High Performance Electric Motorcycle Developed

This project, known as e-Moto, was created and developed by LGN Tech Design, aspin-offcompany that has its origins in a line of research begun in the Laboratorio de Máquinas (MAQLAB -- Machine Laboratory) of UC3M and receives support from the University's Vice-Chancellor's Office of Research through the Business Incubator UC3M Science Park."The technology that we have developed is a result of the design of a platform for the modeling, analysis and evolution of racing motorcycles, which was then applied to the development of the e-Moto," comments the head of the MAQLAB, Professor Juan Carlos García Prada, of the Mechanical Engineering Department at UC3M.

The prototype of the e-Moto recently participated in the first FIM E-Power electric motorcycle world championship (100% electric), organized by the International Motorcycling Federation. The model came in third, a position of merit according to its creators, who point out that, although there were only three contestants on the track at the Magny-Cours circuit in France, the motorcycle managed to finish the race with no mechanical problems whatsoever.

This is a vehicle that was conceived as an electric motorcycle from the very beginning, with battery recharging systems that offer quite remarkable results, and which are similar to those of an automobile. Among the technical features of the prototype, its light weight (145 Kg.) in comparison with other existing models stands out, as does its alternating current motor, which boasts a maximum 95 horsepower. It also features a system for recharging its batteries when braking and an innovative front suspension based on a system that has already been tested in other research projects.

A global e-motorcycle

This first prototype, according to its promoters, is the beginning of the worldwide development of electric motorcycles that goes beyond current electric motorcycles, the majority of which are of the scooter type. The creators of this project recognize that in this phase of the development of Spanish electric motorcycles, the support of public and private institutions is needed, in order to allow for the evolution of what will be the first Spanish company to develop high performance electric motorcycles.

The idea is that an electric motorcycle offers great advantages over a conventional motorcycle."The most important thing, when considering its use in society, is the nearly complete elimination of gasses and the considerable reduction of noise and vibrations," explains Juan Carlos García Prada. Summing up, this is a Spanish research project that attempts to take advantage of advanced technology in order to create a more sustainable future.

The results of the different projects carried out within the university setting have lead to the creation of the UC3M LGN Tech Design Chaired Professorship."We have created this professorship in order to offer technological support to the students who have developed this project and who have carried out other research projects as well," comments Professor García Prada. A direct consequence of all of this interrelated activity by the university and the productive world is the stimulation of new teaching (through students' final projects, practicums, etc), as well as of R + D within UC3M in the automobile components area, within the context of the potentially huge market, considering both the institutional demand and that of society at large.

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Engineers Scale Up Process That Could Improve Economics of Ethanol Production

Now he knows the idea, which produces a new animal feed and cleans water that can be recycled back into ethanol production, works more efficiently in batches of up to 350 gallons than on a lab bench.

"We're learning we can reliably produce good quality and good quantities," said van Leeuwen, Iowa State's Vlasta Klima Balloun Professor of Engineering in the department of civil, construction and environmental engineering.

What van Leeuwen and a team of Iowa State researchers are producing is a fungus, Rhizopus oligosporus, that makes a high-quality, high-protein animal feed from the leftovers of ethanol production. The process of growing the fungus also cleans water from ethanol production so that it can be recycled back into fuel production. And the process, called MycoMeal, could one day produce a low-cost nutritional supplement for people.

The project has two patents pending and has won several major awards, including a 2008 R&D 100 Award presented by R&D Magazine, the 2008 Grand Prize for University Research presented by the American Academy of Environmental Engineers and a 2011 Honor Award in University Research from the academy. The project also contributed to R&D Magazine naming van Leeuwen its 2009 Innovator of the Year.

The research team working on the project is led by van Leeuwen and includes Nick Gabler and Mike Persia, assistant professors of animal science; Mary Rasmussen, a post-doctoral research associate in food science and human nutrition; Daniel Erickson, Christopher Koza and Debjani Mitra, graduate students; and Brandon Caldwell, a graduate of Iowa State. The project is supported by a three-year,$450,000 grant from the Iowa Energy Center and a Smithfield grant from the Office of the Iowa Attorney General. Lincolnway Energy of Nevada, Cellencor Corp. of Ames and Iowa State's Center for Crops Utilization Research and BioCentury Research Farm are also supporting the project.

Here's how their process works to improve dry-grind ethanol production:

For every gallon of ethanol produced, there are about five gallons of leftovers known as stillage. The stillage contains solids and other organic material. Most of the solids are removed by centrifugation and dried into distillers dried grains that are sold as livestock feed, primarily for cattle.

The remaining liquid, known as thin stillage, still contains some solids, a variety of organic compounds and enzymes. Because the compounds and solids can interfere with ethanol production, only about 50 percent of thin stillage can be recycled back into ethanol production. The rest is evaporated and blended with distillers dried grains to produce distillers dried grains with solubles.

The researchers add fungus to the thin stillage and it feeds and grows into a thick mass in less than a day -- van Leeuwen calls it"lightning-speed farming." The fungus removes about 60 percent of the organic material and most of the solids, allowing the water and enzymes in the thin stillage to be recycled back into production.

The fungus is then harvested and dried as animal feed that's rich in protein, certain essential amino acids and other nutrients. It can also be blended with distillers dried grains to boost its value as a livestock feed and make it more suitable for feeding hogs and chickens.

Van Leeuwen said the production technology can save United States ethanol producers up to$800 million a year in energy costs. He also said the technology can produce ethanol co-products worth another$800 million or more per year, depending on how it is used and marketed.

Now that the project has moved from a campus lab to the Iowa Energy Center's BECON facility in Nevada, van Leeuwen said researchers are working to improve the process at larger scales.

"We're adding and subtracting, doing things differently and redesigning our process all the time," he said.

Even so, the process has developed enough that researchers can use simple screens to harvest pellets of the fungus from the project's 20-foot high reactor. They're feeding some of the fungus to chickens and will soon start feeding tests with hogs. A next step could be testing the fungus for human consumption. (University leaders have tried the fungi and researchers regularly eat it, van Leeuwen said.)

As the project has successfully scaled up, so has van Leeuwen's optimism that the process could help the biofuels industry.

"Implementation of this process addresses criticism of biofuels by substantially lowering energy inputs and by increasing the production of nutritious animal feed," van Leeuwen said."The MycoMeal process could truly revolutionize the biofuels industry."

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What Electric Car Convenience Is Worth

Results of one study show the electric car attributes that are most important for consumers: driving range, fuel cost savings and charging time. The results are based on a national survey conducted by the researchers, UD professors George Parsons, Willett Kempton and Meryl Gardner, and Michael Hidrue, who recently graduated from UD with a doctoral degree in economics. Lead author Hidrue conducted the research for his dissertation.

The study, which surveyed more than 3,000 people, showed what individuals would be willing to pay for various electric vehicle attributes. For example, as battery charging time decreases from 10 hours to five hours for a 50-mile charge, consumers' willingness to pay is about$427 per hour in reduction time. Drop charging time from five hours to one hour, and consumers would pay an estimated$930 an hour. Decrease the time from one hour to 10 minutes, and they would pay$3,250 per hour.

For driving range, consumers value each additional mile of range at about$75 per mile up to 200 miles, and$35 a mile from 200-300 miles. So, for example, if an electric vehicle has a range of 200 miles and an otherwise equivalent gasoline vehicle has a range of 300, people would require a price discount of about$3,500 for the electric version. That assumes everything else about the vehicle is the same, and clearly there is lower fuel cost with an electric vehicle and often better performance. So all the attributes have to be accounted for in the final analysis of any car.

"This information tells the car manufacturers what people are willing to pay for another unit of distance," Parsons said."It gives them guidance as to what cost levels they need to attain to make the cars competitive in the market."

The researchers found that battery costs would need to decrease substantially without subsidy and with current gas prices for electric cars to become competitive in the market. However, the researchers said, the current$7,500 government tax credit could bridge the gap between electric car costs and consumers' willingness to pay if battery costs decline to$300 a kilowatt hour, the projected 2014 cost level by the Department of Energy. Many analysts believe that goal is within reach.

The team's analysis could also help guide automakers' marketing efforts -- it showed that an individual's likelihood of buying an electric vehicle increases with characteristics such as youth, education and an environmental lifestyle. Income was not important.

In a second recently published study, UD researchers looked at electric vehicle driving range using second-by-second driving records. That study, which is based on a year of driving data from nearly 500 instrumented gasoline vehicles, showed that 9 percent of the vehicles never exceeded 100 miles in a day. For those who are willing to make adaptations six times a year -- borrow a gasoline car, for example -- the 100-mile range would work for 32 percent of drivers.

"It appears that even modest electric vehicles with today's limited battery range, if marketed correctly to segments with appropriate driving behavior, comprise a large enough market for substantial vehicle sales," the authors concluded.

Kempton, who published the driving patterns article with UD marine policy graduate student Nathaniel Pearre and colleagues at the Georgia Institute of Technology, pointed out that U.S. car sales are around 12 million in an average, non-recession year. Nine percent of that would be a million cars per year -- for comparison to current production, for example, Chevy plans to manufacture just 10,000 Volts in 2011.

By this measure, the potential market would justify many more plug-in cars than are currently being produced, Kempton said.

The findings of the two studies were reported online in March and February inResource and Energy EconomicsandTransportation Research, respectively.

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Lasers Take the Lead in Auto Manufacturing

The era of gas guzzlers that clatter through streets and pollute the air is over. Cars rolling off the assembly line today are cleaner, quieter and -- in terms of their performance weight -- more efficient than ever before. Nevertheless, development continues. Ever-stricter environmental regulations and steadily rising fuel costs are increasing the demand for cars that further reduce their impact on the environment. But customer demands are often tough for manufacturers to meet: car bodies should be safe yet light-weight and engines durable yet efficient. Year after year, new models must be developed and built that can claim to be better, more efficient, and more intelligent than the last.

The race against time and competitors places high demands on manufacturers and their suppliers. Lasers can help them win the race. Resistant to wear and universally applicable, laser light is an ideal tool in the manufacture of vehicles. Lasers can be used to join, drill, structure, cut or shape any kind of material. Surfaces can be engineered for motors and drive trains that create less friction and use less fuel. Lasers are not only a decisive key towards faster, more efficient and economical production, but also towards energy-saving vehicles. At Laser 2011, Fraunhofer scientists will demonstrate how we can use lasers to save time, money and energy.

