China plans to retrofit its conventional submarines with lithium-ion batteries, a power move that could dramatically increase its fleet’s combat and survivability capabilities.
This month, the South China Morning Post reported that China’s fleet of conventional submarines may soon be powered by lithium-ion batteries, taking advantage of technological developments in the country’s electric vehicle (EV) industry. , currently the largest in the world.
The report notes that China produces three-quarters of the world’s electric vehicle batteries, giving it advanced battery technology.
Lithium-ion batteries can more than double a sub’s underwater endurance and dramatically improve its acceleration for high-speed operations, according to researchers from the Naval Submarine Academy in Qingdao quoted in the Chinese committee-based journal Marine Electric and Electronic Engineering reading material.
The South China Morning Post notes that the People’s Liberation Army-Navy has been trying to replace traditional lead-acid batteries with lithium-ion batteries for more than a decade, but has hesitated due to the danger. China is believed to have the largest fleet of conventional submarine forces in the world with around 60-70 boats.
Lead acid batteries have been used in submarines since World War II. However, they suffer from low energy storage capacity, slow charging, low power output, short lifespan, and generation of toxic fumes. In contrast, lithium-ion batteries have a higher energy density, faster charge, faster discharge rate, and longer life.
However, lithium-ion batteries suffer from thermal runaway and fire hazard, which is particularly acute in submarines, notes GlobalData Thematic Research. An overheating cell can cause a chain reaction of thermal runaway failures throughout the battery bank, leading to catastrophic fires, he said.
Lead researcher Wang Fang said safety solutions in lithium-ion technology derived from a significant development in China’s electric vehicle industry have been discovered, mitigating some of the earlier risks, the South China Morning Post said.
“After resolving these issues, the replacement of lead-acid batteries with lithium batteries in conventional submarines is imminent,” Feng noted.
The research team said the use of low-cost, readily available iron and phosphate can replace the usual but dangerous combination of nickel and cobalt in lithium-ion batteries, improving safety without compromising performance.
According to industry data cited by the South China Morning Post, the number of electric vehicles in the Chinese market using iron phosphate battery technology exceeds those using nickel-cobalt batteries.
The research team’s other safety innovations for underwater lithium-ion batteries include hard carbon and ceramic coating for battery packaging, which could improve their safety aboard submarines. .
This development may also be enabled by China’s military-civilian fusion strategy, which has broken down past barriers between civilian research, commercial entities, and the military and defense industrial sectors. The strategy aims to exploit the dual-use nature of the technologies with civilian and military applications such as lithium-ion batteries.
The South China Morning Post notes that both Japan and South Korea use lithium-ion batteries in their submarines, with the former doing so in 2018 and the latter in 2021. However, the article mentions that Japan uses manganese metal in its lithium-ion batteries to increase safety but at the expense of performance. In contrast, South Korea uses nickel and cobalt but has more security features.
The source mentions that Germany and France have also developed prototype underwater lithium-ion batteries with plans for future military service.
Lithium-ion batteries have many advantages over air-independent propulsion (AIP) systems, such as the Stirling engine and closed-cycle steam turbines. Navies can pair them with hydrogen fuel cells to compensate for the limitations of the former.
Tyler Rogoway, in a 2020 article for The Warzone, notes that Stirling AIP submarines such as the Swedish Gotland class must carry liquid oxygen on board, which has inherent dangers, takes up substantial internal space, and includes many moving parts that require additional soundproofing. Stirling engines are also limited by their low power output, potentially limiting them to close-range littoral combat operations.
Similarly, Rogoway notes that closed-cycle steam turbines such as the French Autonomous Underwater Energy Module (MESMA) share the same limitations with the Stirling engine as it needs a supply of ethanol and liquid oxygen. on board.
Additionally, Rogoway claims that while the MESMA system can generate plenty of power for high-speed operations, it has many moving parts that also require expensive soundproofing.
While fuel cells are a high-tech TAI solution, their main drawbacks stem from their different means of storing hydrogen fuel. These disadvantages range from poor gravity density, high oxygen demand, CO2 and other emissions, and unproven technology.
Nevertheless, Rogoway mentions that while fuel cells are a high-tech AIP solution, they are not capable of increasing power levels as quickly as a MESMA system.
Rogoway notes that pairing lithium-ion with fuel cells in submarines can yield extreme endurance, incredibly quiet operation, rapid acceleration and high top speeds, but cost and complexity remain issues. important.
Lithium-ion submarines also have the advantage of being quieter than nuclear-powered submarines. Although nuclear submarines have theoretically unlimited range and endurance, their nuclear reactors generate detectable heat and therefore must keep their cooling pumps always running, potentially creating detectable noise.
Additionally, nuclear submarines emit tiny traces of radiation in their wake, which can be detectable with specialized wake-tracking sensors, such as the Soviet/Russian SOKS system.
The technical advantages of lithium-ion batteries can translate into operational advantages. Anand Datla and Paul Giarra note in an October 2021 article in Proceedings that their faster discharge times equate to faster dive times and faster sink speed.
Meanwhile, their rapid recharge has far-reaching operational implications, including operations amid the surface and underwater features of the first strategic island chain extending from Japan, Taiwan and the Philippines.
An upgrade to the lithium-ion battery of conventional Chinese submarines will significantly improve their ability to enforce a blockade of Taiwan. Asia Times previously reported that advanced conventional submarines, such as the Type 39 C/D, would be the workhorses if China decides to block Taiwan in a conflict scenario.
Such an upgrade would improve the ability of Chinese submarines to remain stealthily on patrol off the coast of Taiwan, interdicting the movements of Taiwanese and possibly US navies aimed at breaking the blockade of the self-governing island.
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