Navantia’s shipyard in Cartagena has completed installing the first hydrogen-based air-independent propulsion (AIP) system into a Spanish Navy S-80 class diesel-electric submarine, the company announced on 26 November 2024.
The AIP system, commercially known as BEST (Bio-Ethanol Stealth Technology), is billed by Navantia as the first third-generation AIP system to be fitted into a submarine. It will allow the Spanish Navy’s submarines to remain submerged for several days compared to a just few for conventional diesel-electric submarines.
The BEST system is based on a process that reforms bioethanol – a renewable fuel obtained from organic feedstock – to produce a hydrogen-rich stream that is fed, together with pure Oxygen, to a fuel cell to stealthily generate electrical power. Unlike equipment already operational in other navies, Navantia’s third-generation system does not require stored hydrogen on board; instead the system generates it on demand. As well as making the submarine quieter and thus more difficult to detect, the BEST AIP system further enhances the safety of the crew and the submarine itself while minimising the number of personnel required to operate it.
Navantia stated that the development of the system, “which has posed a top-level challenge for the national industry, allows Navantia to offer unique capabilities in international submarine construction tenders”.
The first boat to receive an AIP system is Cosme Garcia (S-83): the third of four submarines in the class. First-in-class Isaac Peral (S-81), which was commissioned on 30 November 2023, and second-in-class Narciso Monturiol, which is still building, did not initially receive an AIP system, which will be retrofitted during their first major overhauls.
Installation of the first AIP system in an S-80-class submarine, which Navantia stated had begun by 31 October 2024, is a welcome milestone for a programme that is substantially behind schedule. Construction of the four boats was authorised in 2003, with deliveries originally expected to begin around 2015, but excessive weight issues and a consequently required redesign caused significant delays. The redesigned class is now larger than when first conceived, with a length of 81 m instead of 71 m and a 3,000-tonne submerged displacement instead of 2,465 tonnes.
The S-80 Plus class, as the AIP-equipped boats will be known, can accommodate a crew of 32 plus eight additional personnel and will have a surface speed of 10 kts, a submerged speed of 19 kts and an endurance of 50 days. The submarines are armed with six 21-inch (533 mm) bow torpedo tubes and can carry heavyweight torpedoes, mines and Harpoon anti-ship missiles.
Navantia is hoping to see significant export interest in the S-80 Plus class once Spanish Navy AIP-equipped boats become operational.