A weight-loss program in automotive manufacturing

Extra pounds cost energy. They have to be accelerated and slowed down every time you drive -- over the entire lifespan of the car. To reduce weight, manufacturers are increasingly turning to the use of fiber-reinforced plastics, which are 30 to 50 percent lighter than metal. The disadvantage, however, is that these new materials are difficult to process. Fiber-reinforced plastics are brittle, meaning cutting and drilling tools are quickly worn out and the conventional assembly techniques used for metal components are often not appropriate."Lasers represent an ideal alternative here," explains Dr. Arnold Gillner of the Fraunhofer Institute for Laser Technology ILT in Aachen."Lasers can cut fiber-reinforced plastics without wear and can join them too. With the appropriate lasers, we can cut and ablate components with minimal thermal side-effects. Lasers can also be used for welding light-weight components -- a viable alternative to conventional bonding technology. We can even join fiber-reinforced plastics to metals with laser welding. The laser roughens the metal surface, while the plastic, briefly-heated, penetrates the pores of the metal and hardens. The results are very stable."

Weight reduction can also be achieved with high-strength metallic materials. These, however, are difficult to process."Joining combinations of various materials allows us to make optimal use of the individual materials' specific properties. But this proves to be difficult in many cases," explains Dr. Anja Techel, Deputy Director of the Fraunhofer Institute for Material and Beam Technology IWS in Dresden. Her team believes in lasers:"With our newly-developed integrated laser tools, we can now even weld together combinations of materials, free of fissures or cracks." At Laser 2011, Fraunhofer scientists will present, for the first time, a new welding head capable not only of focusing with extreme precision but of moving back and forth across the seam with high frequency to mix the molten materials. When they harden, they create a stable bond.

Laser replaces chemistry

Lasers also save time and money in tool design. The molds used in the production of plastic fixtures and steering wheels, for example, have to be structured to give the finished component a visually and tactilely appealing surface. Most car manufacturers order a design from their suppliers, whose surface typically has the appearance of leather. Until now, the negative pattern used to create the design has been etched out of the steel tools used in injection molding -- a tedious and time-consuming process."With lasers, the steel surface can not only be patterned more quickly, but also with greater scope for variety," explains Kristian Arntz of the Fraunhofer Institute for Production Technology IPT."We can transfer any possible design directly from the CAD model to the tool surface: What will later become a groove in the plastic is preserved as a ridge, while the surrounding material is vaporized. The process is efficient, fully automatic, and highly variable."

Saving energy with low friction motors

Laser technology is also in demand in engine optimization. Engineers strive to keep friction as low as possible in order to improve efficiency."That is true not only for the electric engines currently being developed, but also for classic internal combustion engines and diesel motors, as well as transmissions and bearings," says Arnold Gillner of the ILT. Ceramic, high-performance coatings are especially desirable, because they are not only resistant to wear but also smooth, which generates less friction. Coated metal components have until now been prohibitively expensive, being produced in plasma chambers in which the ceramic was vaporized and applied to the surface of the components. Fraunhofer scientists have now developed a less expensive and faster method in which work pieces are coated with ceramic nano-particles, then treated with a laser. This finishing process has already been applied to gear wheels and bearings.

Lasers can even be used to make specific modifications to the properties of engine parts."Friction between the cylinder wall and piston is responsible for a big part of a motor's energy consumption. That is why we try to minimize it. This is especially important for engines featuring modern, automatic start-stop functions that are stressed by frequent ignition," says Gillner."To protect them, we have to ensure that the cylinder is always coated with a film of oil. Laser technology can help reduce friction with special structuring processes that improve oil adhesion." Fraunhofer researchers aim to increase the engine's life-span and reduce energy consumption in this way.

Fitness program for electric cars

Lasers can even increase the efficiency and life-span of electric batteries. That is good news for manufacturers and owners of electric cars, since batteries continue to be extremely expensive. The engineers and scientists at Fraunhofer are currently working on various solutions to make batteries more durable and less expensive. One approach is to increase the surface area of the electrodes with appropriate coating in order to increase their efficiency. Another approach involves analyzing and optimizing production processes.

Manufacturers produce batteries using one anode and one cathode cell, which they then connect. In theory that sounds pretty simple, but in practice the fusing of copper anodes with aluminum cathodes creates brittle connections that break easily. That presents a problem for application in cars that sometimes drive on cobblestone or dirt roads. With the help of lasers, researchers at the ILT have succeeded in forming durable connections between electrodes without creating the culprit brittle alloys. Researchers at the IWS in Dresden have developed an alternative solution in which a laser warms the surfaces and rollers press them together."Using roll plating with lasers and inductive pre-heating, we were able to create very stable connections with high electrical conductivity, with only a minimal loss of power," reports Anja Techel."The finished batteries are very efficient. And since only small amounts of electrical energy are transformed into heat, these batteries do not require as much cooling."

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Toward Faster Transistors: Physicists Discover Physical Phenomenon That Could Boost Computers' Clock Speed

In this week's issue of the journalScience,MIT researchers and their colleagues at the University of Augsburg in Germany report the discovery of a new physical phenomenon that could yield transistors with greatly enhanced capacitance -- a measure of the voltage required to move a charge. And that, in turn, could lead to the revival of clock speed as the measure of a computer's power.

In today's computer chips, transistors are made from semiconductors, such as silicon. Each transistor includes an electrode called the gate; applying a voltage to the gate causes electrons to accumulate underneath it. The electrons constitute a channel through which an electrical current can pass, turning the semiconductor into a conductor.

Capacitance measures how much charge accumulates below the gate for a given voltage. The power that a chip consumes, and the heat it gives off, are roughly proportional to the square of the gate's operating voltage. So lowering the voltage could drastically reduce the heat, creating new room to crank up the clock.

MIT Professor of Physics Raymond Ashoori and Lu Li, a postdoc and Pappalardo Fellow in his lab -- together with Christoph Richter, Stefan Paetel, Thilo Kopp and Jochen Mannhart of the University of Augsburg -- investigated the unusual physical system that results when lanthanum aluminate is grown on top of strontium titanate. Lanthanum aluminate consists of alternating layers of lanthanum oxide and aluminum oxide. The lanthanum-based layers have a slight positive charge; the aluminum-based layers, a slight negative charge. The result is a series of electric fields that all add up in the same direction, creating an electric potential between the top and bottom of the material.

Ordinarily, both lanthanum aluminate and strontium titanate are excellent insulators, meaning that they don't conduct electrical current. But physicists had speculated that if the lanthanum aluminate gets thick enough, its electrical potential would increase to the point that some electrons would have to move from the top of the material to the bottom, to prevent what's called a"polarization catastrophe." The result is a conductive channel at the juncture with the strontium titanate -- much like the one that forms when a transistor is switched on. So Ashoori and his collaborators decided to measure the capacitance between that channel and a gate electrode on top of the lanthanum aluminate.

They were amazed by what they found: Although their results were somewhat limited by their experimental apparatus, it may be that an infinitesimal change in voltage will cause a large amount of charge to enter the channel between the two materials."The channel may suck in charge -- shoomp! Like a vacuum," Ashoori says."And it operates at room temperature, which is the thing that really stunned us."

Indeed, the material's capacitance is so high that the researchers don't believe it can be explained by existing physics."We've seen the same kind of thing in semiconductors," Ashoori says,"but that was a very pure sample, and the effect was very small. This is a super-dirty sample and a super-big effect." It's still not clear, Ashoori says, just why the effect is so big:"It could be a new quantum-mechanical effect or some unknown physics of the material."

There is one drawback to the system that the researchers investigated: While a lot of charge will move into the channel between materials with a slight change in voltage, it moves slowly -- much too slowly for the type of high-frequency switching that takes place in computer chips. That could be because the samples of the material are, as Ashoori says,"super dirty"; purer samples might exhibit less electrical resistance. But it's also possible that, if researchers can understand the physical phenomena underlying the material's remarkable capacitance, they may be able to reproduce them in more practical materials.

Triscone cautions that wholesale changes to the way computer chips are manufactured will inevitably face resistance."So much money has been injected into the semiconductor industry for decades that to do something new, you need a really disruptive technology," he says.

"It's not going to revolutionize electronics tomorrow," Ashoori agrees."But this mechanism exists, and once we know it exists, if we can understand what it is, we can try to engineer it."

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Super Energy Storage: Activated Graphene Makes Superior Supercapacitors for Energy Storage

"Those properties make this new form of carbon particularly attractive for meeting electrical energy storage needs that also require a quick release of energy -- for instance, in electric vehicles or to smooth out power availability from intermittent energy sources, such as wind and solar power," said Brookhaven materials scientist Eric Stach, a co-author on a paper describing the material published inScienceon May 12, 2011.

Supercapacitors are similar to batteries in that both store electric charge. Batteries do so through chemical reactions between metallic electrodes and a liquid electrolyte. Because these chemicals take time to react, energy is stored and released relatively slowly. But batteries can store a lot of energy and release it over a fairly long time.

Supercapacitors, on the other hand, store charge in the form of ions on the surface of the electrodes, similar to static electricity, rather than relying on chemical reactions. Charging the electrodes causes ions in the electrolyte to separate, or polarize, as well -- so charge gets stored at the interface between the electrodes and the electrolyte. Pores in the electrode increase the surface area over which the electrolyte can flow and interact -- increasing the amount of energy that can be stored.

But because most supercapacitors can't hold nearly as much charge as batteries, their use has been limited to applications where smaller amounts of energy are needed quickly, or where long life cycle is essential, such as in mobile electronic devices.

The new material developed by the UT-Austin researchers may change that. Supercapacitors made from it have an energy-storage capacity, or energy density, that is approaching the energy density of lead-acid batteries, while retaining the high power density -- that is, rapid energy release -- that is characteristic of supercapacitors.

"This new material combines the attributes of both electrical storage systems," said University of Texas team leader Rodney Ruoff."We were rather stunned by its exceptional performance."

The UT-Austin team had set out to create a more porous form of carbon by using potassium hydroxide to restructure chemically modified graphene platelets -- a form of carbon where the atoms are arrayed in tile-like rings laying flat to form single-atom-thick sheets. Such"chemical activation" has been previously used to create various forms of"activated carbon," which have pores that increase surface area and are used in filters and other applications, including supercapacitors.

