Researchers at MIT University in the US have built an innovative battery that uses seawater. It is intended to power electricity autonomous submarine vehicles so that they can travel much longer and reach greater depths than today.
This aluminum-water battery increases up to ten times the radius of an undersea robot compared to conventional lithium-ion batteries (from 100 to about 1,000 nautical miles). MIT researchers, led by engineer Ian Salmon Mackay, did not succeed in creating their subsidiary Open Water Power (OWP) to promote their invention and their company was acquired by L3 Technologies.
The new battery is expected to offer new capabilities to underwater robots to investigate shipwrecks, mapping the seabed, exploration for oil exploration, and other scientific studies – beyond, of course, the various military applications. Already, OWP is working with the US Navy to replace the batteries of acoustic sensors that have been mooted in the seas to detect hostile submarines.
The new battery works as follows: when the underwater vehicle enters the seawater, it flows into the battery and separates to the cathode in hydroxide anions and hydrogen gas. The anions interact with the anode from aluminum, creating aluminum hydroxide and releasing electrons. These return to descent, thus providing electricity to the battery circuit.
Both aluminum hydroxide and hydrogen gas are discharged from the battery as harmless waste. When the aluminum anode pole is eroded, it can be replaced at a low cost. The battery only works when it is immersed in water.
Thanks to this new long-lasting battery, underwater robots no longer need to be released from parent ships in the middle of the sea, but they can start shipping off the coast, opening up new possibilities and reducing their operating costs. Underwater vehicles with such batteries will be able to cover hundreds of nautical miles and then return from where they started, without any new source of energy being needed in the meantime.