Stirling Heat Engine
This is a closed cycle heat engine which operates by cyclic compression and expansion of air or other gas at different temperature levels, so the mechanical energy is produced.
It was conceived in 1816 as a competitor of the steam engine by Robert Stirling and its use was limited to various domestic applications that require low power, compared with the steam engine, is more efficient, quiet and easy to use, since you can use it with almost any heat source.
In the below video, you can see how a stirling heat engine works:
http://www.youtube.com/watch?list=PL4AA8E4EB073924A5&v=Dc2QoP0JQSA
At present, due to the compatibility with alternative sources it has become very important, as concerns about depletion and increases in oil prices have led to increase the interest in this type of engine that combines heat and electricity.
Some of its main applications are: automotive engines, electric vehicles, aircraft engines, marine motors, or pump motors.
The Stirling engine is well suited for power systems under water where electrical work is required continuously. Many submarines work from the hand of these engines since 1980, and it is still used today.
Peltier Device
Also known as thermoelectric modules are small solid-state devices that work as heat pumps, when electricity is applied, the heat is absorbed from one side of the device to the other, so that one will be cold and the other hot (Peltier effect).
It serves to heat exchange without the need for moving parts, that is, to heat or cool in both directions.
Currently, its most common use is as part of the CPU cooling computers, but can also be found in household dehumidifiers equipment as it is quieter and more compact than the compression system.
Sources:
http://www.physics.rutgers.edu/ugrad/351/oldslides/Lecture11.pdf
https://www.stirlingengine.com/
http://www.heatsink-guide.com/peltier