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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.
actually, I suppose it could well be more environmentally friendly to just use these, if they can provide power on par with, or greater than fuel cells for size/weight. There wouldn't be any emissions with a capacitor? and weather you use fuel cells or these, there are power requirments to charge them/produce the hydrogen for their respective systems..
This is a really good plan in theory and on "cost is no object" plans it's a great idea BUT theres no real way this can replace batteries because your cost per unit is going to be much higher than standard batteries already are. No one is going to pay $20 for a pack of AAAs that you can get for $4 and just have to replace in six months.
Some time ago a 10 uF capacitor in a PSU exploded close to my face while servicing a PC. Luckily the PSU box was pretty well robust, and I had no injuries at all, but I'll remember for ever the loud BANG that followed (with a lot of smoke). I wonder if the same could happen by misfortune with one of these devices. AFAIK cellphone batteries seldom explode, so I am not so sure if capacitors would be a safer alternative.
The problem with capacitors is energy density. They can charge and discharge quickly, but the amount of energy per unit volume or per unit weight is usually not very good, even compared to batteries.
New supercapacitors (existing term, really) will improve the energy per weight or energy per volume, but they may cost more (energy per dollar).
If this is cheap and hig density, it could be a great step forward.
PS, check out the powerlabs guys. They do lots of dangerous stuff with bit caps
http://www.powerlabs.org/railgun.htm
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
When I was in the Army, they taught us to use those 9V batteries with a fistful of fine steel wool to make fire.
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Have you ever play with those insane charger that charges an AA NiMH battery in 15 minutes?
There is a fan cooling the batteries while charging. Even then they comes out too hot to hold.
Assuming the one of the mill NiMH AA cell at 2AHr. That's it can store 2A of current for 1 hours.
Charging currents (assuming 100% efficiency) for 15 minutes is on the order of 8A. In reality more likely 10A.
Now if you were to increase the charging rate by another factor of a 100 downs to 10 seconds,
what kind of current are you applying to the capacitor and what type of serious heat is going to be
generated by the internal resistance?
To charge it in 10 seconds requires 720A of current (assuming again 100% efficiency).
That's a few times the cranking current in a car battery on the order of 100A or higher.
Remember that Power = I * I * R, even with 1/100 ohms internal resistance,
that's 518 Watts (or more) of heat loss for that 10 sec.
Good news is that a cup of water can easily absorb that amount of heat.
What type of crazy jumper cables you need to jump start this beast in 10 sec?
You need to have 2 AWG0000 wire for each terminal (each rated for 380A) for that.
The 0000 copper wire itself is 0.46" diameter.
Sorry guys, water cooled charger and 0.64" dia jumper cables for charging an AA cell
just is not practical. Someone is lying.
People are already paying that much for rechargeable set-ups. I use it for my Digital camera and my wireless video game controller. Theyre great, when they go dead i just stick em in the charger for an hour then Im back off to save the universe.
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.
...less [time] if you use a dedicated high-current circuit...
There's no reason why the charger/base station unit couldn't load up an internal capacitor over a longer period of time and then rapidly dump that energy into a portable device in a few seconds. That give you the rapid recharge times without using a clothes-dryer style power plug or browning out your lights whenever you recharged your cellphone (or, worse yet, laptop).
I think the biggest obstacle to rapid charging will be the physical connectors: nobody wants a 3x8 cm charging connector on an iPod or Razor! (But a few of minutes charge time instead of a few seconds is no big deal: you plug in your cellphone, brush your teeth, and by the time your're done it's fully charged and ready to go).
Caps charge fast, but they can also discharge fast.
Batteries have an inherent resistance that stops them discharging all at once. Without a resistor in the circuit, caps can discharge fast enough to be a hazard.
Depending on your application, this can be a good or bad thing. I haven't heard of any pocket flash cameras shorting out and hurting someone (unless modified it to be a "ghetto taser"), but larger devices like laptops could be another matter.
The guy has a poster discussing uses such as electric car batteries, so I would say no. One part that bugged me in the "poster" is the energy density. A value of 60Wh/kg (is this gravimetric charge density?) is less than lead-acid. The power density is a whole lot higher at 100kW/kg, would someone care to explain the difference between the two?
The recharge time problem was solved with safe, high voltage recharging technology which has since been withdrawn from the market. You could get an 80% charge in five minutes, which would then take you 100 miles (real miles - unlike gas burners, EVs don't burn fuel at stop lights) making range comparable to 1960s compact cars. You will be sued if you try to deploy the technology today; and GM (the patent owners) have been forcing California businesses to rip their installations out.
Every EV1 ever built was immediately snapped up and thousands of people were left waiting in line when GM successfully subverted the will of the people of California and killed the vehicle. They only built 800, despite their promises, and they have spent more $$ on preventing EV production and distribution than they ever spent building them (most of their development costs were defrayed by Clinton & Gore's EV subsidies).
Who Killed the Eletric Car(Warning: hideous flash and cookie onslaught)
Hmp. Years ago an MIT outfit also created eInk, and look how quickly that's hitting the market. MIT became an IP factory some years ago, and that's affected how they release tech, tho I couldn't tell you how, other than it seems slower.
The thing to avoid like the end of the world is selling the patents to Exxon-Mobile, as was the patents to the nickel-metal hydride battery tech. Exxon-Mobile is not, er, the very best steward of technologies that could supplant the internal combustion engine. This tech sounds like the promised land for electric cars. We've the motors, the controllers, the charging tech. We just need power storage, and it's TKO for the IC engine. Electric cars have more torque, if they don't have to worry about ekeing out range because of the battery limitations. They cost much less per mile to use. And you can convert your own car for less than ten thousand dollars. Tech's there. And fewer moving parts, no oil pan, no radiators, no coolant, no catalytic converters, no muffler, no fuel filters to clog; ah paradise. Just electricity and a motor and a road. Damned things will last twenty years or more. Which might explain why car manufacturers don't like EC's.
Hurry, MIT! We're in a spot here. Oil, wars, price gouging, pollution. We need EC's, and it looks like you'll be sitting on the capacitor tech we need. Just, give it away, save the world?