Massachusetts Institute of Technology (MIT) (Cambridge, Massachusetts) spinout Open Water Power (OWP), recently acquired by L3 Technologies (New York, New York), is developing an aluminum/water power system that it says is safer, cheaper, and more durable for unpiloted underwater vehicles (UUVs) than lithium-ion batteries.
While many UUVs use lithium-based batteries, OWP says these batteries are flammable, have limited energy density, and must be encased in expensive metal pressure vessels.
In contrast, their system consists of an alloyed aluminum anode, a cathode alloyed with several elements (primarily nickel), and an alkaline electrolyte positioned between electrodes.
When these UUVs are placed in the ocean, seawater is pulled into the battery and splits at the cathode into hydroxide anions and hydrogen gas. The hydroxide anions interact with the aluminum anode, creating aluminum hydroxide and releasing electrons. Those electrons travel back toward the cathode, donating energy to a circuit along the way to begin the cycle anew. Both the aluminum hydroxide and hydrogen gas are jettisoned as harmless waste.
Components are only activated when the battery is flooded with water. Once the aluminum anode corrodes, it can be replaced at low cost.
With their system, OWP says UUVs can launch from shore and without a need for service ships. To that end, the group is working with the U.S. Navy (Washington, DC) to replace batteries in acoustic sensors designed to detect enemy submarines. In mid-2017, a pilot was launched with Riptide Autonomous Solutions (Pembroke, Massachusetts) to use the UUVs for surveys. Currently, Riptide’s UUVs can travel ~100 nautical miles (185 km), but OWP believes it can raise the distance to ~1,000 nautical miles (1,852 km).
Source: MIT, news.mit.edu.