Ocean Grazer will test an energy storage system in a sand quarry

In the future, we will use more sustainable wind and solar energy. However, due to weather conditions, energy availability fluctuates. That’s why electricity storage systems are essential. The Ocean Grazer hydroelectric plant can store excess energy from wind farms on the seabed or in sand quarries. This year they will test the prototype.

The transition towards more sustainable energy requires the expansion of offshore wind farms. An important advantage of the Ocean Grazer system is its ability to scale with the efficiency of wind farms. The storage system consists of many interconnected, independent units, which allows for smooth expansion as the wind farm grows. Moreover, in the event of a failure, maintenance can be carried out without having to shut down the entire system.

How it’s working

The system consists of a pump and large bags installed on the seabed. When the wind turbine generates surplus energy, it activates a pump that draws water from an underground reservoir into bags. The pressure of seawater compresses the bags, and when energy is needed, they release water that drives turbines to generate electricity. In addition, the ocean battery is suitable for operation in shallow waters, including the North Sea.

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Compete with conventional systems

Ultimately, the company wants to compete with conventional storage systems. Company president Frits Bliek, earlier during a webinar hosted by KIVI Elektrotechniek: “In those moments when you have a surplus, you can convert energy into hydrogen. We are moving more and more towards hydrogen solutions also in the Netherlands. However, this does not provide a very high level of performance.” Converting electricity to hydrogen is about 75 percent efficient, while an ocean battery can reach 80 percent, the company says.

There are other advantages too. The battery is balanced on several levels. “With the exception of the magnet in the pump, we do not use any rare earth materials. This happens, for example, when you start using lithium batteries in large quantities. In addition, we use water in the storage system. So if the system were to leak, no pollutants would enter the sea.” According to Blik, the storage system could be used as an artificial reef. “All in all, I think we have a very positive impact on the environment.”

What can we learn from the sea? What role can the ocean play in generating renewable energy? And how can innovation help us take better care of the sea? You will find out in our latest issue: IO Next: The Ocean.

Prototype testing

In 2021, Ocean Grazer completed the first phase of testing of its storage system in Eemshaven, Groningen. Now it’s time for the next step. Ocean Grazer is preparing a demonstration plant for sand mining in Sellingerbeetse, also Groningen. The battery will be placed at a depth of 50 meters and has a power of 3MW. The system includes an underground tank 200 meters long and 15 meters in diameter. By implementing a project on land, the company can closely monitor conditions and easily make any adjustments without the challenges of working at sea. Moreover, this land-based project shows that it is possible to use inland waters.

“There are about 500 sand quarries in the Netherlands where our system can be built,” Bliek said. “There are plans to build floating solar parks in multiple locations. The discovery of numerous locations in the Netherlands intended for the construction of photovoltaic parks was an eye-opener. This is another completely new market for us.”

By 2025, the company intends to demonstrate the readiness of the batteries to store energy on the seabed.