Are Electric Cars A Pointless Effort?

[CapelDodger]

Methane Cracking:

First hit from google here:

I think the trouble is that you are still losing energy compared to burning methane...

(But I am a semicondutor engineer, with a first degree in Applied Physics, so... YMMV )

I stand corrected .

My knowledge of Applied Physics more or less ends at a lump hammer (aka a No 3 Adjuster).

 

[Ziggurat]

My thoughts for electrical transport . . .

An electrified network of “main” routes that directly power vehicles for long distance travel. The vehicles have on-board batteries that allow for shorter travel independent of the network. The batteries are recharged when travelling on the network. This system could also be utilised to distribute electricity around cities and countries (better than ugly power poles and pylons).

What would the main flaws of such a system be?

I'd like to make some further comments about the expense required for such an infrastructure. Long-distance power transmission uses high voltages and low (relative) current in order to reduce transmission losses. Overhead high-tension power lines are very well insulated, and so you can achieve pretty high voltages. But if you want to power cars, you can't use very high voltages - even aside from safety concerns (how do you deal with a highway accident if the road itself is dangerous?), you'll just get too much leakage current because you cannot insulate well at or even near ground level. So you're dealing with low voltages and high current - MUCH larger currents than electric rail systems use, because you've got so many more vehicles. How do you carry that much current without the transmission losses wiping out any advantage the system might have? The only way, really, is lots and lots and lots of very thick cabling. Which is very, very, very expensive. And because it would be low voltage, you wouldn't even want to try to use it for transmitting power for any use other than the roads.

The issue of making contact with the rails is also highly nontrivial, and I'm not sure how you envision that being done, but it presents a whole host of problems, none of which have cheap solutions.

 

[Earthborn]

how do you deal with a highway accident if the road itself is dangerous?

Switch off the power? Seems like this is actually an advantage of such a system; in a highway accident with fueled vehicles you can't magically whisk away the thing that powers them and remains a concern for any rescue workers.

MUCH larger currents than electric rail systems use, because you've got so many more vehicles.

Vehicles that are each much smaller and lighter than an electric train, which means they draw much less power from the grid they are connected to.

 

[soylent]

Just a thought. Since we drive to work and then park outside. For most people wouldn't adding solar cells to the hood and roof to charge the battery while parked reduce the amount of time needed to charge at night? And make the electric car even cheaper as a work car?

1.37 KW/m^2 would be pretty nice, but that's at noon at the equator with 100% efficient solar cells, no shade, clear skies, no dust or protective coating on the solar cells.

If the solar cells aren't precisely flush with the chassis I'd be surprised if you could even recoup the loses due to increased drag. If you insist on using solar cells at least stick them on a building or something where they'll be consistently in sunshine, can be tilted to provide a little higher average power and you won't be forced to make them in exotic shapes or subject them to vibration and other wear.

 

[Ziggurat]

Vehicles that are each much smaller and lighter than an electric train, which means they draw much less power from the grid they are connected to.

Individually, yes. But look at, for example, BART in San Francisco and the traffic crossing the Bay Bridge. Yes, a train is a lot bigger than a car (though not that much bigger than a loaded semi), but the total traffic crossing the bridge is a hell of a lot bigger than the train traffic from BART. Same with pretty much any light rail system. A highway would draw far more current, and over far larger distances if you actually want a national grid, than any electric rail system. And it's the total current which matters when calculating the resistive losses, not simply the current from one car. In order to keep resistive losses under control, the power transmission lines would probably cost more than the roads themselves.

And I still have yet to hear a realistic scheme of how cars would physically connect to this grid.

 

[Matlatzinca]

Great thread.

Mass Transit systems based on electricity would seem like an attractive alternative.

However with high oil/fuel costs construction prices are high and getting higher. Do we need electric construction machinery in place to reduce construction prices?

 

[Earthborn]

Yes, a train is a lot bigger than a car (though not that much bigger than a loaded semi),

That depends on the train doesn't it? The mass of a loaded semi truck may be similar to many locomotives, but trains generally don't consist of only a locomotive.

but the total traffic crossing the bridge is a hell of a lot bigger than the train traffic from BART. Same with pretty much any light rail system.

Why are you comparing it with a light rail system? Why not compare it with a serious rail system like the french TGV?

In order to keep resistive losses under control, the power transmission lines would probably cost more than the roads themselves.

So? The systems to provide cars with petrol probably costs more then the roads themselves as well.

And I still have yet to hear a realistic scheme of how cars would physically connect to this grid.

I've provided one possibility, which probably is as realistic as it comes.

 

[Ziggurat]

Why are you comparing it with a light rail system? Why not compare it with a serious rail system like the french TGV?

You think the TGV runs more weight than a US highway? I don't think so. Furthermore, the voltage for the TGV is fairly high (25 kV), using overhead cabling. That won't work for cars on a highway.

So? The systems to provide cars with petrol probably costs more then the roads themselves as well.

I'm not sure you're correct, but it doesn't matter: it's already a sunk cost.

