Larsen & Toubro (L&T) and Defence Research and Development Organisation (DRDO) on 22 June, 2023 signed a contract for the realisation of two air independent propulsion (AIP) system modules for Kalvari-class submarines of the Indian Navy.

The modules constitute the core of the fuel cell-based AIP System, which is indigenously developed by the Naval Materials Research Laboratory (NMRL) of DRDO with L&T as industry partner. The energy modules (EMs) comprising fuel cells will produce the required power, along with on-demand hydrogen generation on the submarine.

The manufacturing, integration and factory acceptance trials of the EMs would be undertaken in L&T's AM Naik Heavy Engineering Complex in Surat, Gujarat as the EMs would be integrated into the AIP plug to be retrofitted into the submarine.

An AIP module, which is a niche technology, extends the endurance of conventional submarines. Moreover, it is a green technology since the by-product of the reaction is non-polluted water which can be released into the oceans.

In January, 2023, DRDO and Naval Group of France, the manufacturer of Scorpene class submarines, signed an agreement to fit the indigenous AIP system on INS Kalvari, the first Scorpene-class submarine.

L&T has received Transfer of Technology (ToT) for the AIP system from DRDO and the ToT documents were handed over to L&T by the Defence Minister Rajnath Singh during Aero India, 2021.