"The Stirling engine is fuel independent, it doesn't even need any fuel- the sun is enough!"
Lund Institute of Technology,Sweden
Scottish clergyman Reverend Robert Stirling (1790- 1878) began work on a new type of engine in the hope of replacing steam engines in the workplace. At the time steam engines were unstable, dangerous, and prone to explode, frequently causing horrific accidents. Spurred on by the number of people attending his parish who were in danger, he developed what would subsequently be called the Stirling or hot-air engine.
The Stirling engine needs an external heat source that can be almost anything—solar, chemical, or nuclear energy. The engine is then powered by the heating and cooling of a gas contained in a cylinder. As the Stirling engine does not rely on explosions it is quiet in operation and at the time was much safer than the steam engine. Stirling's design added an economizer that increased the efficiency greatly, and in 1850 Sadi Carnot worked out the thermodynamics of engines-, showing that Stirling's could theoretically be very close to perfect.
For the hot-air engine to produce energy efficiently, it needed to run at very high temperatures, and the materials of the day could not cope. It was almost entirely overshadowed by the steam engine throughout the Industrial Revolution. By the time the materials had caught up with Stirling's idea, electric motors had taken over.
These days you are most likely to find a hot-air engine in a submarine, where quiet operation is essential for stealth. However, a possible application for the future might be to use them for converting solar energy into electricity.
