We introduced a solution to minimize engines sizes by using an engine that uses the environment as a heat source. The heat is introduced directly to the working fluid (cryogenic gas).
This type of engines has the potential to have small dimensions and high efficiencies. Also, this kind of engines does not need oxygen from the surroundings (un-aerobic) and can therefore operate in a non-air environment.
In this project we discussed the thermodynamic properties of the engine, and an ideal optimal miniaturization range was proposed.