Second-generation fuel cells

Second-generation fuel cells

Breakthrough. Naval Group new-generation fuel cells are now available to extend the submerged endurance of conventional submarines.

Following a ten-year R&D programme, Naval Group has now completed the development of the FC-2G second-generation fuel cell. Like Mesma, the group’s first air-independent propulsion (AIP) system, the FC-2G module is packaged as a dedicated hull section about 8m in length and suitable for either new-build boats or modernisation programmes. The design can be tailored to any hull that is at least 6m in diameter, including Scorpène types, without compromising the boat’s dive capabilities or acoustic discretion. After extensive testing of a full-scale shore demonstrator, Naval Group now guarantees the system’s reliability and a submerged endurance of two to three weeks depending on operational factors. As of mid-2018, this demonstrator had logged over 5000 hours — the equivalent of five years’ normal use — including tests replicating a range of operational mission scenarios and profiles.

In technological terms, the FC-2G module combines two innovations. First, it produces hydrogen directly from  diesel fuel by hydrocarbon reforming. Process gases are expelled into the sea where they dissolve instantaneously, thus preserving the submarine’s acoustic discretion. The second innovation is a patented system that produces synthetic air by injecting nitrogen into oxygen from a large cryogenic storage tank. This air reacts with hydrogen in the fuel cell to yield electricity plus water. The resulting electricity is used to charge the submarine’s batteries and power the main propulsion motor. The module is housed in a ventilated enclosure designed to ensure that any leak is safely controlled.

The FC-2G concept offers important advantages over the weight and refuelling difficulties inherent in competing systems using external hydrogen tanks. Note also that current-generation fuel cells using pure oxygen significantly increase component wear and call for filters and membranes that must be replaced at regular intervals. According to the design team, the French system offers improved performance and major overhaul intervals that are five times longer than competing technologies. The decision to produce hydrogen directly from fuel oil not only simplifies refuelling and storage (one fuel for all onboard applications), but is also significantly safer than systems using fuels like methanol which is both flammable and produces a toxic vapour in the event of a leak.

AIP FC2G

 

Scorpen AIPFC2G

 

More information in Mer et Marine Euronaval 2018 Special issue : "Naval Forces : focus on french technology"