie Mellon's Robotics Institute that may allow the use of systems instead of
soldiers for dangerous search-and-rescue missions, IED disposal, and cargo and checkpoint inspections. The incarnation is
the Robotic Tentacle Manipulator, described as an "arrangement of the bases of several snakes in a circular array that
functions like a team using multiple parts of their bodies to manipulate an object, scan a room, or handle improvised
explosive devices." An interesting aspect is that the system is scalable and therefore can be built as a subsystem to larger
platforms such as the iRobot Warrior which is designed to traverse rough terrain and even climb stairs. It is also extensible
in that, by varying the number of links on each tentacle, you can adjust its reach and its ability to crawl, swim, climb, or
otherwise move through narrow spaces. Plus, fitted with a
camera, it can simultaneously send images back to the operator.
In fact, the subsystem can be equipped with an array of sensors,
including LADAR, allowing it to generate 3D images. It even
features touch sensitivity which allows it to balance objects and
detect applied forces. Researchers are hoping that the
manipulator will soon solve the "opening a door problem" — a
challenge posed by the variety of knobs, handles, levers, bars,
etc., used on doors. Summarizing, an Army rep observed, "This is
a distributed intelligence framework that permits advanced
manipulation algorithms to run on a complex but affordable
hardware platform." ▲
■ The Army’s snakebot will improve maneuverability
and autonomy for search-and-rescue and other operations.
10
November 2010