How One Startup Plans to Turn the Ocean into a Giant Battery

A Childhood Spark

When Manuele Aufiero was a kid, his parents often took him hiking around a reservoir tucked in the hills of northern Italy. At first glance, it looked ordinary calm water, rocky banks, that faint scent of wet stone. But there was something unusual about this reservoir. It never stayed still. The water level would rise and fall in strange rhythms, like the whole lake was breathing.

As Aufiero later learned, those fluctuations weren’t random. Massive pumps deep below the surface were working tirelessly pushing water uphill when electricity was cheap and letting it flow back down when power demand spiked. It was an elegant dance between gravity and engineering, turning stored water into stored energy.

That reservoir, though he didn’t know it then, was teaching him about pumped storage hydropower one of humanity’s oldest and most quietly brilliant methods of storing electricity.

The Power of Water, Reimagined

Pumped hydro has been around for more than a century. It’s deceptively simple: when there’s excess electricity, you use it to pump water uphill into a reservoir. When you need that energy back, you let gravity do the work the water rushes down, spins turbines, and voilà, electricity returns to the grid.

These systems are massive. The International Energy Agency estimates that pumped hydro facilities worldwide store roughly 8,500 gigawatt hours of electricity. That’s not some small backup system it’s the world’s biggest “battery,” quietly humming in the background of the global power grid.

And it’s not just a relic of the past. As wind and solar power have surged, pumped hydro’s importance has actually grown. Unlike lithium ion batteries, which fade after a few hours, pumped hydro can keep generating power for much longer often for entire nights or cloudy days when renewable output dips.

There’s just one big catch: geography. You need two large bodies of water at different elevations and the right geological conditions to make it work. And there are only so many spots on Earth that meet those criteria.

An Idea Born at Sea

That geographical limitation is what pushed Aufiero to think differently. “I’m in love with pumped hydro,” he told TechCrunch with a grin. “It’s just not enough to keep up with renewables.”

So he decided to take the idea somewhere most people wouldn’t think to look underwater.

He co founded Sizable Energy, a startup that aims to take the same basic principle of pumped hydro and transplant it into the ocean. No mountains, no dams just pressure, gravity, and clever design.

How It Works The Hourglass Beneath the Waves

Imagine a giant, flexible hourglass floating in the deep sea. That’s roughly what Sizable’s design looks like. The system relies on two massive reservoirs one buoyant and floating near the surface, the other resting on the seabed below. A large tube connects the two, housing turbines that spin as water moves between them.

When electricity is plentiful (say, on a sunny afternoon when solar panels are flooding the grid), pumps push water downward from the top reservoir into the bottom one. Later, when energy demand rises perhaps after sunset the system reverses. Water rushes upward through the turbines, generating electricity in the process.

The beauty of the idea lies in its scalability. You can place these systems almost anywhere in the ocean, adjusting depth and capacity based on local conditions. There’s no need for mountains or rivers just the natural weight of seawater and engineering precision.

Backed by Big Names

The idea isn’t just theoretical anymore. Sizable Energy recently secured $8 million in funding, led by Playground Global and joined by EDEN/IAG, Exa Ventures, Satgana, Unruly Capital, and Verve Ventures.

That’s a serious vote of confidence in a concept that sits somewhere between bold and borderline futuristic using the ocean itself as a massive, decentralized energy storage network.

Of course, $8 million isn’t much in the world of energy infrastructure, where single turbines can cost millions on their own. But it’s enough to move from whiteboard to prototype and that’s where ideas either sink or swim, quite literally in this case.

Why Ocean Storage Matters

Energy storage is one of the biggest hurdles in the shift to renewables. Solar and wind are incredible, but they’re also unpredictable. The sun doesn’t always shine, and wind patterns are fickle. Without efficient storage, grids either waste excess energy or fall short when demand peaks.

Lithium ion batteries, while improving, can’t yet handle the scale or duration needed for national grids. They’re great for short bursts a few hours of balancing but not for sustaining power overnight or across several cloudy days.

That’s where systems like Sizable’s could change the game. The ocean offers nearly unlimited “space” and consistent pressure, which can be harnessed for long duration energy storage. In theory, an underwater pumped hydro system could run for many hours or even days depending on the setup.

Not Without Challenges

Of course, the ocean isn’t exactly a friendly lab environment. Saltwater corrodes almost everything. Marine life complicates construction. Maintenance at depth is expensive and logistically demanding. And then there’s the issue of environmental impact placing massive structures on the seafloor could disrupt ecosystems we still barely understand.

Aufiero and his team are well aware of that. They claim their design minimizes interference, using flexible materials and sealed reservoirs rather than rigid concrete. Still, it’s early days. The real test will come when prototypes face months of actual sea conditions waves, currents, pressure, and all.

The Bigger Picture

What’s exciting about Sizable Energy isn’t just the specific technology it’s the mindset behind it. For decades, renewable energy has been limited by geography: solar in sunny places, wind in windy ones, hydro in mountainous regions. Moving storage offshore could loosen those constraints, making clean energy more adaptable and widespread.

There’s also something poetic about the idea. The same oceans that once powered early civilizations through trade, exploration, and even myth might one day serve as the batteries of a sustainable world.

It’s a reminder that sometimes innovation isn’t about inventing something entirely new. It’s about looking at an old idea in this case, pumped hydro and asking, what if we just moved it somewhere unexpected?

A Future Still Underwater

For now, Sizable Energy is still in the early stages. Its prototype is under development, and it’ll be a while before we see ocean batteries dotting coastlines. But the potential is enormous and so is the challenge.

The sea has always been both a friend and a test for human ingenuity. If Aufiero’s team can make their underwater hourglass work reliably and affordably, it could transform how we store and distribute renewable energy around the globe.

And maybe, one day, those quiet tides lapping against the shore won’t just be a sound of nature they’ll be the hum of stored electricity waiting patiently beneath the waves.

Open Your Mind !!!

Source: FlipBoard

Open Your Mind