I've provided one possibility, which probably is as realistic as it comes.

You mean overhead wires? Nope, not happening. They would need to be very high in order to allow semis to pass under them. You want to connect a compact car to electric lines 14 feet up? You want that to work while that compact car is doing 70 mph and changing lanes? You want this system to be able to connect and disconnect? You want our highway system converted so that oversized loads can't travel anywhere on it? If that's as realistic as it comes, then it's not realistic.

 

[TjW]

The answer to that is to re-charge during off-peak hours, which is when most people are asleep (and, hopefully, not driving at the same time). Peak-time electricity is already more expensive than off-peak because it involves stop-start of generating capacity, which is inefficient. The generating industry would love to spread base-load across the day, and they will price accordingly as an encouragement. Factor in intelligent re-chargers connected via internet and base-load generation (nuclear, for instance) becomes a more attractive proposition. As you're driving to work the base-load generation is shifted to heating up the office you're driving to.

Solar power has an inherent stop-start quality, of course, but it does generally conicide with when we're awake and demanding, and it doesn't cost anything to turn the Sun on.

This doesn't scale very well. At some level of electric car adoption, the peak usage will become whatever the peak charging time is.

Also, electric vehicles are not currently taxed to pay for their use of the road. (The equivalent of the gas tax.) This would have to change, making them less attractive economically.

 

[Earthborn]

You think the TGV runs more weight than a US highway?

Not more weight, no. Probably a lot less weight, but a whole heck of a lot faster. I wouldn't be surprised if at a slower speed it would be possible to move the same amount of weight as a US highway with about the same amount of energy as the TGV uses. Freight trains in the US often move far more with just electricity generated inside the locomotive. (Though to be fair, there is probably also a lot less friction).

You mean overhead wires?

No, overhead wire nets, somewhat similar to those used for bumpercars. That should make changing lanes perfectly doable.

You want to connect a compact car to electric lines 14 feet up?

Sure, why not? That's like 3 or 4 times the height of the car, right? Works for bumpercars.

 

[robinson]

That would not end well, considering the nature of most drivers.

 

[ponderingturtle]

No, overhead wire nets, somewhat similar to those used for bumpercars. That should make changing lanes perfectly doable.

So you are makeing the roads out of metal also like bumper cars?

 

[Ziggurat]

Not more weight, no. Probably a lot less weight, but a whole heck of a lot faster. I wouldn't be surprised if at a slower speed it would be possible to move the same amount of weight as a US highway with about the same amount of energy as the TGV uses.

Not a chance. A train's wheels have much less rolling resistance than a car's tires, and the fact that a train is long means that its aerodynamic profile is much better as well.

Freight trains in the US often move far more with just electricity generated inside the locomotive. (Though to be fair, there is probably also a lot less friction).

Indeed they do. But that's exactly the point: the electricity is generated on the train, so there are essentially no transmission losses.

Sure, why not? That's like 3 or 4 times the height of the car, right? Works for bumpercars.

Generally speaking, bumper cars don't use a net, they use a flat ceiling. It works at low speeds, in a controlled environment (constant floor-ceiling height), and at fairly low voltages. But the biggest problem is the fact that they use the metal floor as a ground. They can only use one polarity on the overhead, which is the only thing which lets the system work independently of the car's position. Asphalt makes a lousy ground, especially if your primary contact with it is through rubber. Making our roads out of metal would be absurdly expensive.

 

[MattusMaximus]

Very good, informative thread.

You've electrified the roads?

Shocking.

Horrible pun! You get one o' these...

 

[DavidS]

Switch off the power? Seems like this is actually an advantage of such a system; in a highway accident with fueled vehicles you can't magically whisk away the thing that powers them and remains a concern for any rescue workers.

Let me get this straight: Your proposed response to an accident that might disable one or two vehicles is to disable *all* the electric vehicles dependent on the associated power circuit? Great - a thousand of my closest friends and I get stuck because Bob Somebody can't drive straight. How do the responders arrive -- in a combustible-fuel-powered vehicle? To the scene of high probablility of damage to high-power electrical circuitry? Seems like this is actually a novel use of the term "advantage".

There may be good arguments for electrical vehicles and energized roadways. I seriously doubt this is one of them.

If you intend to counter that those other vehicles could carry on with their batteries, I suggest you consider the relative risks of combustible fuel and high-energy-density batteries. An uncompromised, unignited fuel tank isn't that great a threat to emergency responders. Once possibility of mechanical damage is admitted it's not obvious to me that a storage battery is terrifically safer or less environmentally threatening. It's pretty easy to tell if (conventional) fuel is burning or leaking; a lethally-energized door handle might not be so obvious.

 

[CapelDodger]

Very good, informative thread.

Also intriguing, stimulating, and above all amusing. Fortunately none of it will make the slightest difference to what actualy transpires, so it's guilt-free.

 

[robinson]

Fortunately none of it will make the slightest difference to what actualy transpires, so it's guilt-free.

That sums up almost EVERY thread here!