EnGen Roadshow Demo: Stirling Engine

How It Works

Source: Wikipedia

Stirling engines are heat engines. They operate by cyclic compression and expansion of air and turn a wheel. Inside of the cylinder there is a fixed quantity of air which is divided into two sectors by a cylindrical displacer through which air can pass that is affixed to the crank shaft wheel. Sector one is at the heated end, and sector two is between the barrier and the crank shaft. Heat is applied to sector one and while sector two is affixed with a heat sink.

Source: Mechanical Engineering Department, Ohio University

In process 1-2, sector one has zero volume and sector two is compressed by the crank shaft. The air in sector two is cooled as well. In process 2-3, sector one expands and sector two contracts to zero volume while the crank shaft remains motionless. In process 3-4, sector one continues expansion pushing the crank shaft. In process 4-1, sector one shrinks to zero volume due to the displacer moving out of phase with the crank shaft.

How It Is Used Today

One application of Stirling engines today is in solar power generation, as we have demonstrated. When placed at the focus of a parabolic mirror, a Stirling engine can convert solar energy to electricity at a higher efficiency than non-concentrated photovoltaic cells. There is a 1.5 MW solar power plant in Peoria, Arizona that consist of 60 sun tracking dishes that focus the sun light onto a power conversion unit which contain Stirling engines. In addition, Stirling engines can be used to heat or cool by inputting mechanical work.


The Stirling engine was invented and patented in 1816 by Robert Stirling. It was first used in 1818 to pump water into a quarry. These types of engines were produced in substantial numbers from about 1860 for applications where a reliable low to medium power source was required. In these applications they were powered by a wood burning fire, and provided a cheap, safe alternative to steam engines. By the late 1930s the only Stirling engines produced were for small toys and a few small ventilating fans. Philips developed the Stirling generator MP1002CA in 1951. However only 150 of these models were produced. In addition, they pursued development of Stirling engines in a wide variety of applications. The only one to find success was the reversed Stirling engine cryocooler in the 1970s.

Projects You Can Do At Home

$16 Stirling engine kit

Additional Information