MIT: Move Over Batteries, Here Come the Nanotube-Enhanced Capacitors
by Michael Graham Richard, Gatineau, Canada on 03. 5.08
MIT, light of my life, fire of my brains. My sin, my soul. Em-eye-tee: the tip of the tongue taking a trip of three steps down the palate to tap, at three, on the teeth. Em. Eye. Tee. Or so might russian writer Vladimir Nabokov say if he had as much interest in electric cars as we do. Why? The Lab for Electromagnetic and Electronic Systems (LEES) at the Massachusetts Institute of Technology (MIT) is getting close to a big breakthrough in capacitor technology.
Currently, ultracapacitors can only hold a small fraction of the electrical charge that batteries can hold (about 5%), but they do have many very important advantages over their chemical cousins, such as no battery memory caused by partial discharging, no reduction in capacity with each charge (they last almost forever), and much faster charge-discharge times. If only we could improve their capacity... Well, we're getting there. Read on!
The way to increase ultracapacitor capacity is to increase surface area inside of them.
By replacing the porous activated carbon used in ultracapacitors with tightly bunched nanotubes, Schindall believed that the ion-collecting surface area could be increased by as much as five. Since current ultracapacitors can store around 5 percent of the energy in an equivalent-size battery, the addition of nanowires could bring this up to 25 percent. “And you can also operate [the ultracapacitor] at a higher voltage with the nanotubes, and that’s about another factor of two in energy,” he says. “We are hopeful—we haven’t proven it—that we can get up somewhere between 25 and 50 percent of a battery’s energy. At that point, it becomes a compelling device for many applications.”
This would completely change the game, because batteries in hybrids and electric vehicles are never fully discharged to prolong their life. In fact, there's only about 15% that is used, so an ultracapacitor with 25-50% of battery capacity but no restrictions on full discharge could actually provide more power and a longer range!
They're not quite there yet. Theoretical capacity hasn't been reached in the lab, and even after that it will probably take a few years for enough nanotube-enhanced ultracapacitor to make their way to market, but this is extremely promising (not just for cars, but maybe also as a way to store clean energy from intermittent sources). Thank you MIT!
See also: ::The Economist on Ultracaps and Tribrids, ::EEStor Capacitors- "This could change everything", ::EEStor Ultra Capacitors: The Science Explained, ::Big News: EEStor Says Something, ::Technology Review on EEStor
Photo: Popular Mechanics
That is cool news, but Nabokov would never have said that, even if he was interested in electric cars. Why? Because M and I do not cause your tongue to hit the palate.
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author note: You just out-geeked me! Congrats ;)
Bully!
Don't get overly excited just yet. It's a far way from an array of a few tiny carbon nanotubes under a microscope to a densely packaged, fully electrically hooked up battery-size module.
Okay so they hold 5% as much as a battery by (volume?), so I'd need 20 times as many ultracapacitors that take up the space of the current space that batteries use?
Perchance with the reduced weight of ultracapacitors v.s. batteries I'd only need 1/2 as many since I wouldn't need to use more energy since the weight is less. Can we get some real numbers here?
If I can travel 60 miles on a charge and recharge in 10 minutes I'd be like real happy for a daily commuter car. And I wouldn't care if my entire under the hood area was packed with these mothers since the in-wheel motors don't need much space.
Just do it, baby! Gosh I hope this passes as a civil AND intelligent comment.
Okay so they hold 5% as much as a battery by (volume?), so I'd need 20 times as many ultracapacitors that take up the space of the current space that batteries use?
Perchance with the reduced weight of ultracapacitors v.s. batteries I'd only need 1/2 as many since I wouldn't need to use more energy since the weight is less. Can we get some real numbers here?
If I can travel 60 miles on a charge and recharge in 10 minutes I'd be like real happy for a daily commuter car. And I wouldn't care if my entire under the hood area was packed with these mothers since the in-wheel motors don't need much space.
Just do it, baby! Gosh I hope this passes as a civil AND intelligent comment.
