Tiny data centre used to heat public swimming pool | Hacker News Reader

Tiny data centre used to heat public swimming pool

bbc.com

73 pointsbreitling97 comments

https://www.techspot.com/news/97995-data-center-uses-waste-h...

What a useless article! I found some actual information here:

https://www.techspot.com/news/97995-data-center-uses-waste-h...

The "data center" produces about 28 kW of heat and the swimming pool has cut its gas bill by 62%. They are saving US$24,000 per year.

I don't know about in swimming centers in England but I do know YMCAs in the US often have budgets that look like:

- Revenue: $25.01M

- Expenses: $25M

So "small savings" like this can add up for them.

This is mostly just due to how nonprofits work. If you have excess revenue, you can’t return it to shareholders so you might as well spend it on mission-oriented activities.

You can, and should, keep it in case you have less revenue next year though.

You can do this up to a point but if it looks like you're actually making a profit it might raise questions eventually. Keeping enough to cover one year's operating costs is pretty common though.

God forbid a non-profit try and compete honestly

Non-profits usually don't "compete" at least in the economic sense. They exist for a charitable purpose that isn't normally well-served by the competitive market.

First of all, charity is a christian concept that has no role in modern secular society. Anything worth doing out of the kindness of our hearts is worth doing collectively without expecting individuals do disproportionately sacrifice.

Second, of course zero-margin processes have an economic role. That is what market efficiency looks like. The entire point of competition is to produce these economic processes. The american brain can't fathom getting their money's worth lol

> Anything worth doing out of the kindness of our hearts is worth doing collectively without expecting individuals do disproportionately sacrifice.

What are you saying here? Like, how are you distinguishing individual charity from the thing "worth doing collectively"? Presumably you don't consider individuals voluntarily giving and thus voluntarily organizing insofar as they coordinate to be the same as collective action, so I can't help but wonder which part is different, and I worry it's the voluntary bit....

Yes. I think people should be forced at gunpoint to contribute to their society. Typically that gunpoint is the state, but we seem to be allergic to having a functional society. Why be proud of your country when you can be a narcissist who steps over the homeless on the way to your job?

Non-profits have treasury functions.. it is prudent that many of them have some sort of cash reserves.

> They are saving US$24,000 per year.

Keeping in mind that the datacenter operator is also paying the power bill for that (which presumably is roughly 28 kW), amounting to something like £65,000/year at current UK rates

> 28 kW

So not even a single rack by modern standards.

All data centers that are in controversial areas should offer free heated swimming pools for the neighborhood. You could add a giant pool complex as a percentage or two of the cost of a big data center.

This is an unironically good idea

unfortunately, it's like saying all billionaires should let people swim in their pools when they're away.

also not a bad idea

Surely it's just cheaper to build further away from residential areas? For this to work you'd need to be close to residential areas, but that's where you get the most NIMBY opposition. And if the datacenter is in the middle of some industrial park, who would want to drive 30 minutes to an industrial park to have a swim?

The last place I lived, the nearest data centre was a few hundred meters from the local swimming pool, in a business park. Most people would never have known the data centre was there.

Elsewhere, e.g. in London, Docklands is both full of high density data centres and high-end residential buildings and offices that could certain use the waste heat in winter at least.

Most of the data centres there just looks like office buildings on the outside, and most residents won't know they are there.

The best waterparks in Tucson, AZ were on the outskirts of the city and worked great as a place to "travel" to for the parents as the kids would be wiped out on the way back. Breakers....Justins....how i miss those days of running around on hot pavement or gravel in bare feat only to also step on some cactus...

Hah yeah if you, as a parent, can survive a day at the water park in the sun then you’re all set for some quiet time when you get home. Waterparks zap kids and they pass out cold in the car as soon as the doors close. Same goes for the beach.

