free piston linear alternator engines

[dpeilow]

Green Car Congress: GM and U Mich receive patent on plug-in series hybrid/extended range electric vehicle powertrain using multiple free piston linear alternator engines)

[Doug_G]

Wow - what a radical design! There's no mechanical connection to the piston - it generates electricity directly by moving magnets past coils. And spark plugs at each end. Cool!

[rabar10]

More info on the concept: Wikipedia - Free-piston engine

The free-piston engine is in practice restricted to the two-stroke operating principle, since a power stroke is required every fore-and-aft cycle.
...
These engines are mainly of the dual piston type, giving a compact unit with high power-to-weight ratio. A challenge with this design is to find an electric machine with sufficiently low weight, and control challenges in the form of high cycle-to-cycle variations have been reported for dual piston engines.

Certainly a different series-hybrid-only approach, as opposed to the traditional ICE powerplant in the Volt and Karma.

[ItsNotAboutTheMoney]

More info on the concept: Wikipedia - Free-piston engine

Certainly a different series-hybrid-only approach, as opposed to the traditional ICE powerplant in the Volt and Karma.

It's an advantage of PHEV that as long as the motor is powerful enough engineers are free to use a generator instead of an engine and therefore they have greater flexibility. Potentially, anyway. They do need time and money.