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Ultracapacitors could also be useful in a very different type of hybrid vehicle called a microhybrid, says Andrew Burke, a research engineer at the Institute of Transportation Studies at UC Davis. As designed today, these vehicles use small electric motors and batteries to augment a gasoline engine, allowing the engine to switch off every time the car comes to a stop and restart when the driver hits the accelerator. A microhybrid's batteries can also capture a small part of the energy that is typically wasted as heat during braking. Because ultracapacitors can quickly charge and discharge without being damaged, it would be possible to design microhybrids to make much greater use of an electric motor, providing short bursts of power whenever needed for acceleration. They could also collect more energy from braking. According to computer simulations performed by Burke, such a system would improve the efficiency of a conventional engine by 40 percent during city driving. Conventional microhybrids only improve efficiency by 10 to 20 percent.
In both plug-in hybrids and microhybrids, ultracapacitors would offer improved cold weather performance, since they do not rely on chemical reactions that slow down in the cold. "In very cold weather, you have to heat the battery, or you can't drive very fast--you'd have very low acceleration," Bohn says. In contrast, ultracapacitors could provide fast acceleration even in cold temperatures.
Mark Verbrugge, director of the materials and processes lab at GM, says that of the two uses for ultracapacitors, it will be easier to use them in microhybrids. In this case, he says, ultracapacitors would simply replace batteries, since they store enough energy to augment the gasoline engine without the help of batteries. In plug-in hybrids, which require much more energy, ultracapacitors would need to be paired with batteries, and this would require complex electronics to coordinate between the two energy storage devices. "By and large, you never want to add parts to a car," he says. "You want the simplest system possible" so that there are fewer things to go wrong.
For ultracapacitors to be practical in microhybrids, Verbrugge says, the cost of making them has to decrease by about half, which may be possible because many parts of the manufacturing process for large ultracapacitors aren't yet automated. But to justify the added complexity in plug-in hybrids, he says, the entire system would have to cost significantly less than using batteries alone.
The researchers at Argonne have already taken steps toward proving that ultracapacitors can provide these savings, having shown that they reduce the heat stress placed on batteries by a third. They are continuing to test ultracapacitors to demonstrate that they can make batteries last longer, which would allow automakers to use smaller batteries and save money.
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Guest (johnrerrey)
CSIRO is Australia's premier research organization and has been testing Ultracapacitors combined with conventional batteries for years now.
http://www.csiro.au/science/Ultra-Battery.html
Ahh yes, and I hear its going into commerical production with a Japanese battery manufacturer, but it isn't leading edge ('only' lead acid) , so it doesn't excite the most of the industry ..... sad, isn't it. The industry seems to strive for complexity and complicated solutions, rather than simplicity, so we have cars with over 1000 litium ion batteries joined together....
Another advantage of an ultracapacitor in a microhybrid is that a much smaller (maybe 1/3 less), lower cost engine can pair with it. Much of the horsepower in our car engines is used only when we need short bursts of acceleration.
Nice article.
The reduced size of the battery could help offset the reported short supply of lithium.
I also like the idea of Ultracaps combined with the inexpesively produced proven technology of the lead acid battery...It would make all those wind turbine farms that are being stood up to be a more consistent supply of energy rather than just when the wind blows.
Other technology also - It's the economics!
Ultracaps might be useful in a mixed-technology battery pack, but other technologies might be used as well, e.g. Lithium Phosphate/Titanate (A123/Enerdel), or even the old fashioned NiMH. It really comes down to economics. Right now, the price for ultracaps is pretty high. It's really appropriate to plug in some actual numbers. Of course an ultracap could be used, but is an alternative technology cheaper and/or better in weight/volume?
It turns out, that both old-fashioned NiMH and the newer Li batteries are better in cost, size, and weight than the current ultracapacitor modules (pictured).
I don't have a price for the Maxwell Technologies module shown, but 47 of the cells it uses costs $6000, and the module is rated a little under 20kW continuous. That's about $300-400/kWc though about $60/kWp for 1-s peak. (300W/kg 200W/l) Compare that to LiFePO4 at $130/kW, 1200W/kg-- the batteries used in Prius plug-in kits and to be used in the Volt are cheaper/W and higher power/kg.
Compare the ultracap module to the old-fashioned ordinary Prius battery. Each of the 28 individual modules (not the pack) are rated at 1300W/kg and about $30/kWp (I don't remember where I got the price/module.) The pack is rated at about 20kW (not the derived 37kW), so this comes out to be ~$60/kWc. So the <20kW ultracap pack is >$6K and weighs 60kg, but the old-tech Prius (2004-9) >20kW pack is >$1K at 45kg. The Prius battery is better and cheaper than the ultracap!
Maybe in the future, ultracaps might be much less expensive-- it's just another possibility. EEStor's promised nirvana relies on increasing the voltage, but we have to wait and see what they can actually do. In the mean time, new generations of Li batteries (e.g. with Si nanomaterial as reported here) could also come along with lower cost, high power and life.
The Tesla needs $30K of Li-Co batteries to get the 50kW power, and that also gives the >200mi range. By adding a Prius pack (or LiPO4), then only a $20K battery system would be needed at half the range, or maybe $15K at a third of the range. The plug-ins like Fisker & Volt just use the straight high-power Li phosphate/titanate, but presumably a more complex combination with the LiCo (used in the Tesla & laptops) would be lower in cost, higher in range. The main problem with the traditional LiCo is the lifetime of 500x cycles-- expensive compared to the >5000x new Li.
Re: Other technology also - It's the economics!
Hi--
I think your comparison of battery to ultracap is missing the point. We all know batteries have more juice for $. But consider the cost of the life-time of the product and we have a different story. Ultracaps last a long time, and can be used as power buffers to extend the life time of the battery pack too. Calcutate the total cost over the life time of the vehicle and you will see there is a significant savings.
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Keith Tomilson
9 Comments
Hybrids and Ultra Capacitor Research
Kevin,
The researchers who are doing the work with Ultra Capacitors had better wake up or they are going to come in to the lab some morning and find out that the research has already been done and they are out of work .
The time when a lifetime could be spent doing the same research over and over is past and research on Ultra Capacitors and Hybrid drive has been going on for years already .
It is already known that a 600 cc gen-set and regenerative breaking with power stored in Ultra Capacitors is the next method of storing power for Hybrid Electric Vehicles and batteries will only be used for Pure Electric Vehicles .
It is also known that Ultra Capacitors used in Pure Electric Vehicles will extend the life and remove stress from the batteries .In Extended Range Electric Vehicles like the GM Volt they would make it possible to have a smaller battery pack and could sell the cars for thousands less with a very robust drive from the capacitors .
Apparently they (GM) are saving that for the next "new" development in version two of the Volt.
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