Colorado engineers plan to test 3D-printed concrete spheres that store electricity by moving seawater in and out

An innovative concrete sphere technology could transform long-duration renewable electricity storage.

Clean energy generation is rapidly expanding nationwide to meet rising power demand more sustainably.

But storing excess energy has become more challenging, as traditional land-based storage options face severe limitations.

By using seafloor-based energy storage, offshore communities can overcome traditional bottlenecks while accelerating offshore green capacity.

To overcome these barriers, a unique 3D-printed subsea technology has been developed.

Will using underwater concrete spheres powered by natural water pressure meet coastal power networks’ grid-scale storage needs?

How coastal communities are facing worsening grid-scale challenges

Power grid pressures have become more compounded across the United States’ coastal regions.

Along these shoreline communities, rapid electrification and heavy urban concentration are driving record-high electricity demand.

At the same time, land-based power assets are increasingly facing severe physical risks.

This is due to rising sea levels, extreme marine weather, and salt-spray corrosion.

Likewise, accelerated offshore renewable growth has further complicated grid balance.

Offshore wind capacity is rapidly expanding off the U.S. coasts to meet ambitious state and federal targets.

Total U.S. offshore wind generation capacity has reached approximately 974 megawatts.

However, this offshore electricity production remains highly variable.

When production hours peak, quick offshore power surges threaten to overload onshore transmission lines and substations.

This has created an urgent need for high-capacity storage for excess clean energy production.

Unfortunately, traditional storage systems face significant bottlenecks.

As a result, federal agencies are actively seeking innovative technologies to address these worsening grid-scale challenges.

A rising need for more unconventional electricity storage solutions

While large-scale battery storage capacity has significantly grown in the U.S., these systems still face challenges.

Land-based utility-scale battery facilities require vast tracts of land.

In densely populated coastal regions, this triggers severe land-use competition.

Chemical batteries also have high capital costs and suffer from accelerated degradation in humid marine environments.

While pumped-hydro storage solutions have become more popular in the U.S., conventional methods require specific elevated terrain.

This is usually lacking across flat shoreline topography.

To overcome these terrestrial limitations, developers are exploring unconventional marine storage systems.

The U.S. Department of Energy (DOE) is driving this storage shift.

Operating through its Hydropower and Hydrokinetic Office (H2O), 14 innovative hydropower projects have been selected across 12 states.

Each of these projects has earned voucher support through the Hydropower Testing Network program.

Among these funded initiatives is a groundbreaking subsea 3D-printed concrete sphere project.

By gaining critical federal support, this technology’s commercial readiness can be accelerated.

Achieving long-duration energy storage using ocean pressure

Long-duration energy storage projects are taking off across the country.

The 3D-printed concrete sphere project chosen by the U.S. DOE was developed by Colorado-based company Sperra.

Modular, hollow concrete spheres are produced in port facilities using automated 3D concrete printing and locally sourced materials.

The spheres are then submerged and anchored to the seafloor at depths between 1,900 and 2,600 feet.

At these depths, natural hydraulic pressure is exceptionally high.

Functioning as an underwater pumped-storage hydropower system

When intermittent energy generation exceeds demand, excess electricity powers subsea pumps to push seawater out of the sphere.

A vacuum-like low-pressure cavity is created inside the structure.

As electricity consumption increases, a valve opens, letting high-pressure seawater rush into the sphere.

The high pressure of water entering spins an integrated turbine-generator.

Clean electricity is then dispatched back to the grid.

Sperra partnered with Polaris EcoSystems to conduct comprehensive modeling, techno-economic validation, and physical testing.

Should the federally supported testing deliver positive findings, the system will move toward commercial deployment.

However, this subsea concrete sphere technology does offer a scalable framework for coastal grid stability.

By using seafloor-based energy storage, offshore communities can overcome traditional bottlenecks while accelerating offshore green capacity.

Ultimately, turning to innovative long-duration energy storage systems is key to meeting the country’s grid-scale needs.