Let me try ask it this way. How efficient is current power generation thermodynamic cycles in space? Is it even used? My info is that most spacecraft use PV solar panels, is the heat turned to energy via a standard Rankine cycle?

If engineers developed a thermodynamic heat recovery cycle that's 92% efficient at converting heat to energy / electricity, would it therefore be better than current tech and have applications in space exploration and for example the international space station?

  • $\begingroup$ Hi, Steyn. This version is much improved from your previous question, but I think you could improve it further by narrowing it - is the core of your question about the marketability of regenerative heat engines for space applications, or about whether current spacecraft use such engines? @Hobbes appears to have used the second interpretation, and he's correct: for near-Earth applications heat is usually viewed as harmful waste that needs to be dissipated. $\endgroup$
    – Bear
    Commented Jul 12, 2017 at 19:11
  • $\begingroup$ Thanks I'm a bit of a newb here but am fascinated by space exploration and would love to be able to add to the world's efforts in advancing this frontier. So I'm trying to ascertain whether advancement in our thermodynamic cycle technology on earth would be advantages for space exploration. No marketing being done here, no engines built or anything of the sort it's all still just math and paper and trying to understand possible applications to work towards. $\endgroup$ Commented Jul 12, 2017 at 19:52
  • $\begingroup$ The original question mentioned a specific new absorption cycle with 92% high claimed efficiency. I appreciate that you cleaned up the question, but can you put that info in the comments? I was researching it and now I've lost my reference. Also, are you a developer or affiliate of the new absorption cycle originally referenced? $\endgroup$
    – Kengineer
    Commented Jul 12, 2017 at 20:11
  • $\begingroup$ The engineer developing this is my father, not sure if we can post links here but there has been a few articles published by EE publishers. ee.co.za/article/renewable-energy-baseload-power.html $\endgroup$ Commented Jul 12, 2017 at 20:33
  • $\begingroup$ And his website is found at www.heatrecovery.co.za $\endgroup$ Commented Jul 12, 2017 at 20:58

1 Answer 1


Most spacecraft I know of use PV panels (so direct conversion of sunlight into electricity). Waste heat is not recovered, but rejected using radiators.

The biggest use of heat recovery I know of is in RTGs, where the heat from Pu-238 decay is converted to electricity using thermocouples. These are inefficient (less than 10% of the heat energy is converted to electricity). At one point, NASA had a project for an RTG that used a Stirling engine to drive a generator, with an efficiency in the region of 30%. The ASRG project was cancelled as a cost-reduction measure, though.


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