But because this new form of carbon was so superior to others used in supercapacitors, the UT-Austin researchers knew they'd need to characterize its structure at the nanoscale.

Ruoff had formed a hypothesis that the material consisted of a continuous three-dimensional porous network with single-atom-thick walls, with a significant fraction being"negative curvature carbon," similar to inside-out buckyballs. He turned to Stach at Brookhaven for help with further structural characterization to verify or refute this hypothesis.

Stach and Brookhaven colleague Dong Su conducted a wide range of studies at the Lab's Center for Functional Nanomaterials, the National Synchrotron Light Source, and at the National Center for Electron Microscopy at Lawrence Berkeley National Laboratory, all three facilities supported by the DOE Office of Science."At the DOE laboratories, we have the highest resolution microscopes in the world, so we really went full bore into characterizing the atomic structure," Stach said.

"Our studies revealed that Ruoff's hypothesis was in fact correct, and that the material's three-dimensional nanoscale structure consists of a network of highly curved, single-atom-thick walls forming tiny pores with widths ranging from 1 to 5 nanometers, or billionths of a meter."

The study includes detailed images of the fine pore structure and the carbon walls themselves, as well as images that show how these details fit into the big picture."The data from NSLS were crucial to showing that our highly local characterization was representative of the overall material," Stach said.

"We're still working with Ruoff and his team to pull together a complete description of the material structure. We're also adding computational studies to help us understand how this three-dimensional network forms, so that we can potentially tailor the pore sizes to be optimal for specific applications, including capacitive storage, catalysis, and fuel cells," Stach said.

Meanwhile, the scientists say the processing techniques used to create the new form of carbon are readily scalable to industrial production."This material -- being so easily manufactured from one of the most abundant elements in the universe -- will have a broad range impacts on research and technology in both energy storage and energy conversion," Ruoff said.

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Pairing Quantum Dots With Fullerenes for Nanoscale Photovoltaics

"This is the first demonstration of a hybrid inorganic/organic, dimeric (two-particle) material that acts as an electron donor-bridge-acceptor system for converting light to electrical current," said Brookhaven physical chemist Mircea Cotlet, lead author of a paper describing the dimers and their assembly method inAngewandte Chemie.

By varying the length of the linker molecules and the size of the quantum dots, the scientists can control the rate and the magnitude of fluctuations in light-induced electron transfer at the level of the individual dimer."This control makes these dimers promising power-generating units for molecular electronics or more efficient photovoltaic solar cells," said Cotlet, who conducted this research with materials scientist Zhihua Xu at Brookhaven's Center for Functional Nanomaterials (CFN).

Scientists seeking to develop molecular electronics have been very interested in organic donor-bridge-acceptor systems because they have a wide range of charge transport mechanisms and because their charge-transfer properties can be controlled by varying their chemistry. Recently, quantum dots have been combined with electron-accepting materials such as dyes, fullerenes, and titanium oxide to produce dye-sensitized and hybrid solar cells in the hope that the light-absorbing and size-dependent emission properties of quantum dots would boost the efficiency of such devices. But so far, the power conversion rates of these systems have remained quite low.

"Efforts to understand the processes involved so as to engineer improved systems have generally looked at averaged behavior in blended or layer-by-layer structures rather than the response of individual, well-controlled hybrid donor-acceptor architectures," said Xu.

The precision fabrication method developed by the Brookhaven scientists allows them to carefully control particle size and interparticle distance so they can explore conditions for light-induced electron transfer between individual quantum dots and electron-accepting fullerenes at the single molecule level.

The entire assembly process takes place on a surface and in a stepwise fashion to limit the interactions of the components (particles), which could otherwise combine in a number of ways if assembled by solution-based methods. This surface-based assembly also achieves controlled, one-to-one nanoparticle pairing.

To identify the optimal architectural arrangement for the particles, the scientists strategically varied the size of the quantum dots -- which absorb and emit light at different frequencies according to their size -- and the length of the bridge molecules connecting the nanoparticles. For each arrangement, they measured the electron transfer rate using single molecule spectroscopy.

"This method removes ensemble averaging and reveals a system's heterogeneity -- for example fluctuating electron transfer rates -- which is something that conventional spectroscopic methods cannot always do," Cotlet said.

The scientists found that reducing quantum dot size and the length of the linker molecules led to enhancements in the electron transfer rate and suppression of electron transfer fluctuations.

"This suppression of electron transfer fluctuation in dimers with smaller quantum dot size leads to a stable charge generation rate, which can have a positive impact on the application of these dimers in molecular electronics, including potentially in miniature and large-area photovoltaics," Cotlet said.

"Studying the charge separation and recombination processes in these simplified and well-controlled dimer structures helps us to understand the more complicated photon-to-electron conversion processes in large-area solar cells, and eventually improve their photovoltaic efficiency," Xu added.

A U.S. patent application is pending on the method and the materials resulting from using the technique, and the technology is available for licensing. This work was funded by the DOE Office of Science.

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Forklift Trucks That Run on a Green Charge

Risavika harbour just outside Stavanger is among the candidates for trials of ten of the 30 forklift trucks, says SINTEF's Steffen Møller-Holst.

SINTEF is a participant in the project's development phase, which will bring the green European truck to its final goal. Under its bodywork, the truck houses a miniature power station in the shape of a fuel cell that runs on hydrogen, and which delivers power to its electric motor. All that the truck emits in operation is water vapour!

The best of both worlds

"A hydrogen-driven forklift truck running on fuel cells combines the advantages of diesel and battery-driven vehicles. The hydrogen-based technology means rapid refuelling, just like diesel, while it is also energy-efficient and every bit as environmentally friendly as a battery truck," says Møller-Holst.

The SINTEF scientist points out that a forklift truck fitted with fuel cells and operating two eight-hour shifts a day reduces CO₂emissions by the equivalent of eight private cars.

Developed under the European Union's auspices

The truck's power system has been developed in the course of a joint European effort run by the European Union.

SINTEF is to perform laboratory tests that will explore how much fuel cell performance falls by over time. At the same time, SINTEF will systematise and analyse feedback from the trials of the 30 demonstration trucks. The knowledge gained in this process will be used to improve the control system and optimise operation, which will ensure that the fuel cell will have a life-cycle that meets the commercial requirements of the market.

Danish projects

The Danish company H2 Logic AS has been responsible for developing the trucks' fuel-cell technology. The solution is a development of a fuel cell that the company had previous developed with Scandinavian backing; its partners included SINTEF and Statoil.

These large forklift trucks in the joint European project have been designed to carry heavy loads. They are manufactured by the Danish company Dantruck, which is showing them off this week at the enormous CeMAT trade fair in Hanover.

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Battery-Less Chemical Detector Developed

The device overcomes the power requirement of traditional sensors and is simple, highly sensitive and can detect various molecules quickly. Its development could be the first step in making an easily deployable chemical sensor for the battlefield.

The Lab's Yinmin"Morris" Wang and colleagues Daniel Aberg, Paul Erhart, Nipun Misra, Aleksandr Noy and Alex Hamza, along with collaborators from the University of Shanghai for Science and Technology, have fabricated the first-generation battery-less detectors that use one-dimensional semiconductor nanowires.

The nanosensors take advantage of a unique interaction between chemical species and semiconductor nanowire surfaces that stimulate an electrical charge between the two ends of nanowires or between the exposed and unexposed nanowires.

The group tested the battery-less sensors with different types of platforms -- zinc-oxide and silicon -- using ethanol solvent as a testing agent.

In the zinc-oxide sensor the team found there was a change in the electric voltage between the two ends of nanowires when a small amount of ethanol was placed on the detector.

"The rise of the electric signal is almost instantaneous and decays slowly as the ethanol evaporates," Wang said.

However, when the team placed a small amount of a hexane solvent on the device, little electric voltage was seen,"indicating that the nanosensor selectively responds to different types of solvent molecules," Wang said.

The team used more than 15 different types of organic solvents and saw different voltages for each solvent."This trait makes it possible for our nanosensors to detect different types of chemical species and their concentration levels," Wang said.

The response to different solvents was somewhat similar when the team tested the silicon nanosensors. However, the voltage decay as the solvent evaporated was drastically different from the zinc-oxide sensors."The results indicate that it is possible to extend the battery-less sensing platform to randomly aligned semiconductor nanowire systems," Wang said.

The team's next step is to test the sensors with more complex molecules such as those from explosives and biological systems.

The research appears on the inside front cover of the Jan. 4 issue ofAdvanced Materials.

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Solar-Thermal Flat-Panels That Generate Electric Power: Researchers See Broad Residential and Industrial Applications

Two technologies have dominated efforts to harness the power of the sun's energy. Photovoltaics convert sunlight into electric current, while solar-thermal power generation uses sunlight to heat water and produce thermal energy. Photovoltaic cells have been deployed widely as flat panels, while solar-thermal power generation employs sunlight-absorbing surfaces feasible in residential and large-scale industrial settings.

Because of limited material properties, solar thermal devices have heretofore failed to economically generate enough electric power. The team's introduced two innovations: a better light-absorbing surface through enhanced nanostructured thermoelectric materials, which was then placed within an energy-trapping, vacuum-sealed flat panel. Combined, both measures added enhanced electricity-generating capacity to solar-thermal power technology, said Boston College Professor of Physics Zhifeng Ren, a co-author of the paper.

"We have developed a flat panel that is a hybrid capable of generating hot water and electricity in the same system," said Ren."The ability to generate electricity by improving existing technology at minimal cost makes this type of power generation self-sustaining from a cost standpoint."

Using nanotechnology engineering methods, the team combined high-performance thermoelectric materials and spectrally-selective solar absorbers in a vacuum-sealed chamber to boost conversion efficiency, according to the co-authors, which include MIT's Soderberg Professor of Power Engineering Gang Chen, Boston College and MIT graduate students and researchers at GMZ Energy, a Massachusetts clean energy research company co-founded by Ren and Chen.

The findings open up a promising new approach that has the potential to achieve cost-effective conversion of solar energy into electricity, an advance that should impact the rapidly expanding residential and industrial clean energy markets, according to Ren.

