A Modular "Ocean Battery" Could Revolutionize Offshore Wind Power

As the rush to renewable energy intensifies, offshore wind power has grown in prominence. Although wind power has become dramatically cheaper because of technological advances, utilities still need a way to store excess energy when the demand is low.

In addition, there is skepticism of grids supported by renewable energy sources becoming unreliable. During the California blackouts last year, solar and wind power were wrongly blamed for grid failure due to their “intermittency.”

In addressing this concern, long-duration energy storage (LDES) is seen as a solution. LDES encompasses conventional and novel technologies, including mechanical, thermal and electrochemical storage, which can be deployed to store energy for days or even weeks. Essentially, LDES provides flexibility to renewable energy grids, enabling them to absorb and manage fluctuations in demand and supply by storing energy at times of surplus and releasing it when needed.

A recent report prepared by KPMG on behalf of power company Drax found that enough wind power to supply more than a million homes was wasted in 2020, as excess renewable energy could not be stored anywhere. No long-duration storage energy projects have been built in the UK since the 1980s, according to KPMG.

Remarkably, some start-ups are already experimenting with scalable solutions to address storage gaps for excess offshore wind power. Ocean Grazer, a Dutch start-up, has developed an ‘Ocean Battery’ capable of storing energy below an offshore wind farm.

The ocean battery applies the concept of Pumped Storage Hydropower (PSH). This is a type of hydroelectric energy storage that consists of two different elevation water reservoirs, which can generate power as water flows from one to another, passing a turbine. It is commonly utilized in some hydroelectric dams which pump water into a reservoir behind the dam when electricity demand falls, storing it to come back through facility’s turbines.

In the case of ocean battery, excess renewable energy is routed to the ‘battery’ to pump water from its rigid underground reservoirs into flexible bladders (tubes) sitting on the seabed. The water in the tubes is stored under pressure, so when released the water flows quickly and is directed through turbines on the seabed, generating electricity when needed. According to Frits Bliek, the CEO of Ocean Grazer, a prototype designed for deep water has already been tested at the Port of Groningen in Netherlands. A second test for a system modified for shallower waters is also underway.

Last year, the UK government launched a competition targeting innovative “long duration energy storage technologies.” The successful projects, which can store energy for longer than four hours to support renewable energy generation, will be provided with as much as $90 million in capital funding.

A key milestone is in the offing for LDES when renewable energy reaches 60 to 70 percent market share in bulk power systems. Many countries with high climate ambitions aim to reach this target between 2025 and 2035, especially the UK and US, as well as other developed nations which have made net-zero commitments.