Our Guide to Liquid Cooling in Data Centres

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Release date: 25 July 2024

Diving into Heat Management for HPC Data Centres

According to a recent survey by The Register, over a third (38.3%) of enterprises expect to deploy liquid cooling in their data centres by 2026, a significant increase from 20.1% in early 2024. We saw this trend reflected during our time at Computex 2023, where a huge number of vendors showcased liquid cooling solutions. Not long ago, these were seen as exotic solutions for a few enthusiasts and specialists. Now with CPUs and GPUs becoming denser and more power-hungry, liquid cooling is entering the mainstream.

This is a validation of what those of us in the industry have known for some time: liquid cooling provides unparalleled heat dissipation capabilities, energy efficiency, and cost savings. As data centres face rising energy costs and increasingly dense computing environments, traditional air-cooling methods are struggling to meet thermal management demands effectively.

The market is fast accepting this fact – but with the pace of innovation, even seasoned industry leaders can find it difficult to evaluate the return on investment from liquid cooling. Here’s a quick guide to help keep you up to date with the top types of liquid cooling systems and their implementation, to their benefits and real-world applications in modern data centre infrastructures.

Why Liquid?

The benefits of liquid cooling are worth spelling out in detail. Fundamentally, each generation of GPUs and CPUs is going to be more powerful than the last, and that comes with more heat buildup. Liquid cooling can manage significantly higher heat loads per rack compared to traditional air cooling, so is better suited to the incoming wave of chips.

This is the key strategic consideration, but there’s a host of other advantages as well. Liquid cooling is significantly less energy intensive than air cooling, meaning electrical costs are slashed along with the centre’s carbon footprint. The increased cooling efficiency keeps hardware at a lower operating temperature overall, prolonging its life. Liquid systems also take up minimal space, allowing greater computing density.

Liquid Cooling: The Future of Thermal Management is Here

Its many and varied benefits make liquid cooling a virtual no-brainer when it comes to the future of data centres. The next question leaders need to ask themselves is: what kind of liquid cooling is right for my business?

Direct Liquid Cooling (DLC)

Direct Liquid Cooling (DLC) is probably what most people think of when they hear the term liquid cooling. This approach involves coolant being circulated directly over components.

DLC is currently the most widespread form of the technology and businesses are deploying it in a fast-growing number of platforms. This is a case of necessity being the mother of invention: as models become more complex and, therefore, more resource intensive, standard cooling methods are proving insufficient to manage the increased heat output. As such, there’s been an explosion in the number of major companies offering DLC products.

Innovations like trillion-parameter AI models promise to revolutionise the world we live in, from real-time translation to medical uses – but they can only do so if the hardware used to run and train them is up to the job. Chip companies have taken note. Earlier this year, NVIDIA announced the GB200 NVL72 system, which uses DLC and can deliver 25x lower cost and energy consumption. The fact that leading AI companies like NVIDIA are putting serious effort into DLC cements the technology as vital to the future of the AI ecosystem.

Immersion Cooling

Immersion technology works on the same principle as DLC, but rather than using liquid to cool individual components, servers are fully submerged in a dielectric liquid. With ever more scrutiny on data centre sustainability, this as an attractive option for many providers. Total submersion provides the best possible thermal dissipation, reducing electricity usage on cooling and improving energy efficiency.

On top of this, companies can use excess heat from immersion cooled systems to provide heating to local communities, cutting energy bills and reliance on energy from fossil fuels. Examples of this have already been trialled in the UK, with data centre provider Deep Green using small data centres to heat local swimming pools.

Of course, placing expensive electrical equipment in large vats of liquid isn’t without its risks. Companies must have detailed knowledge of their whole supply chain to ensure that every single component is suitable for immersion. With the recent move towards supply chain transparency in the industry, immersion cooling is set to become ever more widespread.

Hybrid Approaches

Finally, those managing data centre infrastructure might want to consider an approach which fuses both air and liquid cooling to maximise efficiency.

For many, this is the most realistic option. Equipment in existing centres may be incompatible with full liquid cooling solutions – but careful hybrid applications can be tailored or retrofitted to suit the needs of each unique centre. Hybrid solutions like this are therefore likely to see increased usage as the transition towards liquid cooling gathers pace. On the flipside, some liquid cooled centres may wish to maintain air-cooled functionality for some mission critical applications.

However, it’s worth noting that, in a comparative analysis published by IEEE, a hybrid air-water cooled system achieved a partial Power Usage Effectiveness (PUE) of 1.48, while a fully immersed liquid-cooled system attained a partial PUE of 1.14, making the liquid-cooled system 34% more efficient.[i]

Critical Considerations

With all this in mind, how can enterprises decide what’s best for their business?

Among the first things to consider is how to choose a coolant. The liquid should be stable, eco-friendly, and conductive. Options such as fluorinated liquid and mineral oil are common due to their low-volatility. On top of this, data centre managers need robust leak detection, and careful planning to ensure current systems are integrated effectively.

Cooling All Stations!

It’s clear that for data centres, the future is liquid. After all, the technology is fluid—constantly evolving and improving to meet business needs—and companies that want to be prepared for the future must remain vigilant to these changes. Leaders should expect heat reuse and sustainable infrastructure to move to the forefront of public discourse in the next few years, and begin to consider how liquid cooling can be integrated into public infrastructure for mutual benefit. Ultimately, it’s about implementing the wide and exciting array of new technologies in whichever way best suits your business.

At Vespertec, we work hard to remain one step ahead of industry trends, so that our clients know about cutting edge developments before they hit the mainstream. Connect with us today if you’d like to learn more about how liquid cooling can future-proof your data centre operations.

References:

[i] Y. Q. Chi et al., “Case study of a data centre using enclosed, immersed, direct liquid-cooled servers,” 2014 Semiconductor Thermal Measurement and Management Symposium (SEMI-THERM), San Jose, CA, USA, 2014, pp. 164-173, doi: 10.1109/SEMI-THERM.2014.6892234. keywords: {Direct dielectric liquid cooling;immersed microelectronics;data centre cooling},