An outdoor heated pool that’s open all winter in a cold climate would be a destination worth a drive. A rather decadent use of energy otherwise, it’d be a good use for waste heat. There’s prior art in the Blue Lagoon in Iceland, a destination spa that uses water from a geothermal power plant.

The Blue Lagoon is more like using waste cold than waste heat.

As a kid I have memories of driving a bit out the edge of town to a big steel plant for almost exactly this reason, it's not totally insane.

There's plenty of free parking, free admission, giant pool with some small waterslides and stuff, a bunch of picnic tables and public barbecues, generally some nice greenery and trees for shade, ponds and fountains and stuff, a bandstand, etc.

It's not somewhere you'd pop over to for a "quick swim", but especially for lower income people it's a great place to have around as a "grab a pack of hotdogs and your swim trunks and make a day of it" sort of thing. As a kid we couldn't afford to, say, go to the actual waterslide park or anything so I have a lot of fond memories of visiting the steel plant.

I'm sure the construction and upkeep was less than a rounding error in terms of construction and upkeep costs for the plant itself.

Rather than pools specifically, maybe they could design District Heating systems.

I was thinking more like if they externalized the heat release of the data centers enough they might even be able to heat the whole globe!

Most of the globe is above the boiling temperature of water due to trapped radionuclides since, well, the beginning.

Probably not, at least, I’m pretty sure the heat directly produced by power consumption is minuscule compared to the global warming contribution of the fossil fuels used to produce it, right?

and AI deniers were saying we were gonna get boiled like frogs, instead we got free heated swimming pools, wait a minute ...

Have some free garlic butter cube - and some congnac to cool down.. its on the house.. truffles?

I like to think that the heating, much like their ideal govermental oversight, would have no regulation. I can almost hear the anguished cries of pool goers when a new model gets released and the temperature spikes.

I feel like this is one of those things that sounds good, but it's not. It's probably cheaper to build it far away from residential areas, and it's probably better for the people living there to not live too close to a data center.

Why, is there some hidden downside to living by a data center? Northern VA real estate is super pricey but they’ve got tons of them

The new ones are being built with massive numbers of unpermitted gas turbines with the exhaust filters removed, because there's not enough electricity and there isn't enough grid power and exhaust filtering costs money. So they're giving entire nearby towns asthma. They're also so loud the whole town can't sleep.

Data centers were, and still can be, some of the cleanest industrial facilities - but the ones being built in this AI wave are not, because they are being built as cheaply and as quickly as possible and without regards to proper infrastructure.

> The new ones are being built with massive numbers of unpermitted gas turbines with the exhaust filters removed

That’s every local investigative journalist’s wet dream. Can you link us to a source please?

PS saw an interview with he who shouldn’t be named and they made an interesting point that there isn’t a way to scale the manufacturing of gas turbine blades, there will never be enough gas turbines for these DCs to come online as scheduled.

https://www.epw.senate.gov/public/index.cfm/2026/4/whitehous... not quite local investigative journalism but should suffice

here's something more local and what i would expect. However, it's murky [link at the bottom]

"Mississippi officials told xAI it could run the generators without an air permit because they were deemed “temporary” and “mobile” units.". Makes sense because as far as i can tell they were on trailers.

but then there's this: "But lawyers at the Southern Environmental Law Center, representing the NAACP in the federal lawsuit, have long maintained that such a loophole doesn’t exist, and that running such turbines without a permit violates the federal Clean Air Act.

“Mobile, temporary, portable, whatever you want to call them, turbines need air permits,” Patrick Anderson, a center attorney, told Mississippi Today."

as per typical, it's not clear who's right

https://mississippitoday.org/2026/04/15/data-center-turbines...

why must we tear up undeveloped areas for data centers instead of backfilling vacant industrial areas? Humanity will never rest until all of the world is a brownfield

It's cheaper to build on vacant land than to get construction equipment and materials into a built up area, possibly discovering underground tanks and other surprises that can inflate the project cost, etc. City ordinances may also limit work hours and/or noise.

