Ultracaps and drag racing comes up quite frequently. It's been tried and it's not a good match. Dragsters need more power the the further down the track they go. Ultracaps ability to deliver power drops the more you discharge them due to their voltage dropping. (E = 0.5CV^2)
Essentially you run out of ooomph by the time you get to the end of the track where you need it the most. So to compensate you have to oversize the pack and due to their low energy density you end up at a disadvantage. High power lithium cells have a flat discharge voltage, under heavy loads it can even increase due to internal heating reducing the internal resistance. Their internal resistance is also very competitive with ultracaps so there is no advantage to using ultracaps, yet. On Thu, Aug 14, 2014 at 10:09 AM, Ben Goren via EV <[email protected]> wrote: > "As hemp makes a comeback in the U.S. after a decades-long ban on its > cultivation, scientists are reporting that fibers from the plant can pack > as much energy and power as graphene, long-touted as the model material for > supercapacitors. They're presenting their research, which a Canadian > start-up company is working on scaling up, at the 248th National Meeting & > Exposition of the American Chemical Society (ACS). > > "David Mitlin, Ph.D., explains that supercapacitors are energy storage > devices that have huge potential to transform the way future electronics > are powered. Unlike today's rechargeable batteries, which sip up energy > over several hours, supercapacitors can charge and discharge within > seconds. But they normally can't store nearly as much energy as batteries, > an important property known as energy density. One approach researchers are > taking to boost supercapacitors' energy density is to design better > electrodes. Mitlin's team has figured out how to make them from certain > hemp fibers—and they can hold as much energy as the current top contender: > graphene." > > http://phys.org/news/2014-08-hemp-nanosheets-topple-graphene-ideal.html > > The full article gives energy density at 12 Wh / kg, which, if I have my > figures right, is an order of magnitude shy of CALB and similar popular BEV > batteries. Still, I imagine that's more than enough for a quarter mile, and > I can't imagine what supercapacitor discharge rates will mean for the drag > racing crowd. A supercapacitor-powered dragster could well mark the end of > hydrocarbon-based racing. > > I can also imagine hybrid battery / supercapacitor systems, if these > become affordable, even if energy density doesn't significantly improve. > Use a supercapacitor with just enough Wh to go all-out for a dozen seconds > to power the motor and to accept regen charge, and have a battery just > barely capable of continuous discharge at freeway speeds uphill charging > the supercapacitor. The battery can be optimized for capacity and density > (and price) without worry about discharge rates. The supercapacitor is > already optimized for discharge; it just needs to be big enough to hold > enough to get up to speed. > > Cheers, > > b& > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: signature.asc > Type: application/pgp-signature > Size: 801 bytes > Desc: Message signed with OpenPGP using GPGMail > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140814/97d7ed04/attachment.pgp > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- www.electric-lemon.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140814/337cb467/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
