I replied to Jed's earlier post before seeing this one. The number he uses
0.2-0.3 kWH/km is creeping in 'rush hour' traffic, not at expressway
speeds -- I assume Atlanta is as bad as the Philadelphia area, where it is
70+ MPH. Pick your own number. The catch is not only at the service station,
but the interface with the car itself and the tolerable wait time for a full
refill.
The next idea is the battery swap, but who will trust that the swapped
battery is fully charged and not defective? The cost is not trivial. An
accidental short in a fully charged battery will be an even more spectacular
event that shorting a lead-acid battery.
All technical problems, all solvable, but requiring some very strong
motivation to accomodate.
Mike Carrell
-------------------------------
----- Original Message -----
From: "Jed Rothwell" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, February 08, 2007 4:53 PM
Subject: Re: [Vo]: "Bettery" on-the-way?
Mike Carrell & I wrote:
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?
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.
This is easy to estimate, actually. Electric cars use 0.2 to 0.3 kWh/km.
Assume the range is 500 km (310 miles) -- which I suppose is about average
for U.S. gasoline cars, but I wouldn't know. Anyway, suppose it is . . .
and 120 fully discharged cars fill up per hour. That's 18,000 kWh per
hour, or 18 MW.
Looking up Gas Stations & Truck Stops for sale here:
http://www.mergernetwork.com/industries/Gas-Stations-and-Truck-Stops/00002.htm
. . . I find that a lucrative station pumps 160,000 gallons per month with
12 stations (see lot # BFS-110285). The pump rate is limited to 10 gallons
per minute by law, sez the EPA. So that's 13,333 gallons per pump, or
1,333 minutes of operation per month. There are 43,800 minutes per month,
so the duty cycle -- I guess it would be called --
is 3%. The pumps are idle 97% of the time.
If the place is full up for 10 minutes a day, and then each pump is used a
couple times an hour during daylight hour, that would be about 3%.
3% of a day is 43 minutes, so if this were the electric charging station
it would use 12,950 kWh per day. With a bank of super-capacitors that can
spread that demand evenly throughout 12 hours of daylight, it comes to a
steady 1.08 MW of power. Or with a whole bunch of supercapacitors to
spread consumption through the entire 24-hour day it is a steady 500 kW.
According to Arthur D. Little this would place it in range of:
"Hospitals (200-300 beds)
Large Hotels (750 rooms)
Office (200,000 sq. ft.)
School (125,000 sq. ft.)
Large Retail"
"200 kW - 1,000 kW baseload power requirements" See p. 8 here:
http://www.osti.gov/bridge/servlets/purl/475277-moRBKG/webviewable/475277.pdf
That's big, but not unthinkable. There are plenty of "large hotels" and
300-bed hospitals located near U.S. highways, with large power supplies.
- Jed
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