"Existing solar-thermal technologies do a good job generating hot water. For the new product, this will produce both hot water and electricity," said Ren."Because of the new ability to generate valuable electricity, the system promises to give users a quicker payback on their investment. This new technology can shorten the payback time by one third."

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New Way to Control Conductivity: Reversible Control of Electrical and Thermal Properties Could Find Uses in Storage Systems

"It's a new way of changing and controlling the properties" of materials -- in this case a class called percolated composite materials -- by controlling their temperature, says Gang Chen, MIT's Carl Richard Soderberg Professor of Power Engineering and director of the Pappalardo Micro and Nano Engineering Laboratories. Chen is the senior author of a paper describing the process that was published online on April 19 and will appear in a forthcoming issue ofNature Communications. The paper's lead authors are former MIT visiting scholars Ruiting Zheng of Beijing Normal University and Jinwei Gao of South China Normal University, along with current MIT graduate student Jianjian Wang. The research was partly supported by grants from the National Science Foundation.

The system Chen and his colleagues developed could be applied to many different materials for either thermal or electrical applications. The finding is so novel, Chen says, that the researchers hope some of their peers will respond with an immediate,"I have a use for that!"

One potential use of the new system, Chen explains, is for a fuse to protect electronic circuitry. In that application, the material would conduct electricity with little resistance under normal, room-temperature conditions. But if the circuit begins to heat up, that heat would increase the material's resistance, until at some threshold temperature it essentially blocks the flow, acting like a blown fuse. But then, instead of needing to be reset, as the circuit cools down the resistance decreases and the circuit automatically resumes its function.

Another possible application is for storing heat, such as from a solar thermal collector system, later using it to heat water or homes or to generate electricity. The system's much-improved thermal conductivity in the solid state helps it transfer heat.

Essentially, what the researchers did was suspend tiny flakes of one material in a liquid that, like water, forms crystals as it solidifies. For their initial experiments, they used flakes of graphite suspended in liquid hexadecane, but they showed the generality of their process by demonstrating the control of conductivity in other combinations of materials as well. The liquid used in this research has a melting point close to room temperature -- advantageous for operations near ambient conditions -- but the principle should be applicable for high-temperature use as well.

The process works because when the liquid freezes, the pressure of its forming crystal structure pushes the floating particles into closer contact, increasing their electrical and thermal conductance. When it melts, that pressure is relieved and the conductivity goes down. In their experiments, the researchers used a suspension that contained just 0.2 percent graphite flakes by volume. Such suspensions are remarkably stable: Particles remain suspended indefinitely in the liquid, as was shown by examining a container of the mixture three months after mixing.

By selecting different fluids and different materials suspended within that liquid, the critical temperature at which the change takes place can be adjusted at will, Chen says.

"Using phase change to control the conductivity of nanocomposites is a very clever idea," says Li Shi, a professor of mechanical engineering at the University of Texas at Austin. Shi adds that as far as he knows"this is the first report of this novel approach" to producing such a reversible system.

"I think this is a very crucial result," says Joseph Heremans, professor of physics and of mechanical and aerospace engineering at Ohio State University."Heat switches exist," but involve separate parts made of different materials, whereas"here we have a system with no macroscopic moving parts," he says."This is excellent work."

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Portable Tech Might Provide Drinking Water, Power to Villages

Such a technology might be used to provide power and drinking water to villages and also for military operations, said Jerry Woodall, a Purdue University distinguished professor of electrical and computer engineering.

The alloy contains aluminum, gallium, indium and tin. Immersing the alloy in freshwater or saltwater causes a spontaneous reaction, splitting the water into hydrogen and oxygen molecules. The hydrogen could then be fed to a fuel cell to generate electricity, producing water in the form of steam as a byproduct, he said.

"The steam would kill any bacteria contained in the water, and then it would condense to purified water," Woodall said."So, you are converting undrinkable water to drinking water."

Because the technology works with saltwater, it might have marine applications, such as powering boats and robotic underwater vehicles. The technology also might be used to desalinate water, said Woodall, who is working with doctoral student Go Choi.

A patent on the design is pending.

Woodall envisions a new portable technology for regions that aren't connected to a power grid, such as villages in Africa and other remote areas.

"There is a big need for this sort of technology in places lacking connectivity to a power grid and where potable water is in short supply," he said."Because aluminum is a low-cost, non-hazardous metal that is the third-most abundant metal on Earth, this technology promises to enable a global-scale potable water and power technology, especially for off-grid and remote locations."

The potable water could be produced for about$1 per gallon, and electricity could be generated for about 35 cents per kilowatt hour of energy.

"There is no other technology to compare it against, economically, but it's obvious that 34 cents per kilowatt hour is cheap compared to building a power plant and installing power lines, especially in remote areas," Woodall said.

The unit, including the alloy, the reactor and fuel cell might weigh less than 100 pounds.

"You could drop the alloy, a small reaction vessel and a fuel cell into a remote area via parachute," Woodall said."Then the reactor could be assembled along with the fuel cell. The polluted water or the seawater would be added to the reactor and the reaction converts the aluminum and water into aluminum hydroxide, heat and hydrogen gas on demand."

The aluminum hydroxide waste is non-toxic and could be disposed of in a landfill.

The researchers have a design but haven't built a prototype.

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New Solar Cell Technology Greatly Boosts Efficiency

The technology substantially overcomes the problem of poor transport of charges generated by solar photons. These charges -- negative electrons and positive holes -- typically become trapped by defects in bulk materials and their interfaces and degrade performance.

"To solve the entrapment problems that reduce solar cell efficiency, we created a nanocone-based solar cell, invented methods to synthesize these cells and demonstrated improved charge collection efficiency," said Xu, a member of ORNL's Chemical Sciences Division.

The new solar structure consists of n-type nanocones surrounded by a p-type semiconductor. The n-type nanoncones are made of zinc oxide and serve as the junction framework and the electron conductor. The p-type matrix is made of polycrystalline cadmium telluride and serves as the primary photon absorber medium and hole conductor.

With this approach at the laboratory scale, Xu and colleagues were able to obtain a light-to-power conversion efficiency of 3.2 percent compared to 1.8 percent efficiency of conventional planar structure of the same materials.

"We designed the three-dimensional structure to provide an intrinsic electric field distribution that promotes efficient charge transport and high efficiency in converting energy from sunlight into electricity," Xu said.

Key features of the solar material include its unique electric field distribution that achieves efficient charge transport; the synthesis of nanocones using inexpensive proprietary methods; and the minimization of defects and voids in semiconductors. The latter provides enhanced electric and optical properties for conversion of solar photons to electricity.

Because of efficient charge transport, the new solar cell can tolerate defective materials and reduce cost in fabricating next-generation solar cells.

"The important concept behind our invention is that the nanocone shape generates a high electric field in the vicinity of the tip junction, effectively separating, injecting and collecting minority carriers, resulting in a higher efficiency than that of a conventional planar cell made with the same materials," Xu said.

Research that forms the foundation of this technology was accepted by this year's Institute of Electrical and Electronics Engineers photovoltaic specialist conference and will be published in the IEEE Proceedings. The papers are titled"Efficient Charge Transport in Nanocone Tip-Film Solar Cells" and"Nanojunction solar cells based on polycrystalline CdTe films grown on ZnO nanocones."

The research was supported by the Laboratory Directed Research and Development program and the Department of Energy's Office of Nonproliferation Research and Engineering.

Other contributors to this technology are Sang Hyun Lee, X-G Zhang, Chad Parish, Barton Smith, Yongning He, Chad Duty and Ho Nyung Lee.

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Electronics: A Step Toward Valleytronics

The discovery was published inPhysical Review Letterson March 28, 2011 and was also the subject of a separate Viewpoint article inPhysics.

Information in solid-state, either classical or quantum, is generally carried by electrons and holes. The information can be encoded in various degrees of freedom such as charge or spin. Charge representations, for example the absence or presence of an electron in a quantum dot, are attractive as they are easily manipulated and interrogated through electric fields. The advantage of spin representations, used in the field of spintronics, is their superior shielding from undesired electric fluctuations in the environment, making the information in these latter representations more robust. In the future, there might be a third middle-ground alternative in the valley degree of freedom that exists in certain crystals, including graphene.

The valley degree of freedom in graphene gained attention in 2007 when it was proposed that electrons and holes could be filtered according to which valley they occupy. Unfortunately, the structures required for this and subsequent valley filters are difficult to fabricate, and as a result a valley filter has yet to be demonstrated experimentally. The present study from NRL shows that an extended line defect in graphene acts as a natural valley filter."As the structure is already available, we are hopeful that valley-polarized currents could be generated in the near future" said Dr. Daniel Gunlycke who made the discovery together with Dr. Carter White. Both work in NRL's Chemistry Division.

Valley refers to energy depressions in the band structure, which describes the energies of electron waves allowed by the symmetry of the crystal. For graphene, these regions form two pairs of cones that determine its low-bias response. As a large crystal momentum separates the two valleys, the valley degree of freedom is robust against slowly varying potentials, including scattering caused by low-energy acoustic phonons that often require low-bias electronic devices to operate at low temperatures typically only accessible in laboratories.

Valley polarization is achieved when electrons and holes in one valley are separated spatially from those in the other valley, but this is difficult to do as the two valleys have the same energies. It was found, however, that this spatial separation can be obtained in connected graphene structures that possess reflection symmetry along a particular crystallographic direction with no bonds crossing the reflection plane. This property turns out to be present in a recently observed line defect in graphene. The reflection symmetry only permits electron waves that are symmetric to pass through the line defect. Anti-symmetric waves are reflected. By projecting an arbitrary low-energy wave in graphene onto its symmetric component, one gets the transmission amplitude through this defect, which is strongly dependent on the valley. Electron and hole waves approaching the line defect at a high angle of incidence results in a polarization near 100%.

There is a long way to go before valleytronics can become a viable technology, explains Gunlycke. The recent advance, however, provides a realistic way to reach a crucial milestone in its development. This research was supported by the Office of Naval Research, both directly and through the Naval Research Laboratory.

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Two Graphene Layers May Be Better Than One

Graphene, a single layer of carbon atoms, is prized for its remarkable properties, not the least of which is the way it conducts electrons at high speed. However, the lack of what physicists call a band gap -- an energetic threshold that makes it possible to turn a transistor on and off -- makes graphene ill-suited for digital electronic applications.

