24
votes
‘World’s largest’ industrial heat battery is online and solar-powered
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- Authors
- Michelle Lewis, Fred Lambert, Jo Borrás, Micah Toll
- Published
- Oct 16 2025
- Word count
- 584 words
From the article:
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Their first customer is not that inspiring, but proving that the heat battery works at scale seems like a big milestone.
There was another story about a 100 MWh heat battery, also said to be the world’s largest of its kind. They seem to be different kinds?
There is a another startup at a much earlier stage that wants to replace the bricks with something cheaper, just heating up an enormous pile of dirt until it becomes sort of brick-like.
It's possible that one is measuring by MW and the other one MWh, but I think they're using a special measurement system called Straight-Up Fucking Lying™. Nobody want's to be the world's second biggest, and the only people who'll notice their Lie are people actively following multiple heat battery companies, and we basically all want heat batteries to succeed (also time spent nitpicking which is the biggest battery is time not spent lecturing on the different heat battery techs, and we both know the latter is more interesting).
I like to understand the situation better before accusing people of straight-up lying. There is often a way in which a claim is technically true, and understanding the details can be interesting.
I did check the details. But then I realized they don't matter (this is a claim in an article's clickbait title, sourced from the company's hypey press release, it's not even the low-low bar of a guinness world record), nobody really cares, and thus I don't need to do more than 5 minutes of checking on such a trivial topic before stating my opinion (couched in "it's possible that [], but I think []"). Especially when I'm looking for a lack of evidence, and I'd already found lack of evidence.
I get what you're saying, but I volunteer someone else to go do that extra legwork.
Fair enough! Other than noticing a similar claim, I’m not going to research it either. But I would go with something like “seems dubious” rather than “straight-up fucking lying.” I guess that’s a matter of style, understatement versus exaggerating for effect.
If only I could invest, eh?!
It looks like you have an editing error. The last paragraph of the first quote is identical to the second quote.
Also, feel free to noise this.
Thanks, fixed!
When it comes to thermal batteries, bigger is definitively better. Square-cube ratio.
I’d read the article but it didn’t make it very clear what this thing actually was, or how it worked. I think I’m more impressed by how simple it all really is.
This is literally a large warehouse filled with bricks. Between some of the rows of bricks are resistive wires that heat up and glow (think of an incandescent lightbulb).
The bricks retain that heat and they can then push air through the bricks to draw the heat out. This acts as a literal heater, like your home furnace, but on an industrial scale.
Truth be told, I’m more curious as to why this isn’t seen more often. Is there some impediment that I’m not seeing here preventing more wide scale adoption in the general market?
Traditionally, you'd just get heat from directly burning fuel, instead of burning fuel to generate electricity to power an electric heater.
It only makes sense in the context of renewables, and more specifically in the context of large scale industrial heat use specifically powered by renewables. Even if it's already profitable to implement Rondo's system, large scale industrial plants are conservative by nature and it's not clear which tech will be the best.
That's how I understand it also.
There are sand based heat batteries that work on the same idea, using sand to store heat energy. They look promising for private property use. Store excess solar during the day, release it at night as heating directly, interesting stuff for sure.
At my mother’s house, we have electric heaters with bricks in them, originally installed to take advantage of cheaper night rates for electricity. Nowadays a heat pump would be a better option.
Why is that? Genuinely curious.
Is it a matter of scale? Are these brick batteries better the bigger you get?
I'm assuming it is meant that it is a better option when purchasing grid electricity because even with lower nightly costs the costs don't fall below the effects of heat pumps. This would happen because heat pumps have an interesting property that allows them to look like they produce more heat than even perfect conversion from electricity to heat. This is due to the fact that they don't use the input electricity to produce heat, they use it to move heat from elsewhere.
I'm just going to make up some random numbers to illustrate. Let's say this is a system with no losses and night time electricity is 80% the cost of day time, 100% effective resistive heating is the baseline, and a low end heat pump that produces 150% as much heat per unit of electricity. With those made up numbers you can see that even if 100% of your heat load from the grid was at the cheaper prices you are still worse off than a heat pump. Notably 150% is a bad heat pump, even for residential. My novice understanding is that 250%+ is more realistic.
Where the batteries really shine is when the energy would otherwise go to waste entirely. For example, the one in the article that uses solar as an input but wants 24/7 heat as output. Without the battery they'd just have too much energy during the day and none at night. Or maybe a solar-powered home could use them as part of their heat by taking the waste solar from the day and holding onto it for the cold nights (effectively the reverse of a standard rate-optimizing home system).
The night rate used to be lower than the day rate but there is little difference now. Also, there is no thermostat. They are set manually and you have to guess a day in advance how much heat you'll need, based on the weather forecast.
It still seems like having lots of insulated thermal mass is good. It doesn't need to be integrated with the heaters.
Maybe they would make more sense if run off solar power?
It wasn't economically useful until relatively recently. Before solar became by far the cheapest source of power generation, there was no reason to create large scale batteries like this. Though simple, it still requires a large amount of engineering, space, and infrastructure.
Honestly as depressing as it is, I suspect the only reason we're seeing this specific project is because the Oil Industry is trying to greenwash itself ("oh wow look at our entirely green solar power source that just so happens to be powering our oil processing plant so we can make real energy. We're making a difference isn't it beautiful how amazing oil and coal can work together with silly little solar!!")
Pessimism aside, it is really cool to see these projects finally come online after hearing about them for so long, there are actually a ton of things like this being prototyped and market tested in the past few years. My favorite being the giant gravity batteries that are being installed in a few places.
Keep in mind that it’s just their first customer who ordered a battery of this size. Energy startups face a lot of skepticism, but after showing that it works well, they can build more for other customers.
Also, using solar power to make fossil fuel infrastructure more efficient seems like further evidence that solar is winning. It’s going to save on natural gas.
I love seeing evidence of solar and other renewables winning out economically over fossil fuels. It's made opponents have to pivot to even more ridiculous arguments against them like their environmental impact (lol) or perhaps something even sillier.