“Seawater-drinking” battery could expand range of underwater drones

The recent acquisition of MIT spinout Open Water Power (OWP) by defence company L3 Technologies will help with the development of its innovative battery technology for a wide range of undersea applications, the company says.

OWP is currently working with the US Navy to develop new batteries for acoustic sensors designed to detect enemy submarines. It now also plans to work on technologies for unmanned underwater vehicles (UUVs) for ocean floor monitoring, sonar buoys and other marine research devices. Its next partnership will be with Riptide Autonomous Solutions, which will UUVs for underwater surveys.

The new type of battery is claimed to be safer and more durable than lithium ion technology, and according to OWP could increase the range of UUVs tenfold, while also making their operation easier.

The system consists of three main components: an aluminium alloy anode, an alkaline electrolyte containing potassium hydroxide, and a nickel-alloy cathode designed to split water into hydrogen and hydroxide ions, similar to those used in systems for enriching the air in crewed submarines with oxygen. When the battery is submerged in the sea, seawater is pulled in and split at the cathode. The hydroxide ions react with the aluminium anode, creating aluminium hydroxide and releasing electrons which travel back to the cathode, donating energy to a circuit along the way. The anode gradually corrodes, and can be replaced at low cost, while the hydrogen and aluminium hydroxide — precipitated as a solid into a foam rubber sponge — are jettisoned as waste.