The benefits of liquid cooling for data centres

The current global market for liquid cooling is still in its infancy, with most of the world’s data centres still relying on convective airflow cooling. However, as the ever-increasing demand for frontier technologies adds greater need for cost effective energy and environmental-friendly solutions, it’s estimated that liquid cooling will grow 10.7% by 2025. With more forward-thinking from the industry, we hope that adoption will rise even further.

The scale of a nation’s data centres has become an indicator of national ICT competitiveness, yet maintaining large-scale data centres comes at a price. The internal cooling systems of data centres consume enormous amounts of electricity each year, significantly increasing their operating and maintenance costs and impacting the environment. Adopting liquid cooling could reduce data centre energy requirements, cut associated carbon emissions, improve water efficiency, and provide multiple sustainability benefits. But no one would suggest this is an easy fix. The biggest barrier to liquid overtaking air in data centre cooling is the cost of switching. The majority of data centres are built in a way that makes retrofitting difficult. To swap over, many data centres need to maintain two separate cooling systems while they convert to liquid cooling, one rack at a time.

But the effort is worth it— and not just for the costs saved. Without a better cooling solution, it will be hard to keep up with the increased digitalisation, kicked off by the Covid-19 pandemic, that has seen all aspects of everyday life generating more data, increasing the utilisation of IT infrastructure and, in turn, increasing rack power density at data centres all over the world.

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As reported in the UNEP DTU-ITU Policy Brief on Innovative Data-Centre Cooling Technologies in China – Liquid Cooling Solution, leading Chinese Internet company Alibaba deployed liquid-cooling at its 2MW power capacity Winter Olympic Cloud Data Centre in the Bashang area of North China in 2020. It can accommodate thousands of servers at scale, using a single-phase immersion liquid-cooling server solution that doesn’t require operators to use traditional air-cooling equipment. Outdoor cooling equipment such as cooling towers or dry coolers are used year-round, significantly reducing energy consumption. It’s estimated that the energy consumption of the liquid-cooled data centre is less than 35% of a comparable centre of the same size. And, when 100,000 servers are running, about 235 million kWh of electricity and 200,000 tons of carbon dioxide emissions can be saved each year.

Liquid cooling uses less energy because the heat capacity of liquids is larger than that of air. And, once heat has been transferred to a liquid, it can be removed from the data centre efficiently. This means that, in addition to cutting emissions, liquid cooling technology has the potential to generate heat for a wider group of homes and offices than their air-cooled counterparts. Data centres can distribute waste heat to a wider market, providing an environmentally friendly way for more businesses and families to heat their homes and offices. Liquid cooling still faces many challenges in the development process. There is an urgent need to promote the development of technology and industry by strengthening industry guidance, standardising the evaluation system, and improving the industrial ecosystem, among other measures. In this regard, ITU developed a new standard (ITU-T L.1381) on “Smart energy solutions for data centres”, which considers a smart control strategy for the entire energy system, including power cooling solutions of data centres to achieve higher energy efficiency and to decrease overall energy consumption.

ITU, the United Nations’ Agency for ICT, champions liquid cooling of data centres because of its potential to positively impact at least four of the 17 United Nations Sustainable Development Goals, including the drive for better access to affordable and clean energy, and the improvement of industry and city sustainability.

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Full scale adoption is going to require some forward-thinking. The physical space requirements and layout of a liquid-cooled facility affects the design of the data centre, from structural floor loading, ceiling heights, lift facilities and logistics routes. Without a flexible building design, legacy data centres will struggle with retrofitting. This does mean that liquid cooling is easier to implement in new data centres, or in those undergoing a major overhaul. What’s more likely, in the short-term, is a plethora of hybrid facilities that use a mix of air and liquid cooling systems.

For the successful deployment of liquid cooling solution in data centres, policies supporting sustainable digital transformation need to be developed at the national, state and local levels. Addressing data centre cooling remains imperative if we are to remain within the UNFCCC’s prescribed temperature limit increase of 1.5°C by achieving full carbon neutrality within the ICT sector. Liquid cooling technology is not new but, adopted widely, its impact could be world changing.

Written by Cristina Bueti, Focal Point on Environment and Smart Sustainable Cities & Communities at the International Telecommunication Union (ITU), the United Nations’ agency for ICT.

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