|
Dear
Subscriber,
We are happy to announce that
Dr. Eric Wachsman, the Director of the Energy Research Center at
the University of Maryland, will be a plenary speaker at the
upcoming 2011 joint SPESIF conference (click on "COFE4" from our
homepage). He will also be leading the Maryland Clean Energy Summit
2010 at the Hilton Inner Harbor, October 4, 2010 with a wide range
of speakers and panelists.
This month we are featuring stories that convert or store
electricity. It is fascinating to see the improvement in conversion
of solar light and heat as Stanford University has achieved for up
to 40% efficiency. In 2007, Rensellaer Polytech reported a similar
invention with moving lenses for up to 80% efficiency
(ScienceDaily.com, "Bringing Sunlight Inside").
The "artificial leaf" article is the most recent one and certainly
an energy breakthrough. The flexible, rechargeable battery and
organic battery articles are also cutting edge technology. However,
that's what you have come to expect from Future Energy eNews!
Mark your calendars if you are in the DC area for the "USA Science
& Engineering Festival and Expo" on the National Mall, October
23-24, 2010, 10AM - 5:30 PM, which should be very educational and
scientific! See www.usasciencefestival.org for more
details.
Onward and upward,
|
|
|
|
1) A
New Way to Use the Sun's Energy |
by Katherine Bourzac.
Technology Review, August 2010.
Researchers have demonstrated a new mechanism for
converting both sunlight and heat into
electricity
A
new type of device that uses both heat and light from the sun
should be more efficient than conventional solar cells, which
convert only the light into electricity.
The device relies on a physical
principle discovered and demonstrated by researchers at Stanford
University. In their prototype, the energy in sunlight excites
electrons in an electrode, and heat from the sun coaxes the excited
electrons to jump across a vacuum into another electrode,
generating an electrical current. The device could be designed to
send waste heat to a steam engine and convert 50 percent of the
energy in sunlight into electricity--a huge improvement over
conventional solar cells.
NIcholas
Melosh .
|
The most common
silicon solar cells convert about 15 percent of the energy in
sunlight into electricity. More than half of the incoming solar
energy is lost as heat. That's because the active materials in
solar cells can interact with only a particular band of the solar
spectrum; photons below a certain energy level simply heat up the
cell.
One way to
overcome this is to stack active materials on top of one another in
a multijunction cell that can use a broader spectrum of light,
turning more of it into electrical current instead of heat, for
efficiencies up to about 40 percent. But such cells are complex and
expensive to make.
Looking for a
better way to take advantage of the sun's heat, Stanford's
Nicholas Melosh was inspired by highly efficient cogeneration systems
that use the expansion of burning gas to drive a turbine and the
heat from the combustion to power a steam engine. But thermal
energy converters don't pair well with conventional solar devices.
The hotter it is, the more efficient thermal energy conversion
becomes. Solar cells, by contrast, get less efficient as they heat
up. At about 100 �C, a silicon cell won't work well; above 200 �C,
it won't work at all.
The breakthrough came when the Stanford
researchers realized that the light in solar radiation could
enhance energy conversion in a different type of device, called a
thermionic energy converter, that's conventionally driven solely by
heat. Thermionic converters consist of two electrodes separated by
a small space. When the positive electrode, or cathode, is heated,
electrons in the cathode get excited and jump across to the
negative electrode, or anode, driving a current through an external
circuit. These devices have been used to power Russian satellites
but haven't found any applications on the ground because they must
get very hot, about 1,500 �C, to operate efficiently. The cathode
in these devices is typically made of metals such as
cesium.
Melosh's group replaced the cesium cathode with
a wafer of semiconducting material that can make use of not only
heat but also light. When light strikes the cathode, it transmits
its energy to electrons in the material in a way that's similar to
what happens in a solar cell. This type of energy transfer doesn't
happen in the metals used to make these cathodes in the past, but
it's typical of semiconductor materials. It doesn't take quite as
much heat for these "pre�xcited" electrons to jump to the anode, so
this new device can operate at lower temperatures than conventional
thermionic converters, but at higher temperatures than a solar
cell.
The Stanford researchers call this new mechanism
PETE, for photon-enhanced thermionic emission. "The light helps
lift the energy level of the electrons so that they will flow,"
says Gang Chen, professor of power engineering at
MIT. "It's a long way to a practical device, but this work shows
that it's possible," he says.
