Hit "Print" for Solar Panels
July 13, 2011
Ah, solar panels: so clean, so elegant—and so bloody expensive.
Covering your roof with photovoltaics may save you money in the long
run, but it requires the installation of a lot of heavy and
expensive equipment up front. Thin-film solar panels, printed on
sheets at industrial scales, are slowly making inroads, but suppose
you wanted to power something much smaller than a house — an
appliance or an alarm clock, say. Never mind waiting for industry to
invent the product you're waiting for. According to a paper
published in the journal Advanced Materials, it's now possible to
print photovoltaic cells on paper almost as you would a document —
and almost as cheaply too.
The improbable new “solar papers,” developed by a team of MIT
researchers, start out looking like an ordinary sheet of paper — and
that's because they are. Anything from printing paper to tissue,
tracing paper, or newspaper can be used. It's what happens next
that's special. As the paper is run through the solar printer, it
enters a vacuum chamber, where a spray of photovoltaic material
passes through a mask in the shape of solar cells and is deposited
onto the surface of the sheets. After five such layers are applied,
a functioning photovoltaic device emerges from the other end. The
work any one sheet can do is modest, but it's real all the same. In
an MIT video, a researcher clips some wires to one end of a paper
and shines a light onto it. An LCD clock at the other end of the
wires starts to display the time.
There are a lot of things that make solar paper preferable to
traditional panels — particularly the radical difference in cost.
Conventional solar cells waste a lot of money on inactive components
– especially the substrate, typically glass, used to support the
active photovoltaic stuff. Researchers note that paper costs
one-thousandth as much as glass for a given area. Then there's the
printing process itself. Conventional panels rely on expensive
chemicals deposited at very high temperatures. The MIT printer uses
cheaper vapor deposition and can operate at temperatures below 120C
(248 F). That's hot, but nothing compared to the 800C (1,470) needed
for today's panels.
Solar paper is also rugged. Print it out and you can fold it up and
tuck it in your pocket without damaging its light-reactive surface.
The MIT scientists demonstrated this quality by printing one of the
cells onto a sheet of PET plastic, which is thinner than the stuff
used for soda bottles, and folding and unfolding the plastic 1,000
times. The cells performed at the same level even after all that
abuse, whereas commercially produced solar cells printed on the same
material usually crash after just a single folding.
“Often people talk about deposition on a flexible device — but then
they don't flex it, to actually demonstrate [that it can survive the
stress],” study author Karen Gleason said in a press release. She
and her team also ran a sheet through the high temperatures of a
laser printer to demonstrate that it would still function — and it
did. And solar cells produced a year ago are still working, which
shows that they last for quite a while.
Nobody pretends that solar paper is ready to make a big dent in the
world's energy problem just yet. Odds are you don't need to operate
your alarm clock outside and there are already plenty of small
electronic items manufactured with small, old-fashioned solar panels
built in just in case you do. But as a proof of principle — that
principle being that you don't have to go broke to go green — the
MIT announcement is a very important one. Put together enough of
those small steps and, over time, you can get where you're going.
Source: www.time.com