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Structural supercapacitors could make batteries and power cords obsolete

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May 26, 2014

Structural supercapacitors could allow energy to be stored directly in structural material...

Structural supercapacitors could allow energy to be stored directly in structural materials, such as a phone's casing (Photo: Joe Howell / Vanderbilt)

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Imagine using a mobile phone powered entirely by its casing, or an electric car that runs off power stored in its chassis. Researchers at Vanderbilt University have created a structural supercapacitor that could, they believe, bring this closer to reality, making batteries and power cords obsolete. The structural supercapacitor could make it possible to store energy directly in structural materials, allowing them to deliver power long-term while surviving the real-life mechanical stresses they're bound to experience.

The team's new supercapacitor looks like a thin grey wafer, and is made of silicon electrodes that have been chemically treated to have inner surfaces containing nanoscale pores. Instead of storing energy in chemical reactions, like batteries, the supercapictor stores power by assembling electrically-charged ions on the surface of the porous material. In a recent test, the supercapacitor was able to store and release power without a hitch, the team reported, even when it was subjected to vibrational accelerations exceeding 80 g and stresses of up to 44 psi.

“These devices demonstrate – for the first time as far as we can tell – that it is possible to create materials that can store and discharge significant amounts of electricity while they are subject to realistic static loads and dynamic forces, such as vibrations or impacts,” said Cary Pint, Assistant Professor of Mechanical Engineering at Vanderbilt University.

Being able to create hardy structural materials that can efficiently store and deliver energy opens up many exciting possibilities. For instance, instead of being inert, the walls of a home or a building could store and deliver power to all the home's lights and appliances.

"The majority of building materials that we use in these systems have absolutely no function than to just maintain mechanical integrity," Pint tells Gizmag. "What if we could take the tons of materials used in homes and convert them to energy storage systems that were not more expensive, could perform the same mechanical function as building materials, but could have decades worth of energy storage capability built in?".

"For a home or stationary powered system, this technology is the seed to putting solar panels on the roof and enabling power delivery around the clock without the need for a grid, even when the sun isn't shining," he adds.

The engineers suspended a heavy laptop from the supercapacitor to demonstrate its strength...
The engineers suspended a heavy laptop from the supercapacitor to demonstrate its strength (Photo: Vanderbilt Nanomaterials and Energy Devices Laboratory)

While we've seen a lot of high-energy storage and powerful supercapacitors before, including a silicon supercapacitor from Pint's lab, the present research is reportedly the first to test how structural supercapacitors function under realistic mechanical loads. Making the device more mechanically robust to withstand stresses, Pint says, didn't compromise its energy storing capabilities.

"In an unpackaged, structurally integrated state, our supercapacitor can store more energy and operate at higher voltages than a packaged, off-the-shelf commercial supercapacitor, even under intense dynamic and static forces,” says Pint.

Compared to batteries that charge for hours and operate for thousands of cycles, the way the structural supercapictor stores energy, the researchers say, will allow it to charge and discharge in minutes and operate for millions of cycles. That's a clear advantage, especially when you consider how supercapacitors typically lag behind batteries when it comes to energy storage.

“Battery performance metrics change when you’re putting energy storage into heavy materials that are already needed for structural integrity,” says Pint. “Supercapacitors store ten times less energy than current lithium-ion batteries, but they can last a thousand times longer. That means they are better suited for structural applications. It doesn’t make sense to develop materials to build a home, car chassis, or aerospace vehicle if you have to replace them every few years because they go dead.”

A mobile phone powered by supercapacitors and charged wirelessly would only need upgrades to its processor or other components over time. While the researchers' current silicon-based structural supercapacitors are more suited for solar cells and consumer electronics, they're confident that they'll be able to carry over the core technology into other materials like aluminum and carbon nanotubes. It may even be possible, they say, to eventually incorporate integrated energy storage into airborne systems.

"I feel that the bridge to a world where flying robots deliver our mail, or police our streets – something that may seem like science fiction now, but the technology has already been developed for – is to develop ways to efficiently power these systems," Pint tells us. "What makes me most excited about load-bearing energy storage is not necessarily the advances that we can achieve to the technology that is 'known,' but rather the advances that will come in technology when we start to put some imagination to what these materials can do."

