Submerging servers in liquid helps data centres cut energy use

The Star

19-06-2025

When Daniel Pope first floated the idea of submerging servers in liquid as an energy-efficient way to cool them a few years ago, his proposal was met with overwhelming scepticism from data centre equipment makers. But now, Pope's startup – Barcelona-based Submer – is a multimillion-dollar business, teaming up with technology giants such as Intel Corp and Dell Technologies Inc.
The change in attitude reflects a pressing challenge: figuring out how to run data centres with less energy. The facilities, which support digital services ranging from TikTok to ChatGPT and Google Maps, last year consumed more electricity than Poland, Belgium and Norway combined, according to an April report by the International Energy Agency.
That figure is set to more than double by 2030, driven largely by the massive computing requirements of artificial intelligence. As much as 40% of data centres' energy use goes towards cooling computing hardware, making it a ripe space for innovation.
Among the possible pathways to achieve better efficiency, liquid cooling – an umbrella term that includes solutions such as Submer's – will likely help lower the data centre energy demand by more than 10%, according to Schneider Electric, a leading energy management firm.
'While 10% may not seem like a lot, consider the fact that a large AI data centre can consume over 100 megawatts of power, equivalent to about 75,000 US homes,' says Steven Carlini, who specialises in data centre solutions at Schneider Electric. 'At this scale, cutting energy usage by 10% is progress to be excited about.'
Data centres' power-guzzling nature has made them unwelcome neighbours. Local authorities in Dublin last year rejected an application by Alphabet Inc's Google to build a data centre there, citing concerns over its potential impact on an already stressed electric grid. In recent months, anti-data centre signs have shown up in communities across the US.
While big tech companies have spent billions of dollars sponsoring clean energy projects, their efforts to add more carbon-free electricity lag far behind what's needed. Microsoft Corp, for example, emitted 23% more carbon dioxide last year compared to 2020, due in part to a rapid expansion of data centres. Similarly, Google has seen its carbon emissions up by 48% over the past five years.
A coolant that looks like baby oil
To help tackle that problem, semiconductor manufacturers and data centre operators in recent years have been exploring using liquid to directly cool chips. Microsoft's Maia 100 chip, for instance, is designed to be attached to a cold plate, a metal device that's kept cool by liquid flowing beneath its surface. The tech company has also expressed interest in taking a step further, developing data centres where the whole computing hardware can operate in liquid baths.
Known as immersion cooling, the technology involves plunging an entire server rack – the enclosure that houses servers, switches, routers and other computing components – into a specialised liquid that doesn't conduct electricity. The approach can be more efficient than direct-to-chip cooling, industry watchers say, but immersion cooling doesn't come without its problems, and the nascent sector has a long way to go before it can reach a meaningful scale.
Submer uses a non-flammable synthetic liquid that looks like baby oil. The coolant – created at the startup's laboratory with feedstocks from the oil and gas industry – can also be made with palm oil, says Pope, the company's cofounder. Many immersion cooling liquids in the market contain PFAS, also known as 'forever chemicals' that don't break down naturally, but Pope says Submer's coolant is biodegradable. The liquid absorbs the heat generated by electronics, dissipates it through a heat exchanger built within the cooling container and then returns to the rack for the next round of cooling.
The approach not only reduces energy use; it also tackles another problem. In the US, an average 100-megawatt data centre consumes about 2 million liters of water per day, a big portion of which is used for cooling, the IEA says. Intensive water demands have become an additional flashpoint between data centre developers and local communities, though some operators have started to equip data centres with water reuse or recycling systems to mitigate their environmental impact.
In a way, computing hardware is like a human body: It functions best at certain temperatures. To prevent servers from overheating, many data centres deploy a potent version of air conditioning to blow chilled air across massive server rooms. But liquids can remove heat from solids more efficiently than air, and Submer says its cooling container is able to complete the same task at a higher temperature.
That temperature difference, combined with the fact that immersion cooling targets the equipment that generates heat rather than an entire room, means this strategy uses less energy, Pope says. In a 2023 study funded by the Dutch government, researchers from the University of Groningen found that data centres equipped with immersion cooling used roughly 50% less energy than traditional air cooling. It also enables data centres to occupy less space, the researchers said.
Too hot to handle
Liquids have been used for cooling in high-voltage equipment like transformers for more than a century, but the technique was practically nonexistent in data centres until the recent computing boom started pushing conventional cooling methods to the limit.
The world's appetite for high-performance AI tools not only has sparked a data centre building spree but also made it a lot harder to keep computing hardware operating at its optimal temperature, says Carlini of Schneider Electric. For instance, Nvidia's latest AI chip, the Blackwell B200 GPU, consumes almost two times more power than its predecessor, the Hopper H200. The more power a chip uses, the more heat it dissipates, and thus the more cooling it needs. And a data centre may deploy hundreds, or even thousands, of those chips.
So far, Submer has deployed its cooling containers at dozens of data centres across 17 countries. The startup's revenue climbed to more than €150mil (RM 732.66mil or US $169mil) last year, up from about €600,000 (RM 2.93mil) in 2018, when its commercial sales debuted, Pope says. 'It's gone exponential in the last two years.'
Other companies are also eyeing a slice of this emerging market. That list includes the Netherlands's Asperitas, Texas-based LiquidStack and Fujitsu in Japan. But even so, the market for this technology remains a fraction of what the industry spends on cooling: The global immersion cooling market reached US$400mil (RM 1.70bil) in 2023, compared to nearly US$13bil (RM 55.36bil) in global data centre cooling spending.
Some hurdles stand in the way of wider adoption. While immersion cooling can help data centres lower their utility bills, it isn't cheap. Submer's system can cost as much as 25% more to deploy than the status quo, the company estimates, though it says that it's reached cost parity against air cooling at data centres with a substantial cooling demand.
And for data centre operators with existing facilities, switching over to a whole different cooling technique not only requires modification of computing hardware, but also raises concerns over infrastructure safety: Can their floors withstand the weight of all the cooling containers flooded by liquids?
The lack of industry standards in immersion cooling solutions adds another layer of complexity. Since data centres typically phase out servers every few years, operators would have to consider, for instance, how to ensure the cooling containers they deploy today remain compatible with future computing hardware. Soaking servers in liquid also makes it harder to do maintenance.
'Once you put them in the tubs, it's very messy to do any kind of replacement,' Carlini says.
That doesn't worry Pope, who likens servers designed for air cooling to cars. 'You shouldn't put a car in the water,' he says. To that end, Submer is working with the semiconductor industry to develop 'boats' – a new generation of servers designed for the new cooling method. – Bloomberg