Rural land is cheap and there are fewer neighbors to annoy with the 24/7 construction activity.

The current NIMBY trend with respect to DCs guarantees it.

All data centers that are in controversial areas should subsidize the electric bill of residents within the county affected

free sauna

free hot tub

free publicity and good will gathered

("free")

Personally, I think these data centers should be championing and pushing for district heating and cooling.

Even smaller data centers will be producing enough waste heat to heat 10s of thousands of homes. So why not make residents love you by funding the installation of a district heating system which gives your compute power a symbiotic relationship with the community. Their energy bills go down naturally because your cooling efforts are heating their homes and cooling their homes and you spend less in the winter cooling your servers because that heat is being distributed throughout the community.

It doesn't even have to be free district heating/cooling, just cheaper than using electric or gas heaters.

Here is a Swiss one that heats 6,000 apartments.

https://d4project.org/

> The data center delivers up to 1.7 MW of reusable heat – enough enough to warm 6,000 energy-efficient homes in winter or provide 20,000 five-minute showers every day in summer.

https://blog.siemens.com/2026/05/sustainable-data-infomaniak...

https://news.infomaniak.com/en/infomaniak-inaugurates-a-revo...

Something I have been wondering: Why don't data centres use the excess heat for a sort of energy recuperation, turning at least some of it back into electricity?

I saw on TV a long time ago that a funeral home's "energy" (burning bodies) was used to heat homes somewhere in Europe.

We can just use data centers for heating too...maybe turn around all these protests against them

If wishes were fishes.

There's lots of district heating in Germany for example, but it's usually fed from either big heat pumps, bio mass plants, or heat from waste incineration plants. There's no reason to not use excess heat from data centres too - I'm pretty sure I read that already being done in several places.

But in some cases, a data centre might be too remotely located, or the infrastructure is too lacking to make it economically feasible, which still leaves me wondering why you couldn't try to recuperate at least some of it as electricity on-site...

> I'm pretty sure I read that already being done in several places.

Presumably you read this very recently, since it's mentioned at the end of the article.

Sid Meier's Alpha Centauri: "It is every citizen's final duty to go into the tanks, and become one with all the people."

Doesn't "tanks" imply some sort of composting operation, rather than burning bodies?

Yes, it's not an identical situation, but I thought it was relevant because of the concept of recovering a dead body's resources for consumption by the remaining living humans.

It's not anywhere near hot enough to generate steam and make electricity.

There are uses for low grade heat but they require colocation and careful design, which costs more than just dumping the heat.

It actually is, just not water steam. There's a hot springs resort in Alaska that uses pentane (boiling point 38C) to generate energy. The efficiency is terrible, of course.

True. Chena Hot Springs [1]. They are famous in the "direct use" geothermal community.

A lot of the thermal energy is not used for electrical generation. Although a small portion actually is -- made possible by the \Delta T rejecting heat at a low annual average atmospheric T.

Most of the rest of the heat is used to run an absorption chiller to maintain the ice "palace" in the summer.

(This info might be slightly outdated. It was true about 2018 or thereabouts when I met the owner of the resort at a geothermal conference.)

[1] <https://www.chenahotsprings.com/>.

Because it's not economical, the required hardware is unlikely to pay for itself during its lifetime. The gradient is too small (~50C), which means low Carnot efficiency. Additionally, extraction of low-enthalpy energy involves obstruction of heat transfer, meaning lower cooling efficiency. It may have been a different story if we had computer hardware able to efficiently operate at 200-300C.

Even steel plants which deal with significantly higher waste heat gradients rarely bother with recovering energy.

> It may have been a different story if we had computer hardware able to efficiently operate at 200-300C.

Do I see a market opening here?

The degree to which you can extract energy from heat depends on the temperature difference compared to ambient. Efficient power stations all need super heated steam (like 600C). This would be like 100C max which is not very useful for generating electricity. It's fine for heating houses and swimming pools though.

