“La sabiduría de la vida consiste en la eliminación de lo no esencial. En reducir los problemas de la filosofía a unos pocos solamente: el goce del hogar, de la vida, de la naturaleza, de la cultura”.
Lin Yutang
Cervantes
Hoy es el día más hermoso de nuestra vida, querido Sancho; los obstáculos más grandes, nuestras propias indecisiones; nuestro enemigo más fuerte, el miedo al poderoso y a nosotros mismos; la cosa más fácil, equivocarnos; la más destructiva, la mentira y el egoísmo; la peor derrota, el desaliento; los defectos más peligrosos, la soberbia y el rencor; las sensaciones más gratas, la buena conciencia, el esfuerzo para ser mejores sin ser perfectos, y sobretodo, la disposición para hacer el bien y combatir la injusticia dondequiera que esté.
MIGUEL DE CERVANTES Don Quijote de la Mancha.
La Colmena no se hace responsable ni se solidariza con las opiniones o conceptos emitidos por los autores de los artículos.
21 de marzo de 2017
Researchers Think They're Getting Closer to Making Spray-On Solar Cells a Reality
by
Chisaki Watanabe
Study by Japanese scientists in 2009 sets off perovskite boom
Oxford PV may begin commercializing technology by end of 2018
The creation process of perovskite solar cells. Source: Segawa Laboratory at Tokyo University
Imagine a future when solar cells can be sprayed or
printed onto the windows of skyscrapers or atop sports utility vehicles
-- and at prices potentially far cheaper than today’s silicon-based
panels.
It’s not as far-fetched it seems. Solar researchers and
company executives think there’s a good chance the economics of the $42
billion industry will soon be disrupted by something called perovskites,
a range of materials that can be used to harvest light when turned into
a crystalline structure.
The hope is that perovskites, which can
be mixed into liquid solutions and deposited on a range of surfaces,
could play a crucial role in the expansion of solar energy applications
with cells as efficient as those currently made with silicon. One
British company aims to have a thin-film perovskite solar cell
commercially available by the end of 2018.
“This is the front-runner of low-cost solar cell technologies,” said Hiroshi Segawa,
a professor at the University of Tokyo who’s leading a five-year
project funded by the Japanese government that groups together
universities and companies such as Panasonic Corp. and Fujifilm Corp. to
develop perovskite technology.
Comparing efficiencies of solar cells based on silicon and perovskite. Source: Martin Green at UNSW Sydney
Not
everyone is sold on perovskite as a game-changer from the industry’s
heavy reliance on silicon photovoltaic cells. That said, recent research
pointing to the material’s potential continues to grip the solar energy
research community.
The World Economic Forum picked the material as one of its top 10
emerging technologies of 2016. Meanwhile, solar panel makers and top
universities in Europe, the U.S. and Asia are racing to commercialize
the technology, with researchers churning out as many as 1,500 papers a
year on the material.
Momentum Builds
Perovskite’s usefulness was first hinted at back in 2006 when Tsutomu Miyasaka, a
professor at Toin University of Yokohama, was approached by a graduate
student interested in testing how well the material could convert
sunlight to electricity. Though he’d been testing a number of different
materials for solar panels, the Japanese academic had never heard of the
synthesized crystal, Miyasaka said in an interview.
The idea to
use perovskite, which is based on the same structure as a mineral named
after Russian mineralogist Lev Perovski, initially went nowhere. Its
structure was poorly understood and the industry had already latched on
to silicon as the best material to convert sunlight into electricity.
Silicon solar cells have been around since the early days of the space program and now dominate the industry, with global shipments
of solar products expected to have totaled $41.9 billion in 2016,
according to market researcher IHS Markit. But they have limitations.
For one, tremendous amounts of energy are needed to produce the silicon
in solar cells.
Things began to change for perovskite with the
first publication of research on the material by Miyasaka’s group in the
Journal of the American Chemical Society in 2009.
“We
had been turned down by magazines like Nature and Science and I suspect
that’s because it was low in efficiency and also the material was
unheard of,” Miyasaka said. “We talked about perovskite on many
occasions but there was no feedback. Ninety-nine percent of people
didn’t understand the structure of perovskite and they decided to ignore
it.”
Efficiency Gains
Since then, the buzz has grown,
thanks to research showing perovskite can convert sunlight more
efficiently than initially thought. The big breakthrough came in 2012
when the material’s conversion efficiency -- the portion of sunlight
that can be converted into electricity -- rose above 10 percent for the
first time.
Passing that threshold attracted the attention of
researchers toiling away on different types of solar cells that were
then yielding lower efficiency, according to Martin Green, a professor at the University of New South Wales who also studies perovskite.
The
efficiency of perovskite cells has improved further -- exceeding 20
percent in the lab -- to reach a level that took silicon cells years to
achieve. Though conventional solar cells are still more efficient at
about 25 percent, they’ve been stuck at that level for about 15 years,
according to the World Economic Forum.
“All of a sudden you got about 10,000 researchers switching over to this field overnight,” Green said.
The
efficiency improvements keep coming. In December, engineers at Green’s
University of New South Wales announced they achieved a record 12.1
percent efficiency rating on a cell measuring 16 square centimeters.
That’s the highest efficiency on a large-size perovskite solar cell to
date, according to the university’s website. Higher efficiency ratings
have been reported on smaller surfaces.
In September, Ecole
Politechnique Federale de Lausanne (EPFL) in Switzerland said their
scientists achieved an efficiency rating of 21.6 percent by adding
rubidium to improve stability. Panasonic, a Japanese maker of
silicon-based solar panels, took part in the Swiss project.
Researchers at Stanford University and the University of Oxford
wrote in October their technology obtained a 20.3 percent efficiency,
according to the Science website. The gain was achieved by stacking two
perovskite cells to capture low-energy and high-energy light waves.
Solar Walls
The advances have raised the possibility that perovskite cells could one day be placed on top of cars, windows, and walls. Oxford Photovoltaics Ltd.,
a spin-off from the University of Oxford, says it’s developing
thin-film perovskite solar cells able to be printed directly onto
silicon solar cells. In December, Oxford PV said it got 8.1 million
pounds ($10 million) of additional funding from investors including Statoil ASA.
“We
expect to have a product that meets industry requirements by the end of
2017,” Frank Averdung, chief executive officer at Oxford PV said by
email. “Adding some time for qualification, certification and
production, our first product could be commercially available towards
the end of 2018.”
Challenges remain. For one, researchers must
still come up with a way to ensure the material remains stable outdoors
for long periods of time. Methods for painting the material on large
surfaces must also be improved, said Masanori Iida, an official at the
technology and design sector at Panasonic. “It is difficult to
continuously make the coating even,” Iida said by email.
“Perovskites aren’t ready for prime time,” said Robert Armstrong,
director of the Massachusetts Institute of Technology’s Energy
Initiative. “They degrade too quickly,” he said, but added that progress
is being made to make them more stable.
Others are also cautious
about the commercial viability of this new solar technology. “It
certainly is going to be more than five years and it could be never,”
Green, the professor at the University of New South Wales, said,
referring to how soon perovskite solar cells will be commercially
available. “For any technology to be marketable, it has to be certified
and the testing process could take time. You need someone to bankroll an
operation to scale up to go into manufacturing.”