Batteries are the selection of choice for small UUVs due to their simplicity and low cost, but fuel cells are quickly becoming the choice for powering larger UUVs. When the energy storage volume of a UUV starts to exceed 50 liters, fuel cells are capable of offering 2-5x more run time than a Li-Ion battery.
Fuel cells have several secondary benefits when used in larger vehicles. Unlike batteries which take a long time to charge, the fuel cell’s tanks can be refueled quickly, resulting in rapid turnaround times between back to back missions.
The added energy capacity of the fuel cells also allows for reduced operation costs due to the longer run times. Manned surface vessel operating costs are the largest cost associated with operating UUVs. By transitioning from run times of several hours/days to several days/weeks, the need for continuous top-side support is removed. This can result in savings that can recoup the added upfront cost of the fuel cell after just a few missions.