Offshore wind farms are poised to become a major source of electricity in the coming years, with China and the UK leading the charge. The higher wind speeds over the ocean provide a steady supply of power in a convenient location. But what happens when demand for electricity is low? One emerging thought is to use the ocean itself as a battery — and, as far-fetched as it sounds, the idea just might hold water.

The Problem

The wind has no off switch. It turns the world’s turbines even when people are sleeping, generating excess power that has no outlet. In 2020, the UK — a wind energy leader — wasted enough wind-generated electricity to supply over one million homes due to a lack of storage facilities.

Fluctuations in energy supply and demand can affect the price of electricity, leading to unstable energy bills for consumers. Brownouts and blackouts could occur in communities relying solely on wind power without a storage system.

The ocean represents a vast untapped resource for energy storage. Water covers 71% of the planet’s surface, of which 96.5% is salty. However, lithium — an essential mineral for building on-shore batteries — corrodes easily, especially in the presence of seawater. The price of lithium has also skyrocketed and made the material hard to come by.

Wind power decreases global carbon dioxide emissions by about 1.1 billion tons annually and is gaining popularity as an energy source. As many countries ramp up their offshore wind production, there is a mounting need for durable underwater batteries.

Ocean Battery

Dutch startup Ocean Grazer may have found a way to harness the water with its Ocean Battery. Resembling a garden hose encased in a concrete reservoir, the bladder-based storage system swells with water when energy production is high, storing the water’s potential energy. During peak demand periods, it relaxes and lets the water flow out again, powering a turbine that creates electricity.

The concept — which won a Best of Innovation award at the 2022 Las Vegas Consumer Electronics Show — is similar to pumped-storage hydroelectricity, in which pumps raise water to a higher altitude during low energy demand and release it to drive turbines when people need it most. It features a modular design for easy customization. Builders can connect as few or as many rigid reservoir building blocks as they need for each project, creating the desired storage volume.

Buoyancy Energy Storage Technology

Another contender for an ocean storage battery is the Buoyancy Energy Storage Technology (BEST) from the International Institute for Applied Systems Analysis (IIASA). BEST operates on the same principle as Ocean Battery, but it uses compressed air instead of water.

As wind turbines generate power, they drive electric motors that pull high-density polyethylene pipes toward the ocean floor. Because the air-filled pipes are straining to float upward, they hold tremendous potential energy. BEST releases the tubes during periods of peak energy demand to drive a motor that generates electricity.

Pumped-Storage Hydropower

Theoretically, pumping water to a higher altitude could work just as well underwater as it does on land. An underwater pumped-storage system would include a power plant on the water and an enclosed, seawater-filled vessel on the ocean floor.

When wind turbines generate excess electricity, the pumps direct water out of the vessel, leaving the inside almost empty. The water flows through a turbine and back into the vessel during peak energy demand periods to generate electricity.

The Stored Energy at Sea project put this idea to the test in 2016. Researchers tested a model one-tenth of the actual size in a lake in Germany, finding that it worked well at around 700 meters deep and could store 20 MWh of electricity on a full charge.

Testing the Waters

Engineers are hard at work researching various underwater battery designs. Offshore wind has become a crucial energy source in recent years, and putting it to good use means not letting anything go to waste. Currently, all battery designs operate on the principle of stored potential energy, saving precious resources like lithium and cobalt while operating out of the public eye. Before long, these batteries could be an integral part of the world’s energy infrastructure.