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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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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Better Glasses-Free 3-D: Mew Approach to Make 3-D Illusions More Realistic

Researchers at MIT's Media Lab have developed a fundamentally new approach to glasses-free 3-D, called HR3D, which they say could double the battery life of devices like the 3DS without compromising screen brightness or resolution. Among other advantages, the technique could also expand the viewing angle of a 3-D screen, making it practical for larger devices with multiple users, and it would maintain the 3-D effect even when the screen is rotated -- something that happens routinely with handheld devices.

According to Doug Lanman, a postdoc in Associate Professor Ramesh Raskar's Camera Culture Group at the Media Lab, the 3DS relies on a century-old technology known as a parallax barrier. Like most 3-D technologies, this one requires two versions of the same image, one tailored to the left eye and one to the right. The two images are sliced into vertical segments and interleaved on a single surface.

By itself, the composite image looks like an incoherent jumble. But if you place a screen with vertical slits in it -- the parallax barrier -- just in front of the image and stand the right distance away, a 3-D image pops out. The opaque sections of the screen shield the parts of the image intended for the right eye from the left eye, and vice versa, but the slits allow each eye to see the segments intended for it.

The 3DS screen consists of two parallel liquid-crystal displays (LCDs) a small distance apart. When the device is operating in 3-D mode, the front display serves as the parallax barrier, depicting a series of opaque vertical stripes. Since the stripes block half the light coming from the screen, the device's backlight has to be twice as bright, which drains the battery twice as quickly. Moreover, because the spacing of the stripes is calibrated to the horizontal separation of human eyes, if the screen is tilted, the 3-D illusion disappears.

All the angles

Raskar and Lanman, along with postdoc Yun Hee Kim and graduate student Matthew Hirsch, decided to rethink glasses-free 3-D from the ground up. In the real world, as a viewer moves around an object, his or her perspective on it changes constantly. A convincing simulation of 3-D visual experience, Lanman argues, might require a display that offers a dozen different perspectives as the viewer moves from right to left.

But with parallax-barrier 3-D, each new perspective further restricts light emission. Adding multiple perspectives in the vertical direction as well as the horizontal would require a parallax barrier with horizontal as well as vertical bands. For a display with enough different views, the parallax barrier ends up looking like an opaque sheet with pinholes poked in it.

Like the 3DS, the MIT researchers' HR3D system uses two layers of liquid-crystal displays. But instead of displaying vertical bands, as the 3DS does, or pinholes, as a multiperspective parallax-barrier system would, the top LCD displays a pattern customized to the image beneath it.

Going into the project, the researchers had no idea what the customized pattern would look like. But once they'd done the math, they found that the ideal pattern ends up looking a lot like the source image. Instead of consisting of a few big, vertical slits, the parallax barrier consists of thousands of tiny slits, whose orientations follow the contours of the objects in the image.

Number crunching

Because the slits are oriented in so many different directions, the 3-D illusion is consistent no matter whether the image is upright or rotated 90 degrees. Adding more perspectives changes the pattern of the slits, but they allow just as much light to pass.

If a device like the 3DS used HR3D, Lanman says, its battery life would be longer, because the parallax barrier would block less light. The 3-D effect would also be consistent no matter the device's orientation: applications could actually take advantage of screen rotation, particularly in devices that have built-in motion sensors."But the real win," Lanman says,"comes with full parallax motion" -- that is, a display that shows multiple perspectives in both the horizontal and vertical directions.

"The great thing about Ramesh's group is that they think of things that no one else has thought of and then demonstrate that they can actually be done," says Neil Dodgson, professor of graphics and imaging at the University of Cambridge in England, who was one of the reviewers of the paper when it was accepted last year to the SIGGRAPH Asia graphics conference."It's quite a clever idea they've got here."

Dodgson points out, however, that HR3D is very computationally intensive."If you're saving battery power because you've got this extra brightness, but you're actually using all that battery power to do the computation, then you're not saving anything," he says.

While Lanman acknowledges that the algorithm for calculating the barrier pattern that he and his colleagues described in the SIGGRAPH Asia paper is computationally complex, he believes that it can be refined so that"it requires far less computation." He also points out that special-purpose chips designed specifically to run a refined version of the algorithm would consume much less power than a general-purpose processor performing the same computations.

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Novel Ionic Liquid Batteries

Rather than depend on highly acidic electrolytes, ionic liquids are used to create a solid polymer electrolyte composed of an ionic liquid and polyvinyl alcohol, developing novel types of solid state batteries with discharge voltages ranging up to 1.8 volts.

