US works on underwater UUV recharging

The US Navy is developing ways to use undersea wireless technology for recharging underwater unmanned vehicles (UUVs), with the goal of significantly reducing the time between missions by charging UUV batteries while they are underwater.

UUVs are used for a variety of missions by the navy, including the location and identification of underwater threats such as mines, ocean floor mapping, and optimising remote sensing platforms. The ability to transfer data and energy underwater is expected to multiply the effectiveness of these operations.

Work is currently focused on the development of a vehicle-agnostic method for autonomous underwater energy charging.

A number of demonstrations have been carried out in this field, including the Naval Surface Warfare Center, Carderock Division (NSWCCD) carrying out a successful underwater wireless energy transfer demonstration in a 6,000 gallon tank.

These concepts of wireless underwater energy transfer, such as Forward Deployed Energy and Forward Deployed Energy and Communications Outpost (FDECO), were born in NSWCCD's Disruptive Technologies Lab.

The demonstration used the Naval Undersea Warfare Center-developed Mid-sized Autonomous Research Vehicle (MARV) UUV – a 16.5ft system designed to test different UUV programmes and technologies. 

Power was successfully transmitted wirelessly from an underwater docking station to a MARV UUV section, and ultimately to the UUV's battery, which was charged at 2 kilowatts while submerged.

In order to test that the batteries charged to the highest fidelity, a battery State of Charge (SOC) programme was integrated that used algorithms to pull in data from the battery and then run voltage, current and temperature data through the data acquisition system. 

Mayer Nelson, NSWCCD technical project manager, said: ‘We want to recharge a battery underwater through wireless technology, and we want to know the batteries charge to the highest fidelity.’