The only problem I see with liquid gas systems including LNG, is that if the material is stored in a Dewar, you have to use it or lose it.
It could be a major PITA to come out to your car, after not driving it for a couple of weeks to find the fuel tank empty.
B.E.
The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor
From everything I can see there is no engine here. This is a compressed gas motor. It works. It is a "steam motor" if you call Nitrogen gas "liquid Nitrogen steam". Note that the expansion cylinder of a water steam engine is the motor part. The "engine" includes that plus the furnace and boiler. This is my opinion of how those terms should be used, but there is no strict convention, AFAIK.
In this case, the Nitrogen in liquid form is stored mechanical energy like any other compressed gas except that in liquid form it is not under pressure. The pressure is generated as it boils. The recapture of the energy it took to liquify it is probably not achieved with decent efficiency. Also as mentioned, LN2 at atmospheric pressure, like this, boils off continuously.
Nice back yard project. Not an interesting idea, IMHO.
The guy doesn't claim it to be anything more than an air (steam?) engine.
I just loved the heath-robinson approach. Why-oh-why did I let 'er indoors beat me into scrapping our shed and replacing it with an unused greenhouse?
I also liked his thinking about improving the thermodynamic efficiency with all that working fluids and heat exchanger stuff. Might need to watch it a few more times and do some analysis.
Smart go at it; his heat exchangers help to reduce the icing issues. While at the U of Wash. (Seattle), my old advisor (and several slave laborers grad students) worked up a Grumman mail jeep converted to use LN2. They found that the price of LN2 is driven solely by the demand for liquid oxygen (mostly medical, but also some industrial uses); LN2 is a byproduct that is grossly underutilized. Thus, it can be quite economical to run such a vehicle, though the range is pretty limited...and yes, the minor H&S issues.