Researchers have known that bilayer graphene, consisting of two stacked graphene layers, acts more like a semiconductor when immersed in an electric field.

According to NIST researcher Nikolai Zhitenev, the band gap may also form on its own due to variations in the sheets' electrical potential caused by interactions among the graphene electrons or with the substrate (usually a nonconducting, or insulating material) that the graphene is placed upon.

NIST fellow Joseph Stroscio says that their measurements indicate that interactions with the disordered insulating substrate material causes pools of electrons and electron holes (basically, the absence of electrons) to form in the graphene layers. Both electron and hole"pools" are deeper on the bottom layer because it is closer to the substrate. This difference in"pool" depths, or charge density, between the layers creates the random pattern of alternating charges and the spatially varying band gap.

Manipulating the purity of the substrate could give researchers a way to finely control graphene's band gap and may eventually lead to the fabrication of graphene-based transistors that can be turned on and off like a semiconductor.

Still, as shown in the group's previous work, while these substrate interactions open the door to graphene's use as a practical electronic material, they lower the window on speed. Electrons do not move as well through substrate-mounted bilayer graphene; however, this may likely be compensated for by engineering the graphene/substrate interactions.

Stroscio's team plans to explore further the role that substrates may play in the creation and control of band gaps in graphene by using different substrate materials. If the substrate interactions can be reduced far enough, says Stroscio, the exotic quantum properties of bilayer graphene may be harnessed to create a new quantum field effect transistor.

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Exploring the Superconducting Transition in Ultra Thin Films

"Understanding exactly what happens when a normally insulating copper-oxide material transitions from the insulating to the superconducting state is one of the great mysteries of modern physics," said Brookhaven physicist Ivan Bozovic, lead author on the study.

One way to explore the transition is to apply an external electric field to increase or decrease the level of"doping" -- that is, the concentration of mobile electrons in the material -- and see how this affects the ability of the material to carry current. But to do this in copper-oxide (cuprate) superconductors, one needs extremely thin films of perfectly uniform composition -- and electric fields measuring more than 10 billion volts per meter. (For comparison, the electric field directly under a power transmission line is 10 thousand volts per meter.)

Bozovic's group has employed a technique called molecular beam epitaxy (MBE) to uniquely create such perfect superconducting thin films one atomic layer at a time, with precise control of each layer's thickness. Recently, they've shown that in such MBE-created films even a single cuprate layer can exhibit undiminished high-temperature superconductivity.

Now, they've applied the same technique to build ultrathin superconducting field effect devices that allow them to achieve the charge separation, and thus electric field strength, for these critical studies.

These devices are similar to the field-effect transistors (FETs) that are the basis of all modern electronics, in which a semiconducting material transports electrical current from the"source" electrode on one end of the device to a"drain" electrode on the other end. FETs are controlled by a third electrode, called a"gate," positioned above the source-drain channel -- separated by a thin insulator -- which switches the device on or off when a particular gate voltage is applied to it.

But because no known insulator could withstand the high fields required to induce superconductivity in the cuprates, the standard FET scheme doesn't work for high-temperature superconductor FETs. Instead, the scientists used electrolytes, liquids that conduct electricity, to separate the charges.

In this setup, when an external voltage is applied, the electrolyte's positively charged ions travel to the negative electrode and the negatively charged ions travel to the positive electrode. But when the ions reach the electrodes, they abruptly stop, as though they've hit a brick wall. The electrode"walls" carry an equal amount of opposite charge, and the electric field between these two oppositely charged layers can exceed the 10 billion volts per meter goal.

The result is a field effect device in which the critical temperature of a prototype high-temperature superconductor compound (lanthanum-strontium-copper-oxide) can be tuned by as much as 30 degrees Kelvin, which is about 80 percent of its maximal value -- almost ten times more than the previous record.

The scientists have now used this enhanced device to study some of the basic physics of high-temperature superconductivity.

One key finding: As the density of mobile charge carriers is increased, their cuprate film transitions from insulating to superconducting behavior when the film sheet resistance reaches 6.45 kilo-ohm. This is exactly equal to the Planck quantum constant divided by twice the electron charge squared -- h/(2e)². Both the Planck constant and electron charge are"atomic" units -- the minimum possible quantum of action and of electric charge, respectively, established after the advent of quantum mechanics early in the last century.

"It is striking to see a signature of such clearly quantum-mechanical behavior in a macroscopic sample (up to millimeter scale) and at a relatively high temperature," Bozovic said. Most people associate quantum mechanics with characteristic behavior of atoms and molecules.

This result also carries another surprising message. While it has been known for many years that electrons are paired in the superconducting state, the findings imply that they also form pairs (although localized and immobile) in the insulating state, unlike in any other known material. That sets the scientists on a more focused search for what gets these immobilized pairs moving when the transition to superconductivity occurs.

Superconducting FETs might also have direct practical applications. Semiconductor-based FETs are power-hungry, particularly when packed very densely to increase their speed. In contrast, superconductors operate with no resistance or energy loss. Here, the atomically thin layer construction is in fact advantageous -- it enhances the ability to control superconductivity using an external electric field.

"This is just the beginning," Bozovic said."We still have so much to learn about high-temperature superconductors. But as we continue to explore these mysteries, we are also striving to make ultrafast and power-saving superconducting electronics a reality."

This research was funded by the DOE Office of Science and the Swiss National Science Foundation.

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Solar Power Goes Viral: Researchers Use Virus to Improve Solar-Cell Efficiency

In a solar cell, sunlight hits a light-harvesting material, causing it to release electrons that can be harnessed to produce an electric current. The new MIT research, published online in the journalNature Nanotechnology, is based on findings that carbon nanotubes -- microscopic, hollow cylinders of pure carbon -- can enhance the efficiency of electron collection from a solar cell's surface.

Previous attempts to use the nanotubes, however, had been thwarted by two problems. First, the making of carbon nanotubes generally produces a mix of two types, some of which act as semiconductors (sometimes allowing an electric current to flow, sometimes not) or metals (which act like wires, allowing current to flow easily). The new research, for the first time, showed that the effects of these two types tend to be different, because the semiconducting nanotubes can enhance the performance of solar cells, but the metallic ones have the opposite effect. Second, nanotubes tend to clump together, which reduces their effectiveness.

And that's where viruses come to the rescue. Graduate students Xiangnan Dang and Hyunjung Yi -- working with Angela Belcher, the W. M. Keck Professor of Energy, and several other researchers -- found that a genetically engineered version of a virus called M13, which normally infects bacteria, can be used to control the arrangement of the nanotubes on a surface, keeping the tubes separate so they can't short out the circuits, and keeping the tubes apart so they don't clump.

The system the researchers tested used a type of solar cell known as dye-sensitized solar cells, a lightweight and inexpensive type where the active layer is composed of titanium dioxide, rather than the silicon used in conventional solar cells. But the same technique could be applied to other types as well, including quantum-dot and organic solar cells, the researchers say. In their tests, adding the virus-built structures enhanced the power conversion efficiency to 10.6 percent from 8 percent -- almost a one-third improvement.

This dramatic improvement takes place even though the viruses and the nanotubes make up only 0.1 percent by weight of the finished cell."A little biology goes a long way," Belcher says. With further work, the researchers think they can ramp up the efficiency even further.

The viruses are used to help improve one particular step in the process of converting sunlight to electricity. In a solar cell, the first step is for the energy of the light to knock electrons loose from the solar-cell material (usually silicon); then, those electrons need to be funneled toward a collector, from which they can form a current that flows to charge a battery or power a device. After that, they return to the original material, where the cycle can start again. The new system is intended to enhance the efficiency of the second step, helping the electrons find their way: Adding the carbon nanotubes to the cell"provides a more direct path to the current collector," Belcher says.

The viruses actually perform two different functions in this process. First, they possess short proteins called peptides that can bind tightly to the carbon nanotubes, holding them in place and keeping them separated from each other. Each virus can hold five to 10 nanotubes, each of which is held firmly in place by about 300 of the virus's peptide molecules. In addition, the virus was engineered to produce a coating of titanium dioxide (TiO2), a key ingredient for dye-sensitized solar cells, over each of the nanotubes, putting the titanium dioxide in close proximity to the wire-like nanotubes that carry the electrons.

The two functions are carried out in succession by the same virus, whose activity is"switched" from one function to the next by changing the acidity of its environment. This switching feature is an important new capability that has been demonstrated for the first time in this research, Belcher says.

In addition, the viruses make the nanotubes soluble in water, which makes it possible to incorporate the nanotubes into the solar cell using a water-based process that works at room temperature.

Prashant Kamat, a professor of chemistry and biochemistry at Notre Dame University who has done extensive work on dye-sensitized solar cells, says that while others have attempted to use carbon nanotubes to improve solar cell efficiency,"the improvements observed in earlier studies were marginal," while the improvements by the MIT team using the virus assembly method are"impressive."

"It is likely that the virus template assembly has enabled the researchers to establish a better contact between the TiO2 nanoparticles and carbon nanotubes. Such close contact with TiO2 nanoparticles is essential to drive away the photo-generated electrons quickly and transport it efficiently to the collecting electrode surface."

Kamat thinks the process could well lead to a viable commercial product:"Dye-sensitized solar cells have already been commercialized in Japan, Korea and Taiwan," he says. If the addition of carbon nanotubes via the virus process can improve their efficiency,"the industry is likely to adopt such processes."

Belcher and her colleagues have previously used differently engineered versions of the same virus to enhance the performance of batteries and other devices, but the method used to enhance solar cell performance is quite different, she says.

Because the process would just add one simple step to a standard solar-cell manufacturing process, it should be quite easy to adapt existing production facilities and thus should be possible to implement relatively rapidly, Belcher says.

The research team also included Paula Hammond, the Bayer Professor of Chemical Engineering; Michael Strano, the Charles (1951) and Hilda Roddey Career Development Associate Professor of Chemical Engineering; and four other graduate students and postdoctoral researchers. The work was funded by the Italian company Eni, through the MIT Energy Initiative's Solar Futures Program.

