Hybrid Proplusion Vehicles Using Ultracapacitors
by John Laumer, Philadelphia on 01.10.06
Yesterday we strode on luminous deck tiles that used ultracapacitors to store solar-generated charge. Now we're on the road: cruising on a breakthrough design, hybrid bus that uses a bank of ultracapacitors instead of rechargeable batteries. While conventional nickel metal hydride batteries are common for hybrid-powered vehicles, Maxwell Technologies claims its BOOSTCAP ultracapacitors deliver up to 10 times the power and longevity of batteries.
Per the maker of the pictured Thundervolt system: "A similar size box of low-cost, high-power ultracapacitors will produce up to 10 times the electrical current - 1000 amperes over 100 amperes," says Maxwell Technologies executive vice president Richard Smith. "They are absolutely maintenance-free and the efficiency gain over a battery pack is about 15 to 20 percent."
Just as with the NiMH battery packs used for current hybrid propulsion systems, ultracapacitor blocks are made up of individual cells such as the BoostCap model pictured above.
Hybridize that big inernal combustion engine driven bus with them and you get this ride.
Ultracapacitors function similar to batteries, but store the charge in an electrostatic
field instead of using chemical reactions. Because of this, ultracapacitors offer advantages in maintenance, efficiency, charge rate, temperature range, cycle life and cost.
The drawback is they have a lower energy density than batteries. Excellent for the take-off, then, but less useful for extended cruising under electrical power. Buses, large vans, delivery trucks, liquid tankers, even SUV's would benefit from hybridizing with ultracapacitors if the primary use is stop and go.
And the reason we bring this up? Glad you asked. The reason is, that automotive reviewers often end their articles with a buyer beware, warning consumers that 'no one knows how long those hybrid batteries will last...so be sure to get the extended warranty' Ooooh, scary scary batteries. It's ok to order $900 pin stripes and the $1,200 "spoiler" that has absolutely no function at legal speeds though. Oh, and don't forget the $4,000 custom wheel caps that spin around like a toy on an infant's crib fence. Those are cool. 'But don't say we didn't warn you to be more practical about cars with lots of batteries'.
"Ultracapacitor" sounds so newfangled we might be able to romanticise about having some in our cars. Just imagine a line of blue LED lights spilling down on your ultracapcitor bank, blinking with the beat. For the fast takeoff artist, nothing could be finer than that blinking bank of tire squealing appeal. No more throw away lines about those scary scary batteries then.
If they really want to make the bus more Green they can put in the excersize bikes that can be used to charge the capacitors. This way people can still ride a bike to work even in the worst weather conditions.
So would ultracapacitors be useful alongside rechargable batteries? As in, capacitors providing the drive off the starting line, and the batteries picking up the slack after that?
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One of the things I like about TreeHugger is that it's readers are clever and insightful. So yes, that would be the hope. No doubt it would take some bit wrangling with embedded processors to optimize all the system components around the kinds of driving actually being done, but it ought to be doable. This is one of those rare situations where an adaptive expert system would be a help. For now I'm just glad to see some basic recognition of ulracapacitors. Next come flywheels. Put all three in a bus and you would have a marvel of efficiency and quiet comfort.
these ultracapacitors sound fantastic but what of the flux capacitor?
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I'm not an electonics design engineer; but, I assume you may be describing a device that trims voltage peaks from a circuit so that input requirements of funtioning devices on that circuit are met and they are not put at risk of overheating? A simple resistor in parallel does that by turning the trimmed current into heat. Would be a good idea to store it for subsequent use if that could be accomplished. Is that what you are getting at?
I think the flux capacitor question was a joke, referencing the movie "Back to the Future." A flux capacitor can't possibly exist according to one of my old physics professors, although it's been far too long for me to remember why.
"The drawback is they have a lower energy density than batteries. Excellent for the take-off, then, but less useful for extended cruising under electrical power."
And Dave's comment: "So would ultracapacitors be useful alongside rechargable batteries? As in, capacitors providing the drive off the starting line, and the batteries picking up the slack after that?"
The answer is yes, they can be coupled quite effectively with traditional batteries or fuel cells. In fact, Electric-Fuel's Zinc Air Bus uses a zinc air battery/fuel cell (which have excellent energy densities) coupled with ultracaps (with their exellent power densities) to create a hybrid electric-electric system that seems to work quite well.
They would be particularly useful in plug-in or full EV applications where the battery pack could hold the longterm charge from the plug in and the ultracaps could quickly and efficiently deal with the charge from regenerative braking. Currently, much of the energy from regenerative braking can't be absorbed quickly enough by chemical batteries and is lost so using ultracaps instead would be great.
And yes, power management would be a bit more complicated but probably quite worth it.
I want ultra capacitors for my electric/human hybrid bike. I could use the burst of power for take-off, and "regen" the power for braking. My pedal efforts would be for the steady riding!