Nanopore power: Arrays of capacitors built inside nanopores are shown here in a scanning electron micrograph image overlaid with an illustration that shows their design. The pores are etched into an aluminum substrate (dark yellow). The capacitors form two thin layers of metal (blue) separated by a layer of insulating material (light yellow).
A. James Clark School of Engineering, University of Maryland
Nanopore arrays combine high power and storage capacity.
The ultimate electronic energy-storage device would store plenty of energy but also charge up rapidly and provide powerful bursts when needed. Sadly, today's devices can only do one or the other: capacitors provide high power, while batteries offer high storage.
Now researchers at the University of Maryland have developed a kind of capacitor that brings these qualities together. The research is in its early stages, and the device will have to be scaled up to be practical, but initial results show that it can store 100 times more energy than previous devices of its kind. Ultimately, such devices could store surges of energy from renewable sources, like wind, and feed that energy to the electrical grid when needed. They could also power electric cars that recharge in the amount of time that it takes to fill a gas tank, instead of the six to eight hours that it takes them to recharge today.
There are many different kinds of batteries and capacitors, but in general, batteries can store large amounts of energy yet tend to charge up slowly and wear out quickly. Capacitors, meanwhile, have longer lifetimes and can rapidly discharge, but they store far less total energy. Electrochemists and engineers have been working to solve this energy-storage problem by boosting batteries' power and increasing capacitors' storage capacity.
Sang Bok Lee, a chemistry professor, and Gary Rubloff, a professor of engineering and director of the Maryland NanoCenter, created nanostructured arrays of electrostatic capacitors. Electrostatic capacitors are the simplest kind of electronic-energy-storage device, says Rubloff. They store electrical charge on the surface of two metal electrodes separated by an insulating material; their storage capacity is directly proportional to the surface area of these sandwich-like electrodes. The Maryland researchers boosted the storage capacity of their capacitors by using nanofabrication to increase their total surface area. Their electrodes work in the same way as ones found in conventional capacitors, but instead of being flat, they are tubular and tucked deep inside nanopores.
The fabrication process begins with a glass plate coated with aluminum. Pores are etched into the plate by treating it with acid and applying a voltage. It's possible to make very regular arrays of tiny but deep pores, each as small as 50 nanometers in diameter and up to 30 micrometers deep, by carefully controlling the reaction conditions. The process is similar to one used to make memory chips. "Next you deposit a very thin layer of metal, then a thin layer of insulator, then another thin layer of metal into these pores," says Rubloff. These three layers act as the nanocapacitors' electrodes and insulating layer. A layer of aluminum sits on top of the device and serves as one electrical contact; the other contact is made with an underlying aluminum layer.
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Guest (advancednano)
Difficult to compare farads and cm. There are other systems with 60 microfarads per cm or more. And there are 1000 meters^2/gram.
So 250 times area is what area per gram ?
100 times more energy of conventional capacitor. What is conventional capacitor ? The best commercial one currently capacitor ? 30 W-h/kg ? The rumored eestor 400 W-h/kg ? An average commercial capacitor 6 W-h/kg or less ?
So is 3000-W-h/kg the potential if they can scale?
Re: What's the breakdown voltage?
durs, You hit the first key question right on the button. As of course Q=CV, the voltage limitation inhibits the goal of charge (density) as I understand it. Then of course increasing the dielectric thickness decreases C so, there is a sweet spot somewhere when considering these relationships. Being retired and having worked with ceramic capacitors for many years I can only extrapolate on some other factors having never worked on the nanoscale.
Insulation resistance, dielectric absorption, dissipation factor and dielectric constant with it's relation to temperature range come to mind. As the dielectric material is not identified there are more opportunities and bumps in the road to come. It appears the work being done is sort of a "single layer" capacitor made as an accordian type structure. Unfortunately if this is the case, any one flaw will breakdown the whole structure. Then with a number of units connected together they would have to be in parallel as total C is additive. Once again if one goes bad they all go out of service. Reliability is a must. Hopefully I have been accurate. Let's hope progress can proceed quickly to get away from Carbon.
The technology of high energy storage that can burst energy in or out already exists....flywheel energy storage with P/E Ratios near 100. Flywheels last nearly 20 years and are not effected by temperatures or weather, they can be submerged in water and require almost no maintenance....mass production would bring the costs down lower than lead-acid batteries but unfortunately in today's business society we have buffoons with MBA's making the decisions....
I love the idea of flywheel storage. It is fairly advanced technology.
Any reason why this has not inspired interest from the train industry? They have started putting batteries in their locomotives....
Or any interest from the Navy? They are looking for a way to power their ships and electromagnetic cannons at the same time...
On an interesting side note, the new electromagnetic catapults use three generators that they spin up to 6000 thousand RPM. As one fires off the catapult, the one that fired before it is getting back up to proper RPM. So it can fire again.
They are storing energy in rotation. Very large, slow moving (compared to Flywheel storage) energy storage.
Any thing that caries its energy needs to consider specific energy (megajoules/kilogram)
a quick check at http://en.wikipedia.org/wiki/Energy_density indicates flywheel specific energy ranges .36 to .5 . At the same time lithium thionyl chloride battery is about 2.5
Batteries ability to store more power per kilogram makes it a better choice for locomotives, Flywheel angular momentum and corresponding Gyroscopic effect require complicated design challenges on naval ships
the idea of "swappable batteries" for the electric cars will become soon COMPLETELY UNNECESSARY since the new, 100+ times faster to recharge/discharge, Li-Ion batteries and the, 100+ times electric charge, supercapacitors (to be available soon) may solve ALL the existing problems to build and sell electric cars!!!
Imagine if government had set up policies that coerced us to build a battery swap infrastructure, and then advances like this obsoleted it in a few short years. All those resources would have been poorly applied.
This is so cool !
We have been working on electrochemical coatings of this sort at our lab in Milan.
First the alumina on the substrate is precisely patterned using lithography and then etching is performed using chemicals. Then the substrate with etched alumina is electrochemically coated with Copper or Nickle in a suitable bath.
This high density of charge storage opens up enormous applications for this technology...
This could turn out to be the Perfect marriage of the Capacitors and Batteries.
all this stuff is great in terms of new tech for truly enabling a viable generation of electric vehicles, etc but when the grid system that feeds such vehicles electricity is so inefficient and produces so much C02 whats the point? until the system changes we're better of with efficient combustion engines!
Here's the point.
Electrical power generation is far more efficient than internal combustion automotive engines. Losses in engery conversion in electic cars are low. Energy can be recovered from braking in electic cars. The overall result is a substantial reduction in fuel requirements.
The electrical grid can be fed by sources that do not produce CO2 such as nuclear, solar and wind.
Even if power to get from point a to point b using grid energy produces the same CO2 as ICE do today using gasoline and diesel, advances in solar, wind and other energy sources will supplement the our energy usage and offset CO2 in the future as newer technology is implemented
What really matter most is the cost to get from a to b. Since energy storage is a major factor, advances in storage capacity are exciting. Even more so if they mean a lower cost per unit of storage.
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seamountie
19 Comments
Nanocapacitors
The other problem with capacitors is their ability to hold a charge is relatively short term - compared to batteries. Does this technique improve the "shelf life" of the charge?
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Katherine Bourzac
27 Comments
Re: Nanocapacitors
Hi seamountie
Yes, compared with other nanostructured capacitors, the shelf life of charge is 40 times longer. I don't have a number for how this compares with batteries or commercial capacitors. My sources told me that this was not really the big news with this story since, as Joel Schindall from MIT said, "Storing charge longer is nice, but not too important for most applications (months instead of weeks, in practical terms)."
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