Energy sponge: A micrograph shows the porous structure of a new electrode material that helps increase the storage capacity of ultracapacitors. Credit: Nanotune
Posted on 05/24/2011 8:39:47 AM PDT by Red Badger
New energy-storage technology could surpass today's batteries in capacity and durability.
A startup called Nanotune says its ultracapacitor technology could make electric cars cheaper and extend their range. The company, based in Mountain View, California, has developed a way to make electrodes that results in ultracapacitors with five to seven times as much storage capacity as conventional ones.
Conventional ultracapacitors, which have the advantage of delivering fast bursts of power and can be recharged hundreds of thousands of times without losing much capacity, are too expensive and store too little energy to replace batteries.
Nanotune, however, which has raised $3 million from the venture capital firm Draper Fisher Jurvetson, says its ultracapacitors are close to competing with batteries in terms of energy storage, and could soon surpass them. Using a conventional electrolyte, the company has demonstrated energy storage of 20 watt-hours per kilogram, as opposed to roughly five watt-hours for a conventional ultracapacitor. Using a more expensive ionic-liquid electrolyte, it has made ultracapacitors that store 35 watt-hours per kilogram. By the end of the year, the company hopes to approximately double this storage capacity, says Nanotune CEO Kuan-Tsae Huang. At 40 watt-hours per kilogram, the ultracapacitors would be an improvement over the batteries used in some hybrid vehicles.
In recent months, several startups have announced that they're using nanotechnology to make better ultracapacitors. Each hopes to help solve one of the biggest problems with electric cars today: their batteries' high cost and limited storage capacity. Nissan, for example, to make its electric Leaf affordable, had to limit the size of the battery pack, resulting in a range of just 73 miles.
Part of the reason battery systems are so expensive and bulky is that the batteries degrade as they're used, especially when exposed to extreme temperatures—so automakers often augment them with cooling and heating systems, and add extra battery cells to offset losses in performance over time. Ultracapacitors could sidestep this problem, because they can be recharged without degrading and can work well in a wide range of temperatures.
Eventually, Huang says, it may be possible to make ultracapacitors that store 500 watt-hours per kilogram—about three to four times more than the lithium-ion batteries used in cars today. The practical benefit could be even greater. Cars are often engineered to use only half the storage capacity of their batteries, to keep them from degrading. But almost all of an ultracapacitor's storage capacity can be used.
Nanotune's technology is very expensive now—between $2,400 and $6,000 per kilowatt-hour. (The Department of Energy has proposed a goal of $250 per kilowatt-hour to make electric vehicles competitive with conventional ones.) Nanotune says, however, that its costs could come down to less than $150 per kilowatt-hour if the prices of some key materials, such as electrolytes, continue to fall, and as manufacturing is scaled up.
The company's energy-storage projections are based on several advances it is working on. Nanotune is currently making electrodes with pores that are about 4 to 5 nanometers across, but it says it can make them smaller (high porosity leads to high surface area, which makes it possible to store a large amount of charge) and tune them to match the needs of different electrolytes—the ion-conducting materials the electrodes are immersed in.
The company is also looking into using ionic liquids rather than conventional organic electrolytes. These increase the voltage of the system, greatly increasing energy storage, but typically they aren't compatible with conventional ultracapacitor electrodes. Finally, the company hopes to make use of recent academic findings that suggests that adding small amounts of ruthenium to the ultracapacitors can increase energy storage.
Nanotune isn't the first company to claim it can make ultracapacitors with very high energy storage. Others have found this promise hard to deliver. Increasing surface area can improve storage capacity only so much, since at some point the storage is limited by the ions in the electrolyte. Ionic liquids help with this, but they have significant shortcomings, says Joel Schindall, a professor of electrical engineering and computer science at MIT. (A company called FastCap Systems, which is developing ultracapacitors using carbon nanotubes, was spun out of his lab.) They're very expensive, for one thing, and some operate well only in a limited temperature range, making them impractical for cars.
Schindall says, however, that Nanotune can fall short of its very high energy goals and still improve the competitiveness of electric vehicles and hybrids. Given the durability of ultracapacitors, even achieving energy storage of 100 watt-hours per kilogram—close to that of lithium-ion batteries—"would be fantastic."
Energy sponge: A micrograph shows the porous structure of a new electrode material that helps increase the storage capacity of ultracapacitors. Credit: Nanotune
Electric car ping...............
Flux capacitor?!
I’d love for electric cars to be reasonable in range and cost. I could actually use one. If the car had a reliable range of 150 miles and cost the same or less than a comparable gas model, I could do it.
So they can "improve competiveness" on an electric or hybrid? That's still just polishing a turd.
They are celebrating 40 watt hours per kilogram.
Lithium batteries are at 125 and are still pathetically inadequate.
This won’t work.
“Huang says, it may be possible to make ultracapacitors that store 500 watt-hours per kilogram”
And shorting a cap to ground, discharges it in a nano second. Might be some interesting car wrecks in the future!
Lithium batteries are at 125 and are still pathetically inadequate.
The theoretical advantage of ultracapacitors over lithium batteries is their ability to both accept and deliver much higher instantaneous currents than Li-Ion batteries can.
During regenerative braking, you can only dump so much energy into the Li-Ion battery pack, and during acceleration you can only tap so much current per pack.
Hence, you need a larger pack just to deliver the current, never mind total energy storage capacity.
