'Nut's Place

Here we have information on a recently re-discovered Victorian-era mechanical invention. Invented as an alternative to the dangers of exploding steam boilers, the Stirling engine's operation is based on moving a gas (air or helium) between enclosed areas which are at an imbalance in temperature.

Small model Stirling engines can operate on the heat difference between a candle and room temperature. Larger Stirlings can be heated by anything that will burn; oil, gasoline, kerosine, wood, charcoal, dried plant husks, paper.

Most Stirling engines built today are desktop toys, albeit assembled with finely-machined, intricate and visually artistic mechanisms. There is a growing interest in wedding Stirling engine power with solar energy to provide renewable electricity.

My personal interest in the Stirling is that it can be built using scrap parts, runs more quietly than a gasoline or diesel engine, can use various fuels, has none of the danger nor certification requirements of steam power, and it is one way to reduce dependence on the existing power grid.  I've entertained the thought to build an aquaponics-based greenhouse for year-round food harvesting, and power it using a Stirling engine for heat and electricity.

Big-time kudos go to www.keveney.com for his effort and time given to creating these animations!  

The single-cylinder Stirling configuration below features a "displacer" and a power piston. The displacer does not seal to the cylinder walls as does the power piston. It simply moves air from the hot end of the cylinder (left) to the cooler end (right). The cooling and re-heating of the gas inside the cylinder acts upon the power piston through expansion and contraction. The linkage at the crank sets the two pistons motion's at 90 degrees apart.

The following dual-cylinder Sterling features two pistons in two cylinders. Again, the working gas is moved between the hot cylinder and the cooler cylinder via a connecting tube. To increase efficiency, a "regenerator" pre-heats the gas moving back into the hot cylinder, and pre-cools the gas moving into the cool cylinder.

This dual-cylinder Sterling features two pistons in two cylinders, but with three changes: there is no regenerator, the hot cylinder's piston (left) is shaped to act like the displacer in the first example above, and the linkage is changed (Ross yoke) to minimize side forces on the pistons as they move through their travel.