Carbon dioxide treatment method for autonomous underwater vehicles powered by direct methanol fuel cells: A multi-criteria decision analysis approach

Abstract Autonomous Underwater Vehicles are very valuable tools in a great variety of marine related sectors that demand new capacities and improvements. These improvements go through increasing their endurance and, in this sense, the use of Direct Methanol Fuel Cells can be very interesting with an adequate CO2 Treatment Method. This work investigates four CO2 Treatment Methods for their application onboard Autonomous Underwater Vehicles powered by a Direct Methanol Fuel Cell-based power plant. The evaluation was carried out considering different working conditions defined by the fuel cell power, navigation depth and endurance. To rank the treatment methods, three Multi Criteria Decision Methods and eight selection criteria were used. The results show that direct disposal of CO2 ejecting it outside the Autonomous Underwater Vehicle is the most adequate method for navigation depths up to 50 m. For deeper waters CO2 storage embedded in an adsorbent material and CO2 stored as a pressurized gas seem to be the best choices. In all cases, the results present a good stability against changes in the criteria weights vector.