http://www.kockums.se/products/products.html
This is from the Kockums website and includes details of the AIP ("air independent propulsion") system onboard the Swedish "Gotland," a non-nuclear SSK recently leased by the US Navy for evaluation. Appears the US is now considering non-nuclear subs for the first time since the 50's. The Gotland, taking part in fleet exercises, proved itself to be FORMIDABLE (to say the least!)