[LINK] Rice unveils super-efficient solar-energy technology
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stephen at melbpc.org.au
Tue Nov 20 23:10:35 AEDT 2012
Rice unveils super-efficient solar-energy technology
By Jade Boyd November 19, 2012
HOUSTON (Nov. 19, 2012) Rice University scientists have unveiled a
revolutionary new technology that uses nanoparticles to convert solar
energy directly into steam. The new solar steam method from Rices
Laboratory for Nanophotonics (LANP) is so effective it can even produce
steam from icy cold water.
Details of the solar steam method were published online today in ACS
Nano. The technology has an overall energy efficiency of 24 percent.
Photovoltaic solar panels, by comparison, typically have an overall
energy efficiency around 15 percent. However, the inventors of solar
steam said they expect the first uses of the new technology will not be
for electricity generation but rather for sanitation and water
purification in developing countries.
This is about a lot more than electricity, said LANP Director Naomi
Halas, the lead scientist on the project. With this technology, we are
beginning to think about solar thermal power in a completely different
The efficiency of solar steam is due to the light-capturing nanoparticles
that convert sunlight into heat. When submerged in water and exposed to
sunlight, the particles heat up so quickly they instantly vaporize water
and create steam. Halas said the solar steams overall energy efficiency
can probably be increased as the technology is refined.
Were going from heating water on the macro scale to heating it at the
nanoscale, Halas said. Our particles are very small even smaller than
a wavelength of light which means they have an extremely small surface
area to dissipate heat. This intense heating allows us to generate steam
locally, right at the surface of the particle, and the idea of generating
steam locally is really counterintuitive.
To show just how counterintuitive, Rice graduate student Oara Neumann
videotaped a solar steam demonstration in which a test tube of water
containing light-activated nanoparticles was submerged into a bath of ice
water. Using a lens to concentrate sunlight onto the near-freezing
mixture in the tube, Neumann showed she could create steam from nearly
Steam is one of the worlds most-used industrial fluids. About 90 percent
of electricity is produced from steam, and steam is also used to
sterilize medical waste and surgical instruments, to prepare food and to
Most industrial steam is produced in large boilers, and Halas said solar
steams efficiency could allow steam to become economical on a much
People in developing countries will be among the first to see the
benefits of solar steam. Rice engineering undergraduates have already
created a solar steam-powered autoclave thats capable of sterilizing
medical and dental instruments at clinics that lack electricity. Halas
also won a Grand Challenges grant from the Bill and Melinda Gates
Foundation to create an ultra-small-scale system for treating human waste
in areas without sewer systems or electricity.
Solar steam is remarkable because of its efficiency, said Neumann, the
lead co-author on the paper. It does not require acres of mirrors or
solar panels. In fact, the footprint can be very small. For example, the
light window in our demonstration autoclave was just a few square
Another potential use could be in powering hybrid air-conditioning and
heating systems that run off of sunlight during the day and electricity
at night. Halas, Neumann and colleagues have also conducted distillation
experiments and found that solar steam is about two-and-a-half times more
efficient than existing distillation columns.
Halas, the Stanley C. Moore Professor in Electrical and Computer
Engineering, professor of physics, professor of chemistry and professor
of biomedical engineering, is one of the worlds most-cited chemists. Her
lab specializes in creating and studying light-activated particles. One
of her creations, gold nanoshells, is the subject of several clinical
trials for cancer treatment.
For the cancer treatment technology and many other applications, Halas
team chooses particles that interact with just a few wavelengths of
light. For the solar steam project, Halas and Neumann set out to design a
particle that would interact with the widest possible spectrum of
sunlight energy. Their new nanoparticles are activated by both visible
sunlight and shorter wavelengths that humans cannot see.
Were not changing any of the laws of thermodynamics, Halas
said. Were just boiling water in a radically different way.
Paper co-authors include Jared Day, graduate student; Alexander Urban,
postdoctoral researcher; Surbhi Lal, research scientist and LANP
executive director; and Peter Nordlander, professor of physics and
astronomy and of electrical and computer engineering. The research was
supported by the Welch Foundation and the Bill and Melinda Gates
VIDEO is available at:
A copy of the ACS Nano paper is available at:
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