The unique properties of ionic liquids have fostered this explosive interest in battery applications. Ionic liquids are room temperature molten salts that possess many important characteristics, such as nearly no vapor pressure, non- flammability and lack of reactivity in various electrochemical or industrial applications."It is the high thermal and electrochemical stability of the ionic liquids which has fostered the growing interest in ionic liquids for use in various electrochemical processes," said Dr. Thomas Sutto."These new types of solid-state cells mimic standard alkaline cells, but without the need for caustic electrolytes."

Limits imposed by using corrosive electrolytes often result in severe restrictions to standard battery geometry and the need for special corrosive-resistant battery containers. The use of reactive ionic liquids in non-aqueous cells replaces the more hazardous highly alkaline electrolytes such as manganese oxide (MgO) and zinc (Zn) found in traditional batteries.

The root of this work began during standard corrosion studies of different metals in ionic liquids. While working with ionic liquids based on mineral acids, such as hydrogen sulphates, it was observed that Zn metal would react to form zinc sulphate. Since this is similar to that observed for the zinc anode in a standard alkaline cell, a series of experiments were then performed to determine how different metal oxides reacted in these types of ionic liquids.

Electrochemical experiments demonstrate that not only can these reactive ionic liquids act as the electrolyte/separator in both solid state and liquid batteries, but they can also act as a reactive species in the cell's electrochemical makeup. Using a non-aqueous approach to primary and secondary power sources, batteries are designed using standard cathode and anode materials such as magnesium dioxide (MgO₂), lead dioxide (PbO₂) and silver oxide (AgO). The ionic liquid that is the main focus of this work is 1-ethyl-3-methylimidazolium hydrogen sulphate (EMIHSO₄), however, other ionic liquids such as those based on the nitrate and dihydrogen phosphate anions (negatively charged ions) have also been found to work well in this type of a battery design.

The use of these electrolytes suggests the potential for new types of rechargeable systems, such as replacement electrolytes in nickel-metal hydride (NiMH) batteries, or even the standard lead-acid battery. Experimental work is currently underway to develop such a rechargeable ionic liquid power source. The ability to create solid separators also allows for the formation of many new types of batteries via a number of fabrication techniques.

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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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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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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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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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River Water and Salty Ocean Water Used to Generate Electricity

Anywhere freshwater enters the sea, such as river mouths or estuaries, could be potential sites for a power plant using such a battery, said Yi Cui, associate professor of materials science and engineering, who led the research team.

The theoretical limiting factor, he said, is the amount of freshwater available."We actually have an infinite amount of ocean water; unfortunately we don't have an infinite amount of freshwater," he said.

As an indicator of the battery's potential for producing power, Cui's team calculated that if all the world's rivers were put to use, their batteries could supply about 2 terawatts of electricity annually -- that's roughly 13 percent of the world's current energy consumption.

The battery itself is simple, consisting of two electrodes -- one positive, one negative -- immersed in a liquid containing electrically charged particles, or ions. In water, the ions are sodium and chlorine, the components of ordinary table salt.

Initially, the battery is filled with freshwater and a small electric current is applied to charge it up. The freshwater is then drained and replaced with seawater. Because seawater is salty, containing 60 to 100 times more ions than freshwater, it increases the electrical potential, or voltage, between the two electrodes. That makes it possible to reap far more electricity than the amount used to charge the battery.

"The voltage really depends on the concentration of the sodium and chlorine ions you have," Cui said."If you charge at low voltage in freshwater, then discharge at high voltage in sea water, that means you gain energy. You get more energy than you put in."

Once the discharge is complete, the seawater is drained and replaced with freshwater and the cycle can begin again."The key thing here is that you need to exchange the electrolyte, the liquid in the battery," Cui said. He is lead author of a study published in the journal Nano Letters earlier this month.

In their lab experiments, Cui's team used seawater they collected from the Pacific Ocean off the California coast and freshwater from Donner Lake, high in the Sierra Nevada. They achieved 74 percent efficiency in converting the potential energy in the battery to electrical current, but Cui thinks with simple modifications, the battery could be 85 percent efficient.

To enhance efficiency, the positive electrode of the battery is made from nanorods of manganese dioxide. That increases the surface area available for interaction with the sodium ions by roughly 100 times compared with other materials. The nanorods make it possible for the sodium ions to move in and out of the electrode with ease, speeding up the process.