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Replacing Batteries May Become a Thing of the Past, Thanks to 'Soft Generators'

A class of variable capacitor generators known as"dielectric elastomer generators" (DEGs) shows great potential for wearable energy harvesting. In fact, researchers at the Auckland Bioengineering Institute's Biomimetics Lab believe DEGs may enable light, soft, form-fitting, silent energy harvesters with excellent mechanical properties that match human muscle. They describe their findings in the American Institute of Physics' journalApplied Physics Letters.

"Imagine soft generators that produce energy by flexing and stretching as they ride ocean waves or sway in the breeze like a tree," says Thomas McKay, a Ph.D. candidate working on soft generator research at the Biomimetics Lab."We've developed a low-cost power generator with an unprecedented combination of softness, flexibility, and low mass. These characteristics provide an opportunity to harvest energy from environmental sources with much greater simplicity than previously possible."

Dielectric elastomers, often referred to as artificial muscles, are stretchy materials that are capable of producing energy when deformed. In the past, artificial muscle generators required bulky, rigid, and expensive external electronics.

"Our team eliminated the need for this external circuitry by integrating flexible electronics -- dielectric elastomer switches -- directly onto the artificial muscles themselves. One of the most exciting features of the generator is that it's so simple; it simply consists of rubber membranes and carbon grease mounted in a frame," McKay explains.

McKay and his colleagues at the Biomimetics Lab are working to create soft dexterous machines that comfortably interface with living creatures and nature in general. The soft generator is another step toward fully soft devices; it could potentially be unnoticeably incorporated into clothing and harvest electricity from human movement. When this happens, worrying about the battery powering your cell phone or other portable electronics dying on you will become a thing of the past. And as an added bonus, this should help keep batteries out of landfills.

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Cheaper Hydrogen Fuel Cells: Utility of Non-Precious-Metal Catalysts Documented

In a paper published April 21 inScience, Los Alamos researchers Gang Wu, Christina Johnston, and Piotr Zelenay, joined by researcher Karren More of Oak Ridge National Laboratory, describe the use of a platinum-free catalyst in the cathode of a hydrogen fuel cell. Eliminating platinum -- a precious metal more expensive than gold -- would solve a significant economic challenge that has thwarted widespread use of large-scale hydrogen fuel cell systems.

Polymer-electrolyte hydrogen fuel cells convert hydrogen and oxygen into electricity. The cells can be enlarged and combined in series for high-power applications, including automobiles. Under optimal conditions, the hydrogen fuel cell produces water as a"waste" product and does not emit greenhouse gasses. However, because the use of platinum in catalysts is necessary to facilitate the reactions that produce electricity within a fuel cell, widespread use of fuel cells in common applications has been cost prohibitive. An increase in the demand for platinum-based catalysts could drive up the cost of platinum even higher than its current value of nearly$1,800 an ounce.

The Los Alamos researchers developed non-precious-metal catalysts for the part of the fuel cell that reacts with oxygen. The catalysts -- which use carbon (partially derived from polyaniline in a high-temperature process), and inexpensive iron and cobalt instead of platinum -- yielded high power output, good efficiency, and promising longevity. The researchers found that fuel cells containing the carbon-iron-cobalt catalyst synthesized by Wu not only generated currents comparable to the output of precious-metal-catalyst fuel cells, but held up favorably when cycled on and off -- a condition that can damage inferior catalysts relatively quickly.

Moreover, the carbon-iron-cobalt catalyst fuel cells effectively completed the conversion of hydrogen and oxygen into water, rather than producing large amounts of undesirable hydrogen peroxide. Inefficient conversion of the fuels, which generates hydrogen peroxide, can reduce power output by up to 50 percent, and also has the potential to destroy fuel cell membranes. Fortunately, the carbon- iron-cobalt catalysts synthesized at Los Alamos create extremely small amounts of hydrogen peroxide, even when compared with state-of-the-art platinum-based oxygen-reduction catalysts.

Because of the successful performance of the new catalyst, the Los Alamos researchers have filed a patent for it.

"The encouraging point is that we have found a catalyst with a good durability and life cycle relative to platinum-based catalysts," said Zelenay, corresponding author for the paper."For all intents and purposes, this is a zero-cost catalyst in comparison to platinum, so it directly addresses one of the main barriers to hydrogen fuel cells."

The next step in the team's research will be to better understand the mechanism underlying the carbon-iron-cobalt catalyst. Micrographic images of portions of the catalyst by researcher More have provided some insight into how it functions, but further work must be done to confirm theories by the research team. Such an understanding could lead to improvements in non-precious-metal catalysts, further increasing their efficiency and lifespan.

Project funding for the Los Alamos research came from the U.S. Department of Energy's Energy Efficiency and Renewable Energy (EERE) Office as well as from Los Alamos National Laboratory's Laboratory-Directed Research and Development program. Microscopy research was done at Oak Ridge National Laboratory's SHaRE user facility with support from the DOE's Office of Basic Energy Sciences.

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New Spin on Graphene Makes It Magnetic

The results, reported inScience, could be a potentially huge breakthrough in the field of spintronics.

Spintronics is a group of emerging technologies that exploit the intrinsic spin of the electron, in addition to its fundamental electric charge that is exploited in microelectronics.

Billions of spintronics devices such as sensors and memories are already being produced. Every hard disk drive has a magnetic sensor that uses a flow of spins, and magnetic random access memory (MRAM) chips are becoming increasingly popular.

The findings are part of a large international effort involving research groups from the US, Russia, Japan and the Netherlands.

The key feature for spintronics is to connect the electron spin to electric current as current can be manipulated by means routinely used in microelectronics.

It is believed that, in future spintronics devices and transistors, coupling between the current and spin will be direct, without using magnetic materials to inject spins as it is done at the moment.

So far, this route has only been demonstrated by using materials with so-called spin-orbit interaction, in which tiny magnetic fields created by nuclei affect the motion of electrons through a crystal. The effect is generally small which makes it difficult to use.

The researchers found a new way to interconnect spin and charge by applying a relatively weak magnetic field to graphene and found that this causes a flow of spins in the direction perpendicular to electric current, making a graphene sheet magnetised.

The effect resembles the one caused by spin-orbit interaction but is larger and can be tuned by varying the external magnetic field.

The Manchester researchers also show that graphene placed on boron nitride is an ideal material for spintronics because the induced magnetism extends over macroscopic distances from the current path without decay.

The team believes their discovery offers numerous opportunities for redesigning current spintronics devices and making new ones such as spin-based transistors.

Professor Geim said:"The holy grail of spintronics is the conversion of electricity into magnetism or vice versa.

"We offer a new mechanism, thanks to unique properties of graphene. I imagine that many venues of spintronics can benefit from this finding."

Antonio Castro Neto, a physics professor from Boston who wrote a news article for theSciencemagazine which accompanies the research paper commented:"Graphene is opening doors for many new technologies.

"Not surprisingly, the 2010 Nobel Physics prize was awarded to Andre Geim and Kostya Novoselov for their groundbreaking experiments in this material.

"Apparently not satisfied with what they have accomplished so far, Geim and his collaborators have now demonstrated another completely unexpected effect that involves quantum mechanics at ambient conditions. This discovery opens a new chapter to the short but rich history of graphene."

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The Heat Is On: Zeroing in on Energy Consumption of Ice Makers

With only one-fourth of the extra energy actually used to cool and freeze water,"there are substantial opportunities for efficiency improvements merely by optimizing the operations of the heaters associated with the ice makers" or by introducing a more efficient alternative technology, report NIST mechanical engineer David Yashar and guest researcher Ki-Jung Park.*

Since refrigerators account for 8 percent of the total energy consumed by 111 million U.S. households according to the Department of Energy (DOE), the potential savings are significant.

Currently, ice maker energy consumption is not reflected in federal minimum efficiency standards for refrigerators or in the voluntary Energy Star program, which requires energy usage to be significantly lower than the regulatory limit.

DOE, which helped to fund the NIST study, has announced that it will increase the minimum efficiency standard by 25 percent over the current level, starting in 2014. DOE also intends to incorporate the energy used by ice makers into their regulatory test. Because no widely accepted test for ice makers was available when they announced these intentions, DOE plans to add 84 kilowatt hours to the energy efficiency rating of every refrigerator equipped with an ice maker, Yashar explains.

Once a reliable, straightforward test is available, he adds, DOE will eliminate the"placeholder" energy consumption and use actual ice maker test results in efficiency ratings.

To speed progress along this path, Yashar and Park evaluated several different approaches to measure the energy consumption of ice makers. Their goal was to identify a method that consistently yielded accurate results but did not add substantially to the complexity of appliance energy consumption tests under current regulations.

Yashar and Park examined four refrigerators, which sampled a variety of ice maker technologies. Their study used a uniform test setup, consistent with current regulatory procedures, and measured the energy consumption of the four units while their ice makers were actively producing ice and, again, while the ice makers were not operational.

The results point the way to a standard test methodology that appears promising for several different ice maker technologies and configurations. Next steps include sharing their approach with other laboratories, which also will test ice makers and compare results for similar units. Also, Yashar says he intends to evaluate the measurement techniques on other styles of automatic ice makers.

*D.A. Yashar and K.J. Park, Energy Consumption of Automatic Ice Makers Installed in Domestic Refrigerators. NIST Technical Note 1697, April 2011.

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Solar Power Without Solar Cells: A Hidden Magnetic Effect of Light Could Make It Possible

The researchers found a way to make an"optical battery," said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.

In the process, they overturned a century-old tenet of physics.

"You could stare at the equations of motion all day and you will not see this possibility. We've all been taught that this doesn't happen," said Rand, an author of a paper on the work published in theJournal of Applied Physics."It's a very odd interaction. That's why it's been overlooked for more than 100 years."

Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. What Rand and his colleagues found is that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than previously expected. Under these circumstances, the magnetic effects develop strength equivalent to a strong electric effect.

"This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation," Rand said."In solar cells, the light goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power source."

What makes this possible is a previously undetected brand of"optical rectification," says William Fisher, a doctoral student in applied physics. In traditional optical rectification, light's electric field causes a charge separation, or a pulling apart of the positive and negative charges in a material. This sets up a voltage, similar to that in a battery. This electric effect had previously been detected only in crystalline materials that possessed a certain symmetry.

Rand and Fisher found that under the right circumstances and in other types of materials, the light's magnetic field can also create optical rectification.

