Simplicity At Its Finest

While most of us have heard of the internal combustion engine, in fact most of us use one daily, few have heard of the Stirling heat engine and even less use one on a daily basis. Unless you happen to live on your massive family yacht or are currently 20,000 leagues under the sea in your submarine, you probably fall into the category of those who have never had to utilize a Stirling engine. These are just two examples of the current uses for a Stirling engine, quiet applications that a combustion engine would be ill suited for. So what is a Stirling engine?

A Stirling engine uses the thermodynamic expansion and contraction properties of fluids or gases to drive a piston back and forth by cooling and heating in succession. This gif shows the action I am talking about.

By using an external heat source as its driving force the Stirling engine allows for unique possibilities that other standard engines just cannot compete with. It is far more efficient than a combustion engine but alas is nowhere near as practical. Practicality is the major flaw in this design. These engines are finicky to say the least, they need a heating and cooling system and time to initiate the cycle. For most practical uses these attributes rule out the Stirling engine as a possibility. This major issue is how the combustion engine was able to surpass the Stirling engine in popularity and fall by the wayside.

It does beg the question though as to how these engines can be applied to alternative energy uses. Geothermal energy has great potential applicability as well as solar which some organizations have already begun to exploit. Imagine sticking one of these in a hotspring in Montana in the winter? There’s your heat source and cooling agent. There has been a revival in popularity recently with the rediscovery of the Stirling engine and we can only hope that someone will find a way to apply it to our energy crisis because we do so dearly need some new creative alternatives.

A peltier device uses differentiation in temperature in a different way, it creates it. Discovered in 1834 by French physicist Jean Charles Athanase Peltier, the peltier effect is when two different conductors have an electric current put through and heat is either produced at the junction or taken away. The principle is applied today as heat pumps to control heat or cool. They are known in this application as a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC). They are typically used in cooling and like a Stirling engine, can be found where quiet operation is necessary such as a submarine or even the computer you’re reading this on! This is an example of what that may look like: