My understanding is that one of the limitations of the Tesla Roadster is that it is only capable of full power sprints for a limited time before the motors overheat. I suppose if there was some way to channel the heat into the cabin, that would solve that problem. Presumably a conventional car’s liquid cooling system is too heavy at this point?
You could probably use liquid cooling to handle the Tesla’s full-power heat output (it’s only 248 horsepower total), but the real answer is that the Tesla people didn’t intend it to be run at full output for an extended period of time.
If they had, then they’d have designed it to hande dissipating that much heat.
Incidentally, unless you’re towing or climbing a very steep hill, you couldn’t operate the thing at full output for very long anyway-- it’s governed to 125 MPH.
A 1993 model 2700-lb Ford Escort can get to 120 MPH on 127 horsepower, so I doubt the 2700-lb Tesla Roadster needs all 248 horsepower to make 125 MPH.
Like anything, there are both positives and negatives about electric cars. One of the positives is that electric motors are high torque, so the car is very “peppy” and has a great “throttle” response which makes them fun to drive. Unlike an ICE powered car, an electric can operate without a transmission (not all of them do, however).
The big downside to them, however, is the state of battery technology. Right now, even the best batteries are a bit too heavy to give an electric car much range without the use of exotic (and expensive) materials in the construction of the body. They also have slow recharge times. Even assuming one can come up with an inexpensive, lightweight battery which is capable of accepting 50KW in about the same amount of time it takes to fill up your gas tank, you’ve got the problem of getting the juice into the battery. Ignoring potential problems with the electrical grid, the only way this is really practical is with superconducting wires, and those, at present, still require supercooled gases to work. That’s dangerous (and considering you’ve got high voltages added to the mix, I think that kicks it up a notch or two about plain old gasolene).
One idea often tossed out is having batteries which can easily be swapped at something like a gas station, but this is only practical if everyone drives identical cars, and you’ve got the real estate to hold all those batteries (some service stations at peak times can handle several hundred customers an hour, need a lot of batteries to be able to do that). The battery pack designed to power something like a Ford Focus is going to be a lot smaller than the battery pack for a Chevy Suburban.
Right now, however, I can’t see electric vehicles becoming anything more than a niche vehicle for a number of years to come. To be practical, the battery issue is going to have to be beat (and GM’s been quietly shifting the release date of the Volt [which isn’t even a pure electric] farther into the future because of battery issues), and there’s going to have to be significant changes to the infrastructure to handle them. How, for example, are people who live in apartment complexes going to be able to plug their cars in without worrying that some punk is going to come along during the night and unplug their car (assuming that it’s practical for them to plug the car in where they live)?
There’s also shortages in the supply of carbon fibre material (not enough capacity to meet demand), so building the cars out of that is going to keep the prices out of the reach of most Americans.
Really, the only practical technology that automakers can impliment within the near future, which give the benefits of low emissions is a diesel hybrid. That would give the maximum fuel economy, with minimum changes to the production lines. I haven’t heard of too many automakers going that route, however.
You did say identical. Then you mentioned weight specifically. With the new regeneration technologies that are not found in a standard gasoline vehicle, the relationship between weight and aero on fuel economy starts to shift. Areo starts to become more influentual.
Of course from re-reading the OP we’re just talking about HP here…
and I missed the edit window…
Diesel version of the Volt. Concept.
In poking around, I found this explanation of automobile power requirements, which links to a nifty little applet that will calculate required HP as a function of speed (note HP and KW read off opposite sides of the graph, which threw me for a minute). The initial parameters (4000 pound vehicle with just over 2 square meters of frontal area), are, I think, close to a “typical” passenger vehicle.
The results jibe with what I recall as a rule of thumb, which was that passenger vehicles use about 20 KW at highway speeds. Note that this is power delivered to the wheels, and any inefficiencies in the power transmission or generation (electric motor inefficiencies, in your case) will increase the actual power consumed.
