DRDO's Labs NMRL is developing two different types of fuel cells for AIP operation of our diesel electric submarines PAFC ( phosphoric acid fuel cell) for major use and PEMFC (polymer electrolyte fuel cell) for minor use , they are also working upon direct boron hydride fuel cells with integrated fuel bank for mini fuel bank probably will be used in F-INSAS program as soldier battery pack . NMRL has already demonstrated and developed Alloy Catalyst Carbon paper Electrode, Novel low cost membrane as Nafionsubstitute , Graphite gas distributor plate and H2 generated as byproduct for being used for various purposes . PAFC catalyst fuel cell Phosphoric Acid Fuel Cells (PAFC) Electrolyte - Phosphoric Acid Operating temperature -- 160°C-200°C Charge carrier - - H+ Prime cell components - Graphite based Catalyst - Platinum Product water management - Evaporative Product heat management - Process gas + Independent cooling medium Moderate Its by product is H20 which is harmless. PAFC material The phosphoric acid fuel cell operates at about 175–200 8C. This operating temperature is almost double as compared to that of PEMFC which is a cause of concern. It utilizes a liquid phosphoric acid as an electrode. Unlike the other fuel cell developed by DRDO i.e PEMFC . it is very tolerant to impurities in the reformed hydrocarbon fuels. The chemical reaction involved in this fuel cell is same as PEM fuel cell where pure hydrogen is used as its input fuel. One major disadvantage is its non conformation to the ideal operation parameters if frequent start stop operation is performed and also it reduces life of the fuel cell. Advantages Mature technology with proven very high availability (~85%) Higher operating temp allows high CO (<2%) allows direct reformer gas Multi fuel option Highly rugged with long proven life 10,000-50,000 hour DRDO fuel cell PEMFC fuel Cell The PEM fuel cell uses a solid polymer electrolyte (Teflon-like membrane) to exchange the ions between two porous electrodes, which is an excellent conductor of protons and an insulator for electrons. Electrolyte - Ion Exchange Membranes Operating temperature --- 80°C Charge carrier- H+ Prime cell components-- Carbon based Catalyst -- Platinum Product water management -- Evaporative Product heat management -- Process gas + independent cooling mediumTechnology Anode Pt on carbon (Vulcan XC72) typically 0.1-0.5mg/cm2, bonded on carbon paper/cloth support with nafion binder for ionic bridge Cathode Pt on carbon (Vulcan XC72) typically 5-0.5mg/cm2, bonded on carbon paper/cloth support with nafion binder for ionic bridge Electrolyte Fluro sulphonic acid based proton conducting polymer membrane like nafion, dowmembrane etc. The advantages of the PEM fuel cell are its higher power density and quick start up for Naval systems. The low operating temperature makes the technology competitive in transportation. The major drawbacks of the PEM fuel cell are its lower operating efficiency (40–45%) and use of high cost platinum catalyst. It is also intolerant to carbon monoxide. Courtesy- NMRL Reports have emerged that the last 2 Scorpenes of original 6 ordered will have DRDO created PAFC as AIP as these PAFC cells are more efficent than MESMA of France so no need for French AIP cell and further reports of 3 additional scorpenes will be ordered will defenitely have DRDO's PAFC AIP.