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Thermo-acoustic stirling engines have long been a niche product. Seems like a great environment for them to shine, and far better efficiency than RTG's.
by nickhalfasleep 9y ago
Thermo-acoustic stirling engines have long been a niche product. Seems like a great environment for them to shine, and far better efficiency than RTG's.
- jessriedel 9y agoWhat's the advantage over direct thermoelectric conversion?
- nickhalfasleep 9y agoAn RTG uses the Seebeck effect, which gets you microvolts per degree kelvin. A Stirling engine can theoretically extract many times more energy from the same temperature differential, but with a larger complexity.
- jessriedel 9y agoActually, when I mentioned thermoelectric conversion I wasn't referring to an RTG (which is just nuclear decay) but rather to the true nuclear reactors that the Soviets put in space: https://en.wikipedia.org/wiki/Romashka_reactor https://en.wikipedia.org/wiki/Romashka_reactor https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor They used thermoelectric conversion rather than a Sterling engine with moving parts (although I guess TOPAZ is technically "thermionc coversion").
- curtis 9y ago> What's the advantage over direct thermoelectric conversion? Stirling engines can approach 50% efficiency [1], whereas thermocouples are usually less than 10% [2]. [1] https://en.wikipedia.org/wiki/Stirling_engine https://en.wikipedia.org/wiki/Stirling_engine [2] https://en.wikipedia.org/wiki/Thermoelectric_generator#Efficiency https://en.wikipedia.org/wiki/Thermoelectric_generator#Effic...
- jessriedel 9y agoCool, thanks! It's really surprising to me that inserting a mechanical intermediary has such a large efficiency advantage.
- brians 9y agoWhy does mechanical stuff suck? Because of friction of moving parts. Too much energy is lost to heat. For a thermal engine, if you can arrange to put the moving parts mostly on the hot side, that’s no longer loss.
- deleted 9y ago[deleted]
- Groxx 9y agoHuh, interesting device: https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine Is this actually a thermo-acoustic engine, or some other kind of sterling engine? Or are they equivalent? The article doesn't seem to mention "acoustic" (or an equivalent).
- baybal2 9y agoAnother thing to mention is sodium/lithium salt thermochemical generators that run at 15 percent efficiency with liquid salt being the only moving part