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In Deep Water - Retrofitting Data Centres for Liquid Cooling​

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With data centres having an increasingly significant impact on the global economy, and our growing reliance on technology, AI, and information access, these facilities are turning the heads of investors and users.

 

The influx of AI, amongst other things, has prompted a huge surge in demand for additional data centre capacity. As a result of this, the demand for high-performance computer (HPC) chips capable of running AI software has also skyrocketed. Companies like NVIDIA have seen staggering rises in their stock price since 2018 because of this trend. With this, new technical challenges arise. To put the energy usage of these HPC chips into perspective: a single Google search consumes approximately 0.3 watt-hours of energy. In comparison, a single ChatGPT query requires significantly more, with estimates ranging from 1 to 10 watt-hours.

Power of this magnitude requires significantly higher cooling requirements. Failure to displace the heat build-up around these servers can impair their efficiency and even induce component failures. Traditional data centre cooling methodologies, solely utilising air, are no longer powerful enough to deal with the heat flux generated by these HPCs.

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What is the Solution?...

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Water. Water is far more effective at displacing heat compared to air. Its wide availability and relatively low cost make it an obvious choice for use as a coolant. Other liquids offer similar benefits, but in common, they all require bringing liquids into the whitespace. Something which data centre designers are usually keen to avoid.

There is an array of liquid cooling technologies available that have been implemented in the data centre industry for approximately 20 years. These methods include immersion liquid cooling (single-phase and dual-phase), cold plate liquid cooling, rear-door heat exchangers and spray liquid cooling.

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Liquid cooling is emerging as a superior solution for managing the thermal demands of modern IT infrastructure. By directly transferring heat away from components, liquid cooling significantly improves efficiency compared to traditional air-cooling systems. This leads to lower energy consumption, optimised space utilisation, and reduced operational costs. However, while liquid cooling enables higher efficiency, it also supports greater IT equipment density, which can drive up overall energy consumption as more servers are packed into smaller spaces. This is an important consideration when acknowledging the wider environmental impact of these systems.

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Liquid cooling better maintains consistent thermal conditions, reducing the risk of thermal throttling, which slows hardware to prevent it from overheating. This enables optimal performance, improves reliability, and extends the lifespan of IT equipment by minimising wear and tear.

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From an environmental standpoint, extending the operational life of servers has clear benefits. The manufacturing of IT equipment is resource-intensive and contributes significantly to global CO2 emissions. By increasing the longevity of hardware, liquid cooling reduces the frequency of replacements, helping to minimise the ecological footprint associated with the production and disposal of IT equipment.

In response to these fantastic benefits, many operators and investors are looking to upgrade their existing portfolios by retrofitting their IT infrastructure with these liquid cooling technologies.

 

So, What is the Problem?...

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This technology is almost marketed as the ‘wonder drug’ to solve all cooling problems in upgrading data centres, however, there are several challenges the industry is currently facing and things to consider before rushing to implement liquid cooling and jumping on the AI craze.

 

When retrofitting a facility, the existing building shell is, often, going to be sub-optimal for liquid cooling – this is inherent as this is not the building’s original design purpose - careful considerations must be made concerning the cooling capabilities of the site. While liquid cooling will allow greater IT densities, the available space to provide mechanical cooling (i.e. chillers, cooling towers etc.) may not be available, especially if the original facility previously had direct expansion cooling or direct air cooling. As liquid cooling requires chillers for liquid cooling, this problem is more prominent in areas where land prices are high and buildings have been designed to be multistorey, allowing little freedom for additional chiller placement on roofs. This then limits the capacity of IT that can be deployed, and results in a highly inefficient use of data hall space. The increased rack density also means there is a higher floor loading that the existing building may not be designed to withstand.

 

The key to implementing liquid cooling technology is flexibility - specifically, design flexibility. This means the facility must be able to accommodate both air and liquid cooling at later stages of its design/development. The ability to switch between these cooling methods is what defines the facility’s overall adaptability and readiness for future needs. This is much easier said than done. Designing a facility for flexibility is not always straightforward and is expensive, this only gets worse when carrying out a retrofit. Carefully considering customers' needs and working with customers is crucial to ensure you do not end up with an extremely expensive, ghost town of a data hall.

 

On the commercial side of things, you must pay extra attention to what market you are trying to reach. Is there a market for small-scale liquid cooling? Is there a specific use case that operators with larger-scale deployment and more capital are not going to target? It is important to remember the demand for air-cooled IT equipment has not gone anywhere and continues to grow. The market for air-cooling is currently valued at approximately $8bn (2024) and expected to rise to around $11.5bn by 2028, with liquid cooling expected to take up a greater proportion of the market.

 

As this technology has only seen increased use in data centres in recent years, who knows if it is here to stay? Take 3D TVs for example, while the initial prospect of dinosaurs, and explosions coming out of your home entertainment system sounds great, and was for a while - the entire market took a dive when everyone got tired of choosing between spending the remainder of an evening with a headache and strained eyes, or watching a blurry movie because you got sick of wearing the unflattering, awkward and bulky glasses. As a result, many people were left with a pricey, and rather useless gimmicky TV set in their homes after the fad died. While this is clearly being a little cynical, the same scepticism towards the longevity of the liquid-cooling market should be taken before plunging into what should be considered quite a risky venture.

 

There are magnitudes of other technical, social, and regulatory obstacles to consider too that apply to liquid cooling in a more general sense.

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The Takeaway?

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This article takes a sceptical view of this new and exciting emerging data centre technology. However, it is not all bleak…

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As technology progresses, liquid cooling solutions are becoming more cost-effective, making them increasingly favourable for meeting the rising cooling requirements. The growing use of HPCs, limitations in space and power availability, coupled with the high-costs of this technology, will stimulate the development of innovative strategies for converting existing data centre facilities into hybrid liquid cooling setups that can cater to both air and liquid cooling.

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At VIPA Digital, we recognise the potential of these advancements and are here to assist organisations in navigating this transition. Our consultancy services can help you evaluate your current infrastructure and determine the most effective approach to integrate liquid cooling solutions.

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However, before you start putting all your CRAHs and fans in the bin, remember that air-cooling is not going anywhere and the liquid cooling market has many challenges that are both inherent and due to its lack of maturity. Partnering with VIPA Digital can ensure you adopt a balanced, informed approach to your cooling strategies, leveraging the best of both technologies for optimal performance.

 

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Author : Felix Maldonado, VIPA Digital

 

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