Hydrides for submarine applications: Overview and identification of optimal alloys for air independent propulsion maximization

This study identifies possible alternatives in the currently use of hydrides in submarine applications in order to increase the storage capacity and, therefore, the autonomy (Air Independent Propulsion) of the boat. The study proposes a plug and play solution which requires no changes for what concerning the current propulsion system, nor the auxiliary systems of absorption and desorption of hydrogen, nor the power supply system of fuel cells. Different constraints have been taken into account, as the storage volume density, the operating conditions (pressure and temperature), the number of charge and discharge cycles. Taking into account that it is desirable to maintain the set-up of the actual systems (for what concerning the spaces, the pressure and temperature) the solution obtained in the present study ranges in between the following target values: 120 g/dm3 for the storage capacity in volume; 20-50 °C for the operating temperature, 2-3 bar for the hydrogen desorption pressure and 150 charge and discharge cycles that can ensure 5 cycles per year for 30 years. Under these constraints, a significant increase of the autonomy of the boat has been evaluated.