Giant Spinning Wheels Are Preventing Grid Blackouts

When Spain's grid failed on April 28th, 2025, it wasn't just an inconvenience. The blackout cascaded across Portugal, parts of France, and Morocco, leaving tens of millions without power. People died—indirectly, yes, but dead is dead. Emergency services went dark. Transportation stopped. Communication networks collapsed.

The UK faced something similar in 2019. Their response? Forty-ton flywheels. Lots of them. And they're working.

Matt Ferrell's latest video walks through how these massive mechanical batteries are becoming critical infrastructure for renewable grids—and how technology Boeing developed for shooting down missiles with space lasers ended up stabilizing port cranes in Rotterdam. The trajectory from defense research to mundane grid management is a reminder that infrastructure solutions often come from unexpected places.

The Physics Problem Renewables Created

Here's what makes this interesting: fossil fuel power plants have an accidental advantage. All that "spicy rock make steam, steam turn doohickey" infrastructure creates rotational inertia—massive turbines that don't want to stop spinning. That inertia smooths out voltage fluctuations and demand spikes. It's physics doing grid management.

Renewables don't have rotating mass. Solar panels and wind turbines generate electricity differently, and that's created a stability problem as grids shift away from fossil fuels. Spain's grid is mostly renewable now. When voltage surged on April 28th, there wasn't enough inertia to absorb it. The frequency deviated. The grid collapsed.

Flywheels solve this by adding back what renewables removed: big heavy things that spin. A flywheel energy storage system is exactly what it sounds like—a massive wheel (often carbon fiber, sometimes steel) spinning in a vacuum chamber on magnetic bearings. Once it's up to speed, Newton's first law keeps it there with minimal energy input. When the grid needs power, the flywheel's rotational energy drives a generator. When there's excess power, it spins the wheel faster.

The roundtrip efficiency is impressive: 90-95%, making flywheels among the most efficient storage technologies available. They charge and discharge at supercapacitor speeds, which makes them perfect for the kind of rapid response that prevents blackouts.

What the UK Actually Built

After their 2019 blackout, the UK's national energy system operator launched what they called a "world first" program to contract grid-stabilizing projects. Norwegian energy company Statkraft partnered with them to build Greener Grid Park in Liverpool—ironically located next to a decommissioned coal plant.

The facility houses two 40-ton flywheels paired with synchronous compensators (think of it as a flywheel for your flywheel—adding even more voltage stability) and batteries for longer-term storage. According to Statkraft, this single site supplies 1% of the inertia for the entire grid serving England, Scotland, and Wales.

That's just one facility. The UK now has 11 flywheel projects operating since 2023, with more planned. Professor Keith Pullen of City St. George's University of London notes that "these sorts of blackouts are only going to become more common as we incorporate more renewables into the grid and demand gets spikier and less predictable."

It's a preview of what Spain needed and didn't have.

The Commercial Momentum

Ferrell's video also tracks the commercial expansion happening in this space. Torus, a Salt Lake City company, has scaled from ski resorts to Salt Lake City International Airport to utility-scale deployments. In February 2025, they signed a deal with Rocky Mountain Power for 70 megawatts of flywheel-battery hybrid systems. They opened a 540,000 square-foot manufacturing campus and secured $200 million in funding.

Amber Kinetics, a UC Berkeley spin-off, partnered with Kawasaki Heavy Industries to combine flywheel hardware with virtual synchronous generator software—essentially teaching renewable systems to behave like they have rotational mass even when they don't. According to their press release, Kawasaki chose Amber Kinetics for "unlimited cycling, no fire or explosion risk, and no environmental disposal issues," plus 1.5 million cumulative operating hours.

The global flywheel energy storage market was valued at $434 million in 2024 and is projected to hit $983 million by 2033. That's not exponential growth, but it's steady expansion in a specific niche.

From Space Lasers to Port Cranes

The Rotterdam story is where this gets genuinely weird. The Port of Rotterdam is working toward carbon neutrality by 2050, which means electrifying everything—including the massive cranes that load and unload cargo ships. Those cranes sit idle most of the time, then suddenly need enormous power when ships arrive. That creates grid demand spikes that are hard to manage.

A company called Quinttech Energy developed containerized flywheel systems specifically for this use case, and their pilot project showed 65% reduction in peak power demand from the cranes. The saved power can be redirected elsewhere on the grid.

Here's the twist: Quinttech's flywheel technology came from Boeing's research on laser-based space defense systems. The US government wanted lasers that could shoot down projectiles, but lasers need massive power delivered extremely fast. Boeing developed four flywheels for these ultra-high-power space applications. When the program shut down, Quinttech acquired the IP and adapted it for "less lasery applications."

So yes: technology designed to power orbital weapons is now making Dutch port operations more efficient. The path from defense research to civilian infrastructure is rarely linear.

The Engineering Tradeoffs

Flywheels aren't perfect. They lose 5-20% of stored energy per hour due to friction, which makes long-term storage impossible. That's why they're often paired with batteries—flywheels handle rapid response, batteries handle duration. But combining systems adds complexity and cost.

Upfront costs are substantial. These systems need carbon fiber construction, magnetic bearings, vacuum chambers, and custom engineering to handle the physics of extremely heavy objects spinning at extreme speeds. When your entire grid depends on preventing the next deadly blackout, you optimize everything—which means custom solutions with custom price tags.

There's also the kinetic missile problem. Flywheels are very safe, but if something fails catastrophically, a 40-ton wheel spinning at high speed becomes a weapon. Even partial failure can fling carbon fiber shards in all directions. This is why flywheels are often installed in excavated wells—which adds more cost but significantly reduces risk. Ferrell notes the chances of catastrophic failure are slim, but when you're talking about critical infrastructure, "slim" isn't good enough.

The Niche That's Widening

Ferrell is clear in the video that flywheels aren't silver bullets. They excel at rapid charge-discharge cycles and grid stabilization, but they can't do everything. That specificity limits where they'll be deployed.

But that niche is expanding. As fossil fuels exit the grid, the inertia problem gets worse. As data centers proliferate (Torus is specifically targeting them), demand gets spikier. As electrification accelerates, grid stress increases. Flywheels address all of these dynamics.

The UK's approach—building out flywheel infrastructure before the next crisis rather than after—might become the standard playbook. Spain's blackout demonstrated what happens when you wait. The question isn't whether flywheels have a role in renewable grids. The question is whether other countries will deploy them proactively or wait for their own April 28th moment.

—Dev Kapoor