Other researchers have used the salinity contrast between freshwater and seawater to produce electricity, but those processes typically require ions to move through a membrane to generate current. Cui said those membranes tend to be fragile, which is a drawback. Those methods also typically make use of only one type of ion, while his battery uses both the sodium and chlorine ions to generate power.

Cui's team had the potential environmental impact of their battery in mind when they designed it. They chose manganese dioxide for the positive electrode in part because it is environmentally benign.

The group knows that river mouths and estuaries, while logical sites for their power plants, are environmentally sensitive areas.

"You would want to pick a site some distance away, miles away, from any critical habitat," Cui said."We don't need to disturb the whole system, we just need to route some of the river water through our system before it reaches the ocean. We are just borrowing and returning it," he said.

The process itself should have little environmental impact. The discharge water would be a mixture of fresh and seawater, released into an area where the two waters are already mixing, at the natural temperature.

One of Cui's concerns is finding a good material for the negative electrode. He used silver for the experiments, but silver is too expensive to be practical.

His group did an estimate for various regions and countries and determined that South America, with the Amazon River draining a large part of the continent, has the most potential. Africa also has an abundance of rivers, as do Canada, the United States and India.

But river water doesn't necessarily have to be the source of the freshwater, Cui said.

"The water for this method does not have to be extremely clean," he said. Storm runoff and gray water could potentially be useable.

A power plant operating with 50 cubic meters of freshwater per second could produce up to 100 megawatts of power, according to the team's calculations. That would be enough to provide electricity for about 100,000 households.

Cui said it is possible that even treated sewage water might work.

"I think we need to study using sewage water," he said."If we can use sewage water, this will sell really well."

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Batteries Charge Quickly and Retain Capacity, Thanks to New Structure

Braun's group developed a three-dimensional nanostructure for battery cathodes that allows for dramatically faster charging and discharging without sacrificing energy storage capacity. The researchers' findings will be published in the March 20 advance online edition of the journalNature Nanotechnology.

Aside from quick-charge consumer electronics, batteries that can store a lot of energy, release it fast and recharge quickly are desirable for electric vehicles, medical devices, lasers and military applications.

"This system that we have gives you capacitor-like power with battery-like energy," said Braun, a professor of materials science and engineering."Most capacitors store very little energy. They can release it very fast, but they can't hold much. Most batteries store a reasonably large amount of energy, but they can't provide or receive energy rapidly. This does both."

The performance of typical lithium-ion (Li-ion) or nickel metal hydride (NiMH) rechargeable batteries degrades significantly when they are rapidly charged or discharged. Making the active material in the battery a thin film allows for very fast charging and discharging, but reduces the capacity to nearly zero because the active material lacks volume to store energy.

Braun's group wraps a thin film into three-dimensional structure, achieving both high active volume (high capacity) and large current. They have demonstrated battery electrodes that can charge or discharge in a few seconds, 10 to 100 times faster than equivalent bulk electrodes, yet can perform normally in existing devices.

This kind of performance could lead to phones that charge in seconds or laptops that charge in minutes, as well as high-power lasers and defibrillators that don't need time to power up before or between pulses.

Braun is particularly optimistic for the batteries' potential in electric vehicles. Battery life and recharging time are major limitations of electric vehicles. Long-distance road trips can be their own form of start-and-stop driving if the battery only lasts for 100 miles and then requires an hour to recharge.

"If you had the ability to charge rapidly, instead of taking hours to charge the vehicle you could potentially have vehicles that would charge in similar times as needed to refuel a car with gasoline," Braun said."If you had five-minute charge capability, you would think of this the same way you do an internal combustion engine. You would just pull up to a charging station and fill up."

All of the processes the group used are also used at large scales in industry so the technique could be scaled up for manufacturing.

They key to the group's novel 3-D structure is self-assembly. They begin by coating a surface with tiny spheres, packing them tightly together to form a lattice. Trying to create such a uniform lattice by other means is time-consuming and impractical, but the inexpensive spheres settle into place automatically.

Then the researchers fill the space between and around the spheres with metal. The spheres are melted or dissolved, leaving a porous 3-D metal scaffolding, like a sponge. Next, a process called electropolishing uniformly etches away the surface of the scaffold to enlarge the pores and make an open framework. Finally, the researchers coat the frame with a thin film of the active material.

The result is a bicontinuous electrode structure with small interconnects, so the lithium ions can move rapidly; a thin-film active material, so the diffusion kinetics are rapid; and a metal framework with good electrical conductivity.

The group demonstrated both NiMH and Li-ion batteries, but the structure is general, so any battery material that can be deposited on the metal frame could be used.

