Author: Rainbow Kursk
On October 14, the naming and launching ceremony of the latest conventionally powered submarine of the Japan Maritime Self-Defense Force, the Large Whale class No. 2 boat, the Moby Dick, was held at the Kobe Shipyard of Kawasaki Heavy Industries, the 30th submarine built after the war.
Moby Dick is the fourth submarine in the Sea of Japan to adopt a domestic lithium-ion battery power system, so it has abandoned the air-independent propulsion system (AIP) that has been in the limelight in recent years. Coincidentally, the South Korean Navy also announced that it will also replace AIP technology with domestic lithium-ion battery technology in the second batch of construction of the latest KSS-III submarines.
It is foreseeable that lithium-ion batteries, which are very common in smart phones, will gradually become the new favorite of conventional submarines in the future.
Photo: Launch ceremony of the Japanese submarine Moby Dick.
The AIP system is a general term that does not rely on air propulsion systems, and since World War II Germany, countries have developed AIP systems to enable submarines to lurk underwater for a longer time.
In recent years, more and more countries have begun to purchase submarines with AIP systems or embed AIP independent modules into in-service submarines, and the combat capabilities of submarines have been significantly enhanced.
The biggest advantage of the AIP system is that it further enhances the underwater "breath holding" kung fu of conventional power submarines, which can make the submarine lurk in the sea for a longer time, and the concealment is better than that of traditional diesel-electric conventional submarines.
Photo: The French Scorpene-class conventional submarine produced in India has an AIP system cabin arrangement, which is a fuel cell AIP system.
However, the AIP system is not perfect, the main problem is that the current output power of the AIP system has not yet reached the level of replacing the submarine diesel-electric main force, and the AIP system that has been loaded or is planned to be loaded is usually only used as auxiliary power.
Conventional submarines still use diesel engines to charge and sail the battery pack when sailing on the surface or in the snorkel state, and the underwater high-speed navigation is powered by the battery, and the AIP system is used to provide power for the battery only when the underwater low-speed cruising state is used.
That is to say, the AIP system is not able to bring too many speed or maneuverability benefits to submarines in high-speed combat state.
Picture: The AIP system is mainly used for submarine low-speed cruise and cannot be used in underwater high-speed combat state.
At the same time, there is no small price to pay in order to install the AIP system.
The submarine had to add a special AIP system compartment, which increased the displacement of the submarine and reduced the maximum speed.
Taking the Japanese Soryu class submarine as an example, because the single power of the Stirling AIP engine installed is only 75KW, the boat had to install as many as 4 Stirling MK2 engines and corresponding auxiliary turbine devices, and the underwater displacement increased from the previous generation of pro-tide class 3500 tons to about 4200 tons, once becoming the world's largest displacement diesel-electric submarine, and even then the Stirling engine can only allow the submarine to maintain low speed navigation, the boat must also be equipped with 2 diesel engines and 1 propulsion motor.
Fuel cell AIP technology also has similar problems, other closed-cycle diesel engine AIP, closed-cycle steam turbine AIP design scheme also has such and such problems, not enough to become a submarine main force system.
Photo: Japanese Soryu-class submarine, the last Type of Japanese submarine to use a Stirling AIP engine.
For these reasons, modern conventionally powered submarines still use lead-acid batteries as the main power source underwater.
However, the lead-acid battery has low energy density, poor high current discharge characteristics, and there are still problems such as low charging efficiency, easy heating, serious hydrogen evolution, short service life, and serious pollution to the cabin, endangering the health of boat crews.
Compared with the existing lead-acid batteries, lithium-ion batteries have the advantages of high specific energy, good charge and discharge characteristics, normal use of non-hydroanalytic acid, long cycle life, simple use and maintenance, etc., and have been widely used in smart phones, electric vehicles, power grid energy storage, unmanned vehicles and other fields. Submarine power experts quickly recognized the characteristics of lithium-ion batteries, and Japan, Germany, France and South Korea all began to develop lithium-ion power batteries for submarines.
Image: Lithium battery of the phone.
Photo: Lithium-ion power batteries for submarines of Yuasa Corporation of Japan.
In October 2018, the Japanese Soryu-class submarine No. 11 boat "Huanglong" was launched, and it abandoned the Stirling AIP engine, becoming the world's first submarine to use lithium-ion power batteries as the main source of underwater navigation.
At present, a total of 4 submarines in Japan are equipped with lithium-ion power batteries, including the last 2 "Huanglong" and "Denglong" of the Canglong class and the new generation of Whale-class submarines "Big Whale" and "Moby Dick", and the subsequent construction plan of the Big Whale class will all use lithium-ion power batteries.
According to reports, these 4 Japanese submarines removed the original Sterling MK2 engine and 480 lead-acid batteries, and replaced them with 672 lithium-ion batteries developed by Japan's Yuasa Company, which doubled the battery power supply range and halved the battery charging time.
Photo: The power system of the Soryu-class submarine, starting from the 11th ship, abandoned the Stirling engine and switched to a more efficient lithium-ion battery.
South Korea, like Japan, is a major producer of lithium-ion batteries, and began the development of lithium-ion power batteries for submarines in 2018, and plans to replace the existing AIP power system with lithium-ion batteries during the construction of the second batch of the latest KSS-III submarines.
Germany and France also began the development of lithium-ion power batteries for submarines as early as the 1990s, but did not use it as a submarine main force system, but used with the AIP system, which was reflected in the export-oriented conventional submarine programs such as the Type 214 and the Barracuda class, and has not yet been mass-loaded.
Lithium-ion power batteries have obvious advantages in improving the endurance, high-speed maneuverability and concealment of diesel-electric submarines, whether it is installed as a separate boat as a main force system, or used in conjunction with the AIP system, which has good prospects, and China should also take action in this regard.
Photo: China's conventionally powered submarines.