As expected, the first MAREEM fuel cell-based Air Independent Propulsion (AIP) system designed and developed by the DRDO’s Ambarnath-based Naval Materials Research Laboratory (NMRL) and built by an industrial consortium led by Larsen & Toubro (L & T), will be retrofitted to INS Kalvari S-21, starting from 2025. An agreement to this effect was signed between senior officials of NMRL and France-based Naval Group in Mumbai on January 23, 2023 to extend cooperation (meaning such cooperation had already been underway, but was kept under wraps) to enter into the detailed design phase (lasting 12 months) of the MAREEM AIP module for integration with the pressure-hull of the CM-2000 Scorpene. While the retrofit activities (starting in late 2024 and lasting till 2026) will be undertaken by Mazagon Dock Shipbuilders Ltd in cooperation with L & T. Naval Group will certify the AIP design for integration. INS Kalvari is then expected to re-enter service by 2028 after completing the mandatory sea-trials of both the MAREEM AIP module and its yet-to-be-selected on-board Lithium-Ion batteries that will replace the existing lead-acid batteries.
https://pib.gov.in/PressReleasePage.aspx?PRID=1893096
Detailed data on the MAREEM AIP module can be found here:
http://trishul-trident.blogspot.com/2019/12/explained-mareem-aip-plug-in-module-for.html