This could make hybrid cars much, much lighter and still deliver the advantages of regenerative braking.
You are obviously correct that Ultracapacitors alone won't do much for plug-in electrics, where total energy storage is vital. But a "hybrid" Li-Ion/Ultracapacitor plug-in might be worth pursuing.
Ahhhh. Just thinking about the misspent youth at the lab bench in engineering school
> They are celebrating 40 watt hours per kilogram.
> Lithium batteries are at 125 and are still pathetically inadequate.
>> The theoretical advantage of ultracapacitors over lithium batteries is their ability to both accept and deliver much higher instantaneous currents than Li-Ion batteries can.
Actually, that is only half the story. The biggest issue with Li-Ion batteries is the limited number of charge cycles before the battery wears out.
A typical Li-Ion battery is only capable of about 1000 recharge cycles before it is ready for the trash heap. In contrast, a capacitor can still be working perfectly after a million recharge cycles.
40 Wh/kg is what you can get from a good lead-acid battery. If it doesn’t cost too much and is good for over 20,000 recharge cycles, 40 Wh/kg can be enough for a useful electric car.
I call BS on your BS! ;-)
Ultra Caps might be the technology that makes electric cars practical in time. It won’t be tomorrow - but maybe in 3-5 years. Their advantages:
1) Can be recharged a nearly infinite number of times (at least when compared to ANY rechargeable battery technology.)
2) They can be recharge very quickly..measured in minutes instead of hours. That’ll be limited by the connecting wires capacity, not the ability of the device to accept charge.
3) They have a better temperature range, and as pointed out - will be lighter to deploy because you don’t have to over-engineer the power system due to temperature and capacity loss over time.
4) Because of #2 - as pointed out by others, regenerative charging will be more efficient.
5) MAYBE less dangerous in an accident depending on the materials used. Ionic electrolytes might be a “bad” thing from this angle.
What it WON’T do -
1) Remove the overhead on the Electric grid for an increasing number of vehicles that need to be charged.
2) Consequently - it won’t reduce pollution.
3) #1 will require a major infrastructure investments to build the charging capacity - so it’ll be costly to deploy.
4) New and wonderful failure modes in accidents that emergency responders have to worry about.
These deficits are true whether it’s a battery or an Ultra capacitor...they are a general problem with electric cars.
right now, I see the article as advertisement and I cannot take all the claims seriously.
The difference between a capacitor and a battery is the electric charge carrier. Capacitor/ultracapacitor: the carreier is the electron (a very light particle).
For the battery the charge is an ion, the lightest of which is the proton (about 1800 times more massive than an electron).
So the capacitor/ultracapacitor will charge much faster than the battery is the electron has much less mass than the proton.
However, the energy stored per unit volume is a different story: for capacitor/ultracapacitor, the maximum electric field is around 100,000 Volts/cm, beyond that there is arcing.
The less smooth the electrode surfaces, the lower the maximum electric field.
With batteries, the chemical bonding energy reflects electric fields of at least 1,000,000 Volts/cm.
Energy stored is proportional to the squared of the electric field, thus, on the basis of maximum electric field, batteries can carry about 100 times the energy than capacitors.
But what else plays a part in the effective stored energy density? Answer: the supporting structure supporting the electrodes for both batteries and capacitors.
It appears that improvements on capacitor supporting structures are going faster than that of batteries.
An advantage that capacitors have definitely over batteries is the almost infinite times that capacitors can recharge. Batteries eventually produce dendrites which short-circuit the system.
where’s that picture of Doc Brown and his Flux Capacitor when you need it...
And shorting a cap to ground, discharges it in a nano second. Might be some interesting car wrecks in the future!
What happens when rescue workers go at it with the ‘jaws’ ?
Actually - Capacitors and Batteries have similar discharge phenomenon, i.e. ARCING! The easiest way to build an arc welder is to get yourself a freshly charged Lead Acid battery. Those cold-cranking amps numbers are measured in hundreds of amps! So whether an electric car is built with ultracaps or batteries, they both have this issue.
We were burning with an EDM machine here a few years ago when a capacitor in the power supply decided to just explode for no apparent reason.
It was a big one, about 3” dia. and 7 inches tall. When it blew my first thought was someone had tossed a hand grenade through the window behind me.
The entire shop almost had to close down so everyone could go change their shorts I think, at least we know everyone’s heart was in good shape.
Almost.
"Using a conventional electrolyte, the company has demonstrated energy storage of 20 watt-hours per kilogram, as opposed to roughly five watt-hours for a conventional ultracapacitor. Using a more expensive ionic-liquid electrolyte, it has made ultracapacitors that store 35 watt-hours per kilogram. "
So, the cheap ones can only produce half that, but the 'more expensive' (by an unstated margin) type can allegedly achieve 35.
Lithium batteries are at 125 and are still pathetically inadequate.
Absolutely agreed. They don't even mention the kind of power you'd have to be able to generate to "fill" these capacitors fairly quickly. I sure as hell wouldn't want to stand near a charging car that's sucking down 20000 volts.
-——Nanotune isn’t the first company to claim it can make ultracapacitors with very high energy storage———
After the grant is used up, who gives a damn
That’s interesting. So, could I use a ultracapacitor as a reserve power source for my off grid battery bank to store excess power and recharge the batteries as they are used? I think this would result in the need for less batteries, while at the same time keeping them from discharging too far.
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