A paper describing the research recently appeared in the journal Nano Letters.

Source: Vanderbilt University

About the Author
Lakshmi Sandhana When Lakshmi first encountered pig's wings in a petri dish, she realized that writing about scientists and imagineers was the perfect way to live in an expanding mind bubble. Articles for Wired, BBC Online, New Scientist, The Economist and Fast Company soon followed. She's currently pursuing her dream of traveling from country to country to not only ferret out cool stories but also indulge outrageously in local street foods. When not working, you'll find her either buried nose deep in a fantasy novel or trying her hand at improvisational comedy.   All articles by Lakshmi Sandhana
17 Comments

Seems to make sense. As long as it doesn't short out and explode if it gets perforated, perhaps by a nail. Imagine you replace all your wallboard in the house with supercapacitor board, but one day you forget and go to nail up a picture, and your house burns down! Boy that would be embarrassing, eh?

Grunchy
26th May, 2014 @ 10:07 pm PDT

Capacitors were already used in the two Voyager Spacecraft.

I worked with (high voltage) capacitors myself, and when all the power is released at once, the spark is enormous. I even managed to weld a piece of copper on a piece of iron.

So, I figure, if such a capacitor is punched or whatever, it can cause an explosion, destroying the telephone or electric car.

Hans Walrecht
27th May, 2014 @ 01:42 am PDT

While all the potential applications mentioned in the article are clearly going to be transformative, for me there is one application that stands head and shoulders above the rest: Having no battery in the way, 'phone manufacturers will be able to put the camera lens in the centre of their device. Who knows, I might even be able to take a photo without including a finger or two in it.

Mel Tisdale
27th May, 2014 @ 02:43 am PDT

That stuff will make great shell filler, inert till charged then detonate like TNT on impact.

Slowburn
27th May, 2014 @ 04:10 am PDT

I guess the next stage would be making the exterior of the case/ battery/ capacitor also photo-voltaic, recharging itself in daylight or at the very least somewhat extending the operating cycle.

Martin-tu
27th May, 2014 @ 05:09 am PDT

yes, there are lots of possibilities, pro & con. i can see there would have to be protections built in such as Tesla has in it's batteries to keep one cell from destroying all.

i wonder about airplane parts? small motors? electric power poles? roads? Imagine a road that powers cars with solar energy stored in a super capacitor!

No testing done yet on how long the capacitors last?

notarichman
27th May, 2014 @ 06:42 am PDT

All very interesting...

Instead of simply 'withstanding' the stresses and strains the structure undergoes, why not USE them to produce energy (and/or make some photovoltaic, as @Martin-tu suggests, above)?

There have been reports on Gizmag of both flexible batteries AND, I think, charging systems. Every structure flexes somewhat in every kind of weather - think of the amount of energy available, even at initially-low efficiencies!

leafygreen
27th May, 2014 @ 08:33 am PDT

Tesla batteries are of this ilk.

In my day, automobile ignition systems used a capacitor to avoid excessive arcing & burning of the ignition points . We called them condensors

Len Simpson
27th May, 2014 @ 08:47 am PDT

LS - your comment has its points.

Bruce 'bd' Howard
27th May, 2014 @ 11:31 am PDT

There is a couple youtube videos showing how just a few small capacitors are sufficient to start a car. The issue is of course they do not store large amounts of energy and tend to discharge slowly while not in use. One fix was to use a small 12v battery to keep charge up.

with this you could have the capacitors as part of the casing containing some lithium batteries.

Why bother you ask, why not just use the batteries?

One, capacitors give high power to starter and recharge very fast. So better for starter if there are multiple starts. Even connected devices benefit from this as you get a steady power supply.

Two, the combination of the 2 will allow for much smaller battery and save a lot of weight compared to lead acid, good for motorcycles and scooters.

Three, capacitors act as a buffer for the battery, protecting it from sudden discharge and surges.

So even if the battery cost more, it will work better for the system, last 10x as long and weight far less and take far less space.

telocity
27th May, 2014 @ 11:35 am PDT

Ummm. Speaking NOT from my extensive knowledge of the new technology -- but speaking from a forty-year career in electrical engineering and a knowledge of the principles involved...

