External Combustion Engine
An External Combustion Engine is an engine which has its power source outside the engine system as opposed to most modern engines which have their power source internal, as in the diesel, four stroke and two stroke engines.
A prime example of an external combustion engine is the Stirling or Hot Air Engine. The good thing about these engines is that they can run on almost any power source, whether it be wood, coal or even the earths geothermal energy. In fact, Iceland produces a lot of its electricity using their islands volcanic vents and the heat that they release, they simply place a system of pipes several meters below ground level and pump the hot water to the Stirling Engine which then rotates and is connected by a shaft to a large electrical generator.
In the 1970s the Ford Motor Company attempted to make a car with a stirling/external combustion engine as the power source. While this would be a great thing for the consumer, as they could use any fuel source to power the car, the project was eventually deemed not viable. The reasons for the project being disbanded are -
- the stirling engine only produced a fraction of the power of typical car engines
- it had to be preheated before you could drive off (stirling engines take a while to warm up before being fully functional)
- consumers of other cars were used to simply getting into the car and turning a key
Maybe in the near future there will be a breakthrough in stirling engine technology that would allow this project to become viable again.
Here is an example of an external combustion engine, as you can see you could use almost any heat source to power it, in this example a small candle flame is used -