"We like that it's very universal, so if someone comes up with a better battery chemistry, this concept applies," said Braun, who is also affiliated with the Materials Research Laboratory and the Beckman Institute for Advanced Science and Technology at Illinois."This is not linked to one very specific kind of battery, but rather it's a new paradigm in thinking about a battery in three dimensions for enhancing properties."

The U.S. Army Research Laboratory and the Department of Energy supported this work. Visiting scholar Huigang Zhang and former graduate student Xindi Yu were co-authors of the paper.

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Electric Grid Reliability: Increasing Energy Storage in Vanadium Redox Batteries by 70 Percent

In a paper published by the journalAdvanced Energy Materials,researchers at the Department of Energy's Pacific Northwest National Laboratory found that adding hydrochloric acid to the sulfuric acid typically used in vanadium batteries increased the batteries' energy storage capacity by 70 percent and expanded the temperature range in which they operate.

"Our small adjustments greatly improve the vanadium redox battery," said lead author and PNNL chemist Liyu Li."And with just a little more work, the battery could potentially increase the use of wind, solar and other renewable power sources across the electric grid."

Unlike traditional power, which is generated in a reliable, consistent stream of electricity by controlling how much coal is burned or water is sent through dam turbines, renewable power production depends on uncontrollable natural phenomena such as sunshine and wind. Storing electricity can help smooth out the intermittency of renewable power while also improving the reliability of the electric grid that transmits it. Vanadium batteries can hold on to renewable power until people turn on their lights and run their dishwashers. Other benefits of vanadium batteries include high efficiency and the ability to quickly generate power when it's needed as well as sit idle for long periods of time without losing storage capacity.

A vanadium battery is a type of flow battery, meaning it generates power by pumping liquid from external tanks to the battery's central stack, or a chamber where the liquids are mixed. The tanks contain electrolytes, which are liquids that conduct electricity. One tank has the positively-charged vanadium ion V5+ floating in its electrolyte. And the other tank holds an electrolyte full of a different vanadium ion, V2+. When energy is needed, pumps move the ion-saturated electrolyte from both tanks into the stack, where a chemical reaction causes the ions to change their charge, creating electricity.

To charge the battery, electricity is sent to the vanadium battery's stack. This causes another reaction that restores the original charge of vanadium ions. The electrical energy is converted into chemical energy stored in the vanadium ions. The electrolytes with their respective ions are pumped back into to their tanks, where they wait until electricity is needed and the cycle is started again.

A battery's capacity to generate electricity is limited by how many ions it can pack into the electrolyte. Vanadium batteries traditionally use pure sulfuric acid for their electrolyte. But sulfuric acid can only absorb so many vanadium ions.

Another drawback is that sulfuric acid-based vanadium batteries only work between about 50 and 104 degrees Fahrenheit (10 to 40 Celsius). Below that temperature range, the ion-infused sulfuric acid crystallizes. The larger concern, however, is the battery overheating, which causes an unwanted solid to form and renders the battery useless. To regulate the temperature, air conditioners or circulating cooling water are used, which causes up to 20 percent energy loss and significantly increasing the battery's operating cost, the researchers noted.

Wanting to improve the battery's performance, Li and his colleagues began searching for a new electrolyte. They tried a pure hydrochloric acid electrolyte, but found it caused one of the vanadium ions to form an unwanted solid. Next, they experimented with various mixtures of both hydrochloric and sulfuric acids. PNNL scientists found the ideal balance when they mixed 6 parts hydrochloric acid with 2.5 parts sulfuric acid. They verified the electrolyte and ion molecules present in the solution with a nuclear magnetic resonance instrument and the Chinook supercomputer at EMSL, DOE's Environmental Molecular Sciences Laboratory at PNNL.

Tests showed that the new electrolyte mixture could hold 70 percent more vanadium ions, making the battery's electricity capacity 70 percent higher. The discovery means that smaller tanks can be used to generate the same amount of power as larger tanks filled with the old electrolyte.

And the new mixture allowed the battery to work in both warmer and colder temperatures, between 23 and 122 degrees Fahrenheit (-5 to 50 Celsius), greatly reducing the need for costly cooling systems. At room temperature, a battery with the new electrolyte mixture maintained an 87 percent energy efficiency rate for 20 days, which is about the same efficiency of the old solution.

The results are promising, but more research is needed, the authors noted. The battery's stack and overall physical structure could be improved to increase power generation and decrease cost.

"Vanadium redox batteries have been around for more than 20 years, but their use has been limited by a relatively narrow temperature range," Li said."Something as simple as adjusting the batteries' electrolyte means they can be used in more places without having to divert power output to regulate heat."

