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Capacitors to Replace Batteries?
An anonymous reader writes "MIT's Joel Schindall plans to use old technology in a new way with nanotubes.
'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.'
Capacitors contain energy as an electric field of charged particles created by two metal electrodes, and capacitors charge faster and last longer than normal batteries, but the problem is that storage capacity is proportional to the surface area of the battery's electrodes.
MIT researchers solved this by covering the electrodes with millions of nanotubes.
'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.'"
I thought the charge was on the parts of the plates nearest each other, so the surface area would only be that of the ends of the nano-tubes. This would be smaller than if they had a flat plate!
Philip Jose Farmer predicted "batacitors" in his novels decades ago. Chalk annother one up for life imitating science fiction.
The fast charge has its obvious benefits, but I'm wondering about the durability of such nanotube filaments in the face of, say, the treatment your average laptop battery would have. Are these things resilient enough to be bashed around?
Are these capacitors only likely to be suitable for for small scale charges/discharges? Mobile phones? laptops? cars themselves?
More questions than insights, I'm afraid, but I find it fascinating
Thats just fantastic, sounds like the ideal replacment for batteries, and puts fuel cells out of business for small consumer products like laptops I'd have though, especially as they wouldn't cause any problems on planes.
hydrogen fuel cells would still be great for larger things like cars.
could these be produced in a way to fit in existing devices as soon as possible? I'f this really is safer for the environment, I'd love to see these asap, especially as most batteries are standard sizes already, even inside a laptop battery there are often (always?) muliple standard sized cells.
I hope they're easilly recyclable too, for when they do finally fail.
With its longer life and faster recharge time. I wonder if this could lead to an electric car that is good for the masses where they can cross country and take only 5 to 10 minutes to recharge. That is the primary reason why the Electric Car never made popularity it is because it is not convenient enough for normal people.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
My experience with capacitors is limited but I do know that they are extremely dangerous. I do distinctly remember having to discharge the capacitors in my arcade monitor in order to replace some circuitry. This involved a screwdriver with a grounded chain soldered onto it, some rudder gloves, and some flinching like a little school girl when you hear that loud pop from the discharge. I'm not entirely certain I'd want this sort of thing powering my laptops and cell phones.
The capacitance isn't just a function of raw surface area. If that were the case, you could double the capacitance just by roughing up the surface of the capacitor plates. The contribution of any spot on the surface depends on the area of that spot and the distance between it and another oppositely charged surface as well as the dielectric constant of the material between the plates. You can increase the surface area as much as you want but you still have to get the surfaces to line up with each other.
It is hard to exceed a certain energy storage on a capacitor. As you move the plates together, the capacitance goes up and you can store more charge per volt. The breakdown voltage goes down as you move the plates together. So you can store a small charge at a high voltage or you can store a large charge at a low voltage. For a capacitor of a given volume, you can store only so much energy depending on the breakdown voltage of the dielectric material.
I don't doubt that you can double or triple the energy storage of capacitors compared with current technology. On the other hand, I am very skeptical about the possibility of getting enough capacitance to store enough energy to be a general purpose battery replacement.
I leave it to you as an exercise to calculate the capacitance of a 2 volt capacitor necessary to store one amp hour. ie. something similar to an AA battery cell.
You have never created an internal short circuit on a conventional (rechargable) battery, did you? It is also able to deliver all the stored energy on an explosion that will take your hand away.
Now, batteries don't explode all the time, because they are well blinded. Capacitors are less dangerous (carry less energy), so they are not that well blinded, and explode often. There is nothing stopping the people from making blinded capacitos out of economics, and it could be even safer than battteries, because there is no ion trading going on.
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... And thus the comments about the mfg. process 'catching up'. I think we already don't use Li-Ion AA's and AAA's because they're cost-prohibitive, and the packaging is wasteful of space. I already wince at paying about US$2.50 per individual AAA for NiMH. But this technology promises features I think are worth paying for, just like having Li-Ion and Li-Polymer batteries in your cellphone, mp3 player, and PDA right now. Imagine when the battery for your cellphone or iPod is long-lived enough to be printed onto the circuit board and never replaced, and it can receive a charge in only a few seconds. If this is done properly, it'll eventually be the end of removable cells altogether.
This even opens up a lot of integration possibilities that just weren't there before, like peripherals that bring their own capacitor bank in to boost the system's capacity. Everything with a PCB can now cache its power, without all the bulk of a traditional battery. Imagine expansion cards that can carry the power needed for I/O (Wireless, Flash Memory, whatever) and charge with the system. You could even use the memory expansion slot as an auxiliary battery, like on some laptops how the optical drive can be replaced with another battery.
Take this with System-On-Package designs like were just recently discussed here, and we may get some really small electronics in our lifetime. You could even reduce capacity to save space -- I wouldn't mind charging my cellphone almost every night if it only took a few seconds.
True science means that when you re-evaluate the evidence, you re-evaluate your faith.
I used a 1989 vintage computerized stage lighting control console used a big capacitor soldered to the back of the PCB to hold the settings in RAM while the unit was switched off. Typically, the capacitor could hold a show for about three to four weeks and every time it was switched on, the capcitor would recharge. It still had a "modern" 720k floppy disk just in case.
This is a boring sig
Imagine refulling your car by simply stopping at the traffic lights. A swipe system like the toll roads handles payment, and your off again. It would not be hard to have a recharge every 50 - 100km on the highway if they aren't manned. Just a drive though pitstop - and your back on your way.
Who cares if electric cars don't have huge range if recharge stations are everywhere. And if your a "but I like to spend 4 days driving in the wilderness", then you take extra storage... just like you do with petrol.
Oh,... and it would not be hard to fix the complaint about exploding capacitors... Seal them in plastic so there water tight. Only two wires in/out... A very small amount of circuitry would allow high current in for recharging, and have a current limiter on the way out. Not crush proof, but certainly water/short circuit/toddler proof.