Energy systems for autonomous underwater vehicles

January 21, 2025

Scientists have developed a new energy system for autonomous underwater robots, such as ocean gliders. The system uses hydrogen and oxygen as energy source instead of lithium batteries, which pose major challenges during underwater operations and increase project’s costs. 
 
Sustainable than lithium batteries, the hydrogen-based energy system enables a greater range for ocean gliders. Using a membrane technology, the system extracts oxygen from seawater, almost similar to the functions of a fish’s gills. 
 
Scientists from the Helmholtz-Zentrum Hereon introduced the system that powers gliders with a fuel cell, which generates electricity from hydrogen and oxygen. 
 
Fuel cell power supply system for underwater applications
 
Dr. Lucas Merckelbach and Dr. Prokopios Georgopanos claimed that using this system, a glider can filled up with hydrogen at the deployment site. A container with metal hydrides serves as a safe and efficient storage medium. 
 
The fuel cell power supply system for underwater applications, based on a polymer membrane, harvests the required oxygen from the ambient water. 
 
Published in the journal Advanced Science, the study reveals that in the system, a circulating air-flow continuously supplies a proton exchange membrane fuel cell with oxygen, which is replenished using a polymer membrane.

Prototype system was built based on guidelines
 
The membrane serves as the interface between the circulating air-flow and the ambient water, preventing water flux while allowing an oxygen flux across the membrane, driven by a partial oxygen pressure gradient. To demonstrate the feasibility of this concept, a prototype system was built based on guidelines derived from a mathematical model that was developed to describe the oxygen transfer process, according to the study. 
 
Researchers maintained that the a computational fluid dynamics model is developed and validated against the measurements from the prototype, resulting in a digital twin. The analysis indicates that the proposed power supply system has the potential to be superior to any battery-based solution currently available.

“This system eliminates the need for onboard oxygen storage. The weight and volume saved can be used for additional hydrogen storage, enabling higher energy density and lower operating costs compared to current battery solutions,” explained Georgopanos. This would allow the gliders to operate for longer periods. Furthermore, hydrogen is a more sustainable energy source than batteries, reported Tech Explorer. 
 
Researchers will further optimize the system as part of the MUSE project. Hereon will strengthen its teams at the Institutes of Membrane Research and Hydrogen Technology for this effort. MUSE is a collaborative project with the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) in Bremerhaven, and GEOMAR Helmholtz Center for Ocean Research Kiel, aiming to advance marine technology and infrastructure, according to the report.

In the study, researchers maintained that past work with membrane modules has shown that they can function as artificial gills and sustain small animals underwater.

Researchers demonstrated that a membrane module can also be used to provide oxygen to a fuel cell operating underwater. The experiments carried out show that an equilibrium can be reached where the oxygen consumption by a fuel cell is balanced by the membrane module’s uptake of oxygen from the ambient water, as per the study.