Ocean Grazer , a Dutch-based startup and a spinoff from the University of Groningen, developed an inventive way to store offshore renewable energy where it is produced: offshore.


The “Ocean Battery” is a very large energy-storage system designed to capture excess power from floating wind farms. With a combination of pumps, flexible bladders, and rigid reservoirs, the Ocean Grazer team took a tried-and-true energy concept – the hydrodam – and brought it to the sea. How the system works: Excess power from nearby windfarms is routed to the battery, which is installed deep into the ocean floor. The battery pumps freshwater from the stiff underground reservoirs to a bladder just above the seabed. When there is a demand for power, the water, pressurized naturally from the sea, is routed back through hydroturbines to generate electricity.


A prototype of the Ocean Battery has been deployed at Groningen seaports. The small-scale demonstration, along with other planned demos in artificial lakes around the Netherlands, aim to showcase viability for bigger implementations that integrate with large-scale, renewable power generation.


An oversupply of wind energy leads to negative energy prices and eventually blackouts. The Battery addresses the surplus by storing excess output and acting as a potential moderator of supply and demand – an intriguing perk as the world increasingly turns to renewable power.


While the system has been in development at the University of Groningen since 2014, the Ocean Battery was one of 15 technologies selected as “Best of Innovation” at this year’s CES – the annual Las Vegas, NV-based showcase of new and cutting-edge products.

“It’s a very efficient cycle. You can keep 80 percent of the power that you inject,” Ocean Grazer CEO Dr. Frits Bliek said in our Here’s an Idea podcast, available now at TechBriefs.com/podcast.

Contact Dr. Frits Bliek at This email address is being protected from spambots. You need JavaScript enabled to view it. ; +31 (0) 50 211 51 68

A prototype is installed and tested at a Groningen seaport. (Photo: Ocean Grazer)