How Does a Stirling Engine Work and Its Use in Solar Thermal Technology for Energy Generation?

A stirling engine is extremely simple heat exchange engine and works by low temperature difference between two metal surfaces. One surface is heated at one end of the engine while other is cooled down on the other end, causing the air to expand near the hot surface (high temperature) and compress near the cold surface (low temperature). This expansion and compression of air within the engine cylinder enables the movement of displacer or piston in upward and downward motion between the two surfaces into a cycle or loop. This efficient heat engine was invented by Robert Stirling in 1816 as an alte
ative to steam engines at that time and a great contribution in heat engine technology.

Stirling Engine Basics Explained

An ideal model for understanding the basics of a Stirling engine consists of a closed cylinder containing two metal surfaces (aluminium) at top and bottom of the cylinder. A displacer is placed between the two plates which is connected to a flywheel through a wire to transfer mechanical energy during upward motion. When one plate is heated for example; bottom plate, the air near that plate expands and causing the displacer to move upward. On the other hand flywheel is connected to a small piston which takes the mechanical energy from flywheel and push the displacer to aid in downward motion. When displacer reaches top position the small piston moves downward enabling the compress air to fill in the cylinder and push the displacer downward. Making a loop of upward and downward motion of both displacer and piston, resulting in the circular motion of flywheel.

Use in Solar Thermal Technology

In solar thermal technology we use heat energy from sunlight into mechanical energy to drive a generator or turbine to generate electricity. Stirling engine serves exactly the same purpose and they are very powerful solar power generators and produce clean and free renewable energy. Stirling Engines are used in solar thermal technology within solar dishes where a large parabolic reflector directs the sunlight into one focal point where Stirling engine is placed which then runs by using this heat energy from sunlight and giving mechanical energy to generate electricity. Solar thermal dishes are used in both residential and commercial electricity generation. Stirling engine powered solar dishes for residential use are comparatively smaller in size and generate around 1-2 kW of electricity. Whereas in commercial use a large single Stirling Engine powered solar dish can generate up to 25kW (kiloWatt) of electricity.

Your geographical location is important in deciding if solar thermal engines are best option for you. Solar thermal engines are best choice for users in areas that get lot of sunlight throughout the year and not so good for areas that get lot of snow and less sunlight.