Australian Defence Force Academy (ADFA) in Canberra. The invited topic for the computing students was "ICT Sustainability", but to make it more relevant to a military audience I talked on "ICT Energy Saving Measures for DCNS Shortfin Barracuda Block 1A Submarine". Earlier in the week the Australian government announced that Australia had selected French company DCNS to design a submarine, 12 of which are to be built in Adelaide. Described as a "Shortfin Barracuda Block 1A", the design is based on the Barracuda-class nuclear attack submarine.
The 150 MW nuclear reactor of the Barracuda will be replaced with conventional diesel engines and batteries for the Australian variant. Running on battery power these will be very quiet submarines. However, they will will have limited electrical power. The K15 nuclear reactor of the Barracuda only needs to be refueled every ten years and the submarine is only limited by the amount of food it can carry for the crew. The Australian version will have a long range, but still be limited by the amount of diesel fuel which can be carried and the battery capacity underwater.
As I pointed out to the ADFA students, modern military increasingly reply on computers and telecommunications. The sixty crew, plus embarked special forces, will require computer equipment for the mission and for off-duty entertainment. This will make up a significant part of the "hotel power" of the submarine. The more efficient the use of ICT, the longer the range and endurance of the submarines. Even a few percent increase is significant.