How 40-Ton Spinning Wheels Are Saving the Power Grid

When Spain’s power grid failed on April 28th, 2025, it quickly became a very serious issue. Not only for the economic impacts, but life-or-death serious due to multiple, indirect deaths associated to the blackout. Emergency services, transportation, communication and other vital services were halted during this power outage. Not only did it blackout Spain, it also hit Portugal, parts of France and Morocco¹ But here’s the thing … the UK went through something very similar back in 2019. The difference is: they’ve already figured out how to stop it from happening again. Spoiler: it involves 40 metric ton flywheels. Lots of them.

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We’ve covered flywheels before. But there’s a wild new use case involving technology originally designed for space lasers. Yeah, you heard that right.

Are flywheels really gaining momentum or are we just trying to reinvent the wheel?

FESS 101

We’ve covered flywheels, or more accurately, flywheel energy storage systems (or FESSs) before, but if you’re new here, no worries, let’s get you caught up. What is a flywheel? It’s essentially a mechanical battery, a big, heavy wheel that stores energy as inertia. See, Newton’s First Law of Motion means that once that big heavy wheel gets up to speed, it really doesn’t want to stop. With very little extra input we can keep that wheel spinning. How do we get the energy back out? We tap the flywheel’s rotational inertia to turn a generator’s rotor, and voila electricity.²

Flywheels are known for surprisingly good round-trip efficiency (RTE). That’s the percentage of stored electricity you can get back out. No system has 100% RTE, but flywheels routinely hit 90 to 95%, making them energy storage chart toppers. They’re not flawless but we’ll dig into that later.³

Flywheels are also a really good partner for renewables for a variety of reasons. Renewables are great, but they are prone to short-term voltage fluctuations based on the weather, demand spikes and other stressors. See, an unfortunately notable advantage that fossil-fuel-burners have over renewables is that they incorporate some kind of spinning generator or rotor. This is a byproduct of the ol’ “spicy rock make steam, steam turn doohickey, doohickey make electricity.”⁴

This rotational inertia is actually very important as it helps smooth over voltage fluctuations and sudden ups-and-downs in demand that can lead to blackouts. I’m sure you can see where I’m going with this now. Spain’s grid is laudably, mostly renewables. The lack of rotors meant the grid was unable to absorb a sudden surge in voltage and the following deviations in frequency.⁵

Flywheels can add this flexible rotational element back into our renewable systems, all while serving as a mechanical battery. They’re quick on their feet, so to speak, able to charge and discharge at supercapacitor speeds, and thus handily spot-fill those gaps or absorb excess juice and keep everything humming along.⁴

Based on the Spain blackout, it’s clear we really need everything humming along. Remember, the Spain and Portugal blackout didn’t just leave people in the dark. It knocked out power for tens of millions of people and indirectly cost human lives. Once a grid goes down like that, you can’t just flip a switch to bring it back. It takes hours to slowly reenergize the grid and bring it back from zero.

How the UK Already Solved This

Back in 2019, the UK went through some blackouts very similar to Spain’s recent mishap.⁶ And as Professor Keith Pullen of City St George’s, University of London points out, 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. Beyond heating and cooling, consider everything else we need to electrify and then throw in the energy gluttons that are data centers and yeah, we could use some help.⁷

Seeing as the UK already went through something like this, it’s maybe not a surprise that they’re jumping in with both feet. In response to their own blackout, the UK’s National Energy System Operator (NESO) rolled out what they called a “world-first” program to contract grid-stabilizing projects. One of their biggest partners is Norwegian company Statkraft.⁷ Not to be confused with Statcraft or Kraftwerk, Statkraft claims to be Europe’s largest producer of renewable energy. They’ve got all sorts of green energy projects up and running, though the one most relevant to flywheels is Greener Grid Park in Liverpool.⁸

This facility first opened its doors in 2023, and is, maybe ironically, right by a former coal-fired power station. The facility houses two giant flywheels weighing in at 40 metric tons each (40,000 kilograms, or ~88,000 lbs). Each flywheel is attached to a synchronous compensator.⁹ We talked about this in our last flywheel video, but this is like a flywheel for your flywheel: it adds additional voltage stability while boosting that inertia. There’s also some batteries for longer term storage. According to Statkraft this site supplies 1% of the inertia for the entire grid of England, Scotland and Wales. And it’s not alone. NESO has 11 similar projects already operating in Britain since 2023, and there are plans for more.⁹

This is the playbook Spain needed. And it’s already working.

Where Are They Now?

Last year, we explored the spread of FESSs that were popping up around the world. A couple of them have had some big updates. Are they revving up, or spinning out?

