when it comes to thinking of sustainable transport
i think of two things:
1. boats
2. horses
boats its just something that keeps persistent through history,
horses run out of favor in moving cargo, but are still used
at tourist spots, and in poorer regions of the world where
people just can't yet afford to get addicted automobile industry;
personally i would be more interested in Stirling-like
engines and using ice and heat from the sun
as means of storing energy - also compost could be
used as "organic power source"
from Wiki:
"
In contrast to internal combustion engines, Stirling engines have the potential to use renewable heat sources more easily, and to be quieter and more reliable with lower maintenance. They are preferred for applications that value these unique advantages, particularly if the cost per unit energy generated is more important than the capital cost per unit power. On this basis, Stirling engines are cost-competitive up to about 100 kW.
"
https://en.wikipedia.org/wiki/Stirling_engine
in general i'm more in favor of smart, light, clever
solutions rather then bulky and heavy and heavy machinery,
i prefer gentle tech if i can help it;
but to be fair - i would like to know where do you
see the use for those kind of engines that you are
building?
What's the akshual NEED for it?
ps
your "propane batmobile" looks quite awesome
(but a bit noisy i guess...)