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ewh (Aerospace) (OP)
21 Sep 06 9:38
swertel (Mechanical)
21 Sep 06 10:03
Interesting.  I'll wait to judge until something more concrete shows up on the wire.  So far a Google search pulls up a bunch of blogs.

--Scott

http://wertel.eng.pro

civilperson (Structural)
21 Sep 06 10:12
No, power and work are computable numbers.  Existing electric prices to produce power and perform work equivalent to internal combustion engines is much more than the 65 cents per gallon cited. A revolution in friction reduction and rolling resistance  or regenerative braking or some other technology is required.
CJCPE (Electrical)
21 Sep 06 11:16
The Eestor patent (7,033,406) discloses that they have developed an ultra-capacitor. They describe a 31 F capacitor bank that can be charged to 3500 V to store 52 kWh of energy. The capacitor bank weighs about 336 lbs and occupies a space of about 1.2 cubic feet. They claim that it can be charged in 3 to 6 minutes and retains charge with a loss rate of 0.1% per month. They clain that its life is not reduced by deep cycle use.
0707 (Petroleum)
21 Sep 06 11:22

Ultracapacitors are not new

“ultracapacitors use electrodes made of activated carbon; the carbon is porous, so it has lots of surface area for the electrons to build up on. But the pores are irregular in size and shape, which reduces efficiency. That's why capacitors have to be big. But the MIT ultracapacitor has electrodes of vertically aligned carbon nanotubes, each one thirty-thousandth the width of a human hair. The regular shape and alignment of the nanotubes greatly increases the surface area, making the ultracapacitor very efficient at storing electrons.”
 
For hybrid car fuel cells

See also

http://www.pbs.org/wgbh/nova/sciencenow/3210/01-car-03.html

atom
KiwiMace (Mechanical)
21 Sep 06 15:05
So at 52kWh, you'd need three or more to get some reasonable performance and mileage from any size car.  That's 1000lb to pack into a mini.
IRstuff (Aerospace)
21 Sep 06 17:11
The reason the numbers didn't work out is that $9 of electricity at $0.13/kWh works out to about 250 MJ.

At current gas prices, $60 at $2.50/gal buys 24 gal, which contains 2400 MJ assuming that a gal contains 100MJ/gal.  

Assuming the engines in each case are comparable in efficiency, that's a factor of 10 error.  If you correct the required energy, you'd pay $87 to travel 500 mi, not $9, and more than the $60 for the gas.

52kWh=187MJ, which is way less than what 24 gals of gas contains.  Assuming 336 lb per bank, you'd need 4300 lb
to drive 500mi.

The real advance that Eestor seems to have come up with that is not being touted is that the capacitor can be charged up to 3500V.

TTFN



CJCPE (Electrical)
21 Sep 06 17:49
The EEStor ultracapacitor is quite different from the MIT LEES ultacapacitor. The EEStor capacitor uses a barium titanate ceramic material as the dielectric. Operating at 3500 volts is one of the keys to achieving high energy density with their design. Their claimed energy density is 345 Wh/kg vs 60 Wh/kg for the MIT cap. Their example of operating at 60 mph for 5 hours at 14 Hp indicates 0.07 kW/kg power density for continuous operation vs 100 kW/kg for the MIT cap. They claim that the cap can be charged in 3 to 6 minutes. That would indicate a power density of 3.4 to 6.8 kW/kg, but that can be sustained with difficulty for only the time it takes to charge.

The EEStor assumptions about charging cost seems to include an assumption that charging stations will charge ultracapacitor banks at off-peak times and transfer the charge to vehicles when needed. Their example assumes 100% efficiency for capacitor discharge, controller and motor(s). Something above 90% might be achievable.

The technology exists to produce electronic controls for efficiently charging the capacitors to 3500 volts and operating motors by drawing down the charge from 3500 volts to 700 volts or lower. How such a system can be safely operated by consumers and service station personnel in another question.
Helpful Member!(2)  GregLocock (Automotive)
21 Sep 06 20:27
Oh well, the price of oil should drop like a stone.

I think this is a very efficient method...










for transferring money from one place to another







Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

0707 (Petroleum)
22 Sep 06 10:07
this will be a good option for urban places transport and will contribute for the set of oil prices

image http://files.myopera.com/maidinhnguyen/albums/58905/BMW1.jpg
CJCPE (Electrical)
22 Sep 06 11:15

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