MIT's Nano Storage Could Replace Hybrid Batteries

mattnyc99 writes "Last week we discussed Popular Mechanics' reporting from MIT, but missed one of the coolest breakthrough of all, something scientists have been working on quietly as Detroit spends money elsewhere. The Lab for Electromagnetic and Electronic Systems has been doing some mega-efficient work with ultracapacitors, which store drastically less energy than a battery but have essentially none of the drawbacks — especially via carbon nanotube arrays. Automotive experts say the new research is enough to start replacing batteries in hybrid cars, and plug-in vehicles might not be far behind. From the scientist who thinks ultracapacitors are potential competitors for the pack in his Toyota Prius: 'I try to contain myself, because it hasn't been proven yet, but it could be a real paradigm change.'"

Capacitors have drawbacks too

[EmbeddedJanitor]

Even discounting the problems getting very high capacity with low ESR, capacitors still have a drawbacks. The charge is proportional to the voltage which means that the voltage keeps going up with more charge. On the discharge side it means that the voltage keeps reducing as you discharge the capacitor. Thus, the power supplies that are powered by capacitors need to work with a wider range of voltages. This tends to make them less efficient and more complex.

Re:less than batteries?

[BlueParrot]

The main issue with battery technology is not amount of charge held ( there are already electric cars that can get a similar range as petrol ones ), but the batteries that have a good enough performance are very expensive and wear out after a number of years. It also takes quite a while to recharge. If super capacitors can obtain a longer lifetime then the economics may look more attractive and they also have the advantage that the recharge time is more or less limited by the rate at which you can deliver energy, rather than the performance of the storage system.

Ka Booooooom!!!

[Powerbear]

"And by avoiding the chemical reaction that drives traditional batteries, there's no real danger of a capacitor suddenly overloading--or exploding like a laptop's lithium-ion battery pack."

They won't explode like a lithium-ion battery pack, it will be a 100X worse.

If anything pierces the dielectric, all the energy stored in the capacitor will discharge violently in milliseconds.

rtfa

[Scrameustache]

These hold less energy than batteries and yet they're going to be economically feasible? Can someone please explain to me how this is going to work, because it's not making sense to me right now.

there's no battery memory caused by partial discharging and no reduction in capacity with each recharge. "They never wear out, they have no electrolyte, they don't have any chemistry taking place in them," Schindall says. "It's just an electric field that stores the energy. So you can recharge a capacitor a gazillion times. It's very efficient--just the internal resistance of the wires." The ions cling electrostatically to materials in a capacitor, which also allows for much quicker charge times. And by avoiding the chemical reaction that drives traditional batteries, there's no real danger of a capacitor suddenly overloading--or exploding like a laptop's lithium-ion battery pack.

Re:Difference between battery and capacitor

[Scareduck]

A battery [wikipedia.org] stores energy in chemical form (sulfuric acid eventually reacts with lead, for instance), while a capacitor [wikipedia.org] uses physical effects, storing energy in an electrostatic field using an insulator between two conducting plates.

Re:less than batteries?

[Andy_R]

As far as I can see, they have 2 big plus points:

That they can be cycled as many times as you like without degrading, and they don't get damaged by being totally discharged. This opens up possibilities like contunially topping them back up with recovered braking energy, as well as getting rid of the buffer needed to prevent total discharge with conventional batteries.

Secondly, they are not volatile, so they could be built into a lot of places where you couldn't put a lead/acid battery - instead of your dashboard being .25in of plastic, it could easily be .24in of ultracapacitor with .01in of plastic coating. The same goes for every cosmetic part of the car that doesn't need to be transparent or comfy, as well as any structural members that the stuff turns out to have the right properties to replace. There's a hell of a lot of weight in a car that has the potential to be made out of ultracapacitor instead of whatever it's made of now.

Re:less than batteries?

[misleb]

These hold less energy than batteries and yet they're going to be economically feasible? Can someone please explain to me how this is going to work, because it's not making sense to me right now. It sounds like they'll either have to add so many capacitors that it becomes counter productive, or else they'll have a short range and useless for road trips. Either way it won't work.

Probably already addressed adequately by other responders, but I'll chime in.

At the moment, ultra-capacitors may be best suited for systems such as hybrids where you have a constant, low power source such as a small generator in a hybrid. The idea being that you could get good power/acceleration out of a capacitor when needed and the rest of the time is spent recharging from the motor. All without the disadvantages of batteries. Think of it as a sort of electrical flywheel.

-matthew

Re:Ka Booooooom!!!

