Humm...these guys say their "engine" is 50% efficient. If the engine in the Volt is at best 20% efficient (like all internal combustion engines) and returns 50 MPG to the Volt...then would this engine, that is 2.5 times more efficient, allow the Volt to get 125 MPG??

http://www.freepistonpower.com/Default.aspx

Interesting design.

One of the major investors in Free Piston Power is Vinod Khosla, who is a co-investor withy GM on Coskata - a company making cellulostic ethanol. If this engine actually works, there's no reason that Vinod won't make the connection (as he did for Coskata).

There is another thread on this somewhere - search "free piston" ...

It would be a good design to try, as long as your have opposing cylinders to reduce vibration.

This is a great post and makes me think of where I can fit in. I do a little bit of everything mentioned here and I guess I have to find my competitive advantage.

This is a fascinating generator. I like the concept, however I think they have some significant engineering challenges ahead. The concept of lubrication free pistons sounds like a short life span and high heat build up. Blow by from combustion looks like it would interfere and mix with the intake. Significant vibration problems would seem to be a factor. They don't mention it, so it's probably something they don't want to talk about.

Unfortunately, they appear to be stuck in the development. The website hasn't been updated since some time in 2007. In this case, no news is bad news. There also seems to be a bit of a plea for help on the website for funding. The lack of a demonstrator proof of concept is not inspiring. I hope they continue, it's great idea and inventions to use our liquid fuels more efficiently are equally important to battery development.

Humm...these guys say their "engine" is 50% efficient. If the engine in the Volt is at best 20% efficient (like all internal combustion engines) and returns 50 MPG to the Volt...then would this engine, that is 2.5 times more efficient, allow the Volt to get 125 MPG??

http://www.freepistonpower.com/Default.aspx

nice idea... but,

all internal combustion engines are not at best 20% efficient.

there is a wide variety actually ... and most engines varying in efficiency depending on the conditions ... they are not a set % efficient all the time... the average is close to 20% but that is not the best.

The gasoline ICE in the Gen-I Insight for instance was tested by the EPA in 2002...

http://www.geocities.com/ian_p_george/LeanBurnEfficiency.jpg

Which gives a ~48% efficiency ... which is very close to that 50% engine ... so the next question is what are the other problems with maintaining that level of efficiency ...

In the Gen-I Insight for instance ... the Lean burn operation that can result in these high ~48% efficiencies is only functional under low engine loads... and while the efficiency goes up... the power per engine cycle goes down ... this is because while ~20%+ more of the energy content of the fuel is being used... the lean burn mode can reduce the amount of fuel used per engine cycle by over half...

As seen here: (http://autospeed.com/cms/A_110187/article.html) The Air to Fuel Ratio varies from ~12.5 to 1 when more power per engine cycle is needed ... to as lean as ~26 to 1 when more efficiency is needed.

So my question would be more about the required specifics / problems with keeping that efficiency level over a vehicles wide range of conditions.

Since series hybrid engines can run at a constant speed under a constant load, it would be very easy to tune all crucial features for this single setting and achieve high efficiencies. It is far more about the simplicity of the application, and not the engine design.

I agree with Jason...

In certain vehicle designs , like the Volt... the sweet spot efficiencies of an engine can be exploited ... and this is a big boost... but there are down sides too...

While operating the ICE under more ideal / efficient conditions ... a significant portion of the energy will still be lost... in the generator converting to electricity ... then in the control electronics managing the power ... then in the battery packs in their cycle efficiency ... then back through control electronics ... then to the electric motor that converts back to mechanical power.

So at best I would expect a Volt like system to loose about ~20% of the energy it produces from the ICE output by the time it gets back to the wheels ... but thankfully running the ICE under its best efficiency conditions will increase its efficiency by more than that ~20% ... so thus there is a net improvement.

As a side note ... the Prius' Synergy drive tries to do some of this in the transmission system... the pro of that system is the efficiency of the transmission itself is higher than the round trip conversions efficiency from gasoline to wheel in the Volt ... the con of the Synergy drive system is that is does not do as good of a job as the volt will in maintaining the conditions on the ICE to keep it in its best state.

:D

good stuff out there.