This research was supported by DOE's Office of Electricity Delivery and Energy Reliability and internal PNNL funding.

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Testing Smart Energy Systems

In an innovative test laboratory, the SmartEnergyLab, they are investigating how to network various electrical household appliances and operate them remotely. In the residential housing sector in particular there is still a great deal of potential for smart energy-management systems that are capable of tailoring local power generation and consumption optimally to the power grid: What is the best time of day for utilizing solar power? How can we store the energy produced and possibly feed it back into the power grid at a lucrative price?

"Smart energy-systems technology for the consumer end of the distribution grid is the key to sustainable, secure energy supply," explains Christof Wittwer, group manager at Fraunhofer ISE. By mapping all the thermal and electrical energy flows, the lab constitutes a unique platform for analyzing, assessing and developing smart homes and smart grid solutions for the distribution grid."Basically, our lab is a simulator for potential energy systems for houses," says Wittwer.

The lab is equipped with renewable as well as electric and thermal producers and storage devices for tomorrow's single-family dwellings and apartment buildings. It boasts a stand-alone 5kW cogeneration plant, a two-cubic-meter buffer storage tank, a photovoltaic simulator, several PV inverters and various stand-alone inverters, a lithium-ion battery pack, a lead battery bank, a charging infrastructure for electric vehicles as well as other equipment. The combination of virtual and real components means researchers can simulate almost any energy system. For any given system they then assess and evaluate the potential energy savings for the customer associated with managing that system.

The service portfolio includes everything from"Integration assessment of thermal and electrical equipment in the system,""Function and communications testing for energy management systems" to the"Efficiency assessment of energy management and generation equipment." Energy suppliers and grid operators from across Germany are already leveraging the know-how of the Freiburg-based experts to determine the potential inherent in the decentralized management of this kind of equipment. Tariff models need to be assessed and their impact on the power grids investigated.

At the Hannover Messe from April 4 to 8, researchers on the joint Fraunhofer Energy Alliance will be showcasing a small yet very sophisticated device: The Smart Energy Gateway -- a component from the test lab -- organizes the way in which data is shared between energy supplier and consumer. The smart box networks the power meters for heat, water and electricity and ensures that the right control function is used to increase efficiency based on current consumption figures and tariff information. But the Gateway is not just a networked meter and energy management optimization device: It can also be used to control household appliances or heaters and to program on/off times. When should the heat pump, the washing machine or the dishwasher come on? In future, one worry you won't have when you're on vacation is whether you forgot to switch the stove off.

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Better Batteries for Electric Cars

Electric cars are the future -- a view shared by government and the automotive industry alike.  By 2020, a million passenger cars with an electric drive should be on the roads in Germany. The ADAC, the German motoring organization, found out in a survey, 74 percent of those surveyed would buy an electric car if they did not have to compromise in terms of cost, comfort and safety.

Consumers are not willing to compromise one iota when it comes to range. Around one third of drivers are looking for a range of at least 500 kilometers. And here is the crux: A lack of charging stations and limited battery life have so far prevented compact electric vehicles from going mainstream. The lithium-ion batteries used by most automakers are simply too heavy, too expensive and go flat too quickly. New materials should improve the performance, service life and safety of the energy storage device, yet the development of these kinds of materials is time-consuming and costly. In the Fraunhofer System Research for Electromobility (FSEM) project, researchers from the Fraunhofer Institute for Industrial Mathematics ITWM in Kaiserslautern are developing software to simulate lithium-ion batteries, which should in turn speed up this process and make it more efficient. The new software is dubbed BEST, short for Battery and Electrochemistry Simulation Tool.

A lithium-ion battery consists of two porous electrodes kept apart by a separator filled with electrolyte. Lithium ions flow between the electrodes when the battery is charged and discharged."Battery performance depends on the materials used in the components. These materials need to work in harmony with each other," explains Jochen Zausch, a scientist in the Complex Fluids group at Fraunhofer ITWM."Various material combinations can be simulated using our software, enabling us to come up with the ideal mix. The kind of trial-and-error testing done in the past is no longer necessary."

