Would it really kill these people to tallk about engine efficiency when they put out press releases like this? How many kilojoules of electricity gets generated per gramm of petrol, and how does that compare to a regular four-stroke/generator?
Great it's compact. But if it uses twice as much petrol as a regular engine, that's not so good, especially in an alleged 'green' car.

I like it. I have actually been waiting for solutions like this. But gas springs? I suppose the moving parts are packed with neodym magnets. Why don't they use them and some windings to create a linear motor to push the pistons back. Would that be less flexible and precise than a 'mecanical', spring?

"from Florian Kock, FPLG project manager, DLR Thank you for your comments. I am going to provide some more information concerning your questions:
- Upscaling: Upscaling to a greater power output is possible in two different ways. Firstly, the swept volume per cylinder can be increased. Secondly, it is possible to use several units. This is the equivalent to today’s multi-cylinder engines – but in contrast to those, some of the cylinders / units of the FPLG can be deactivated completely in case they are not needed currently. - Cooling: Water cooling for combustion section, linear generator and gas spring with different temperature levels for the 3 subsystems. - Gas exchanged: Indeed, it is necessary to turbo- or supercharge the engine making sure the scavenging process works satisfactorily. - Power output: Our current function demonstrator generates up to 12 kW from a single piston module operated at a frequency of 20 Hz. For a production version the frequency will be increased and a layout with two pistons will be used. We expect an electrical power output between 20 and 35 kW per module to be most beneficial."

I like the part where it can use a range of different fuels. IMO; this would make it more green than a conventional ICE that uses gas.
I think it could help eletric vehicles by extending the range in a green sort of way; IMO.
I just think its cool. :)

I think it's a great concept - multi-fuel, reduced mechanical parts, and a size that provides a fairly high power-density (e.g., volume or weight). What I think is a problem is a strong focus on using it in an automotive application. Sure, it does indeed offer great potential there (though like an earlier comment, I'd love to know more about it's true efficiency). You see, there are MANY other applications for a generator with just these characteristics - backup generator for solar/wind off-grid system, backup generator for regular grid power (part of an UPS), primary power for emergency services or construction sites, etc.
So while the automotive environment might be the most challenging to to design to, please don't neglect consideration for other (more mundane) applications!

Is it a two stroke? Definitely not green. If it is a four stroke, what in the hell pushes the cylinder through the bang-blow cycle?

What's the (projected) gas consumption per kWh?

This looks like it will not produce a lot of vibration and with Homogeneous charge compression ignition (HCCI) and burning high octane fuel you can get some really high efficiency do to all the heat being generated at the very beginning of the power stroke do to all the fuel igniting at the same time rather than starting at the spark plug and burning across the chamber or from the outside of the fuel droplets in like in a diesel. I would rather have the vibration of having cylinders at both ends and a linear generator in the middle and have it run without springs.
re; Adam Lund
It is not a law of nature that 2-stroke engines have to be dirty. Simply giving one direct injection will massively improve its efficiency and clean up its exhaust.

Every time I see a similar design I am thinking about mechanical advantage, actually the lack of it. The required magnetic circuit is more heavy and you need more permanent magnets comparing with the "usual" design with crankshaft, gearbox and generator. Until I see some figures I'm not convinced.

re; clau_sav
Even If the generator is heavier than a conventional generator the weight increase in the generator is significantly less than the weight decrease from not having a crankshaft, and rotator bearings. There is less friction in this design. Only a fool has an ICE powered generator with gears adding friction between the engine and generator.