The exponential increase in compute-intensive workloads for AI and Industry 4.0 combined with sustainability and energy-efficiency requirements create an enormous thermal management challenge for data center operators. Liquid cooling, from direct-to-chip to immersion cooling, is gaining traction this year.
‘Things are changing so rapidly in the data centre space,’ according to Herb Zien, Vice Chair and former CEO at LiquidCool Solutions. Exponential acceleration in computing demand since the rise of cloud computing, advanced analytics, Industrial IoT (IioT) and recently Artificial Intelligence (AI), make processors run increasingly hot. ‘Air can't do it anymore. Cooling electronics with air never made sense, but now it's impossible.’
Herb Zien was previously active in district heating and cooling, running downtown energy systems in eleven cities. ‘Selling chilled water to data centres all over the US, I couldn't believe what I found,’ he recalls. ‘They would have this hot thing in the middle of the room and we're blowing air at it to cool it? It was so preposterous.’
After selling the district heating business, Zien became an angel investor in liquid cooling for data centers. The industry is taking off now. ‘It's in real time,’ he says. ‘It is happening now. All the big data center companies, for example Meta, have announced that they are going to liquid cooling. They are going to even retrofit all their existing data centers, because they have to.’
With demand for compute-intensive workloads increasing, data centers packed more computing power into smaller spaces. At the same time, enterprises were moving away from centralized infrastructures to more distributed models, storing and processing data closer to the source; the paradigm shift to edge computing. Traditional cooling approaches met their breaking point.
Liquid cooling had been used primarily in high density centralized data centers in major metros. ‘Liquid cooling is not really new to us,’ says Elizabeth Langer, R&D Engineering Manager Thermal at CPC - Colder Products Company. ‘The newness now is really about the scale and need for it and how quickly it is being adopted.’ Apart from AI and Industry 4.0, Langer mentions sustainability requirements as a major driver. ‘We have seen a significant spike, hyper growth adoption of liquid cooling of data centers specifically, over the last three years.’
All the major data center operators have announced liquid cooling initiatives in recent months. Microsoft has been experimenting with data centers in underwater ocean pods in Project Natick. Amazon Web Services (AWS) is using recycled, purified wastewater for data center cooling at twenty locations in Virginia and California to leave higher quality water for other uses. Microsoft, Meta and Google have also pledged to be ‘water positive by 2030’.
IBM and others are involved in research and development of advanced cooling technologies, including direct-to-chip liquid cooling. Data center operator Equinix rolled out support for direct-to-chip liquid cooling at 100+ data centers and already supported liquid-to-air cooling through in-rack heat exchangers. In direct-to-chip solutions a cold plate with liquid running through it sits on top of the chip drawing heat out. Solutions like direct-to-chip, cold plate cooling and rear door heat exchangers are relatively easy to implement to retrofit existing data centers.
Immersion cooling is a bit more complicated; entire servers or hardware components are submerged in a dielectric liquid that absorbs and carries away the heat. Immersion cooling is more effective and could help the hyperscale data centers exploding around the world reach the required energy-efficiency levels. In two-phase immersion cooling, the coolant exists as both a liquid and a gas at different stages of the cooling process. However those solutions generally involve “forever chemicals” that are now the target of PFAS regulation.
Herb Zien sees direct-to-chip cooling solutions gaining traction. ‘But I view that as a transition step,’ he says. ‘People aren’t comfortable with immersion quite yet. Most people, when they think immersion, they think “tanks”. Our technology is total immersion, but it is a rack-based technology that effectively cools through forced convection. We think this will be the end game for cooling electronics.’
Elizabeth Langer, Herb Zien and others will discuss the latest development in liquid cooling for data centers at the Thermal Management Expo conference, April 30 – May 1 in Novi, Michigan.
