Are Stirling engines really the most efficient engines possible?
In the mid 1800’s a very bright Frenchman named Sadi Carnot figured out the maximum efficiency possible with any heat engine. It is a formula like this (Temperature of the hot side – Temperature of the cold side)/Temp of hot side x 100 equals the max theoretical efficiency. Of course the temperatures must be measured in degrees Kelvin or Rankine. Stirling engines (with perfect regeneration) match this cycle. Real Stirling engines can reach 50 percent of the maximum theoretical value. That is an incredibly high percentage! • Q: If Stirling engines are so efficient, why don’t I have one in my car? A: The best answer for that is to pick the MM-1 engine up after it gets up to speed. Notice that it keeps running for a minute or so. While it’s very easy to build a Stirling engine that will stop instantly, there is not one thing in the world anyone can do to make one start instantly. When I get in my car I want it to start immediately (if not sooner) and be able to burn rubber off the tires a
