[Dan(9698)]

* Gas-turbine hybrid -- turbines are very efficient, but need to operate at a constant speed and torque -- which they could in a series-hybrid car.

This is a myth. Gas-turbines use twice as much fuel as a piston engine. They also use half the fuel of a full jet, so they are more efficient than a full jet, but less efficient than a piston engine.

If you note, large ships now have very large diesel engines and not gas-turban.

[USFRIENDINVICTORIA]

Gas-turbines are very inefficient at idling speeds — they’re best if they’re revved up to optimal speed all the time. In a non-hybrid car, turbines would have horrible mileage.

Turbines also have horrible acceleration (low torque) compared to piston engines with the same horsepower.

A hybrid system would eliminate both problems.

Gas-turbines are also very fuel-flexible -- so switching between (say) gasoline, diesel, ethanol, and bio-diesel would be easy.

[mamelukesabre]

Trains too.

Nothing beats a lugger diesel for efficiency. Many years ago, they built Huge two cylinder opposed flat twin diesels, and also nat gas burning versions, for pumping. They ran so slow, you could almost cound the revolutions of the exposed flywheel. The pistons were in the neighborhood of 2-3 feet in diameter. These are the most efficient kinds of IC engines ever made.