Tom
I became interested in Stirling engines once, for about one day.
The reason I became intersted was the same as your reason, using up waste heat. The reason that I then became disinterested was after some quick sums, Stirling engines in this situation will not work. The reason is Carnot efficiency.
The maximum theoretical efficiency of a heat engine (of which a Stirling is only one type) is:
(Temp_Source - Temp_Ambient)/Temp_Source
All units in absolute temperature.
Imagine your heat source is hot enough to boil water at 373K, and your ambient temperature is room temperature at 293K. Then you will get an effeciency of 21%.
Assuming your heat source puts out 200W, at the very best (and no one has done it yet) you could get an entire 42W of power out of your system. More realistically, this will be 10W at my guess.
In other words, it is a good toy for the kiddies.
The only Stirling engines that I know that work in a realistic situation burn diesel at high temperatures. They are generally only marginally more efficient that a Diesel engine, have much lower maintenance requirements (few moving parts), take much longer to start up (external combustion engines need a long warm up period), and are much more expensive. The expense is, however, only due to their very low production volumes.
IMHO, a Stirling would be fun to build, but not anything you could make or save money on.
I became interested in Stirling engines once, for about one day.
The reason I became intersted was the same as your reason, using up waste heat. The reason that I then became disinterested was after some quick sums, Stirling engines in this situation will not work. The reason is Carnot efficiency.
The maximum theoretical efficiency of a heat engine (of which a Stirling is only one type) is:
(Temp_Source - Temp_Ambient)/Temp_Source
All units in absolute temperature.
Imagine your heat source is hot enough to boil water at 373K, and your ambient temperature is room temperature at 293K. Then you will get an effeciency of 21%.
Assuming your heat source puts out 200W, at the very best (and no one has done it yet) you could get an entire 42W of power out of your system. More realistically, this will be 10W at my guess.
In other words, it is a good toy for the kiddies.
The only Stirling engines that I know that work in a realistic situation burn diesel at high temperatures. They are generally only marginally more efficient that a Diesel engine, have much lower maintenance requirements (few moving parts), take much longer to start up (external combustion engines need a long warm up period), and are much more expensive. The expense is, however, only due to their very low production volumes.
IMHO, a Stirling would be fun to build, but not anything you could make or save money on.