Japan To Make Major Switch on Sub Propulsion | Defense News | defensenews.com
Japan has decided to power its new batch of Soryu-class submarines with Lithium-ion batteries instead of air-independent propulsion (AIP) technology — a move that could raise eyebrows after similar types batteries were faulted for fires aboard the Boeing 787 Dreamliner.
However, experts brush aside those concerns and instead say this type of technological leap increases power and performance, while reducing maintenance. It also could make Japanese subs more marketable overseas...
...The current Soryu-class submarines are propelled by a large electric motor that has three power sources: diesel engines, the AIP engines and main storage batteries. Diesel engines, which require oxygen for combustion, power the boats on the surface or while snorkeling. The boats can snorkel for extended periods to limit their detectability while transiting submerged (only the snorkel mast is above the water) or for short periods to quickly recharge their batteries after operating underwater. The AIP engines — which burn small quantities of diesel fuel and liquid oxygen — are used for long-range underwater cruising at low speed, and to keep the batteries topped off. The batteries are used for ultra-quiet operation as well as high-speed underwater operations, which quickly depletes them.
By shifting to Lithium-ion batteries, the new Soryus would retain their main propulsion diesels, but be equipped with more powerful and far lower maintenance batteries than lead-acid types widely in use...
...For the Navy, Kojima said AIP technology, which reduces the speed of submerged submarines to just a few knots, is being increasingly seen as too slow for emerging strategic uses and that the Navy regards AIP as maintenance intensive. Improvements in batteries make this technology the better long-term bet.
Bob Nugent, a consultant at naval consulting firm AMI International, said it is "plausible" that going to Li-ion batteries will provide more speed and power.
The Soryu-class is about one-third larger than most European subs that use AIP technology, he said, adding the increased power and energy density of the batteries would allow for longer cruise and sprint bursts of speed...