No, M and I are not palatal. M is labial. I is a vowel. T is alveolar in English, not dental. Nonetheless, that sounds cool.
I went to a seminar at MTU, and they are also working on nanotubes... good stuff.
how long before a big energy corporation buy the technology and keep it from being applied to electric cars the same way CHEVRON is doing with the NiMH batteries ?
Sure capacitors hold less total energy than batteries but that's missing the point.
Hybrid performance is so much better in cities than long distance highway travel because most of the benefit of hybrids comes from the regenerative breaking which recovers the energy orginally used to accelerate the vehical. Instead of burning the fuel to accelerate the mass every time and then wasting it at the brakes at the next stop light, you recover and reuse the energy over and over with only a relatively small loss as heat.
Capacitors are better than batteries when braking because they charge much faster allowing more of the energy to be recovered.
Capacitors are better than batteries when accelerating because they discharge much faster allowing more of the energy to be delivered to the motor faster.
"If I can travel 60 miles on a charge and recharge in 10 minutes I'd be like real happy for a daily commuter car. And I wouldn't care if my entire under the hood area was packed with these mothers since the in-wheel motors don't need much space. "
You only work 10 minutes a day? ;) j/k
If it charges in 8, good enough for most people's commutes.
The present motor technology is perfuctly sufficient and effecient for the needs of most commuters, wheel motors are more of an answer to a question nobody asked (or very few applications require)
A capacitor will burn rubber.
Michael,
you seem to be very enthusiastic about nanotechnology applied to solve serious energy problem. But in that case it seems the cure is worse than the illness - nanotechnology impact on nature might be quite dangerous. The Ecologist has a very comprehensive article on the subject at http://www.theecologist.org/archive_detail.asp?content_id=373
Ugly American:
Another reason why hybrids are better in the city is because electric motors have their highest torque at 0 rpm, while an ICE has relatively low torque at low speeds. For example, even though the EV1 had crappy horsepower, it had the fastest accleration of any GM vehicle ever made other than the corvette.
The discharge rate of batteries really isn't that much of an issue anymore. I saw a show where they showed an A123 (the company that's making the lithium-ion batteries) that they came up with a new battery that can release charge faster than the wheels can handle.
I meant the fastest accleration from 0-20 mph.
Is there proof that the knowledge that Chevron has of NiMh batteries is STILL 'cutting edge' or has Lithium since surpassed it. Ive seen Who Killed the Electric Car- but have yet to hear any complaining from the inventor (Stan Ovshinksy?) that his invention was intentionally shelved. If Chevron released this battery- would the current Toyota hybrids be significantly better? Ive heard this Chevron bashing so often- it starts to sound like the "GE has a lightbulb that has been burning for 60yrs but wont sell it because it would hurt there sales" rumour that seems to regenerate every few years. (and yes i realize if Chevron had allowed the commercialization of this 'superior battery' years ago- we may be well driving electric cars with even better range now).
enlighten me if u can.
Ultra caps sound great, but ones needing carbon nanotubes are going to cost a huge amount till nanotube mfg technology becomes cheap. I expect we must wait many years to see this.
Our best bet for the electric car is still batteries.
re: Dan A
You're right about the acceleration but the fast charge times with the A123s come from very parallel arrays of batteries which ends up being bulky and heavy.
re: John Taylor
Other companies have ultracaps based on other technologies. For example EEStor makes them for the military and is working with a Canadian car company.
Energy Density in MJ/L
34.60 gasoline
24.00 ethanol
10.10 liquid hydrogen
05.67 EEStor's ultracap
04.70 compressed hydrogen
00.90 Lithium Ion
0.170 Lead Acid
So at this point it looks like ultracaps have already passed batteries in power per volume and while they're weak compared to liquid fuels, they are more efficient and since they don't need a huge heavy engine block, you could fit more ultracaps into the space used by the engine block and transmission now.
re Rollie
The Livermore Centennial Bulb has been burning for 106 years. You can click the URL for this post for the page. Please note it uses a carbon filament like Tesla did instead of a metal one like modern mass market bulbs.
