Also known as liquid submersion cooling, immersion cooling is the practice of submerging computer components (or full servers) in a thermally, but not electrically, conductive liquid (dielectric coolant). Liquid submersion is a routine method of cooling large power distribution components such as transformers. Still rarely used for the cooling of IT hardware, this method is slowly becoming popular with innovative data centres the world over. IT hardware or servers cooled in this manner do not require fans and the heat exchange between the warm coolant and cool water circuit usually occurs through a heat exchanger. Some extreme density supercomputers such as the Cray-2 and Cray T90 use large liquid-to-chilled liquid heat exchangers for heat removal. It is proving to be the perfect solution for high performance computing (HPC) and high-density applications such as cryptocurrency mining using any ASIC or GPU hardware.
Two recent wins from Netherlands-based Asperitas are an excellent example of this trend. The first came at the Chartres data centre of Crédit Agricole where it helps to meet the demand for high density compute on a system and server level. This was followed up by a recent application to future proof Shell’s HPC cluster in their Amsterdam data centre. The system will facilitate both CPU and GPU driven applications and offers the flexibility to easily scale with future demands and next hardware generations.
“When it comes to HPC cooling, major global challenges related to densities, efficiency, cost, and sustainability are an ongoing threat,” Peter Uelen, Asperitas CCO says. “On the performance side, next generations of hardware create more heat with higher thermal design power (TDP). Current solutions do not allow for high density or optimal use with air cooling. Data centre facility complexity and cost are growing off the chart and need to be contained and at the same time efficiency needs to be enabled globally.
“Heat removal/reuse and rising operating temperatures are also challenges. These factors can be largely related to different geographical regions, so for a global operator, standardising efficiency is close to impossible. There are different data centre designs and performances across the globe to consider (and with PUE differences between the US, Europe, and Asia). Incorporating next level sustainability performances like heat reuse and high ambient temperature free cooling will bring even more variations in operations.”
Fluid for immersion technology
Both recent successes utilised the Shell Immersion Cooling Fluid product, specifically developed for immersed computing. This is a synthetic, single-phase immersion cooling fluid made from gas using Shell’s gas-to-liquids technology. It is optimised for Asperitas’ natural-convection-driven immersion cooling solutions but can also be used in pumped circulation systems of other providers. The liquid is designed to reduce energy costs and emissions through its high cooling efficiency, excellent flow behaviour as well as its thermodynamic properties. The immersion cooling fluid was introduced to the data centre market at the Global Open Compute Project Summit earlier this year.
“Data is the new oil and is being generated at an exponentially increasing pace,” Sundeep Kamath, global marketing manager for process oils at Shell adds. “Today, data centres account for about one per cent of global energy use and this is only going to increase. This solution can cut the energy footprint of data centres by half, while also increasing compute performance and lowering costs; it is a win-win on all fronts. We are convinced of the great benefits of this innovative technology and hope more of our partners and customers benefit by adopting this solution for their compute needs and their own decarbonisation journeys.”
The path to a liquid future
The urgency for immersion cooling has only arrived in the past few years with the increase in thermal design power (TDP). “Liquid cooling has impacted how we design and operate data centres for the better, therefore it introduces a new model and not just an optimisation of current, air-cooled, facilities,” Uelen continues. “With every innovation, a new model allows for more opportunities and impact, but the adoption requires time as the industry ecosystem needs to move with it.
“Optimised hardware for immersion is a good example, Asperitas maintains close collaborations with OEMs and integrators to help them with the validation and optimisation of IT equipment and future generation processors for immersion.”
It may be hard for data centre operators to see a clear path on how to implement liquid cooling even though immersion cooling enables data centre designs with simplified requirements. In the
past few years, the Open Compute Project (OCP) has taken the leading role in a global data centre transformation with the establishment of the Advanced Cooling Solutions Project.
“Asperitas has taken up the leadership role on behalf of the immersion industry and is actively contributing to the global advancement of not only immersion cooling but for liquid cooling in general,” Uelen explains. “The immersion sub-project which Asperitas is leading, is enabling a broader understanding and adoption of immersion cooling and facilitates the increased potential of the IT equipment.
“In summary, to accelerate one’s mission to enable sustainable data centres on a global scale, heat reuse should be a priority. Facilitating heat reuse not only provides a facility with a free external cooling capability, but also reduces the footprint of a third-party with the heat demand, enabling the transformation of data centres from heavy energy consumers into energy suppliers and contributors to the circular economy.”