Posted on 06/09/2006 4:19:52 PM PDT by listenhillary
Ever wish you could charge your cellphone or laptop in a few seconds rather than hours?
As this ScienCentral News video explains, researchers at the Massachusetts Institute of Technology are developing a battery that could do just that, and also might never need to be replaced.
The Past is Future
As our portable devices get more high-tech, the batteries that power them can seem to lag behind. But Joel Schindall and his team at M.I.T. plan to make long charge times and expensive replacements a thing of the past--by improving on technology from the past.
They turned to the capacitor, which was invented nearly 300 years ago. Schindall explains, "We made the connection that perhaps we could take an old product, a capacitor, and use a new technology, nanotechnology, to make that old product in a new way."
Rechargable and disposable batteries use a chemical reaction to produce energy. "That's an effective way to store a large amount of energy," he says, "but the problem is that after many charges and discharges ... the battery loses capacity to the point where the user has to discard it."
But capacitors contain energy as an electric field of charged particles created by two metal electrodes. Capacitors charge faster and last longer than normal batteries. The problem is that storage capacity is proportional to the surface area of the battery's electrodes, so even today's most powerful capacitors hold 25 times less energy than similarly sized standard chemical batteries.
The researchers solved this by covering the electrodes with millions of tiny filaments called nanotubes. Each nanotube is 30,000 times thinner than a human hair. Similar to how a thick, fuzzy bath towel soaks up more water than a thin, flat bed sheet, the nanotube filaments on increase the surface area of the electrodes and allow the capacitor to store more energy. Schindall says this combines the strength of today's batteries with the longevity and speed of capacitors.
"It could be recharged many, many times perhaps hundreds of thousands of times, and ... it could be recharged very quickly, just in a matter of seconds rather than a matter of hours," he says.
This technology has broad practical possibilities, affecting any device that requires a battery. Schindall says, "Small devices such as hearing aids that could be more quickly recharged where the batteries wouldn't wear out; up to larger devices such as automobiles where you could regeneratively re-use the energy of motion and therefore improve the energy efficiency and fuel economy."
Schindall thinks hybrid cars would be a particularly popular application for these batteries, especially because current hybrid batteries are expensive to replace.
Schindall also sees the ecological benefit to these reinvented capacitors. According to the Environmental Protection Agency, more than 3 billion industrial and household batteries were sold in the United States in 1998. When these batteries are disposed, toxic chemicals like cadmium can seep into the ground.
"It's better for the environment, because it allows the user to not worry about replacing his battery," he says. "It can be discharged and charged hundreds of thousands of times, essentially lasting longer than the life of the equipment with which it is associated."
Schindall and his team aren't the only ones looking back to capacitors as the future of batteries; a research group in England recently announced advances of their own. But Schindall's groups expects their prototype to be finished in the next few months, and they hope to see them on the market in less than five years.
Schindall's research was featured in the May 2006 edition of Discover Magazine and presented at the 15th International Seminar on Double Layer Capacitors and Hybrid Energy Storage Devices in Deerfield Beach, Florida on December 2005. His research is funded by the Ford-MIT Consortium
A house could be powered with these Leyden jars, and in case of UFO attack they could be discharged all at once in an intense beam that would vaporize the space aliens.
Electrode surface is one problem, dielectric and the self-discharge [leakage] is another. If one gets a compact capacitor with really high density energy storage, a serious leak could be catastrophic. Try to short-circuit a NiCad, and watch how hot it will become, and how rapidly.
Batteries = stored energy
Most weapons = stored energy
The capacity for independent power sources, even to power all our home needs - has been available for some time - but will it ever be possible to get it past the power-producing monoliths - unless the new guys on the block have deeps pockets to line the deeper pockets in DC
Gasoline or hydrogen == stored energy.
Get the right fuel air mixture above the fluid add spark, big boom. Hydrogen a bit harder to get the boom, even the old tech Hindenburg didn't explode, but parts did burn pretty quickly.
It'd be nice to see a hybrid AC/DC home. So many people use DC current in so many items it's horribly inefficient to transform so much of it in literally dozens of individual transformers.
The phobne company has almsot everything in their buildings wired for 48VDC which makes it extremely reliable during power outages and fluctuations.
Flux Capacitor? Back to the future?
Some applications size batteries and capacitors primarily for energy capacity, while others size them for power output. A battery or capacitor of a given size optimized for power output will hold less energy than one optimized for energy capacity. Capacitors generally hold a lot less energy, but can output a lot more power, than batteries of comparable size.
I would be surprised if the capacitor technology quickly overtakes the energy capacity of batteries that are optimized for that. For things like laptops where energy capacity is what matters, batteries will probably remain superior. On the other hand, in a hybrid car, the biggest benefit is obtained from having enough capacity to store the kinetic energy of travelling at highway speed; capacity beyond that is far less useful. Batteries with enough power to quickly get a vehicle up to highway speed will have a lot of capacity beyond that. But capacitors that can store the energy needed to reach highway speed might be smaller than such batteries. Even though their capacity would be much smaller, that wouldn't really matter.
A capacitor being a capacitor, if one storing this much power shorts out the result will be quite a devastating kablooie.
Current Lithium-ion batteries deliver 115 to 183 Wh/Kg
So, his ultracaps charge real fast, but only pack half to a third of the energy of a battery. Which in many applications is just fine. I would think that many people would prefer a laptop which could be fully recharged with just a few seconds at any handy outlet, even if you had to charge it 2 or 3 times as often
An issue of potential concern is that if an ultracap is damaged, it may be possible that it will liberate all its stored energy rather suddenly (as in "bang"). For comparison purposes, dynamite has an energy density of 4,300 KJ/kg versus about 200 KJ/kg for the ultracap, but you still would not to have that going off in your lap
I could see this being a big application. Most of the time, you are using the full power of your engine for only a few seconds at a time, namely when you are accelerating. Having an ultracap providing a power boost at such times would make a small-engined car seem to have much more "pep"
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"Could revolutionize our energy systems if it pans out."
Yeah, but in cases like this the "if" is the biggest part of the statement.
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