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Indeed. Like this?

First, electric motors can vary their torque by varying the current. Therefore you don't have gearing / transmission losses. The problem is that starting up from a dead stop requires a lot of torque (high current). On a standard battery this quick discharge quickly affects how many times you can recharge it before it degrades. Ultracapacitors fix that shortcoming.

See:
http://www.afstrinity.com/

Second, since you are discharging a battery or capacitor to accelerate, you can charge the battery while slowing down. This is known as regenerative braking. Most current autos, with the exception of hybrids like the Prius, do not use this. Meaning: all of the braking energy is lost as heat.

Finally, another lossy area is in the pistons and driveshaft. In gas/diesel powered vehicles, you are using an explosion to drive a linear force (the pistons) and converting it into a rotational one. The Mazda RX series uses a rotary engine to avoid this problem, which also allows very high rpms, but its combustion chamber is subject to wear and needs relatively frequent maintenance. Electric vehicles also push their power directly into rotational force but don't suffer from the internal combustion issues.

So in a nutshell, yes there will be heat losses - 1st law of thermodynamics yada yada. But an electric engine will always be far more efficient than an internal combustion engine.

You mean like these guys?

Even so, in terms of energy density, it is hard to beat hydrocarbons, and the distribution system is already in place. Since the algae consume as much CO2 as is produced by the combustion of the diesel, there is no net increase in greenhouse gasses. It is effectively solar power, with an efficient energy carrier. In addition, the OPOC diesel engine, allows for very small size and high efficiency. (it is ~1lb/HP, or ~0.6g/W ;) More details are available here.

Also, when flywheel energy storage matures a bit more, it should allow for some great improvements in electric and hybrid cars. Flywheels have extraordinary power density, and can be charged and dischared in seconds, which allows them to recapture ~80% of the energy during braking, and provide for decent acceleration. There is some information at AFS Trinity, though the site could be a bit better. The basic ideas behind this flywheel tech are fascinating in themselves, but I've already wandered far enough off topic...

i RTFA, and i picked up on something on the second page (people read past the first page! gasp!). :) the quote was from a mr. furia (no, not the one from mystery men) at AFS trinity power.

"If you've got a flywheel with your chemical battery, you can draw down the chemical battery, but when it's time to do a heavy lift, to accelerate or absorb energy, the flywheel is doing the acceleration or the absorption, not the chemical battery," said Mr. Furia, whose company is developing its own plug-in hybrid that it says will get several hundred miles per gallon.

here's some info on the designs they have coming out. i want one now!

Flywheel UPS information is here.

A good break down of Power vs. Energy located here . Not here.

Actually one of the companies mentioned above has a mobile product, using two opposed flywheels:

http://www.afstrinity.com/specs/spec_mfpm.html

Interesting that the currently available systems seem mainly aimed at high-drain short duration applications - would they be less efficient at much lighter loads (e.g. as primary power source)?

Hmmm, a quick search on Google turns up plenty of hits for this stuff - it's not THAT new.

http://www.afstrinity.com/
http://www.activepower.com
http://www.acumentrics.com
http://space-power.grc.nasa.gov/ppo/projects/flywh eel/papers/powertrades-oct98/ - a NASA study from 1998

All with URLs displayed, for you who fear goatse.cx. Somehow, this doesn't look like that new of a technology. (And besides, I thought a REGULAR UPS was heavy!)

Check out AFS Trinity - a company working on high rpm flywheel battery systems. They are working towards a system where the flywheel itself will be able to absorb a vehicle's kinetic energy to slow it down. This in effect recharges your battery every time you brake.

They will probably start out with hybrid gas-electric vehicles, and eventually move to all electric. Very cool stuff.