The concept of waste-heat-to-power (WHP) exists, but its efficiency is limited by thermodynamics. Basically, heat energy is not equal to usable energy. All energy ultimately wants to be heat energy, and it is much easier and more efficient to go from electrical or mechanical energy to heat than vice-versa. Therefore, when you do have an application that actually wants heat, not electricity, such as a public swimming pool or district heating, it is way more efficient to use your waste heat as heat. Even in cases where the desired temperature is wildly different from that of your waste heat, you can convert one heat level into another very efficiently using heat pumps.

Look up Carnot efficiency. The maximum amount of work you can theoretically extract depends only on a temperature difference. For a datacenter running chips at 100C into ambient air at 60F, it's about 25%. So even with perfect capture, you are guaranteed to lose 3/4 of your input energy to the datacenter as heat anyway.

For comparison, an IC engine has a Carnot efficiency of something like 80% on paper, but the reality you get is only 20-30%

Undecided just did an episode on a waste heat machine that is being slowly rolled out to industry. The founder of the company is also the guy who invented the Super Soaker.

https://www.youtube.com/watch?v=MuQRxatte5g

Carnot's law of thermodynamics says you can only do this effectively if you can run the computers at a few hundred, or ideally thousand, degrees C.

Landauer's principle says that even if we could build computers to work at those temperatures, they'd need more power anyway.

I recently watched a short video by Matt Ferrell going over the R&D for an electric generator that does just that [1].

[1] https://youtu.be/MuQRxatte5g?is=GUyY4kPH-7WklV1E

In my home town the local steel plant has been connected to the district heating systems for half a century. This is extremely mature technology and widely used in parts of the world where heating homes is more important than cooling them.

> The heat generated by a washing-machine-sized data centre is being used to heat a Devon public swimming pool.

You mean server.

Eyeballing my washing machine leads me to believe they have a quarter rack or so.

LinusTechTips did this at home. https://www.youtube.com/watch?v=d-4JJbk3ZS0

District heating is a mature technology. Direct Use geothermal heat is the one I am personally most familiar with -- as a geophysicist. However "waste" heat utilization is a definite thing for people with mechanical engineering/heat and mass transfer training.

(Edited to add: there are several examples of public swimming pools being heated with Low T geothermal heat in the Perth metropolitan region of Western Australia.)

Equinix AM3 provides heat to the Amsterdam Science Park.

Undisclosed large Swiss private corporate datacenter provides heat to residential complexes in the surrounding area, as well as being integrated with the grid operator and required to spin up generators and island itself on demand, as part of the license to operate.

Many such cases!

Is it feasible to do this at smaller scales? Would be cool to use my compurers to heat water at home. Put all that useless heat to good use.

Air conditioners could do it too, right? Pump heat into a water reservoir instead of just throwing it away?

Some people use cryptocurrency miners to heat their homes. It's certainly better than dumb resistive heating, but depending on various conditions it can cost more than installing a heat pump.

A dedicated heat pump would be cheaper if we consider heating to be the device's primary purpose. The idea is the computers are doing all sorts of useful things, and the heat is just a free byproduct of that activity.

I have a pool heater and an air conditioner, and I'm running both at the same time. They're fifty feet apart, but this thought crosses my mind constantly.

This does exist btw.

It's a stainless steel coil that you can put on your A/C and then run water from your pool over it to heat the pool.

https://www.youtube.com/watch?v=J7fB8ul9dZw

The sticker on the side of the doohickey in the video really gives the whole thing a feeling of "a dude makes these by hand in his garage." I looked up "AC pool heat exchanger" and lo and behold, the same company showed up as the first result:

https://www.hotspotenergy.com/titanium-pool-heat-exchangers/

I have connected the radiator of my homeserver liquid cooling setup to the heat exchanger of my hot water heat pump. Not sure how efficient it is, but I get a measurable drop in CPU temperatures while the heat pump runs.

