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.'"

Comments

Re:Riverworld anyone?

[Whiney Mac Fanboy]

Philip Jose Farmer predicted "batacitors" in his novels decades ago. Chalk annother one up for life imitating science fiction.

Well - its a bit of a no-brainer to any EE kind of guy. No wasteful energy conversion process, etc etc.

Everyone's been waiting for the materials technology to catch up to the rather obvious idea that's all :-)

Re:A good electric Car.

[pz]

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.

Unlikely at best. The problem is that the rate of energy transfer for chemical storage (that is, fuels, like gasoline) is really, really high. While you could in principle build a station which could recharge your batteries in the same amount of time it takes to gas up your car, it wouldn't be something you'd want to be near.

Why?

When you put gasoline in your car, you are moving power at a rate of about 5 MW. That's the entire output of a small power plant. Liquid fuels, gasoline in particular, are a very dense way to store and transport energy. Electrical wires aren't very good for that in comparison, even with superconductive cables. Think of it this way, even if we could transfer energy from a station to your car with 99.9% efficiency (which is well and far beyond anything we can do in the forseable future), that's 500 W of power that needs to be dissipated at the conversion site between the station and your car. That's going to be too hot to hold like a fueling nozzle for gasoline cars. If we use 48V to move 5MW (48V is gaining traction as a new standard for power transfer), that's 100,000 A of current. Even if we use an insane voltage level like 5 kV, prone to arcing and causing nasty things like fires and death, that's still 1,000 A of current. Not small. If this power is transferred by direct contact, you get immediate electromigration at the contacts, arcing problems when starting and stopping the current (ever wonder why power transmission towers are so tall?). If it's transferred by induction, then the EM fields will be enough to cause cancer (ok, I don't know that one for sure, but it's going to be as if 1000 microwave ovens are all operating right there at your car, something I don't want to be near).

Building an electrical system that can move megawatts of power is not something that will ever happen on the consumer level.

What about improving the efficiency of cars? We can make cars at best an order of magnitude more energy efficient. That isn't going to solve the problems alone.

Now, if, instead of recharging, you swap out batteries (that is, move mass that carries energy instead of moving energy aone), things get far more attractive. Except that people are currently a little leary of exchanging parts of their cars (can you imagine swapping tires every time you went to a filling station?). But that would allow a quick recharging.

The only solution that really makes sense for refueling by recharging is to do it while the vehicle is sitting idle when there is more time available, rather than being driven when there isn't. If you allow 20 hours for a recharge instead of 5 minutes, the power transfer rate drops to 20 kW which isn't so bad. Add in an order of magnitude higher efficiency vehicles and perhaps live with shorter distances between recharges, and you get down to the kilowatt range which is entirely doable (1.5kW can be supplied from a single, standard US household outlet).