The Stanford group's prototype, described this
month in the journal Nature Materials, uses gallium
nitride as the semiconductor. It converts just about 25 percent of
the energy in light into electricity at 200 �C, and the efficiency
rises with the temperature. Stuart Licht, professor of chemistry at
George Washington University, says the process would have an
"advantage over solar cells" because it makes use of heat in
addition to light. But he cautions: "Additional work will be needed
to translate this into a practical, more efficient
device."
The Stanford group is now working to do just
that. The researchers are testing devices made from materials that
are better suited to solar energy conversion, including silicon and
gallium arsenide. They're also developing ways of treating these
materials so that the device will work more efficiently in a
temperature range of 400 �C to 600 �C; solar concentrators would be
used to generate such high temperatures from sunlight.
Even at high temperatures, the photon-enhanced
thermionic converter will generate more heat than it can use;
Melosh says this heat could be coupled to a steam engine for a
solar-energy-to-electricity conversion efficiency exceeding 50
percent. These systems are likely to be too complex and expensive
for small-scale rooftop installations. But they could be economical
for large solar-farm installations, says Melosh, a professor of
materials science and engineering. He hopes to have a device ready
for commercial development in three years.
back to table of contents
|
2) Electron
Switch Between Molecules Points Way to New High-Powered Organic
Batteries |
ScienceDaily (Sep. 16,
2010)
-
The development of new organic batteries -- lightweight energy
storage devices that work without the need for toxic heavy metals
-- has a brighter future now that chemists have discovered a new
way to pass electrons back and forth between two
molecules.
The research is also a necessary step
toward creating artificial photosynthesis, where fuel could be
generated directly from the sun, much as plants do.
University of Texas at Austin chemists
Christopher Bielawski and Jonathan Sessler led the research, which
was published in Science.
This is an illustration of an
assembled set of different molecules. These molecules meet,
exchange electrons and then disassemble because chloride ions,
which are represented as green spheres, are present. If these
chloride ions are removed, the entire process can be
reversed
When molecules meet, they often
form new compounds by exchanging electrons. In some cases, the
electron transfer process creates one molecule with a positive
charge and one molecule with a negative charge. Molecules with
opposite charges are attracted to each other and can combine to
form something new.
In their research, the chemists
created two molecules that could meet and exchange electrons but
not unite to form a new compound.
"These molecules were effectively
spring-loaded to push apart after interacting with each other,"
says Bielawski, professor of chemistry. "After electron transfer
occurs, two positively charged molecules are formed which are
repelled by each other, much like magnets held in a certain way
will repel each other. We also installed a chemical switch that
allowed the electron transfer process to proceed in the opposite
direction."
Sessler adds, "This is the first
time that the forward and backward switching of electron flow has
been accomplished via a switching process at the molecular scale."
Sessler is the Roland K. Pettit Centennial Chair in Chemistry at
The University of Texas at Austin and a visiting professor at
Yonsei University.
Bielawski says this system gives
important clues for making an efficient organic battery. He says
understanding the electron transfer processes in these molecules
provides a way to design organic materials for storing electrical
energy that could then be retrieved for later use.
"I would love it if my iPhone was
thinner and lighter, and the battery lasted a month or even a week
instead of a day," says Bielawski. "With an organic battery, it may
be possible. We are now starting to get a handle on the fundamental
chemistry needed to make this dream a commercial
reality."
The next step, he says, is to
demonstrate these processes can occur in a condensed phase, like in
a film, rather than in solution.
Organic batteries are made of
organic materials instead of heavy metals. They could be
lightweight, could be molded into any shape, have the potential to
store more energy than conventional batteries and could be safer
and cheaper to produce.
The molecular switch could also be
a step toward developing a technology that mimics plants' ability
to harvest light and convert it to energy. With such a technology,
fuel could be produced directly from the sun, rather than through a
plant mediator, such as corn.
"I am excited about the prospect
of coupling this kind of electron transfer 'molecular switch' with
light harvesting to go after what might be an improved artificial
photosynthetic device," says Sessler. "Realizing this dream would
represent a big step forward for science."
Bielawski and Sessler credit
graduate student Jung Su Park for his detailed work growing
crystals of the two molecules. Other collaborators include graduate
student Elizabeth Karnas from The University of Texas at Austin,
Professor Shunichi Fukuzumi at Osaka University and Professor Karl
Kadish at the University of Houston.
