Alpha Stirling engine relates to external combustion engines.it means the ability to work from any heat sources. The engine operation principles are based on the circulation of air between the areas of heating and cooling. This leads to a change of volume and pressure inside the cylinder, whereby the piston motion occurs.
Usually Stirling engines have two pistons. One is to move the gas between the areas of heating and cooling. The second one is a working piston and serves to convert the air pressure energy into mechanical motion. This engine also has a cylinder filled with a porous mass, which is used to save energy and to transfer it to gases that circulate inside the system.