New
Solar Panel Technology Stylish and Sustainable
The new cell technology combines
nanoparticles and organic dyes that can be produced in any number of colors and
designs.
The key component of
the new modules is an organic dye which in combination with nanoparticles
converts sunlight into electricity. Due to the small size of the nanoparticles,
the modules are semi-transparent. This aspect makes them well suited for façade
integration. The new solar cells are being developed by members of the
Fraunhofer Institute for Solar Energy Systems ISE, who will be presenting their
new technology in
The solar module prototype is amber in color.
It is possible, however, to produce the modules in other colors, or even to
print images or text on the module so that it serves as a decorative element. These
design options open up an entirely new range of possible applications. Instead
of mounting the solar module on the roof of a building, the electricity
producer could be integrated into windows. Used in this way, the new technology
not only prohibits direct sunlight from entering the building interior but also
generates electricity at the same time.
“We don’t see the dye solar cell as being a
rival to the conventional silicon cell,” says Fraunhofer ISE physicist Andreas
Hinsch. The module prototypes only achieve an efficiency of four percent, which
is not sufficient for rooftop applications in comparison to the performance of
crystalline silicon solar cells. On the other hand, dye solar cells have a
clear advantage when it comes to façade integration.
The wafer-thin electricity-generating film, which
lies between two glass panes, is produced from nanoparticles and applied using
screen printing technique. This technique makes it possible to integrate any
desired image on the module. A glass facade made of this material can be given
a decorative and promotionally effective design, such as a colorful company
logo, and delivers electricity into the bargain.
The dye solar module is still a prototype.
The Fraunhofer researchers have developed it together with industry partners in
the ColorSol project funded by the German Federal Ministry of Education and
Research BMBF.
One particular challenge posed by the new
technology is that the narrow gap between the two glass panes must be
hermetically sealed so that no air can get in and destroy the reactive substances
inside. The Fraunhofer experts have come up with a special solution to this
problem. Instead of using polymeric glue like their competitors, they have
decided to work with glass frit. To this end, glass powder is screen-printed
onto the panes, and fuses with them at a temperature of around 600 degrees
Celcius.
Fatigue tests under various weather
conditions have shown that the solar cells still function properly even after
several thousand hours. The long-term stability as such, however, has yet to be
officially certified.
Article Courtesy
of http://www.nytimes.com/2008/10/12/business/12stream.html?_r=1&emc=eta1&oref=slogin
Intuition
+ Money: An Aha Moment
By JOHN MARKOFF
Published: October
11, 2008
IT started with a Harvard physicist acting on
a hunch. It ended up producing a new material, called black silicon, that could
have a broad impact on technologies ranging from ultrasensitive sensors to
photovoltaic cells.
Rick Friedman for
The New York Times
James Carey, left, and Stephen Saylor of
SiOnyx with black silicon wafers. Harvard plans to announce it has licensed
patents for black silicon to the company.
On Monday,
Harvard plans to announce that it has licensed patents for black silicon to
SiOnyx, a company in
This would never have happened if the
physicist, Eric Mazur, and his graduate students had stuck to the original
purpose of their research. He says their experience offers a lesson in government
financing of science and technology, which is becoming so narrow and applied as
to make discoveries like theirs much less likely.
A more narrow focus does have its advantages:
for one, it can be more likely to produce an immediate payoff.
But in the current research environment, “you
are less likely to be open to serendipity,” said Judith L. Estrin, an
electrical engineer and author of “Closing the Innovation Gap: Reigniting the
Spark of Creativity in a Global Economy” (McGraw-Hill, 2008).
Black silicon was discovered because Dr.
Mazur started thinking outside the boundaries of the research he was doing in
the late 1990s. His research group had been financed by the Army Research
Organization to explore catalytic reactions on metallic surfaces.
“I got tired of metals and was worrying that
my Army funding would dry up,” he said. “I wrote the new direction into a
research proposal without thinking much about it — I just wrote it in; I don’t
know why.” And even though there wasn’t an immediate practical application, he
received the financing.
It was several years before he directed a
graduate student to pursue his idea, which involved shining an exceptionally
powerful laser light — briefly matching the energy produced by the sun falling
on the surface of the entire earth — on a silicon wafer. On a hunch, the
researcher also applied sulfur hexafluoride, a gas used by the semiconductor
industry to make etchings for circuits.
The silicon wafer looked black to the naked
eye. But when Dr. Mazur and his researchers examined the material with an
electron microscope, they discovered that the surface was covered with a forest
of ultra-tiny spikes.
At first, the researchers had no idea what
they had stumbled onto, and that is typical of the way many scientific
discoveries emerge. Cellophane, Teflon, Scotchgard and aspartame are among the
many inventions that have emerged through some form of fortunate accident or
intuition.
“In science, the most exciting expression
isn’t ‘
Black silicon has since been found to have
extreme sensitivity to light. It is now on the verge of commercialization, most
likely first in night vision systems.
“We have seen a 100 to 500 times increase in
sensitivity to light compared to conventional silicon detectors,” said James
Carey, a co-founder of SiOnyx who worked on the original experiments as a
Harvard graduate student.
Dr. Mazur is an investor in SiOnyx and
chairman of its scientific advisory board. As a result of his research, a
number of academic and corporate research groups are still exploring the
material, which absorbs about twice as much visible light as normal silicon and
has the ability to detect infrared light that is invisible to the current generation
of silicon detectors.
SiOnyx is already commercializing
sensor-based chips as a technology development platform for other companies and
for use in next-generation infrared imaging systems.
