An alternative to batteries: researchers store electricity in the ocean

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Written By Marc Helman

Tackling new challenges with a passion for the environment.

New forms of storage are needed to use sustainable energies more efficiently. But where should these be located on a large scale? Some research teams think: The ocean floor is the perfect place!

“How the ocean could be the future of energy storage” is the title of a recent YouTube video on the “Undecided with Matt Ferrell” channel. 

In it, the YouTuber introduces an interesting method of storing solar and wind energy that, rather than covering large land areas, is designed to be placed on the ocean floor.

Only a limited amount of solar and wind energy can be stored using current systems

In the video, Ferrell discusses the problems and limitations of solar and wind power. According to him, more efficient ways to store energy are needed for longer-term use.

Among conventional storage systems, the use of lithium-ion batteries would be obvious. But these can be very expensive, especially if they are to be used for longer-term energy storage. Pumped hydropower storage would also be an option, but they can only be installed in specific locations; thus, their applicability is limited.

But if oceans cover 96 percent of the Earth, why not look at the world’s oceans as potential storage sites? 

As Ferrell explains, projects are already looking at this question, developing energy storage systems to be built at the bottom of lakes and oceans.

BEST or FLASC: which system is better?

One such technology is called Buoyancy Energy Storage Technology (BEST). It was developed by researchers at the International Institute for Applied Systems Analysis (IIASA), headquartered in Laxenburg, Austria. The technology would use a 328×328 ft (100×100 m) platform anchored to the seafloor and filled with compressed gas.

In conjunction with wind turbines on the open sea, the system is supposed to work like this: When the wind farms generate power, motors pull the platform, which is floating on the ocean surface, down to the seafloor. When the stored energy is needed, the motor works reversely, acting as a generator that feeds the released energy into the network.

A Netherlands-based company called FLASC, part of the University of Malta, has also developed underwater energy storage technology. The acronym FLASC stands for “Floating Liquid piston Accumulator using Seawater under Compression,” which roughly translates to “floating piston accumulator using seawater under pressure.”

FLASC relies on pressure and thermodynamic efficiency for its technology. The energy generated is pumped into a closed chamber. When the energy is finally needed, the chamber can run the compressed air through a hydraulic turbine to deliver the energy.

The piston accumulators are said to last for 20 years, making the storage units extremely durable compared to conventional lithium-ion batteries. Also, according to its builders, the FLASC system works even in less deep waters of 20 to 30 meters.

Many questions about underwater storage systems remain unanswered

Currently, however, there are also some hurdles and problems with underwater storage that call into question the practicality of the technologies. For example, according to Ferrell, the current price to store energy using the BEST method is $636 per megawatt-hour, making the system more than twice as expensive as storage using lithium-ion batteries, which is already considered expensive. 

Ferrell notes, however, that the MWh price could be reduced to just under 48 euros with appropriate investment and optimization of the technology. However, according to Ferrell, the question of material resistance and other costs is still unclear.

There is also some need for clarification regarding the FLASC system. 

Although the technology is supposed to work particularly cost-effectively and have impressive longevity, according to the manufacturer, it remains to be seen whether the results in practice will be as good as those calculated by resource planning tools.