Journal
Reference:
- Park et al. Ion-Mediated Electron
Transfer in a Supramolecular Donor-Acceptor Ensemble.
Science, 2010; 329 (5997): 1324 DOI: 10.1126/science.1192044
|
3) Flexible
Battery Power |
ScienceDaily http://www.sciencedaily.com/releases/2007/03/070323141052.htm
A paper-like,
polymer based rechargeable battery has been made by Japanese
scientists.
Paper Like Polymer
Based rechargeable Battery
|
With recent advances in the
technology of portable electronic devices, there is a demand for
flexible batteries to power them.
Drs Hiroyuki Nishide, Hiroaki
Konishi and Takeo Suga at Waseda University have designed the
battery - which consists of a redox-active organic polymer film
around 200 nanometres thick. Nitroxide radical groups are attached,
which act as charge carriers.
The battery has a high
charge/discharge capacity because of its high radical
density.
Dr Nishide said: "This is just one
of many advantages the 'organic radical' battery has over other
organic based materials which are limited by the amount of
doping.
"The power rate performance is
strikingly high - it only takes one minute to fully charge the
battery. And it has a long cycle life, often exceeding 1,000
cycles."
The team made the thin polymer
film by a solution-processable method - a soluble polymer with the
radical groups attached is "spin-coated" onto a surface. After UV
irradiation, the polymer then becomes crosslinked with the help of
a bisazide crosslinking agent.
A drawback of some organic radical
polymers is the fact they are soluble in the electrolyte solution
which results in self-discharging of the battery - but the polymer
must be soluble so it can be spin-coated.
However, the photocrosslinking
method used by the Japanese team overcomes the problem and makes
the polymer mechanically tough.
Dr Nishide said: "This has been a
challenging step, since most crosslinking reactions are sensitive
to the nitroxide radical."
Professor Peter Skabara, an expert
in electroactive materials at the University of Strathclyde ,
praised the high stability and fabrication strategy of the
polymer-based battery.
He said: "The plastic battery
plays a part in ensuring that organic device technologies can
function in thin film and flexible form as a complete
package."
Dr Nishide envisages that the
organic radical battery could be used in pocket-sized integrated
circuit cards, used for memory storage and microprocessing, within
the next three years.
He said: "In the future, these
batteries may be used in applications that require high-power
capability rather than high-energy density, such as a battery in
electronic devices and motor drive assistance in electric
vehicles."
The news is reported in the latest
edition of the Royal Society of Chemistry journal Chemical
Communications.
|
4) Mimicking
Nature, Water-Based 'Artificial Leaf' Produces
Electricity |
ScienceDaily (Sep. 24, 2010) http://www.sciencedaily.com/releases/2010/09/100924121218.htm
- A team led by a North
Carolina State University researcher has shown that water-gel-based
solar devices -- "artificial leaves" -- can act like solar cells to
produce electricity. The findings prove the concept for making
solar cells that more closely mimic nature. They also have the
potential to be less expensive and more environmentally friendly
than the current standard-bearer: silicon-based solar
cells.
The bendable devices are composed of water-based gel
infused with light-sensitive molecules -- the researchers used
plant chlorophyll in one of the experiments -- coupled with
electrodes coated by carbon materials, such as carbon nanotubes or
graphite. The light-sensitive molecules get "excited" by the sun's
rays to produce electricity, similar to plant molecules that get
excited to synthesize sugars in order to grow, says NC State's Dr.
Orlin Velev, Invista Professor of Chemical and Biomolecular
Engineering and the lead author of a paper published online in the
Journal of Materials Chemistry describing this new
generation of solar cells.
Velev says that the research team
hopes to "learn how to mimic the materials by which nature
harnesses solar energy." Although synthetic light-sensitive
molecules can be used, Velev says naturally derived products --
like chlorophyll -- are also easily integrated in these devices
because of their water-gel matrix.
Now that they've proven the
concept, Velev says the researchers will work to fine-tune the
water-based photovoltaic devices, making them even more like real
leaves.
"The next step is to mimic the
self-regenerating mechanisms found in plants," Velev says. "The
other challenge is to change the water-based gel and
light-sensitive molecules to improve the efficiency of the solar
cells."
Velev even imagines a future where
roofs could be covered with soft sheets of similar
electricity-generating artificial-leaf solar cells.