The new technology has a tremendous cost
advantage in that it is compatible with current semiconductor manufacturing
plants, according to Stephen Saylor, SiOnyx’s chief executive. It is certain to
attract broad attention from a range of industries, including scientific and
medical imaging markets.
In the future, the low cost and higher
sensitivity of black silicon may also make it a contender in the
multibillion-dollar digital camera and video markets, an area currently
dominated by silicon and charge-coupled-device sensors.
SiOnyx is continuing to experiment with the
photovoltaic properties of black silicon, but Mr. Saylor said the company had
no plans to jump into the market to become a solar cell manufacturer. “Our
engagement is going to be as a technology provider, not as a producer,” he
said.
Instead, he is eager to get a new generation
of supersensitive light detectors into the hands of entrepreneurs and
experimenters who will be able to take the technology in unpredictable
directions.
AND that is how this technology got to where
it is today. To Dr. Mazur, that should be a lesson to technology funding
agencies like the National Science Foundation and the Defense Advanced Research
Projects Agency of the Pentagon.
“This is a very strong case in point for
funding science for the advancement of science,” he said.
Article
Courtesy of http://www.physorg.com/news144940463.html
Solar
power game-changer: 'Near perfect' absorption of sunlight, from all angles
A new
anti-reflective coating developed by researchers at Rensselaer Polytechnic
Institute could help to overcome two major hurdles blocking the progress and
wider use of solar power. The nanoengineered coating boosts the amount of
sunlight captured by solar panels and allows those panels to absorb the entire
spectrum of sunlight from any angle, regardless of the sun's position in the
sky. Credit: Rensselaer/Shawn Lin
No matter which way
you look at it, the notion of harvesting energy from the sun to power our homes
and businesses is more absorbing than ever.
Researchers at
Rensselaer Polytechnic Institute have discovered and demonstrated a new method
for overcoming two major hurdles facing solar energy. By developing a new
antireflective coating that boosts the amount of sunlight captured by solar
panels and allows those panels to absorb the entire solar spectrum from nearly
any angle, the research team has moved academia and industry closer to
realizing high-efficiency, cost-effective solar power.
"To get maximum
efficiency when converting solar power into electricity, you want a solar panel
that can absorb nearly every single photon of light, regardless of the sun's
position in the sky," said Shawn-Yu Lin, professor of physics at
Results of the year-long project are explained in the paper "Realization
of a Near Perfect Antireflection Coating for Silicon Solar Energy,"
published this week by the journal Optics Letters.
An untreated silicon solar cell only absorbs 67.4 percent of sunlight shone
upon it — meaning that nearly one-third of that sunlight is reflected away and
thus unharvestable. From an economic and efficiency perspective, this
unharvested light is wasted potential and a major barrier hampering the
proliferation and widespread adoption of solar power.
After a silicon surface was treated with Lin's new nanoengineered reflective
coating, however, the material absorbed 96.21 percent of sunlight shone upon it
— meaning that only 3.79 percent of the sunlight was reflected and unharvested.
This huge gain in absorption was consistent across the entire spectrum of
sunlight, from UV to visible light and infrared, and moves solar power a
significant step forward toward economic viability.
Lin's new coating also successfully tackles the tricky challenge of angles.
Most surfaces and coatings are designed to absorb light — i.e., be
antireflective — and transmit light — i.e., allow the light to pass through it
— from a specific range of angles. Eyeglass lenses, for example, will absorb
and transmit quite a bit of light from a light source directly in front of
them, but those same lenses would absorb and transmit considerably less light if
the light source were off to the side or on the wearer's periphery.
This same is true of conventional solar panels, which is why some industrial
solar arrays are mechanized to slowly move throughout the day so their panels
are perfectly aligned with the sun's position in the sky. Without this
automated movement, the panels would not be optimally positioned and would
therefore absorb less sunlight. The tradeoff for this increased efficiency,
however, is the energy needed to power the automation system, the cost of
upkeeping this system, and the possibility of errors or misalignment.
Lin's discovery could antiquate these automated solar arrays, as his
antireflective coating absorbs sunlight evenly and equally from all angles.
This means that a stationary solar panel treated with the coating would absorb
96.21 percent of sunlight no matter the position of the sun in the sky. So
along with significantly better absorption of sunlight, Lin's discovery could
also enable a new generation of stationary, more cost-efficient solar arrays.
"At the beginning of the project, we asked 'would it be possible to create
a single antireflective structure that can work from all angles?' Then we
attacked the problem from a fundamental perspective, tested and fine-tuned our
theory, and created a working device," Lin said.
Typical antireflective coatings are engineered to transmit light of one
particular wavelength. Lin's new coating stacks seven of these layers, one on
top of the other, in such a way that each layer enhances the antireflective
properties of the layer below it. These additional layers also help to
"bend" the flow of sunlight to an angle that augments the coating's
antireflective properties. This means that each layer not only transmits
sunlight, it also helps to capture any light that may have otherwise been
reflected off of the layers below it.
The seven layers, each with a height of 50 nanometers to 100 nanometers, are
made up of silicon dioxide and titanium dioxide nanorods positioned at an
oblique angle — each layer looks and functions similar to a dense forest where
sunlight is "captured" between the trees. The nanorods were attached
to a silicon substrate via chemical vapor disposition, and Lin said the new
coating can be affixed to nearly any photovoltaic materials for use in solar
cells, including III-V multi-junction and cadmium telluride.