The Fraunhofer ITWM researchers have managed to simulate on macroscopic and microscopic level the entire battery cell as well as the transport and reaction processes of the lithium ions themselves."We can show the microscopic structure of the electrodes. Every individual pore measuring 10 micrometers can be seen -- something none of today's off-the-shelf programs can do. The position and shape of the electrodes can also be varied," says Zausch. By resolving the structure of the electrodes in three dimensions, parameters such as lithium ion concentrations and current density can be calculated. For these computations a specializes"Finite Volume" code is used that was developed and implemented at the ITWM. The distribution of the current flow provides an indication of heat production in the battery. Therefore, the software can pinpoint possible hotspots that may overheat and can lead to ignition of the battery. Aging effects can also be assessed using BEST. After all, temperature development within the battery affects its service life. The scientists intend to upgrade the program to include aging models which would make these kinds of studies even easier to conduct.

"Ultimately, BEST should help both automakers and manufacturers of electric storage devices to build robust, safe batteries with greater range and, at the same time, improved acceleration," says Zausch in conclusion. The software can be seen at the Hannover Messe from April 4 to 8.

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Solar Power Systems Could Lighten the Load for British Soldiers

With the aim of being up to fifty per cent lighter than conventional chemical battery packs used by British infantry, the solar and thermoelectric-powered system could make an important contribution to future military operations.

The project is being developed by the University of Glasgow with Loughborough, Strathclyde, Leeds, Reading and Brunel Universities, with funding from the Engineering and Physical Sciences Research Council (EPSRC). It is also supported by the Defence Science and Technology Laboratory (Dstl).

The system's innovative combination of solar photovoltaic (PV) cells, thermoelectric devices and leading-edge energy storage technology will provide a reliable power supply round-the-clock, just like a normal battery pack. The team is also investigating ways of managing, storing and utilising heat produced by the system.

Because it is much lighter, the system will improve soldiers' mobility. Moreover, by eliminating the need to return to base regularly to recharge batteries, it will increase the potential range and duration of infantry operations. It will also absorb energy across the electromagnetic spectrum, making infantry less liable to detection by night vision equipment that uses infra-red technology, for instance.

Minister for Universities and Science David Willetts said:"The armed forces often need to carry around a huge amount of kit and the means to power it. It's great that specialists from a range of science disciplines are coming together to develop lighter, more reliable technology that will help to make life easier for them in the field."

Although substantial research into solar power for soldiers has already been conducted worldwide, this new UK project differs in its use of thermoelectric devices to complement solar cells, delivering genuine 24/7 power generation capability. The project team is also investigating how both types of device could actually be woven into soldiers' battle dress, which has never been done before.

During the day, the solar cells will produce electricity to power equipment. During the night, the thermoelectric devices will take over and perform the same function. The system will also incorporate advanced energy storage devices to ensure electricity is always available on a continuous basis.

"Infantry need electricity for weapons, radios, global positioning systems and many other vital pieces of equipment," says Professor Duncan Gregory of the University of Glasgow."Batteries can account for over ten per cent of the 45-70kg of equipment that infantry currently carry. By aiding efficiency and comfort, the new system could play a valuable role in ensuring the effectiveness of army operations."

PV cells, thermoelectric devices and advanced energy storage devices are already widely used in a range of applications. A key aim of the project team, however, is to produce robust, hard-wearing designs specifically for military use in tough, hostile conditions.

Because it will harness clean, free energy sources, the new power system will also offer significant environmental advantages compared with the conventional battery packs currently used by the British army.

To tackle the many challenges that the project presents, the team includes specialists from a wide range of disciplines including chemistry, materials science, process engineering, electrical engineering and design. Feedback from serving soldiers will also play a crucial role in optimising the power system for front-line use.

"We aim to produce a prototype system within two years," says Professor Gregory."We also anticipate that the technology that we develop could be adapted for other and very varied uses. One possibility is in niche space applications for powering satellites, another could be to provide means to transport medicines or supplies at cool temperatures in disaster areas or to supply fresh food in difficult economic or climatic conditions."

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New High-Performance Lithium-Ion Battery 'Top Candidate' for Electric Cars

A report on this innovation appears in ACS'Journal of the American Chemical Society.

Bruno Scrosati, Yang-Kook Sun, and colleagues point out that consumers have a great desire for electric vehicles, given the shortage and expense of petroleum. But a typical hybrid car can only go short distances on electricity alone, and they hold less charge in very hot or very cold temperatures. With the government push to have one million electric cars on U.S. roads by 2015, the pressure to solve these problems is high. To make electric vehicles a more realistic alternative to gas-powered automobiles, the researchers realized that an improved battery was needed.

The scientists developed a high-capacity, nanostructured, tin-carbon anode, or positive electrode, and a high-voltage, lithium-ion cathode, the negative electrode. When the two parts are put together, the result is a high-performance battery with a high energy density and rate capacity."On the basis of the performance demonstrated here, this battery is a top candidate for powering sustainable vehicles," the researchers say.

