@Penguin is it true that Stirling AIP is best suited for cold water environments?
I really wouldn't know without some research.
Stirling Engines
Although well established as a feasible AIP device since their introduction into the Gotland class in 1992 [Ref. 15],
they do not appear to have been further developed for SSK use. This is not withstanding the innovative efforts
being conducted by Whisper Tech of NZ, where multiple cylinder arrangements are being progressed to provide
1kW sets but at a low power density of 5W/litre [Ref. 16].
Figure 3 shows the estimated performance of the Swedish Gotland class when operating with and without the
currently installed battery set and AIP. The plot shows how the 150kW Stirling engine AIP starts to give the SSK
endurance below 8 knots thus allowing extended poise in the Baltic Sea operating area where transit times to the
patrol areas would be small.
It is likely that the trend away from Stirling engines is due to their poor industrial infrastructure and their upkeep
and noise which would be greater than a passive fuel cell system notwithstanding enclosures and modern rafting
methods
http://www.bmtdsl.co.uk/media/10576...r-and-Propulsion-Conpaper-Pacific08-Jan08.pdf.