Indian submarine power system enters next testing phase
Where it stands
India’s indigenous air-independent propulsion system entered its next testing phase at Hazira, Gujarat, on 24 October 2026. The system is being prepared for Kalvari-class diesel-electric submarines. It is intended to help them remain underwater longer between occasions when they need outside air. A conventional diesel-electric submarine uses batteries while submerged. Its diesel engines need air to recharge those batteries. Coming near the surface to draw air creates an opportunity for detection. An additional power source that works without atmospheric air can reduce that need. The new system uses fuel cells to generate electricity. DRDO’s Naval Materials Research Laboratory developed the technology, with Larsen & Toubro building the energy module. The project has now reached another stage of preparation and testing, not operational service aboard a submarine. The next work includes producing power and completing tests under Navy procedures. The planned handover to Mazagon Dock Shipbuilders is for integration into a Kalvari-class submarine in early 2027. Safe operation and successful integration remain necessary before the Navy can gain the intended benefit.
Background
A submarine needs electrical power for movement and onboard equipment. Batteries provide that power quietly while a diesel-electric submarine is submerged. As their stored energy falls, the vessel needs a way to recharge them. Diesel engines can generate electricity, but burning diesel requires oxygen from the air. A submerged submarine can obtain that air through a snorkel raised above the water. This allows recharging without bringing the whole vessel to the surface. However, operating near the surface still makes concealment harder. Air-independent propulsion adds a different source of power. In a fuel-cell system, hydrogen and oxygen react to produce electricity without a conventional combustion engine. The required materials are supplied aboard the vessel, so the system does not need to draw atmospheric air during that operation. “Air-independent” therefore does not mean oxygen-free. It also does not give a submarine unlimited underwater endurance. Fuel, stored materials, power demand and other onboard needs still impose limits. The practical aim is to extend the time between air-dependent charging periods, while meeting the safety requirements of an enclosed underwater vessel.
How it developed
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24 October 2026How it started
Hazira milestone begins another stage before submarine integration
The Setting to Work Phase 2 milestone took place at L&T’s Hazira facility. The energy module will undergo power-production and safety checks before handover for submarine integration. Hydrogen handling and fuel-cell operation require particular care aboard a submarine. The current milestone establishes progress through the development process. It does not establish that an operational submarine has already gained longer underwater endurance.
Why it matters for UPSC
Explain how fuel-cell AIP can improve a conventional submarine’s underwater endurance. Distinguish a land-based testing milestone from completed submarine integration. Connect indigenous design with manufacturing, safety testing and the limits of operational claims.
Key terms
Sources (3)
- PIB / Defence Ministry · official · Indigenous submarine AIP enters Setting to Work Phase 225 Oct, 5:30 am
- Larsen & Toubro · official · DRDO and L&T work on indigenous submarine AIP25 Oct, 5:30 am
- PTI / The Economic Times · Indigenous AIP system reaches testing milestone25 Oct, 5:30 am