The authors acknowledge funding from WCU (World Class University) program through the Korea Science and Engineering Foundation.

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Toward Computers That Fit on a Pen Tip: New Technologies Usher in the Millimeter-Scale Computing Era

And a compact radio that needs no tuning to find the right frequency could be a key enabler to organizing millimeter-scale systems into wireless sensor networks. These networks could one day track pollution, monitor structural integrity, perform surveillance, or make virtually any object smart and trackable.

Both developments at the University of Michigan are significant milestones in the march toward millimeter-scale computing, believed to be the next electronics frontier.

Researchers are presenting papers on each at the International Solid-State Circuits Conference (ISSCC) in San Francisco. The work is being led by three faculty members in the U-M Department of Electrical Engineering and Computer Science: professors Dennis Sylvester and David Blaauw, and assistant professor David Wentzloff.

Bell's Law and the promise of pervasive computing

Nearly invisible millimeter-scale systems could enable ubiquitous computing, and the researchers say that's the future of the industry. They point to Bell's Law, a corollary to Moore's Law. (Moore's says that the number of transistors on an integrated circuit doubles every two years, roughly doubling processing power.)

Bell's Law says there's a new class of smaller, cheaper computers about every decade. With each new class, the volume shrinks by two orders of magnitude and the number of systems per person increases. The law has held from 1960s' mainframes through the '80s' personal computers, the '90s' notebooks and the new millennium's smart phones.

"When you get smaller than hand-held devices, you turn to these monitoring devices," Blaauw said."The next big challenge is to achieve millimeter-scale systems, which have a host of new applications for monitoring our bodies, our environment and our buildings. Because they're so small, you could manufacture hundreds of thousands on one wafer. There could be 10s to 100s of them per person and it's this per capita increase that fuels the semiconductor industry's growth."

The first complete millimeter-scale system

Blaauw and Sylvester's new system is targeted toward medical applications. The work they present at ISSCC focuses on a pressure monitor designed to be implanted in the eye to conveniently and continuously track the progress of glaucoma, a potentially blinding disease. (The device is expected to be commercially available several years from now.)

In a package that's just over 1 cubic millimeter, the system fits an ultra low-power microprocessor, a pressure sensor, memory, a thin-film battery, a solar cell and a wireless radio with an antenna that can transmit data to an external reader device that would be held near the eye.

"This is the first true millimeter-scale complete computing system," Sylvester said.

"Our work is unique in the sense that we're thinking about complete systems in which all the components are low-power and fit on the chip. We can collect data, store it and transmit it. The applications for systems of this size are endless."

The processor in the eye pressure monitor is the third generation of the researchers' Phoenix chip, which uses a unique power gating architecture and an extreme sleep mode to achieve ultra-low power consumption. The newest system wakes every 15 minutes to take measurements and consumes an average of 5.3 nanowatts. To keep the battery charged, it requires exposure to 10 hours of indoor light each day or 1.5 hours of sunlight. It can store up to a week's worth of information.

While this system is miniscule and complete, its radio doesn't equip it to talk to other devices like it. That's an important feature for any system targeted toward wireless sensor networks.

A unique compact radio to enable wireless sensor networks

Wentzloff and doctoral student Kuo-Ken Huang have taken a step toward enabling such node-to-node communication. They've developed a consolidated radio with an on-chip antenna that doesn't need the bulky external crystal that engineers rely on today when two isolated devices need to talk to each other. The crystal reference keeps time and selects a radio frequency band. Integrating the antenna and eliminating this crystal significantly shrinks the radio system. Wentzloff's is less than 1 cubic millimeter in size.

He and Huang's key innovation is to engineer the new antenna to keep time on its own and serve as its own reference. By integrating the antenna through an advanced CMOS process, they can precisely control its shape and size and therefore how it oscillates in response to electrical signals.

"Antennas have a natural resonant frequency for electrical signals that is defined by their geometry, much like a pure audio tone on a tuning fork," Wentzloff said."By designing a circuit to monitor the signal on the antenna and measure how close it is to the antenna's natural resonance, we can lock the transmitted signal to the antenna's resonant frequency."

"This is the first integrated antenna that also serves as its own reference. The radio on our chip doesn't need external tuning. Once you deploy a network of these, they'll automatically align at the same frequency."

The researchers are now working on lowering the radio's power consumption so that it's compatible with millimeter-scale batteries.

