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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