Torus out of Salt Lake City is really gaining momentum. You could say that like their flywheels, Torus is spinning up. They’ve struck deals with a wide range of customers, from ski resorts to Salt Lake City International Airport.¹⁰ And they’re even stepping out of commercial scale into utility scale. In February of 2025, Rocky Mountain Power and Torus signed a memorandum of understanding for 70 MW of FESS-battery combos.¹¹¹⁰

In 2025, Torus opened GigaOne, a 540,000-square-foot manufacturing campus in Salt Lake City. They expect to scale-up production by more than one gigawatt per quarter within three years.¹² And in September 2025, Torus secured a $200 million investment from Magnetar to accelerate deployment for utilities, data centers, and commercial customers.¹³ The data center connection is what really catches my eye there, with how much power they consume. We’ll check in again with Torus soon to see if they can keep up this momentum.

Amber Kinetics has the most exciting news. Quick recap: Amber Kinetics is a technology spin-off from U.C. Berkeley, specializing in FESSs. They’ve been deployed everywhere from Australia, to Hawaii, to the Philippines and more.¹⁴

The big news is that they’re teaming up with Kawasaki Heavy Industries (KHI), the Japanese industrial giant. Amber Kinetics is bringing their FESSs to the table, and KHI is bringing their Virtual Synchronous Generator (iVSG) technology.¹⁵ Think of it as software that helps solar and wind play nice with the grid by smoothing out voltage hiccups. Sound familiar? But unlike a FESS it does this via software that includes dampening effects and implements a “virtual swing equation.” Without going down a whole rabbit hole, this is software that essentially helps power generators that lack that all important rotating component behave like they have one.¹⁶ This is essential for proper frequency control, especially for sensitive electronics like servers and data center hardware.

Why combine these technologies? Well they work well together. The iVSG is the brain and the FESS is the brawn, giving us multiple layers of protection from blackouts while letting renewables go hogwild. According to a press release, KHI chose Amber Kinetics due to:

“…its superior features like unlimited cycling, no fire or explosion risk, and no environmental disposal issues, as well as AK’s proven track record of having more than 1.5 million cumulative operating hours.”¹⁵

The Philippines and Japan are first targets for this combo.¹⁵

There’s a few more updates on companies we’ve covered in the past, which is in the extended cut of this video over on Patreon if you’d like to check that out. But we’ve got to talk about how space lasers tie into this.

Dinglun is the biggest FESS on Earth. That’s the Dinglun Flywheel Energy Storage Power Station in China’s Changzhi. With 120 advanced high-speed magnetic levitation flywheel units, this 30 MW FESS is the biggest on the planet. Since it was connected to the local grid in September of 2024 there hasn’t been much news,¹⁷ but that might be a language barrier issue. Dinglun is the first FESS of its kind for China, and there were hopes that the early success here would lead to more flywheels, especially as China is installing more renewables than any other economy on earth. But so far, nothing. I’m going to have to assume no news is good news on both accounts, at least for now.¹⁸

Moneypoint in Ireland has the single largest flywheel ever made. On June 20, 2025, Moneypoint burned its last load of coal, officially making Ireland the 15th European country to go coal-free.¹⁹ But there’s a catch. They’ve switched to heavy fuel oil for emergency use. Still a fossil fuel, but one that emits less carbon emissions than coal per unit.²⁰ Maybe that’s a win … sort of. If everything goes according to plan, Moneypoint will kick fuel oil in 2029 and go fully green when their offshore windfarm comes online in 2030.¹⁹ Those are the kind of deadlines that historically have a bad habit of slipping or falling through. Given what they’ve accomplished so far, and given what the UK has accomplished, I feel optimistic about Moneypoint.

And that’s just the companies we’ve previously checked out.

Space Lasers to Port Cranes

As you might expect from a technology that’s spinning up as fast as flywheels, there’s some new wheels on the block.

Flywheels are popping up at the Port of Rotterdam in the Netherlands, and the port wants to be CO2 neutral by 2050.²¹

The Port of Rotterdam is working with the German company Rhenus Logistics and Dutch-based QuinteQ Energy on a flywheel pilot demo. QuinteQ has developed a containerized flywheel energy storage system designed to work with cranes. Why cranes? Well, most modern ports are full of them, and they spend a lot of time idle until a massive cargo ship shows up. Then it’s go time, and they need a ton of power. This creates massive power consumption peaks and valleys that can be hard to manage. However, QuinteQ’s system can provide Rhenus Logistics’ cranes with close to 400 kW of power. The pilot project revealed that flywheels can reduce peak power demand from the cranes by up to 65%.²¹ That’s huge.

