As any Chevrolet Volt owner will tell you, the range-extended electric car concept is very well adapted to the average car ownership experience.

The majority of your daily driving can be accomplished on electricity alone, but there's always that engine there waiting to back you up should a longer journey be needed--or those occasions where you've been unable to recharge the car's battery pack.

So far, the range-extending engine is usually based on a production automobile engine--but bigger gains in efficiency could be found with units like the Free Piston Linear Generator (FPLG), reports Fox News.

Essentially, any regular automobile engine is a bit of a compromise for a range-extended vehicle.

It's often heavier than it needs to be, larger than it needs to be, and while optimized for use at constant engine speeds, it's really compromised by its original purpose of working over a large power band.

Developed by engineers at the German Aerospace Center’s (DLR) Institute of Vehicle Concepts, the FPLG doesn't have any of these issues.

As the name suggests, the engine is linear, in that the pistons aren't connected to a crankshaft, where their linear motion is converted into rotational motion.

The engine uses two pistons, facing each other in a single combustion chamber. The pistons are mounted on air springs, which generate electricity as they move back and forth. Combustion happens right at the center of the engine, using the traditional 'Otto cycle'--induction, compression, expansion and exhaust.

Because of the unique design, the engine can also run on all sorts of fuels, including gasoline, diesel, natural gas and hydrogen.

At the moment, the team's prototype is a large laboratory unit, but they say it could be reduced in size to a 125-pound unit putting out around 40 horsepower. Due to its size and shape, several could be mounted side-by-side for larger, more power-intensive applications.

A spokesman for DLR says a production version could be on the road in four to five years--provided they can find an industrial partner to help develop and finance the technology.


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