A friend of mine sent me this, and when I suggested that he post it here, he asked if I would do it. So, any comments?

Saw this on a Slashdot thread. The thread itself is only marginally interesting, and the topic article:
http://money.cnn.com/2006/05/04/tech...2_wrightspeed/
is about a fast, cute, but non-essential racing-class EV.

What caught my eye was this computation in one of the comments, concerning a "fill-up". (The poster got the math wrong, so I've corrected it.)

1. Assume (correctly) that all-electric EVs will catch on with the public once they have approximately the same power, range, and fill-up convenience as typical modern passenger cars that run on chemical energy.

This is because it is demonstrably the case that people do not like to leave their cars on "charge" all night. They want to go out at night sometimes, or are traveling.

2. Assume (suspension of disbelief required here) that all-electric cars and battery technology have advanced to the point where they have approximately the same power and range characteristics as typical passenger cars. Which is to say:

- they can carry the energy required to sustain the ~30 HP required to maintain 55 miles per hour in an average-size passenger car, for a full-charge range of 300 miles.

(No such battery technology is even remotely available, at any cost, today; nor will it be in the near-term. But never mind that, we're suspending disbelief.)

3. What does this amount of energy translate to in terms of a "fill-up"?

=> 300 miles @ 55 miles per hour = ~5.5 hours

=> 30 HP for 5.5 hours = ~165 HP-hrs (A HP-hr = ~2.7 MegaJoules of energy.)

=> 165 x 2.7 MJ = ~450 MJ

4. How long does it take to conveniently pump a tank of gas? About a minute. Okay, charge the EV in a minute.

What's the power level required to deliver 450 MJ in 60 seconds? (A Watt is a Joule/sec.)

About 7 megawatts.

To grasp that figure, think of a 120 VAC line. That's 60,000 Amps. The power required to run 1000 homes with all the lights and appliances on. Consider the ridiculous power connector, and the cable, that would be required to accomplish the charge.

5. A filling station that can service just ONE car at a time will require a 7 Megawatt feed line -- basically, a small electric substation. Multiply by the number of cars in a typical gas station at one time during the day (let's say you might want to fill up to four cars at a time, and remember there's no local electrical storage) and you've got a medium substation.

6. Now unsuspend your disbelief only slightly for a moment, and consider the battery that's being charged. Let's say it's 99% efficient during charging. Only 1% of the incoming power is being wasted as heat. That's around 70KW of heat being generated for a minute. Where's it being generated? In the heart of the battery. That's called a massive explosion, or at best a meltdown, within a few seconds.

7. Remember that the above is predicated on the use of highly-advanced battery technology that isn't remotely available yet, at any price.

Moral #1: You can't ever charge an EV fast enough, and even if you could, you can't dissipate the heat of charging in the battery safely.

Moral #2: Pump and carry chemical energy, and convert to electricity on the fly. This is why hybrids eat all-electric vehicles' lunches, and always will.

The reactive chemicals in a battery can be quickly changed and the energy density of metal-air batteries is quite high. Recharging such a battery entails dumping the oxide and replacing the metal cathode.

Reducing the oxides is best done close to the power source in bulk. However, it can be easily enough decentralized but not likly to home units.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Sweet-a-er-person*

I agree that an electric will never be a one for one replacement for a gas vehicle. That said electrics can still have a place. You might not want to take one cross country but how about to work every day? An EV with only a 50 mile range would get me to work and any other place I typically go in a single day and then back home again. Once home an EV can charge overnight.

Is your cell phone useless because it does not charge up in one minute flat? How far do you typically drive on a normal work day? I submit most could use an EV to get to work and if they need a car for long distance they can have a second vehicle or rent one. Of course this would not work for everybody but think of how many it WOULD work for.

*note:

I normally respond with the first part of a person's log in name followed by "dude". For example: bwilson4web becomes: bwilson-dude or perhaps wilson-dude or maybe Bob-dude. Sweet-Cynthia-Dude just doesn't work (I'm sure you agree). Perhaps you can help me to keep my reply "style" when replying to the fairer sex? Dudette?

Considering pure environmental impact.. since most electricity generated in the US is coal, isn't an EV worse for the environment than a hybrid?

Not really. The emissions controls (after GW's "Clear Skys" ends) are fairly benign compared to vehicle emissions. I also believe we can have sustainable nuclear power but only via a TVA style, public-private corporation begins running the systems.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

I'm curious where the definition of EV as "all-electric" came from? Not trying to be smart, just curious. All electricity has to be generated from somewhere, whether it's fossil fuels, wind, sun, hydro..., so what's to keep from calling a fuel cell vehicle an EV? You're just generating the electricity on-board, rather than off-line. And yes, you have to get the hydrogen from somewhere, but hopefully the only practical source won't always be fossil fuels. I could envision the day when wind or solar could be used to fill your home hydrogen tank, or the tank at the "gas" station, and you "simply" pump it.

Your statement "always will" was what tweeked me...

What caught my attention was the attempt to translate or "normalize" the EV recharge compared to a gas vehicle fillup. What I don't like about that comparison is the fact that an EV is a totally different animal than any car or hybrid with it's own set of rules. Our usage of it will require a change in lifestyle - more appropriately a change in what we define as an automobile and how it operates. Because an EV may not fit our need-it-now fast-food culture doesn't make it a second-class technology - it's fundamentally different. I think the question is not, "can I see an EV working like a car", but, "would an EV, with it's strengths and limitations, suit my needs?"

*** Retired after 65,000 outstanding miles ***

Your statement "I could envision....wind or solar could....."; tweeked me.

I just don't see either having any serious impact any time soon if ever. Utilities need to provide electricity as need, not as the wind or sun provides it. If you want to put up a wind/solar generator fine, but utilities don't have the luxuryof falling back on the grid, they are the grid. We don't have the capacity/technology to store wind/solar so wind/solar doesn't replace conventional energy, especially on a hot, humid overcast, stagnant day. The utility must still provide the electricity rain or shine, wind or not, and wind/solar can OFTEN provide nearly ZERO for weeks. Totally unreliable.

Since when does it only take a minute to fill your tank with gas?

I didn’t do a very good job of asking my question. It is:
What, exactly, is the definition of an Electric Vehicle? Is it;
1. a vehicle propelled only by an electric motor, who’s only power source is from a battery system,
or,
2. a vehicle propelled only by an electric motor,
or,
3. some other definition?



Sorry, worthwads, I don't understand. I was referring to using wind or solar cells as a source of hydrogen for your vehicle, not as a means of replacing the utility company's generating capacity.