IT aside, the vast majority of power usage in a data centre is due to cooling and the need to relocate heat away from the CPU. Traditionally, air cooling is the go-to solution and makes up the vast majority of cooling solutions in the data centre world. Existing air cooling systems are usually firmly embedded into the physical infrastructure of a data centre and are largely effective and still the best option for 60-70% of set-ups.
However, where IT densities require, some organisations are looking at the option of liquid cooling solutions either as an alternative or as a complementary element. The reason is simple – liquid cooling is much more effective at removing heat than air cooling.
To put this into context, currently air cooling has 60kW/ rack limitation, direct liquid cooling 70kW/ rack limitation and full immersion/ fanless liquid cooling 120kW/ rack limitations.
This is important as we are seeing rack densities continue to increase driven by consumer demands for faster and more complex services in certain applications. However, it is also fair to say that alternative cooling methods don’t need to exclusively sit with high performance compute, and presents a great opportunity.
How does it work?
A direct liquid cooling system circulates a liquid through a heat sink attached to the processor. As the liquid passes through the heat sink, heat is transferred from the hot processor to the cooler liquid. The high specific heat capacity of the cooling liquid/ water means it is much more effective than air at removing the heat, enabling higher densities to be achieved.
Finally, immersion cooling involves complete servers being submerged into a thermally conductive dielectric liquid or coolant. Heat is removed from the system by circulating liquid into direct contact with hot components, then through cool heat exchangers. Fluids suitable for immersion cooling have very good insulating properties to ensure that they can safely come into contact with energised electronic components.
In simple terms, a liquid cooled system can reduce a data centre facility’s overall power consumption and improve its power usage effectiveness (PUE) resulting in environmental benefits, including improved power usage, reduced emissions and overall less waste.
The higher grade of heat rejected (70°C+) compared to air systems (<40°C) also opens the doors to heat reuse/ recovery opportunities; through symbiotic relationships with industries that require continuous hot water for their industrial processes and produces less noise than air cooling.
The increased coolant supply and return temperatures mean that full cooling is possible without the need for chillers and, in most UK cases, without adiabatic cooling; this can mean a lower cost to deploy and maintain cooling infrastructure. In addition, the stranded electrical capacity reserved normally for chiller use can be re-purposed into additional IT capacity.
It’s not for everyone
The physical space requirements and layout of a facility that is liquid cooled can require a different type of data centre design than an air cooled facility. This means that for many legacy data centres, the addition of liquid cooling may not be a realistic option. In addition,currently not everyone needs IT systems that require direct liquid cooling, as air cooled servers can be more than adequate and may represent a lower total cost of ownership currently. For many facilities, it may not always be possible to implement wholesale changes in a live environment with inherent space, power and environmental constraints.
At Keysource we are seeing a growing uptake of liquid cooling solutions in specialist institutions and universities. In many cases, existing users are asking us to assist to adapt existing air cooled rooms with chilled water infrastructure to address small scale deployments. This can provide a good opportunity to re-use or supplement existing free cooling chlller capability and then to further optimise existing air cooled systems and infrastructure. Larger scale deployments in specialist facilities are more often scalable and optimise deployments (row and room based), modular and packaged solutions.
So, whilst uptake is steady and we do not expect a widespread commercial shift from an air cooled system to liquid cooling in the near future, it is becoming increasingly relevant.
At Keysource we have been able to assist many customers with the challenges and demands of deploying liquid cooling into new and existing environments. Our significant experience and skills in energy efficiency/ sustainability, facility design (large and small), existing facility optimisation, operation and live upgrade enables us to assist organisations with new and supplementary HPC deployments of all sizes.
We are also keen to play our part in tackling the issues of climate change and supporting our clients’ green agenda, whatever that might be.