"It turns out that the magnetic field starts curving the electrons into a C-shape and they move forward a little each time," Fisher said."That C-shape of charge motion generates both an electric dipole and a magnetic dipole. If we can set up many of these in a row in a long fiber, we can make a huge voltage and by extracting that voltage, we can use it as a power source."

The light must be shone through a material that does not conduct electricity, such as glass. And it must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn't this intense on its own, but new materials are being sought that would work at lower intensities, Fisher said.

"In our most recent paper, we show that incoherent light like sunlight is theoretically almost as effective in producing charge separation as laser light is," Fisher said.

This new technique could make solar power cheaper, the researchers say. They predict that with improved materials they could achieve 10 percent efficiency in converting solar power to useable energy. That's equivalent to today's commercial-grade solar cells.

"To manufacture modern solar cells, you have to do extensive semiconductor processing," Fisher said."All we would need are lenses to focus the light and a fiber to guide it. Glass works for both. It's already made in bulk, and it doesn't require as much processing. Transparent ceramics might be even better."

In experiments this summer, the researchers will work on harnessing this power with laser light, and then with sunlight.

The paper is titled"Optically-induced charge separation and terahertz emission in unbiased dielectrics." The university is pursuing patent protection for the intellectual property.

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Magnetic New Graphene Discovery

The finding by a team of Maryland researchers, led by Physics Professor Michael S. Fuhrer of the UMD Center for Nanophysics and Advanced Materials is the latest of many amazing properties discovered for graphene.

A honeycomb sheet of carbon atoms just one atom thick, graphene is the basic constituent of graphite. Some 200 times stronger than steel, it conducts electricity at room temperature better than any other known material (a 2008 discovery by Fuhrer, et. al). Graphene is widely seen as having great, perhaps even revolutionary, potential for nanotechnology applications. The 2010 Nobel Prize in physics was awarded to scientists Konstantin Novoselov and Andre Geim for their 2004 discovery of how to make graphene.

In their new graphene discovery, Fuhrer and his University of Maryland colleagues have found that missing atoms in graphene, called vacancies, act as tiny magnets -- they have a"magnetic moment." Moreover, these magnetic moments interact strongly with the electrons in graphene which carry electrical currents, giving rise to a significant extra electrical resistance at low temperature, known as the Kondo effect. The results appear in the paper"Tunable Kondo effect in graphene with defects" published this month inNature Physics.

The Kondo effect is typically associated with adding tiny amounts of magnetic metal atoms, such as iron or nickel, to a non-magnetic metal, such as gold or copper. Finding the Kondo effect in graphene with vacancies was surprising for two reasons, according to Fuhrer.

"First, we were studying a system of nothing but carbon, without adding any traditionally magnetic impurities. Second, graphene has a very small electron density, which would be expected to make the Kondo effect appear only at extremely low temperatures," he said.

The team measured the characteristic temperature for the Kondo effect in graphene with vacancies to be as high as 90 Kelvin, which is comparable to that seen in metals with very high electron densities. Moreover the Kondo temperature can be tuned by the voltage on an electrical gate, an effect not seen in metals. They theorize that the same unusual properties of that result in graphene's electrons acting as if they have no mass also make them interact very strongly with certain kinds of impurities, such as vacancies, leading to a strong Kondo effect at a relatively high temperature.

Fuhrer thinks that if vacancies in graphene could be arranged in just the right way, ferromagnetism could result."Individual magnetic moments can be coupled together through the Kondo effect, forcing them all to line up in the same direction," he said.

"The result would be a ferromagnet, like iron, but instead made only of carbon. Magnetism in graphene could lead to new types of nanoscale sensors of magnetic fields. And, when coupled with graphene's tremendous electrical properties, magnetism in graphene could also have interesting applications in the area of spintronics, which uses the magnetic moment of the electron, instead of its electric charge, to represent the information in a computer.

"This opens the possibility of 'defect engineering' in graphene -- plucking out atoms in the right places to design the magnetic properties you want," said Fuhrer.

This research was supported by grants from the National Science Foundation and the Office of Naval Research.

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New Research Advances Understanding of Lead Selenide Nanowires

Now, a research team at the University of Pennsylvania's schools of Engineering and Applied Science and Arts and Sciences has shown how to control the characteristics of semiconductor nanowires made of a promising material: lead selenide.

Led by Cherie Kagan, professor in the departments of Electrical and Systems Engineering, Materials Science and Engineering and Chemistry and co-director of Pennergy, Penn's center focused on developing alternative energy technologies, the team's research was primarily conducted by David Kim, a graduate student in the Materials Science and Engineering program.

The team's work was published online in the journalACS Nanoand will be featured in the Journal's April podcast.

The key contribution of the team's work has to do with controlling the conductive properties of lead selenide nanowires in circuitry. Semiconductors come in two types,nandp, referring to the negative or positive charge they can carry. The ones that move electrons, which have a negative charge, are called"n-type." Their"p-type" counterparts don't move protons but rather the absenceof an electron -- a"hole" -- which is the equivalent of moving a positive charge.

Before they are integrated into circuitry, the semiconductor nanowire must be"wired up" into a device. Metal electrodes must be placed on both ends to allow electricity to flow in and out; however, the"wiring" may influence the observed electrical characteristics of the nanowires, whether the device appears to ben-type orp-type. Contamination, even from air, can also influence the device type. Through rigorous air-free synthesis, purification and analysis, they kept the nanowires clean, allowing them to discover the unique properties of these lead selenide nanomaterials.

Researchers designed experiments allowing them to separate the influence of the metal"wiring" on the motion of electrons and holes from that of the behavior intrinsic to the lead selenide nanowires. By controlling the exposure of the semiconductor nanowire device to oxygen or the chemical hydrazine, they were able to change the conductive properties betweenp-type andn-type. Altering the duration and concentration of the exposure, the nanowire device type could be flipped back and forth.

"If you expose the surfaces of these structures, which are unique to nanoscale materials, you can make themp-type, you can make themn-type, and you can make them somewhere in between, where it can conduct both electrons and holes," Kagan said."This is what we call 'ambipolar.'"

Devices combining onen-type and onep-type semiconductor are used in many high-tech applications, ranging from the circuits of everyday electronics, to solar cells and thermoelectrics, which can convert heat into electricity.

"Thinking about how we can build these things and take advantage of the characteristics of nanoscale materials is really what this new understanding allows," Kagan said.

Figuring out the characteristics of nanoscale materials and their behavior in device structures are the first steps in looking forward to their applications.

These lead selenide nanowires are attractive because they may be synthesized by low-cost methods in large quantities.

"Compared to the big machinery you need to make other semiconductor devices, it's significantly cheaper," Kagan said."It doesn't look much more complicated than the hoods people would recognize from when they had to take chemistry lab."

In addition to the low cost, the manufacturing process for lead selenide nanowires is relatively easy and consistent.

"You don't have to go to high temperatures to get mass quantities of these high-quality lead selenide nanowires," Kim said."The techniques we use are high yield and high purity; we can use all of them."

And because the conductive qualities of the lead selenide nanowires can be changed while they are situated in a device, they have a wider range of functionality, unlike traditional silicon semiconductors, which must first be"doped" with other elements to make them"p" or"n."

The Penn team's work is a step toward integrating these nanomaterials in a range of electronic and optoelectronic devices, such as photo sensors.

The research was conducted by Kim and Kagan, along with Materials Science and Engineering undergraduate and graduate students Tarun R. Vemulkar and Soong Ju Oh; Weon-Kyu Koh, a graduate student in Chemistry; and Christopher B. Murray, a professor in Chemistry and in Materials Science and Engineering.

This work was supported with funding from the National Science Foundation Division of Materials Research, the National Science Foundation Solar Program and the National Science Foundation Nano-Bio Interface Center.

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Flexible Trailing Edge Flap for Blades to Make Wind Power Cheaper

Now a three-year project co-funded by EUDP (the Danish Programme for Energy Technology Development and Demonstration), with three industry partners, is launched and is to develop the promising technology forward to a robust and durable trailing edge which can be tested on a full-scale blade.

The fierce gusts and turbulence, such as wind turbines are exposed to constantly, contribute significantly to the cost of producing electricity from wind turbines. The turbines must be designed to resist these influences throughout their lifespan of at least 20 years since repairs are costly, especially when the turbines are located far out at sea and are more than 100 meters high. Therefore, researchers and industry are aimed at finding technical solutions that can alleviate the loads on the turbines.

"We have already had a good start of the project with our first project meeting in early March. The composition of project partners is well suited in order to solve the challenges in the project" says Research Specialist and Project Manager Helge Aagaard Madsen from Risø DTU.

With a grant of DKK 9,9 million from EUDP and an own appropriation from Risø DTU, DTU Electrical Engineering and three industrial partners on DKK 3 million the exciting technology can now take one step closer to being a commercial prototype that are to be tested on a full-scale blade. Risø DTU coordinates the project and the industrial partners are AVN Energy A/S, Rehau A/S and Dansk Gummi Industri A/S.

Robust, reliable and durable! The buzz words for the project are to develop a technology that is: robust, reliable and durable. The specific solution that has been under development at Risø since 2006, supported by funds from Region Zealand, is a flexible trailing edge of rubber or plastic. Movement of the trailing edge is achieved by elastic deformations caused by fiber reinforced cavities that run through the rear and can be pressurized with air or hydraulics. It is these controlled movements that counteract the forces from the fierce wind gusts.

"The technology has already been tested under laboratory conditions and in a wind tunnel with promising results. Now the task is to have a prototype produced by the end of project that is ready for testing on a full-scale turbine"explains Research Specialist Helge Aagaard Madsen and continues:

"We want to develop and produce prototypes in 2m-long rubber or plastic in the project, depending on what's most robust and give the best result."

The three industrial partners in the project each contribute specific knowledge in key areas. Eg AVN is already experts in the hydraulic systems that are currently used for turbine pitch systems. Since AVN develops, manufactures and sells these systems for different wind turbine manufacturers they can contribute with a unique understanding of how the new flaps systems can operate together with the pitch system.

