Ultracapacitors Make City Buses Cheaper, Greener

Oct 21, 2009 by Lisa Zyga weblog
Buses with ultracapacitors stop at recharging stations, which double as bus stops, to recharge in less than a minute. Image credit: Sinautec.

(PhysOrg.com) -- A fleet of 17 buses near Shanghai has been running on ultracapacitors for the past three years, and today that technology is coming to the Washington, DC, for a one-day demonstration. Chinese company Shanghai Aowei Technology Development Company, along with its US partner Sinautec Automobile Technologies, predict that this approach will provide an inexpensive and energy efficient way to power city buses in the near future.

The biggest advantage of ultracapacitors is that they can fully recharge in less than a minute, unlike lithium-ion batteries which can take several hours. The downside of ultracapacitors is that they currently have a very short range, providing a distance of only a few miles, due to the fact that ultracapacitors can store only about 5% of the energy that lithium-ion batteries can hold.

Although their short range makes ultracapacitors impractical for cars, city buses have to stop frequently anyway. By quickly recharging at bus stops, buses could take advantage of ultracapacitors' other benefits: a bus with ultracapacitors uses 40% less compared to an electric bus with lithium-ion batteries, and requires just one-tenth the energy cost of a typical diesel-fueled bus, which would save about $200,000 during the life of the vehicle. Plus, the buses are environmentally friendly: "Even if you use the dirtiest on the planet, it generates a third of the of diesel when used to charge an ultracapacitor," said Dan Ye of Sinautec.

Today's demonstration will take place at American University in Washington, DC, where an 11-seat minibus powered by ultracapacitors will be shuttling people around campus. At designated charging stations, which double as bus stops, the bus recharges by raising a collector on top of the bus a few feet to touch an overhead electric charging line, which recharges ultracapacitor banks stored under the bus seats.

The two companies hope that this is just the beginning for ultracapacitor buses. The company that makes the Shanghai buses, Foton America Bus Co, based in Tennessee, plans to deliver another 60 buses to the Chinese city in early 2010. The new buses will have ultracapacitors manufactured by Shanghai Aowei that supply 10-watt hours per kilogram, compared with the current ultracapacitors that have an energy density of six watt-hours per kilogram. Other US cities, including New York City, Chicago, and some towns in Florida, have also expressed interest in trialing the buses.

The companies expect that the ultracapacitors will continue to achieve higher densities in the future, which would allow them to hold a charge for longer. This improvement could increase the driving range from a few miles to 20 miles or more, helping to decrease the number of charging stations required on a route and make the technology practical for many more cities and bus routes.

More information: Sinautec

via: Technology Review

© 2009 PhysOrg.com

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User comments : 31

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2.5 / 5 (10) Oct 21, 2009
Charging capacitors wirelessly at every major intersection of a major city would work for urban passenger vehicles as well as buses. Gets rid of city smog at the same time.
1.4 / 5 (11) Oct 21, 2009
This is so stupid. Good old trolleybus (electric bus that draws its electricity from overhead wires) has been there for ages and now they have to invent some stupid ultracapacitor nonsense.
Just the waste of time and money.
3 / 5 (7) Oct 21, 2009
Golf carts and electric bicycles, anyone? Golf carts are inherently short range, and bicycles can be pedaled most of the time, using the electricity only for a boost when climbing hills. Bicycles can also recharge going downhill or braking, further boosting the range, and the (presumed) lighter weight of a capacitor would be an advantage.
4 / 5 (10) Oct 21, 2009
It's not stupid at all. Trolleybuses are not so flexible (can't change their route), it's not so easy to create a new route (building wires infrastructure). In case of power cut, trolleys will stop in the middle of the road.
1 / 5 (9) Oct 21, 2009
The plan was/is to invent some *new* (therefore very expensive) technology like the wheel and then make big bucks out of it.
Oct 21, 2009
This comment has been removed by a moderator.
2.6 / 5 (8) Oct 21, 2009
This is a very interesting idea, that is thinking outside the box. Trolley bus must go where the wires are, so this beats them hands down. also right now, US cities are building light rail trains which cost a fortune, while these type of bus might just be the ticket.

4.1 / 5 (8) Oct 21, 2009
Actually, this would be ideal to combine with the trolley bus. Use wires on the main routes, and the capacitors would allow the bus to deviate from the route, then recharge on returning. In case of power problems, whether failures or maintenance, the capacitors would also allow the bus to run its usual route, as long as the dead sections weren't too long.