"We do not want to overpromise at
this stage, as the devices are still of relatively low efficiency
and there is a long way to go before this can become a practical
technology," Velev says. "However, we believe that the concept of
biologically inspired 'soft' devices for generating electricity may
in the future provide an alternative for the present-day
solid-state technologies."
Researchers from the Air Force
Research Laboratory and Chung-Ang University in Korea co-authored
the study. The study was funded by the Air Force Research
Laboratory and the U.S. Department of Energy. The work is part of
NC State's universitywide nanotechnology program, Nano@NC
State.
NC State's Department of Chemical
and Biomolecular Engineering is part of the university's College of
Engineering.
|
5) GE
Ecomagination Challenge Deadline
Approaching |
Welcome to the GE Ecomagination Challenge,
a $200 million innovation experiment where
businesses, entrepreneurs, innovators and students share their best
ideas on how to build the next-generation power grid - and just
might get funded.
We've teamed up with some of the best-known venture capital firms,
including Emerald Technology Ventures, Foundation Capital, KPCB and
Rockport Capital, to help back the most promising ideas.
Will you join us? Please enter the challenge, submit your ideas,
vote for the most promising teams and help us change the way the
world uses energy in powerful new ways. Who knows? One of the ideas
selected could be yours.
Challenge 1: Create - Renewable
Energy
Renewable energy holds extraordinary
potential for helping us create the energy to meet our growing
needs. But many forms of renewable energy are highly variable in
their output. This is where a more intelligent grid comes in,
integrating and managing renewable energy sources.
At GE, we're developing technologies that protect the quality of
power, compensating for voltage fluctuations and managing output
intermittency. We want to provide utilities with better information
about energy production, transmission, consumption and energy
system health to help them protect equipment and ensure safe,
reliable power.
Making the best use of the energy created by renewable resources is
critical to a reliable supply of affordable energy. What kinds of
technologies or processes do you think will maximize the
penetration of renewables into the grid?
Learn More
Challenge 2: Connect - Grid
Efficiency
The U.S. should have the most efficient
grid in the world. But we don't. Our grid wastes energy at every
point during every day. The solution is to connect advanced power
generation to a more intelligent and more efficient grid -- that
then connects with consumers.
GE is looking at different grid
technologies that help lower delivery losses and those that
anticipate and monitor demand. Reducing losses frees up grid
capacity, reduces the need for infrastructure capital expenditure,
and protects consumers from steep rate increases. Reducing voltage
eliminates the over-delivery of energy, so customers are not paying
for unused energy.
In terms of technology, processes and
policy, what do you think are the best means to help us realize
greater gains in grid efficiency and outage
management?
Challenge 3: Use -
EcoHomes/EcoBuildings
Energy consumption is growing so quickly
that it's creating an imbalance between demand and supply. This
mismatch short-circuits power production and distribution, leading
to higher energy costs for consumers and businesses. We need to
change how, and when, we use energy.
We're looking at many promising
technologies to help power companies and their customers share
information and manage their energy use better.
At GE, we are already working on a
wide range of promising technologies, including smart meters and
appliances that let consumers' appliances "talk" to their power
utility; wireless AMI; home area networks; renewable integration
tools; demand response systems; home energy use monitoring;
time-of-use pricing; plug-in hybrid electric vehicle integration;
and neighborhood micro grids.
What new technologies, processes or
business models can help consumers use energy more wisely and
improve our energy balance?
|
About Integrity Research
Institute
Future Energy
eNews is provided as a public service from Integrity Research Institute, a Non-Profit dedicated
to educating the public on eco-friendly emerging energy
technologies.
FREE copy of the 30 minute DVD
"Progress in Future Energy" is available by sending an email
with "Free DVD" in subject and mailing
address in body.
Your
generous support is welcome by making a tax deductible donation on our secure
website
|
|
|
|
Save 10% |
On
all purchases from IRI by becoming
a member and
a free gift when you join and you save 10% on all conference and
workshop fees as well. You will receive a quarterly mailing with
the latest information on eco-friendly emerging energy
technologies. All 2010 IRI members will receive a free copy of the
special Tesla Issue from Infinite Energy Magazine and a
free copy of the "Story of Stuff" DVD by Annie Lennard as
well as a Free copy of the IRI Future Energy Annual
magazine and Free calendar at year's
end.
|
|
|
|
|