A Scottish pastor and inventor became concerned about his parishoners who worked the local coal mines. Steam engines were used to power pumps and the boilers frequently blew up with disasterous results.

Rev. Stirling developed the closed cycle heat engine bearing his name. It requires a heating and cooling source but no boiler. It runs on air and not steam.

A large displacer moves air between the hot and cold reservoirs. When the air heats, it pushes on a piston and keeps the displacer moving. When the air cools it pulls on the piston and keeps the displacer moving. The displacer moves a quarter of a cycle out of phase with the piston.

Today Stirling engines are used to generate electricity in remote places and on yachts. The may also be used to heat or cool if driven by a motor. They are used for this purpose to cool some optical sensors and also to reach very low temperatures for scientific purposes. Futhermore, if they were used for combined heating, cooling and/or electricity generation in homes, it would be a much more efficient use of natural resources.

Stirling Engine

This Stirling engine usually requires a little fiddling around to get the piston stroke right. Place it on a cup of recently boiling water and spin the propeller in the proper direction (the direction it more easily moves). Once it is going, it will chug along for several minutes.