Ocean Temperature as Energy Source: Subsea Robots Powered by Environment Work Indefinitely Without Intervention

Subsea robots can now map the Earth's entire seafloor while saving money and reducing pollution. This is made possible using an energy source that allows the device to work indefinitely.

Challenges in Seafloor Monitoring

When it comes to territorial mapping, NASA has charted new areas that have never been surveyed before. The agency does not only map planets and stars, but it also takes a view of Earth from a vantage point in space.

In mapping the seafloor, it is important to unlock valuable resources without causing harm to the marine ecosystem. This kind of operation can be carried out by aquatic sonar devices, but they can be restricted by batteries, which leave them dead underwater.

NASA has made it a major priority to study Earth, including its icecaps and oceans. The agency has launched satellites with sensors to measure temperatures, sea levels, salinity, and other parameters. Robotic platforms are also deployed both near and below the surface of the ocean to help them interpret the data they measure from space.

Experts find it hard to access most of the open oceans in the world. Energy serves as the most limiting factor, particularly for underwater sensors which cannot depend on the renewable energy source from the Sun, waves, and wind.

At present, all subsea robots are operated with batteries. This means that when the battery dies, the sensor can either be just left underwater or be charged on a ship. The latter can be costly since a ship stationed in the open ocean costs around $50,000 a day and uses tons of diesel as fuel.

Empowering Robots

To address this challenge, NASA has offered the first energy source for underwater robots entirely powered by its marine environment. It enables the devices to indefinitely conduct their operations in the open ocean without the need for any intervention.

The device is based on technology made at Jet Propulsion Laboratory (JPL) and Licensed by the California Institute of Technology. This project is led by Yi Chao, the project scientist who pioneered the ocean thermal energy harvesting project at JPL.

With the help of colleagues from the Jet Propulsion Laboratory, Chao built a unique source of energy for subsea robots. They used phase-change materials to generate materials at certain temperatures.

Most substances, except water and metals, expand upon melting and contract upon freezing. This volume expansion generates kinetic energy, which spins the motor and converts mechanical energy into electricity.

However, only a 10% expansion is created during the transformation from solid to liquid, so the team wanted to maximize the small amount of energy it generates. Using high-efficiency components, they created SL1, the first power module for diving floats.

The device works by changing the temperature of the material by rising and falling through the ocean. They used industry-grade paraffin material, which can be swapped for a higher or lower melting point depending on the environment.

The JPL team created and demonstrated a prototype float in 2011. In the future, they plan to apply for exclusive licensing from the California Institute of Technology and Seatrec, Inc.

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