December 23, 2007: A U.S. firm (UTC Power) is teaming with Spanish submarine builder Navantia to produce 300 kilowatt fuel cells for the new S-80 submarines AIP (Air-Independent Propulsion) system. The UTC fuel cell design uses ethanol and pure oxygen. There are several other fuel cell designs out there, and AIP is becoming increasingly popular. It costs another $200 million or so to turn a half billion dollar diesel-electric sub into an AIP model that can stay underwater for a week or more at a time. This gives non-nuclear boats the same underwater endurance edge that nuclear powered boats have long possessed. While the U.S. does not build non-nuclear boats, AIP tech is important for the growing number of UUV (unmanned underwater vehicles) being planned or developed for American use.