Steam engines are running because statistics
So to build a steam engine in the world's smallest, researchers from the Max Planck Institute for intelligent systems have to tweak the traditional design.
Here's how it works: Stirling heat engine change to work via compression and expansion of gas-in the case of steam engines, gas is going to be water vapor. In its simplest form, ideal, Stirling cycle is a four step process. Imagine a cylinder filled with gas and covered with a piston. Two of the first steps in the cycle reduces the pressure within the container. First, You increase the piston to increase the volume of the container while using an external reservoir to prevent heat temperature to change. Furthermore, the volume remains constant while the gas is cooled. Step two bring pressure, temperature and volume of return to their country. Piston is lowered to reduce the amount of the original volume while maintaining the temperature of the cold reservoir. Finally, the temperature of the heated back to the original level.
If the cycle Stirling consists solely of compression and expansion, then the work done by the piston and the work done on the piston will cancel, and the machine will not do the work as a whole. Due to changes in temperature, however, net job with pistons will be positive.
Of course, not all machines are based on single cylinder structure this right. Another difference from a simple model is that instead of hot and cold reservoir, they use "regenerators" to "move" the heat in and out of gas. But the basic principles on the use of the Stirling cycle-piston and gas, and a four-step process-expansion-compression cooling-heating-remain the same in a Stirling engine.