Linus Tech Talk (LTT) did a whole series on doing this on the pool at the channel hosts’ house. Extravagant home upgrades are a frequent topic on that YouTube channel… business expense write off yada yada. My general takeaway was, yikes, all that piping and infrastructure would be a nightmare to maintain and will likely just be closed off whenever an issue comes up (or he sells). I’m no expert, but I am a home owner, and have come to form a deep appreciation for maintaining simplicity when it comes to the operation of your house.

>Air conditioners could do it too, right?

Some heat pumps do this. E.g. Panasonic Aquarea EcoFleX. When cooling the house, the domestic hot water tank is used to dump heat into (up to a certain temperature).

Years ago I worked at a fast-food restaurant and they used all the heat from their ice makers to pre-heat water for washing up.

heata.co do precisely this with hot water tanks

(I work there)

> Is it feasible to do this at smaller scales?

You need a lot of heat to do anything useful. I would need to run something like 14 kW of servers to heat my home through winter - that's a couple of hundred thousand in hardware at current prices.

Providing remote heat is a common thing in Switzerland[1]. Just like Waste valorisation plants[2] that additionally produce electricity.

[1] https://www.computerwoche.de/article/2690747/rechenzentrum-h...

[2] https://stefan.schueller.net/posts/kva-winterthur/

France did one better...

Paris 2024: Excess Data Center Heat Used to Warm Olympic Swimming Pools

https://www.datacenterknowledge.com/sustainability/paris-202...

Bathhouse in New York wrote about this. Not sure they still do it to this day.

https://help.abathhouse.com/hc/en-us/articles/16748674443924...

I don't understand how a server (the "washing-machine-sized datacenter") can heat up any fraction of a swimming pool appreciably. Wouldn't it be a few kW tops?

GPU power density is very high. The B300, for example, is rated at 1400W TDP. You can fit a lot of B300s in the space of a washing machine.

And more importantly, once the pool is warm enough (or in a very hot day), doesn't it lose its cooling efficiency?

A 30C swimming pool vs a 70C GPU is plenty of temperature difference for a heat exchanger to work with. And even indoor swimming pools have horrific levels of heat loss due to evaporation. But I think the key thing here is that they've undersized the server rack - if its only offsetting 60% of the heating bill, there's a fair margin still being handled by a regular heat pump, which can cycle down in warmer weather.

Pre-GPU times you'd be right, but these days a 4U server could have 8 GPUs pulling 350+ watts each. A washing machine sized unit could contain perhaps 4 of these 4U servers so the unit as a whole could be drawing upwards of 11kW.

No expert but I would think an indoor pool in a temperature controlled environment would control for a lot of heat loss from the water.

This washing machine sized box draws 50kW of power. It wouldn't be able to heat up a cold swimming pool very much, but it would be enough to keep a pool that's already hot at a stable temperature.

You can fit, according to Nvidia, ~40 H100 GPUs in a 16U rack. That's 40 kW of power draw (and heat!) in roughly the space of a washing machine

> Start-up Deep Green charges clients to use its computing power for artificial intelligence and machine learning.

What about running the compute workloads of the municipality instead?

I doubt the municipality needs 28kW of GPU compute, and certainly not at the prices someone like Deep Green is going to be charging.

So this proves that data centers are bad for the environment? Scale this up, and it's clear our oceans are screwed.

The date of the article is 2023.

> "Sean Day, who runs the leisure centre, said he had been expecting its energy bills to rise by £100,000 this year.

"The partnership has really helped us reduce the costs of what has been astronomical over the last 12 months - our energy prices and gas prices have gone through the roof," he said.

...

Last summer, BBC News revealed 65 swimming pools had closed since 2019, with rising energy costs cited as a significant reason."

That's terrible that pools are closing. No one even builds new public swimming pools anymore, so it's awful to close the few that exist.

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