Greg Chen, a doctoral student in the Department of Electrical Engineering and Computer Science, presents"A Cubic-Millimeter Energy-Autonomous Wireless Intraocular Pressure Monitor." The researchers are collaborating with Ken Wise, the William Gould Dow Distinguished University Professor of Electrical Engineering and Computer Science on the packaging of the sensor, and with Paul Lichter, chair of the Department of Ophthalmology and Visual Sciences at the U-M Medical School, for the implantation studies. Huang presents"A 60GHz Antenna-Referenced Frequency-Locked Loop in 0.13μm CMOS for Wireless Sensor Networks." This research is funded by the National Science Foundation. The university is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

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'Nanoscoops' Could Spark New Generation of Electric Automobile Batteries

The new material, dubbed a"nanoscoop" because its shape resembles a cone with a scoop of ice cream on top, can withstand extremely high rates of charge and discharge that would cause conventional electrodes used in today's Li-ion batteries to rapidly deteriorate and fail. The nanoscoop's success lies in its unique material composition, structure, and size.

The Rensselaer research team, led by Professor Nikhil Koratkar, demonstrated how a nanoscoop electrode could be charged and discharged at a rate 40 to 60 times faster than conventional battery anodes, while maintaining a comparable energy density. This stellar performance, which was achieved over 100 continuous charge/discharge cycles, has the team confident that their new technology holds significant potential for the design and realization of high-power, high-capacity Li-ion rechargeable batteries.

"Charging my laptop or cell phone in a few minutes, rather than an hour, sounds pretty good to me," said Koratkar, a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer."By using our nanoscoops as the anode architecture for Li-ion rechargeable batteries, this is a very real prospect. Moreover, this technology could potentially be ramped up to suit the demanding needs of batteries for electric automobiles."

Batteries for all-electric vehicles must deliver high power densities in addition to high energy densities, Koatkar said. These vehicles today use supercapacitors to perform power-intensive functions, such as starting the vehicle and rapid acceleration, in conjunction with conventional batteries that deliver high energy density for normal cruise driving and other operations. Koratkar said the invention of nanoscoops may enable these two separate systems to be combined into a single, more efficient battery unit.

Results of the study were detailed in the paper"Functionally Strain-Graded Nanoscoops for High Power Li-Ion Battery Anodes," published Thursday by the journalNano Letters.

The anode structure of a Li-ion battery physically grows and shrinks as the battery charges or discharges. When charging, the addition of Li ions increases the volume of the anode, while discharging has the opposite effect. These volume changes result in a buildup of stress in the anode. Too great a stress that builds up too quickly, as in the case of a battery charging or discharging at high speeds, can cause the battery to fail prematurely. This is why most batteries in today's portable electronic devices like cell phones and laptops charge very slowly -- the slow charge rate is intentional and designed to protect the battery from stress-induced damage.

The Rensselaer team's nanoscoop, however, was engineered to withstand this buildup of stress. Made from a carbon (C) nanorod base topped with a thin layer of nanoscale aluminum (Al) and a"scoop" of nanoscale silicon (Si), the structures are flexible and able to quickly accept and discharge Li ions at extremely fast rates without sustaining significant damage. The segmented structure of the nanoscoop allows the strain to be gradually transferred from the C base to the Al layer, and finally to the Si scoop. This natural strain gradation provides for a less abrupt transition in stress across the material interfaces, leading to improved structural integrity of the electrode.

The nanoscale size of the scoop is also vital since nanostructures are less prone to cracking than bulk materials, according to Koratkar.

"Due to their nanoscale size, our nanoscoops can soak and release Li at high rates far more effectively than the macroscale anodes used in today's Li-ion batteries," he said."This means our nanoscoop may be the solution to a critical problem facing auto companies and other battery manufacturers -- how can you increase the power density of a battery while still keeping the energy density high?"

A limitation of the nanoscoop architecture is the relatively low total mass of the electrode, Koratkar said. To solve this, the team's next steps are to try growing longer scoops with greater mass, or develop a method for stacking layers of nanoscoops on top of each other. Another possibility the team is exploring includes growing the nanoscoops on large flexible substrates that can be rolled or shaped to fit along the contours or chassis of the automobile.

Along with Koratkar, authors on the paper are Toh-Ming Lu, the R.P. Baker Distinguished Professor of Physics and associate director of the Center for Integrated Electronics at Rensselaer; and Rahul Krishnan, a graduate student in the Department of Materials Science and Engineering at Rensselaer.

This study was supported by the National Science Foundation (NSF) and the New York State Energy Research and Development Authority (NYSERDA).

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