Railroads did this in the 1920s, using big, heavy batteries. An electric locomotive would have batteries for use where wires or third rail couldn't be used, such as in explosives factories. The Central of New Jersey had the oddest ones. They could run on third rail, battery, or diesel-generator, making them a rechargeable hybrid - with extension cord.
4 / 5 (3) Oct 21, 2009
Tecnobus from Italy manufactures the Gulliver electric bus, which is currently used in several large cities in Canada, England, France, Germany, Italy, Portugal and Spain.
2.4 / 5 (5) Oct 21, 2009
They could run on third rail, battery, or diesel-generator, making them a rechargeable hybrid - with extension cord.

sounds like evangelion, especially the cord.
developments like this shouldn't be viewed in isolation. as the article admits, the source of electric power also has to be green, otherwise, they're only hiding from plain view the source of those greenhouse gases, or even accumulating them since demand for power will be centralized to the dirty coal plants to make electricity for these buses.
2.6 / 5 (7) Oct 21, 2009
What is the composition of these ultra-capacitors? China is currently the largest supplier of rare-earth metals in the world and they are beginning to require all rare-earth containing products be manufactured in China (ie. they are restricting the export of raw or unfinished rare-earth metals.)
2.3 / 5 (4) Oct 22, 2009
Still waiting for nano class capacitors redefine portable power storage, but this is a good step forward none the less- I assume they have a duty cycle that most chemical class batteries would dream of and of course the quick recharging is nice. But I would wager the fanciest component of them is in the polymer insulation. Hopefully soon we will be reading about a graphene/graphane capacitor ;)

I'm sure they are still a great deal greener then lith-ion batteries.
2.3 / 5 (3) Oct 22, 2009
A waste of time and effort? Not hardly! The infrastructure for overhead fired trolley is horrendous. Then the wasted power itself is terrible. And it is fixed to tracks, no cheap modification for other infrastructure maintenance. Cheaper better cleaner. Ultra cap is nice but does have its caveats, but the technology is finally recieving some attention. Titanium nanotube battery tech may prove a nice companion to Ultra cap for storage and power. Too Bad Government Motors cannot quite squeek off an overpriced crap compact. Hmm an Electric Corvair at a Corvette price. Right, that will be a successfull start.
2.3 / 5 (3) Oct 22, 2009
NOT a waste of time and effort. The cost and danger of stretching exposed electrical power lines over an electric bus's entire route is much higher than locating charging stations every several mile. It also gives buses the option of changing lanes, taking detours, or creating custom routes (charter buses).
The same technology and infrastructure can also be used for other short drive urban vehicles, such as delivery vans and trucks, taxis, postal delivery, police cars, and more. Physically connecting a vehicle to a charging station can also exchange information, such as vehicle identity (for billing), distance and time traveled (identify traffic jams), routes taken (identify detours), and more.
1.5 / 5 (8) Oct 22, 2009
What about fitting a 1KW VASIMR engine to a bus? That could propel people around town in less than 39 seconds.
3 / 5 (1) Oct 22, 2009
Charging capacitors wirelessly at every major intersection of a major city would work for urban passenger vehicles as well as buses. Gets rid of city smog at the same time.

They're not talking about wireless transmission. If you read the article, you'd know there will be overhead charging stations at bus stops. Since most normal people don't stop at every bus stop, t'wouldn't work for most normal people
3.7 / 5 (3) Oct 22, 2009
This is so stupid. Good old trolleybus (electric bus that draws its electricity from overhead wires) has been there for ages and now they have to invent some stupid ultracapacitor nonsense.
Just the waste of time and money.

Good thing smart people don't share that view
2 / 5 (8) Oct 22, 2009
I agree with NotAsleep - smart people don't share that view. Smart people would fit a 1KW VASIMR engine to a bus, and they would then be able to get around town in less than 39 seconds!
3 / 5 (3) Oct 22, 2009
I like this progress, but I would prefer to see inductive fields buried in the road at the bus stops and an inductive field mounted under each bus. When the bus stops its coil lowers (if required by the state of the charge). When the coil has lowered the bus sends a signal to turn on the power to the buried field. Power is applied only when needed and the bus would charge only while stopped for loading and unloading passengers. No overhead lines, no powered fields being maintained - waste is minimized. If the bus is hijacked / stolen its access to the charging fields is removed, so no long video clip for the sensationalists.
2.3 / 5 (3) Oct 22, 2009
@ SteveL
How do you propose making the efficiency of an inductive charge match that of a hard-wired charge? As far as I know, it hasn't even close to been done yet. Inductive charges are currently an inefficient convenience for smaller devices. Also, charging a bus to full power in less than a minute as the article implies would require a tremendously powerful inducer, perhaps enough to fry all the electronics nearby?
1 / 5 (6) Oct 22, 2009
How do you propose to inductively charge up a 1KW VASIMR engine?
1 / 5 (1) Oct 22, 2009
@probes, how would you get a VASIMR engine to work in our atmosphere? They require a vaccuum
3.5 / 5 (4) Oct 22, 2009
Most properly-sized and designed transformers run at 95 - 98% effeciency.

