The Stirling Heat Engine was created by Robert Stirling in 1816 and has the potential to be much more efficient than a gasoline or diesel engine. Unlike the internal- combustion engine, the Stirling Engine uses Stirling cycle. The Stirling cycle consists of an external heat source, which can be many different things like gasoline or solar energy or the heat produced by dying plants. However, no combustion takes place inside the cylinders of the engine! Furthermore, the gasses that are used inside the engine never leave the engine. There are no exhaust valves that create high-pressure gasses, thus, there are no explosions and the Stirling engines are very quiet. Also, there is a fixed amount of gas in the engine. What happens is that there are certain things that happen inside the engine that change the pressure of the gasses and cause them to do work.

There are two different types of Stirling Engines, the displacer type and the two piston type. The displacer is consistently heated by a heat source below the the displacer piston and is cooled above it. On the other hand, the two piston is continuously heated above the hot piston and cooled above the cold piston.

Here are pictures of  sterling enginse from The American Stirling company.

The Displacer Type

The Two Piston Type

http://http://auto.howstuffworks.com/stirling-engine1.htm

Here, you will find a moving diagram of how the engine works as well as  the two different types of Stirling Heat Engines and their processes.

Today, there are only three main uses of the sterling engine. These are Submarine engines, cryocoolers, and they are also found in classrooms.

http://www.stirlingengine.com/faq/#1

The Peltier device, often referred to as a  Thermoelectric cooler, due to its  thermo electric facets was created in 1834 by a scientist that built upon the opposite of the Seebeck effect. He found that taking a thermocouple and applying voltage would cause temperature difference between the two. How it works is that the device pumps heat from one side to the other using an abundance of electric power. A module flow of direct current moves heat from a side of the module to the other which in turn cools one side while heating the other. “A single stage can make a temperature variation of 70 degrees Celsius, and more than 100 degrees Celsius in a multistage unit.”

http://www.heatsink-guide.com/peltier.htm

This is what the Peltier device looks like:

 

and this the internal part of it:

www.customchill.com

Uses for the Peltier Device today are most commonly in devices that require heat removal ranging from various ranges. For instance they can be used in something as small as a beverage cooler to something as large as a submarine.