[Powerbear]

Gas tanks don't explode. It takes 3 things to get something to burn. Oxygen, Heat, Fuel. To get something to explode, the fuel needs to be dispersed in the oxgen and there needs to be enough oxygen to support the explosion.

There is hardly any oxygen in a gas tank.

There's an episode of Mythbuster where they shoot tracer rounds (burning bullets) into a gas tank and can't get it to explode. Not enough oxygen, and the fuel isn't dispersed in the oxygen.

Batteries are OK in that the rate of discharge is limited by the chemistry involved. It's takes a while to fully dischage. The battery might get so hot that it melts everything around it, but it doesn't explosively dischage.

Capacitors on the other hand, have extremely high discharge rates and require no fuel, oxygen or heat to explode. Enough energy to power a vehicle for more than 100 miles would cause serious damage if the capacitor were to fail from an accident or manufacturing defect.

Everyone may think putting capacitors in a car is a good thing, but you're essentially mounting bombs in the car.

Re:less than batteries?

[Rei]

1) Li-ion batteries use no toxic components in manufacture, and while conventional li-ions have some chemicals that are poisonous in the end products, A) the latest generations of them designed for automotive use lose those (such as using nicer electrolytes and replacing the LiCoO2 cathode), and B) they break down harmlessly once disposed (no heavy metals or the like).

2) For a given amount of charge, an ultracapacitor is a lot *heavier* than a battery bank. They're lower energy density (assuming EEStor [wikipedia.org] doesn't pull off a miracle).

Re:Capacitors have drawbacks too

[EmbeddedJanitor]

Modern switchers do a pretty good job, but as with everything else there are compromises. As you tune for stability you tend to give away performance. Dealing with wider voltage ranges makes the whole trade-off even harder.

Re:Ka Booooooom!!!

[SEAL]

Gas tanks don't explode. It takes 3 things to get something to burn. Oxygen, Heat, Fuel. To get something to explode, the fuel needs to be dispersed in the oxgen and there needs to be enough oxygen to support the explosion.

Gas *vapor* is what's most dangerous. Dat to day you don't deal with that, except when you fill up or when your car has mechanical problems. But in a crash, if a gas tank were to leak, you suddenly have a high risk situation.

Also, boats -- particularly inboards, are more dangerous. Gas vapor is heavier than air so it tends to collect in the bilge area, whereas a car has open air beneath it. That's why you're supposed to run the blower for a bit before attempting to start a boat engine.

Capacitors on the other hand, have extremely high discharge rates and require no fuel, oxygen or heat to explode. Enough energy to power a vehicle for more than 100 miles would cause serious damage if the capacitor were to fail from an accident or manufacturing defect.

Everyone may think putting capacitors in a car is a good thing, but you're essentially mounting bombs in the car.

A properly designed ultracapacitor would ground out to the car's body in the event of a failure. It should be safer than gas simply because there is nothing that can be dispersed in an accident.

Re:rtfa

[Rei]

1) Li-ions have no memory effect.
2) Modern automotive li-ions are rated for a decade or two of service.
3) Modern automotive li-ions are non-explosive. Compare, for example, this A123 battery with a traditional li-ion [youtube.com].
4) Many modern automotive li-ions have very fast recharge times -- 5-15 minutes, depending on the type.

Don't get me wrong -- ultracapacitors are great. But until they can increase their energy density by an order of magnitude, they're only competing against the batteries in hybrids (and not plug-in hybrids, either).

Re:Electricity

[Rei]

Its easy to be an environmentalist, you don't have to think of the requirements to achieve whatever goals you might have. It just has to sound good.

And it's easy to insult environmentalists when you don't know what you're talking about. We already have tons of spare generating capacity for EVs and PHEVs -- everywhere except the pacific northwest. And even if we had to build more, as if electricity infrastructure was somehow more expensive to build and operate than oil infrastructure (it's far cheaper -- that's part of why a joule of electricity costs so much less than a joule of gasoline). [pnl.gov]

Why electric cars? Here's a primer [daughtersoftiresias.org].

Re:Sigh

[jhw539]

Providing electricity to parking areas in apartment buildings is not much more difficult or costly than providing lighting. In cold climates, parking slots with 120V plug ins are routinely provided for apartment dwellers to power block heaters (for example, check the specs on Minot University student housing apartments in North Dakota [minotstateu.edu]). Hell, I have heard that sometimes even movie theaters have them for public use in non-assigned parking spaces (any Alaska dwellers with first-person support?). The only reason that there is a 'last 10 feet' problem is that there is absolutely bone-zero real demand for a solution. The electrical infrastructure is really a non-issue, it's the rolling storage that's the hold-up.