A capacitor is, broadly, an energy storage device. Two conductors separated by an insulator -- a voltage applied to one conductive (plate) attracts and stores electrons on the other plate. So far, so good? OK. There are interactive criteria between the amount of charge, the magnitude of the voltage, and the SPEED at which the electronic charge can be stored and/or used.

Supercapacitors are traditionally very high-capacity devices of quite-low voltage, with very high storage rates and relatively low rates of charge/discharge. I assume that the technologists involved here are working on those problems. There is NO problem with, e.g., using the technology in the casing of a cell phone or laptop. But it's a big jump to lighting your house...

Which brings us to the next problem. Capacitors store DC electricity. To run present appliances requires AC, at significant quantities of power. A 1/2-hp motor such as you might find in your dishwasher or clothes washer uses 373 watts if operating at 100% efficiency (which it doesn't). Or, like, four 100-watt bulbs. At 110V. So you either need a very large inverter (converts DC to AC) or new appliances that run on DC. And that's fairly high-voltage DC, or you'll need really FAT wire to avoid losing major power (all heat) in the wiring -- which is also a fire hazard.

Don't get me wrong. I'm not pooh-poohing the technology. Remember that when I was a kid 60 years ago, Dick Tracy wore a two-way wrist radio. But I'm pointing out that it's a VERY big jump from this technology to the concept of the walls of a house storing sufficient energy to run appliances (heat-output devices such as toasters, coffeepots, and ovens are fine, as are lighting). Meaning washers, dryers, refrigeration, and the like. Don't expect it to occur within the next few decades.

Of course, once all the technological hurdles have been overcome and it DOES become reality, one still has to deal with the guy who decides to nail a picture to the wall...

Bob Dvorak
27th May, 2014 @ 11:57 am PDT

I noticed that the article does not mention energy densities. In order to fully make obsolete the battery in an electric vehicle, one has to be able to store enough energy to run the car for a reasonable number of miles.

sk8dad
27th May, 2014 @ 12:52 pm PDT

Points out to Bob that if DC-AC power inversion is the limiting factor, then solar cells wouldn't work either. Solar energy is DC power, and DC-AC inverters these days are quite efficient (well above 90%). Not sure how this would limit DC local stoarge.

Time to make nails out of ceramics, instead of metals...

MEguy
27th May, 2014 @ 01:12 pm PDT

Mass produce, awesome, & apply to EVs & auto batteries./

Stephen N Russell
27th May, 2014 @ 02:39 pm PDT

@MEguy

Your contention is quite correct but you are forgetting one major factor. Size. How many panels connected in series will boost the DC output to a level which will charge a storage battery which can then be efficiently inverted to usable AC voltage with enough current capacity?

Another thing one has to keep in mind is the fact about how the inductors and capacitors behave. Capacitors have practically zero source impedance meaning they can supply infinite amount of current if shorted till their total charge is neutralised. Their discharge rate is solely dependent on load impedance. Not something you want around the house !

pmshah
27th May, 2014 @ 08:35 pm PDT

I've seen a lot of different high capacity storage devices in the past. Fuzzy capacitors and so on, but have seen no real life use of such things. Just figured out if we had researched these years ago or maybe not have let the greed of oil drive us, we wouldn't have a lot of the problems we have today! Stop letting things you invent come to naught. It's just sad.

Troy Callahan
28th May, 2014 @ 06:50 am PDT

A few years ago we gathered in Detroit to discuss battery and storage technologies. A123 Systems was the hot topic but the question was raised: what next? After a short while someone asked whether the stressed members of a car's frame (or unibody) could be made to produce a charge in order to compliment regenerative braking, electricity producing shock absorbers and so on. An energy storage consultant (who had worked with government and private industry) said that several universities were already working on it. This must be one of the results.

The forces acting on moving cars, for example, are relatively constant and sometimes reasonably extreme. Think of a wheel mounted camera like those used on any car enthusiast television program - its almost never stationary despite the best efforts of our road builders. Once you get off road the twisting and turning are even more intense. Once these scientists start tuning these material for each application, its going to be a game changer.

Mirmillion
28th May, 2014 @ 06:56 am PDT
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