With regards to niche vehicles, I throw the ZENN your way. A plug-in electric car, tops out at 40 kmh or so, strictly a city slicker.
Regarding the power plant issue, one thing to keep in mind is that load on the power grid is not constant. Most plug-in electrics will be pulling power from the grid when demand is lower.
When people say that the grid is running at or near capacity they mean peak capacity. Electric demand is hardly constant throughout the day. It is high during the day with a large spike in the early evening and a smaller spike in the morning but overnight it is quite low. Most utilities are generating what is known as “dump energy” during the late evening and early morning hours; energy no one wants are uses. They really can’t completely shut down base-load coal or nuclear plants for just a few hours, so they are left running at low levels generating power that is just wasted.
Plug-in electrics that charge overnight could take advantage of this power. There is no additional environmental impact since the plants are already running anyway.
The problem is that when Joe electric car owner runs out of electrons at 10AM he probably isn’t going to sit on his hands until 8PM. He is going to plug in now.
Perhaps the obvious solution is miniature nuclear reactors?
I’ve spent most of the morning trying to figure out what the car I saw this morning was. Now I know!
Certainly some number of plug-in electric owners will do so. But the vast majority of them will unplug their cars in the morning, drive them to work or the bus/train station, leave them sitting in the lot all day (maybe going out for lunch), then drive them back home and the end of the day and plug them back in. Most of the charging (and thus most of the load) will be overnight when the most excess capacity is available.
Plug them in when they get home, just in time for that large spike in usage as everyone turns on TVs, computers, AC systems, cooks dinner etc. 
I don’t see this as a big issue. I have a “time of day” rate plan which makes off-peak electricity usage 1/3 the cost of on-peak. If people start overloading the grid, the utilities will make on-peak power that much more expensive, and encourage people to put a timer on their electric buggy to start charging it after 9 pm…
There’s a company called Altairnano who has developed battery tech which allows superfast charge times. http://www.altairnano.com
This is still dependent upon having a charging facility capable of such high power drains, but we already are using centralized charging facilities for our current cars - gas stations.
Around 1900 or so, Thomas Edison, Henry Ford, Harvey Firestone, and several other titans of American industry set up a joint venture-to produce an electric car.
Ford would develop the body and drive train, Edison the battery and motor controls, and Firestone the special tires needed. After millions expended, the group gave up…because the Nickel-Iron storage batteries (invented by edison0 didn’t give the car adequate range (sound familiar?)
Why don’t we concentrate on ultralight, aerodynamic cars driven by very small, very efficient (>12;1 compression ratio) gasoline engines? 100 MPG ought to be achievable; why mess with electrics?
Because unless you legislate all of the big, heavy cars off the road, the light cars will be at a severe disadvantage during collision events. Think Toyota Land Cruiser versus Harley Davidson motorcycle. You know how when people say (for example) that aluminum is stronger than steel? They mean by weight, not for the same-thickness sheets. So make them thicker, which adds weight. Or you make them from carbon fiber, which is incredibly expensive. It’s easy to say, “just make them lighter,” but it’s not like every auto company in the world isn’t thinking about it. That plus, well, we’re going to run out of gas even if we use less, so we’ll need a replacement anyway.
Most smallish electric motors are air cooled. Some large electric machines are liquid cooled.
It would not be hard at all to to include cabin air in the cooling circuit of an electric motor, and a tens-of-HP motor generates a substantial amount of heat. Around 1.5 KW for a 25 HP motor by my back-of-envelope calculation…about what you’d get from a 115V space heater.
You would need to augment that when starting out, as you can’t let it idle to warm up like many folks do with thier gassers…but hey, in your driveway/garage, it is already plugged in, so you are not burning battery capacity then.
To an extent, it’s not material strength that saves you in an accident. The more massive your vehicle is relative to your crash-dancing partner’s, the less damage you’re going to take.