I think that the best use of ultracapacitors of any sort would be in capturing energy from regenerative braking. Use batteries for long term storage (plug-in hybrid) and to power accessories, but use capacitors to accelerate and decelerate for faster discharge/charge cycles. If on a long downhill grade, charge the battery bank through the capacitors so as not to overheat them. Conversely, the battery and engine can maintain the capacitors when frequent bursts of acceleration would bring down the charge too quickly.
A good supercap/ICE hybrid would help fuel efficiency in several ways. It would enable regenerative braking, recapturing that energy instead of letting it go towards heating the brake pads. It would allow a smaller ICE engine to be used in a more continuous fashion, at its optimum efficiency point, while using the supercaps to take care of the high energy delivery needs of fast acceleration and deceleration. The smaller ICE being run at constant rpm instead of fast & slow would be able to extract far more useful energy from each gallon of gas/diesel.
the ulitmate ev will have deep discharge l-ion battery packs to propel the vechile. a few nano caps can be unstalled outside in weather tight kick panels or side steps to save space. the caps would provide quick boosts of enegy for passing, merging & stop & go. they would also recover 100% of re-gen braking & time charge the slower reacting battery packs that capture only 30%. large digital controller & digital servo motors would conserve enery more efficiently. this translates into greater range & race car performance.
Forget electric cars. I prefer carbohydrate power converted to human muscle power, and healthier too.
But storage with of any kind of capacitor for home, at least for LED lighting, radio and such, is a different matter, especially with intermittent power sources. Neither volume nor weight, nor acceleration, is critical here. The next few decades isn't going to be very cheerful in any case.
Our short term problem is peak oil. Tech such as this will be a big help:
In the short term (
In the medium term (5-10years) we need to move to a complete fleet of HEVs. Toyota pretty much nailed it with the Prius. Aerodynamic and a small Atkinson cycle engine. Some interesting work is being done in 2 stroke engines that would further reduce the size of the ICE and therefore reduce fuel consumption. Taking our current CAFE from 25mpg to 45mpg and throwing in some mild conservation techniques* would nearly eliminate our need for foreign oil.
*Downsizing is obviously conservation. Other techniques include lower rolling resistance tires, better traffic control systems, lower national speed limits, and reducing industry use of oil for things like stationary generation.
To Willie's comment down there you'd need less since ultracapacitors store 25% more than batteries.
I love this! Hey, are any of you in electronics??? A capacitor of normal range as an example. With a standard AA battery, we tapped the terminals of a capacitor a few times. Then, we touched both ends (short circuit) with the same piece of metal and BOOM. They hold ALOT of power, so imagine what these can do at 25% or a normal battery versus 5%!
Sure they discharge fast, but think, a solar panel of 1 square foot could charge these no problem! A small hydrogen tank for cloudy days, and your good.
These have huge practical advantages in the transport industry, let alone anything electronic! I give a huge bow to the MIT engineers/students. I only wish the government would try to fund these kinds of projects more.
As we enter an era of increased wind and solar electricity, one challenge we must face is electric storage. Pumped storage has its limits, and so does balancing the load with current power plant outputs - so carbon nanotube supercapacitors would fill the bill, and with excellent characteristics for charging and discharging, they should do quite nicely. Best of all, it's something we can live with - no attendant heavy-metal mining necessary. The automotive sector is one visible component, but of equal importance is the electricity demand.
As we enter an era of increased wind and solar electricity, one challenge we must face is electric storage. Pumped storage has its limits, and so does balancing the load with current power plant outputs - so carbon nanotube supercapacitors would fill the bill, and with excellent characteristics for charging and discharging, they should do quite nicely. Best of all, it's something we can live with - no attendant heavy-metal mining necessary. The automotive sector is one visible component, but of equal importance is the electricity demand.