Oceanic Energy Storage: How Sizable Energy’s Saltwater Solution Could Revolutionize Grid Power

The Challenge of Renewable Energy Storage

As the world transitions toward renewable energy sources like wind and solar, one critical challenge remains: how to store excess electricity for times when the sun isn’t shining and the wind isn’t blowing. Traditional grid-scale batteries are expensive and have limited duration, while conventional pumped hydro storage requires specific geographical features that aren’t widely available. This storage gap represents one of the most significant obstacles to achieving a fully renewable energy grid., according to recent innovations

The Challenge of Renewable Energy Storage
From Mountain Reservoirs to Ocean Depths
Sizable Energy’s Innovative Design
Advantages Over Traditional Energy Storage
Current Progress and Future Plans
Integration with Renewable Energy Infrastructure
The Future of Ocean-Based Energy Storage

From Mountain Reservoirs to Ocean Depths

Manuele Aufiero, co-founder of Sizable Energy, grew up witnessing an innovative approach to energy storage. His childhood hikes along a pumped-storage hydropower reservoir in northern Italy showed him how water could be used as a massive battery. “I’m in love with pumped hydro,” Aufiero told TechCrunch, “but it’s just not enough to keep up with renewables.”, according to market insights

This childhood inspiration led to a revolutionary idea: what if we could adapt pumped hydro technology for the ocean, where suitable depth is more readily available than the specific mountain topography required for traditional systems?

Sizable Energy’s Innovative Design

Sizable Energy’s solution resembles an underwater hourglass system. The design features two flexible, sealed reservoirs connected by a plastic tube containing turbines. The upper reservoir floats near the surface, while the lower one rests on the seabed. The innovation lies in using salt concentration rather than elevation to create potential energy.

When electricity is abundant and cheap, the system pumps supersaturated saltwater from the bottom reservoir to the top. During periods of high energy demand, a valve opens, and the dense, salty water flows downward due to its higher density compared to surrounding seawater. This flow spins the turbines, which generate electricity back to the grid., according to industry analysis

“From the energy balance point of view, what we are doing is lifting blocks of salt,” Aufiero explained. “But instead of using cranes, we dissolve it and pump it because it’s easier and simpler. Other than that, we are just lifting a heavy amount of salt.”, according to technological advances

Advantages Over Traditional Energy Storage

Sizable’s oceanic approach offers several significant advantages over existing storage technologies:, as as previously reported, according to recent innovations

Mass production potential: Unlike land-based pumped hydro that requires custom engineering for each site, Sizable’s offshore systems can be standardized and manufactured at scale
Location flexibility: The technology can be deployed wherever ocean depths reach at least 500 meters (1,640 feet), making it accessible to coastal populations worldwide
Cost efficiency: The company aims to deliver energy storage at approximately €20 per kilowatt-hour, roughly one-tenth the cost of current grid-scale batteries
Long duration storage: The system can generate electricity for extended periods, addressing one of the key limitations of battery storage

Current Progress and Future Plans

With recent funding of $8 million led by Playground Global, Sizable Energy has moved from concept to testing. The company has successfully tested small-scale models in wave tanks and off the coast of Reggio Calabria, Italy. They’re currently deploying pilot floating components in preparation for a full demonstration plant.

By 2026, Sizable aims to deploy multiple commercial projects worldwide. At full scale, each turbine would generate 6-7 megawatts of electricity, with one turbine installed per 100 meters of pipe. Deeper deployment sites offer greater storage potential, and commercial installations would feature multiple reservoir systems.

Integration with Renewable Energy Infrastructure

The technology presents particularly compelling synergies with offshore wind projects. By sharing electrical connections to shore, both systems can significantly reduce infrastructure costs. According to the International Energy Agency, long-duration energy storage technologies like Sizable’s will be crucial for integrating high percentages of renewable energy into global grids.

“We believe that long duration energy storage is required not only for renewable integration, but also for just making the grid resilient,” Aufiero emphasized. “There’s no way we can keep up with that with traditional pumped hydro or batteries. We need something new.”

The Future of Ocean-Based Energy Storage

As global energy storage capacity continues to grow, innovative solutions like Sizable Energy’s saltwater storage system could play a vital role in creating a reliable, renewable-powered grid. The company’s approach represents a promising middle ground between the massive scale of traditional pumped hydro and the flexibility of battery storage.

If successful, Sizable’s technology could help solve one of renewable energy’s most persistent challenges while opening new possibilities for coastal communities worldwide to harness and store clean electricity from offshore wind, wave, and tidal resources.

References & Further Reading

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