As a charging method it would be expected that the ultracapacitors would pull power at full capacity of the inductive unit until fully charged, so it should be able to be engineered to the exact size for the load. Granted, the aligning of the two coils for best effeciency would still need to be engineered into the system, but I'm of a mind that anything can be done if enough resources are put into the project.

I didn't mention a VASIMIR engine. I am not familiar with them nor the radiation from their plasma exhaust. Besides, unless technology has come up with some way to counter the G-forces involved - any method of getting around town in 39 seconds will be impractically messy for a mode of public transport.
3 / 5 (1) Oct 22, 2009
SteveL, that efficiency can only be found in a sealed, environmentally controlled transformer. Neat concept, though
2 / 5 (2) Oct 22, 2009
We have "hardly scratched the surface" of the ultra-capacitor's ability to store power! One, the size of a bus is tremdous! As for the people -----
1 / 5 (2) Oct 22, 2009

They only take a minute because UC's don't hold much power. A lithium would take just a minute too to charge the same amount.

Lithium batts are 95%+ eff, not 60%.

UC's cost, weigh 100x's more/watt so just what are their advantage? Just use a small A123 lithium pack would be far less and go far more miles.

Under vehicle induction charging has been done for 80+ yrs and 90+% eff.

A combo of battery, third rail/overhead wire bus/trolley would be very flexible and cost effective and been around 110 yrs.

Golf carts on the road with street tires would get 60-100 miles. I built, drive a trike MC with a GC transaxle which with 4 12v lead batteries, 14" car tires/Rabbit fits, gets 40 mile range.
1.5 / 5 (2) Oct 23, 2009
@jerryd, do you have citations for where you got this info? I'd love to read up on it. This article makes it sound like UCs are overall more effective than batteries for the stated purpose (i.e. "a bus with ultracapacitors uses 40% less electricity compared to an electric bus with lithium-ion batteries") but info has been misrepresented here before. I found info on the A123 battery:


However, they only have that small scale for now. If you tried to charge a standard Li battery as fast as a capacitor, you'd ruin it. Maybe the A123 battery will put UCs out of business?

I've never heard of under-vehicle induction charging on anything other than a tracked vehicle, where is this used?
3 / 5 (3) Oct 23, 2009
Another thought I had today on this: If the induction transmission frequency were increased (beyond 60 hz.) the size and weight of the coils could be reduced because you can move more power at a higher frequency than you can at a lower frequency. Less weight, smaller size, quicker charging, less valuable copper required (for the coils). The closer the two coils are to each other, the better the efficiency. There is enough room under a bus that the portable coil should be able to compensate somewhat for misalignment.

Nissan is supposed to be looking into an inductive powering or charging system for their "Zero Emission" cars (More like relocated emissions, but that is a different topic).
2.3 / 5 (3) Oct 23, 2009
This is important work that needs to be explored, we are running out of cheap oil and soon will have to have buses all over the country so we'd better have solutions that work.
1 / 5 (2) Oct 26, 2009
Relative to batteries and fuel cells, the ultracapacitor may be a more durable and efficient return for regenerative breaking.

There is plenty of room for electric vehicles to optimize a power-plant configuration, perhaps by using the storage capacity of plug-in batteries, or even fuel cells, to power the switching advantage of ultracapacitors.
1 / 5 (3) Oct 26, 2009
We should have a system of underground tunnels for these busses. The tunnels could then be kept in a state of high vacuum, high enough for the busses to be fitted with 1KW VASIMR engines. Then the passengers could zip about town in less than 39 seconds.
1 / 5 (1) Nov 03, 2009

Just look up their websites, read the specs and do the math. It's not like it's hidden. It's basic physics.

While some A123 are small, they can be series/paralleled into and rating you want. that's what Tesla did and Panasonic just came out with a 25vdc battery built that way for EV's, plug in hybrids..