Jed's right in that a successful supercapacitor technology could also build
large buffers for peak demands, just like the subsurface gas storage tanks
in ordinary gas stations. It is true that electric cars can be more
efficient than gasoline cars because you bypass the whole mechanical drive
train. However, the efficiency of electric motors is a strong function of
the RPM and basic design, which is why it has taken quite some time and in
the case of Toyota's design, their own semiconductor plant to get the
necessary switching circuitry. I have read that to propel a standard car at
60 MPH over a level highway takes only some 20+ horsepower delivered to the
wheels. That's about 14 kW. Do that for three hours and you have 42 kWH.
Deliver that in 0.1 hr and you have 420 kW craming into your supercapacitor.
Something will melt, if not explode. If you count the internal losses of the
supercapacitor and the drive electronics, the numbers get scarier.
I don't know much about the supercapacitor technology, so hereby stand for
corrections, but I gather it is related to the high dielectric constants of
barium titanate capacitors and transducers. These are remarkable and useful
electronic devices which are also noted for high internal losses compared
to, say, mylar or teflon or quartz as dielectrics. So one should pay
attention to the charge/discharge losses in these materials as well as
internal stresses generated by the piezoelectric properties of these
materials.
Mike Carrell
-----------------------------------------
----- Original Message -----
From: "Jed Rothwell" <[EMAIL PROTECTED]>
To: <vortex-l@eskimo.com>; <vortex-l@eskimo.com>
Sent: Thursday, February 08, 2007 3:45 PM
Subject: Re: [Vo]: "Bettery" on-the-way?
Mike Carrell wrote:
In this bloom of optimism about ultracaps as energy storage for cars and a
theoretically high recharging rate, do a reality check on the power
involved. You fill a gas tank in avout five minutes with enough energy to
drive a car at 70 mph for several hours -- and you are going to charge the
capacitor with that energy in minutes? The power is in the hundreds of
kilowatts -- do the arithmetic yourself. The 'gas' station may have to
service a dozen cars at the same time on an expressway in the middle of
nowhere -- you need a major transformer substation to supply the peak
demand.
Mike has brought up this important point before, HOWEVER, there are two
mitigating circumstances:
1. Electric cars use far less energy per kilometer of travel than gasoline
cars do.
2. In a world in which super capacitors have been perfected enough to
install one in every automobile, they would also be cheap enough to
install in the "gas" station/power station. You would install a bank of
them to cover peak-hour demand.
Suppose you want to recharge a dozen cars at one time, ten times per hour
(six minutes each) during the peak rush hour. That's 120 cars. Say the
power company could only deliver enough power to recharge 4 cars
simultaneously, or 40 per hour. You would fall behind by 80 cars an hour.
So you would have to buy as many super-capacitors as there are in ~80 to
~100 automobiles, to store up electricity before the peak hour. I suppose
this would cost approximately $200,000. Note that it costs ~$300,000 to
construct a typical gas station, with the pumps and underground tanks.
If the super capacitors could not be used for this purpose, because they
are too expensive, not reliable, too big, or for some other reason, they
would also not be suitable for use in millions of automobiles.
Also, by the way, if this gas station was in the middle of nowhere in
North Dakota, it would be an excellent place to put a 5 MW wind turbine.
- Jed
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