"The pitch system is what rotate the blades today so that they are positioned optimal towards the wind, but it costs both loads and energy to turn a 15-ton rotor blade as compared to what it will 'cost' for our small local movements with a flexible blade trailing edge that perhaps only has a weight of 1% of the blade's total weight,"explains Helge Aagaard Madsen

The other two project partners is Rehau, that among other supplies plastic parts for the car industry and Dansk Gummi Industri which manufactures molded rubber and polyurethane to the industry. Rehau will contribute to develop the new materials that the trailing edge can be manufactured from, and the Dansk Gummi Industri will work on the production side of the trailing edge also called CRTEF (Controllable Rubber Trailing Edge Flap).

No mechanical parts The flexible trailing edge is entirely without mechanical parts and we hope completely to avoid metal parts. And this part is important. Helge Aagaard Madsen explains:

"It is important that the technologies we develop now are virtually maintenance free. It is of no use to add another component on the turbine that needs a lot of maintenance and can break. This is also why it is very important that we have a good collaboration with the industry from this early stage. In this way we can ensure that the product matches what the industry needs and wants. Both when it comes to the production and the application side."

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Research Into Batteries Will Give Electric Cars the Same Range as Gas Cars, Experts Say

The electric car was introduced by Edison as early as 1900. But, as we all know, Henry Ford's vehicle concept with a noisy, smelly combustion engine won the race to become people's most treasured individual means of transport, despite the fact that in principle, the combustion engine is hopeless.

Then, as now, the Achilles' heel of the electric car was the limited energy density of the batteries, which will only sustain short drives. Now -- 110 years later -- the battery technology, combined with the effect electronics and the electric engine, have come so far in performance, size and price that the electric car is again becoming interesting. The electric car does not pollute locally and it can, if used cleverly, be utilised to introduce more renewable energy into the electricity supply.

Electric cars are a good match for a society that has abandoned the use of fossil fuels.

This is why electric cars have been reborn as an important factor in the vision of a society without fossil fuels, and the first electric cars have already hit the roads, albeit in very limited numbers and with very short ranges between recharges.

The advantages of the electric car are first and foremost that it can be integrated into the electricity system and potentially serve as a buffer in the electricity system of tomorrow, where most of our electricity originates from fluctuating renewable energy. Where there is excess electricity from e.g. wind turbines, the electric cars can be charged. When there is a shortage of electricity, some of the power can be returned to the electricity grid. The other major advantage is that, if mass-produced, the electric car could be cheaper to produce than the current cars.

2 tonnes of batteries or 50 litres of gasoline

Today, battery packs are expensive and are only able to store a relatively low amount of energy. Researchers all over the world are working to change that. In the current setting, an electric car is no good if you are taking the family on holiday to Lake Garda in Italy. For electric cars to become the consumers' preferred mode of transport, the battery capacity must be significantly increased. In Risø Energy Report 9, page 58, you can read that the energy density in today's batteries is almost two orders lower than that of fossil fuels. This means that a battery pack containing energy corresponding to 50 litres of petrol, would weigh between 1.5 and 2 tonnes.

Lithium is a soft, silver-white metal -- the lightest of all metals. Lithium is extremely reactive and corrodes quickly in a humid atmosphere. There, lithium is typically stored under kerosene or in a protective atmosphere to avoid contact with oxygen and water.

The most promising electric car batteries are based on the metal lithium (Li). Lithium is a soft, silver-white metal -- the lightest of all metals. Lithium is extremely reactive and corrodes quickly in a humid atmosphere. There, lithium is typically stored under kerosene to avoid contact with oxygen and water. The lightness is one of the strengths of lithium. Traditional car batteries are based on lead (Pb), which is one of the heaviest metals in existence. To reduce the weight of batteries, lithium is the way to go, which is also substantiated by the prominence of rechargeable Li-ion batteries in e.g. mobile phones, cameras and MP3 and MP4 players. These batteries have the highest energy density among rechargeable batteries.

The lithium battery market is going to grow exponentially, and a discussion has already emerged whether there is going to be enough lithium to electrify the entire world's car park. Lithium is naturally occurring with approx. 65 g per tonne in top soil and approx. 0.1 g per tonne of water and can be extracted from soil as well as water, but if the lithium content is small, the extraction is costly.

In addition to the use in batteries, lithium is used in anti-depressants, ceramics, glass, aluminium production, lubricants and synthetic rubber. In the future (after 2050), lithium will probably also be used in fusions reactors for electricity production. The world's lithium reserves are found in countries such as Chile, China, Australia, Russia, Argentina, the USA, Zimbabwe and Bolivia. Lately, large deposits have been found in Afghanistan -- so large that the USA has dubbed the country 'the Saudi Arabia of lithium'. In Bolivia, lithium is found in large quantities under Salar de Uyuni -- the world's largest salt lake. Last year, Bolivia's president Morales announced that the country is going to invest DKK 5 billion in extracting lithium from the dried-out salt lake that covers more than 10,000 square kilometres and contains more than a quarter of the world's total lithium deposits.

The fight over the world's lithium resources will intensify in the future, but the upside is that the lithium part of batteries can be recycled, so when the batteries are worn out, the lithium can be extracted and form part of a new battery.

Li-air batteries could have the same efficient energy density as gasoline

Li-air batteries are a promising opportunity in the long term."If we succeed in developing this technology, we are facing the ultimate break-through for electric cars, because in practice, the energy density of Li-air batteries will be comparable to that of petrol and diesel, if you take into account that a combustion engine only has an efficiency of around 30 per cent," says Tejs Vegge, senior scientist in the Materials Research Division. If batteries with an energy density this great become a reality, one could easily imagine electrically powered trucks. Li-air batteries are thus a promising research area, but there are many research challenges to overcome before the batteries find their way to the electric cars.

The development of rechargeable batteries has moved slowly since the invention of the traditional lead-acid batteries, which are still used in the majority of e.g. starter batteries for conventional cars. The development of the Li-ion batteries marked a significant leap in the energy density of the rechargeable batteries. The final break-through may belong to the Li-air batteries which, in practice, could have the same efficient energy density as petrol. Source: Lithium -- Air Battery: Promise and Challenges, G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson and W. Wilcke, IBM Research, published in J.Phys.Chem.Lett.2010,1,2193-2203.

The Li-air battery is designed with a lithium electrode (the anode), and electrolyte and a porous carbon electrode (the cathode), which attracts the oxygen from the air when the battery is in operation. The battery is therefore, so to speak, open at one end, or it has an oxygen supply of its own. During discharge, oxygen reacts with lithium to form lithium peroxide (Li2O2), and during charging, this process is reversed to release oxygen. Both reactions take place on the surface of the porous carbon electrode.

Battery resembles humans: Gains weight and becomes short of breath

The interaction with air requires the electrode to have a very large surface area. The prototypes being worked on now have a current density of approx. 1 milliamp per square centimetre surface area, and this has to be increased by at least one order before the batteries are ready to be used in real life.

The fact that the battery absorbs oxygen atoms from the air means that the battery gains weight as it being discharged. Theoretically, the battery can more than double its weight.

At the same time, the electrode could become short of breath, so to speak. The oxygen absorbed by the battery reacts with lithium to form lithium peroxide, which may cause clogging of aggregates in the battery's channels, causing them to become blocked and preventing the supply of further oxygen."In our trials, we use pure oxygen, so we are okay, but the problems accumulate when the oxygen has to be extracted from ordinary air," says Søren Højgaard Jensen from the Fuel Cells and Solid State Chemistry Division. Ordinary air also contains moisture, and it must be taken into consideration that, as mentioned above, lithium and humidity do not make an attractive combination.

Difficult to charge

En extremely high overvoltage is required to recharge the battery again after a discharge. The so-called equilibrium voltage for the Li-air battery is 3 volts. When the battery is discharged, the voltage drops to 2.6-2.7 volts. But when you want to recharge the battery, the voltage must be increased to 4.5 volts. In comparison, a Li-ion battery can be recharged at an overvoltage of only 10 per cent.

"The discharge process is proceeding really well. Our problem is that the reverse process has a very high energy loss," says senior scientist Poul Norby, Materials Research Division."The high overvoltage for recharging is hard going for the current battery components, which limits the number of times the battery can be recharged," says Poul Norby. The cyclic energy loss in charging/recharging is about 40 per cent in Li-air batteries. The challenge is to reduce this number to 10 per cent, corresponding to Li-ion batteries.

In order to solve this issue, Tejs Vegge performs extensive computer calculations, so-called DFT calculations (Density Functional Theory), on the Li-air batteries. Using this method, it is possible -- at atom level applying an approximation to the famous Schrödinger equation, to calculate how the lithium and oxygen atoms interact."In this way, we hope to find an explanation of the high overvoltage and a solution to what we can do to reduce it, e.g. by adding an appropriate catalyst," says Tejs Vegge.

In addition to the computer calculations, the batteries are examined using X-ray and neutron rays. These techniques allow the scientists to study how ions and electrons move in the electrode-electrolyte interfaces when the battery is charged and discharged."We focus particularly on solid-state electrolytes because they offer safety and transport advantages. Large lithium batteries with liquid electrolytes could pose a safety risk in the event of accidents," says Tejs Vegge.

Finally, the battery properties are tested in practice. Testing of large lithium batteries takes place in a converted chest freezer in the laboratories of the Fuel Cells and Solid State Chemistry Division."The batteries have to be able to withstand heavy frost and extreme heat, and we can subject them to that in our converted chest freezer, which is able to cool objects down to -60°C and heat them to around 50°C," says Søren Højgaard Jensen.

Must recharge quickly -- and at least 300 times

Today, metal-air batteries are only used as disposable batteries for special purposes with high energy density requirements, e.g. for military equipment, and zinc-air batteries are used as disposable batteries in e.g. hearing aids.

If the battery is to withstand a car running e.g. 250,000 kilometres during its lifetime, and the battery is able to deliver approx. 800 kilometres from one charge, it must be able to handle full charging and discharging at least 300 times. Li-air battery prototypes can currently handle 50 charges, so the researchers are faced with other scientific challenges.

In addition to the number of charges the battery must be able to withstand, it must also be possible to charge it quickly."Think about the volume of energy transferred when you put petrol into your car. It takes a couple of minutes, and then you can go another 800-1000 kilometres. This is a true challenge for the Li-air batteries, because they may potentially be able to contain the same amount of energy as petrol, but it takes considerably longer to refuel," says Tejs Vegge.

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