This is just a small and very specific test, though it does bode well. Like other European countries, the Netherlands is facing grid congestion.²² Basically, the country has rapidly electrified, and energy demand has outpaced the grid operator’s current capacity.²³ Getting sufficient power could take years, but flywheels can be the perfect gap-fixer until we get there. And in the port-specific use case, according to Rhenus Logistics, the power that the flywheel saves the cranes is ‘freed up’ and can go somewhere else it’s needed.²¹

Here’s the wild part. QuinteQ’s flywheel technology didn’t originate in the Netherlands. It came from Boeing. The aerospace giant was doing research on laser-based space defenses for the U.S. government. The idea was to have lasers shoot down projectiles, but lasers need a lot of power. And if you’re shooting things down, you need that power fast. Again, with their quick charge and discharge times, flywheels seemed like the way to go. Boeing actually managed to develop and test four flywheels for these kind of ultra high-power space systems. When the program was shut down, QuinteQ was able to obtain the IP with the aid of Boeing and adapted it for less-lasery applications.²⁴

So yeah. Space laser tech is now running port cranes. The future is weird.

Drawbacks

As neat as flywheels are, they’re far from perfect.

Their most obvious flaw is that they’re constantly fighting against friction. Even the most souped-up, carbon fiber bodied, magnetic bearing’d, vacuum chambered of flywheels will encounter some kind of friction that will eventually slow it down. Flywheels lose about 5 to 20% of their energy per hour.²⁵ So, long term storage isn’t really an option. That’s why they’re often paired with batteries, but of course that means additional engineering challenges and costs.

Speaking of costs, we’ve got a bit of a mixed bag. Flywheels have long lives and don’t need a ton of maintenance due to their simple working principle. That does save some costs in the long run. However, they’re very expensive upfront.⁴ By necessity, flywheels need to be made from materials that can stand up to the incredible speeds and weights being thrown around. Often carbon fiber, which isn’t too expensive but also isn’t cheap. For best results, we want to cheat the physics of friction and optimize our flywheel’s performance. This is fairly simple to do. We just mentioned magnetic bearings to reduce mechanical friction, vacuum chambers to reduce air drag and the like. This is especially important when your entire country is relying on the flywheel energy storage system to prevent another deadly blackout. Custom-optimized systems are going to come with custom-optimized price tags.²⁶

Worsening those upfront costs is the danger element. Flywheels are very safe, but they’re very heavy objects spinning at very fast speeds. Should something go wrong, they can instantly become massive kinetic missiles that can destroy everything in their path. Heck, even if a flywheel doesn’t break free of its housing it can occasionally tear itself apart, flinging around many smaller, kinetic shards.²⁷ This means that flywheels have to be placed very carefully, and it’s often best practice to place them in special wells. Excavating these wells isn’t cheap and can really drive up the overall cost. To be clear, the chances of a catastrophic-oopsie are very slim, though it’s best to not take chances.²⁶

It’s also worth mentioning that, in order to meet some of the decarbonization goals, there simply aren’t enough flywheels being produced. Current grid stabilization in the UK is accomplished through gas generators, though they are slowly being replaced by flywheels and other technologies.⁹ It’s not so much a technology problem as it is a scale up problem.

Outlook

What does the future hold for the flywheel? Well, let me be clear. I don’t think these are silver bullets. What do I mean by that? FESSs are very specific technologies, they store and release energy quickly but not for a long time, and that’s necessarily going to limit where and when we can use them. They have a specific niche, and while they’re good at it, they probably won’t expand beyond that niche. However, that niche is widening, if that makes sense.

As we continue to kick fossil fuels to the curb, we’re going to rely on renewables, and for safety that means, likely relying on flywheels. And as successes in the UK and several other countries have shown flywheels are doing a pretty solid job out here in the real world.

The demand for energy will only continue to grow, thanks to the exponential growth of data centers These things are being built at a crazy rate and consume an even crazier amount of power. FESSs can help make these centers place less pressure on the grid, or at the very least, make the grid better able to handle a brand new data center that’s suddenly consuming a ton of energy.²⁸

Also, one of the key advantages with flywheels is their ability to go many “charging” and “uncharging” cycles without diminished capacity. ²⁹ Batteries suffer from this. When paired with batteries, flywheels offer some advantages, such that if there is a grid dip, one or the other can be implemented. This type of pairing will likely become more common in the future. ²⁹

The markets reflect this. According to one estimate from Straits Research, the global flywheel energy storage market size was valued at $434.58 million USD in 2024 and is projected to more than double to $983.55 million USD by 2033.³⁰ So, while flywheels might not solve all of our energy problems, they feel like an increasingly important tool to have in our utilities’ utility belt.