Stirling engine is one kind of external combustion engine. Stirling engines convert heat energy to mechanical energy. Stirling engines get heat energy required for engine start from outside of engine. Therefore stirling engines are in the category of external combustion engines.
Engines can be divided into two types as external combustion and internal combustion engines. (Internal combustion engines get heat energy required for engine start in inside of the engine. External combustion engines get heat energy required for engine start from outside of the engine.)
There is a piston attached to chamber in structure of the stirling engine. There is air ,nitrogen or helium like gases in the chamber of engine. Mechanical energy is provided by heating of these gases.
Manufacturers had been using only hot air for providing to mechanical energy in the stirling engines as firstly. Therefore these engines had been naming as engine of hot air. But manufacturers started to using nitrogen or helium (similar gases) for providing to mechanical energy subsequently. Therefore stirling engines has losted this name.
One side of stirling engine always heated by heat sources. And another side of stirling engine always cooled by regenerator.
Gas in the chamber of engine routes to heated sides as firstly. Pressure of this gas increases in here. Thus piston will pushed by this pressurized gas.
Gas in the chamber of engine is routed to cooled sides after these processes. Pressure of this gas in here decreases. Thus piston will pulled by cooled gas.
Pressure difference occurs because of all this operations. Pressure difference provides to operate of stirling engine. Stirling engines continues to operate as creating the pressure difference. All these operations have been continuing throughout processes of cooling and heating.
Stirling engines are very clean and environmentally friendly engines.
For example, air or various gases used for start of the stirling engine does not exhaust to outside of engine. So there is not cycle of exhaust in the stirling engine. At the same time, there is not continious refueling in the stirling engine.
Most important feature of the stirling engine is the diversity of heat sources and fuels required for generate the heat energy. The heat source or fuel can be diesel ,coal, alchol ,sunlight ,olive oil.
Stirling engines have been using in low power aviation engines, powerboats, heat pump. But stirling engines are often used for generate to energy of electric in fields of solar panels.
We can generate various types of energy with the stirling engine.