Datacentre Immersion Cooling Solutions and The Benefits over Air Cooling Solutions

Immersion cooling is a transformative technology that could help to solve the dilemma facing data centres trying to deliver ever-higher levels of operational performance whilst also trying to reduce their energy consumption, carbon emissions, and overall operational costs.

Whilst traditional air-based cooling systems manufacturers continue to develop the capacity and cooling efficiency of their systems, it can be argued that they are reaching their practical limits, especially where server rack power exceeds 80kW per rack.

What is Immersion Cooling?

As the name implies, immersion cooling involves submerging high-power IT servers, GPUs, and storage devices directly into a thermally conductive, and electrically non-conductive, dielectric liquid. This specialist liquid developed by companies such as BP (Castrol) and Shell, can absorb heat far more effectively than air and transfer the heat aware from the sunken components without the need for traditional air-conditioning and/or expensive airflow management and containment systems.

For more information see:
https://datacentremagazine.com/data-centres/top-10-liquid-cooling-companies
https://datacentre.solutions/news/70037/shell-launches-direct-liquid-cooling-fluid

Two Types of Immersion Cooling

Immersion cooling is available in two distinct types. The first is Single-phase immersion cooling and the second is Two-phase immersion cooling.

• Single-phase immersion cooling: Components are submerged in liquid that absorbs heat and is then circulated through a heat exchanger. The liquid remains in a single state (liquid).
• Two-phase immersion cooling: Heat causes the liquid to boil and vaporize at low temperatures. The vapor then condenses on a cooled surface, returning to liquid form.

Compared to traditional air-cooling systems, both immersion cooling methods can dramatically improve heat management for high-density data centres running Artificial Intelligence (AI), machine learning, cloud-scale, and other High-performance Computing (HPC) applications.

The Advantages of Immersion Cooling in High Performance Data Centres

The key reasons behind the rapid adoption of immersion cooling in HPC environments is improved thermal efficiency, large energy savings, increased server rack density (and floor space optimisation), longer hardware lifespans, improved sustainability and lower carbon footprints, reduced noise pollution and an improved working environment, simplified infrastructure with reduced maintenance requirements, and the enablement of next-gen workloads.

Superior Thermal Efficiency

One of the primary benefits and adoption drivers is the superior thermal efficiency over air cooled systems.
Air is a poor conductor of heat and even more so compared to dielectric fluids of the types used in immersion systems. Such fluids can be up to 1,000 times more effective than air at absorbing and transferring heat from critical datacentre infrastructure such as high compute servers.
Within server racks (and server rooms) hot spots can exist with fluctuations in the temperature, humidity, and flow of cold and warm air around the space. Within an immersion cooled environment, there is more even cooling as component is evenly surround with the cooling dielectric fluid.
In addition to hot-spots, air-conditioned server rooms and datacentres, are sometimes limited to around 15-20kW per server rack. Immersion systems are better suited to higher rack densities and typically of 100kW or more. This makes immersion cooling more suited to meet the next generation of datacentre requirements as server rack IT loads continue to rise.

For high density server rack environments, immersion cooling brings the additional benefit of more computing power per square foot of floorspace compared to air cooled environments, with a lower risk of downtime.

Energy Savings

In a datacentre, cooling can account for 40-60% of the operational budget. The reason being is that substantial amounts of electricity are required to power external chillers, computer room air conditioners (CRACs), computer room air handlers (CRAHs), and the pumps required to move the large amount of air required. Free cooling can help to lower costs, where available but where this is not, immersion cooling can be used to significantly reduce electricity consumption.
Lower power consumption also means a lower Power Usage Effectiveness (PUE) ratio can be achieved. With immersion cooling, PUE values as low as 1.02 are reachable, compared to the more traditional 1.5 and higher of air-cooled environments.

Air cooling systems are made up from a larger number of moving and static parts. Immersion cooling systems are less complex and use less floor space. Their adoption allows the removal of air-cooled systems or at least for their capacity to be downsized and used to support less critical areas and server racks within a data centre environment.

Savings of up to 40-50% are possible with immersion-based systems over traditional cooled air-movement types. This translates directly into lower energy usage and lower operating costs and improved PUE and sustainability metrics.

For more information read:
https://www.stulz.com/newsroom/detail/free-cooling-in-data-centers-more-cost-efficiency-through-dynamic-control-1-2/

Increased Server Rack Density and Floor Space Optimisation

Space within most data centres is often constrained, especially where additional data halls and server rooms cannot be added. Typical examples include urban or collation facilities with limited land and space availability.

Air cooling places lower densities on server racks usage and potentially requires more planning in terms of white-space layout, hot and cold-aisle containment, and thermal pathways.

In contrast, Immersion-cooled server rooms can support higher density racks of typically 80-100kW with a far lower risk of overheating which can present a fire risk. Additionally, more computing power per square foot can be deployed in more simplified environments, without the need for large-scale airflow management or raised access floors.

This can lead to additional benefits for datacentre operations running AI and HPC clusters. They can more rapidly deploy additional systems to meet growing high-end computing and achieve a higher utilisation of their floor space and real estate.

Longer Hardware Lifecycles

No matter what the industry, heat kills electronics. Compared to cool airflows, immersion cooled systems provide greater protection and in ways that can help to extend the operational life of IT servers, storage systems, and GPUs.

The use of immersion cooling leads to reduced thermal stress from a more stable environment with a more uniform temperature. This subjects the electronics to less wear and tear from expansion or contraction and heat-generated ageing.

Dust within any server room or data centre environment presents risks and the potential for corrosion and short circuits. Placing electronics on a sealed immersion tanks and dielectric fluid protects them from the types of dust related risks inherent in air cooled applications.

Air cooled environments rely on the movement of air to manage heat and lower temperatures. This includes having fans within the IT servers to draw air into the units and exhaust the hot air to the rear of the racks. Computing equipment for use in immersed environments do not require fans and therefore the risk of mechanical failure or need to dust clean cooling fans and related areas is removed.

Together, these factors can lead to an extended working lift for IT equipment. In the longer term this can lead to lowering capital expenditures and reduced environmental impact as hardware requires less frequent replacement.

Sustainability and Lower Carbon Footprints

Datacentres face increasing regulations and social drives to reduce their environmental impact in terms of energy and water usage, and material waste.
Immersion cooling supports sustainability and can help to achieve lower carbon footprints for a datacentre operation. Immersion-based systems consume less power and resources leading to lower carbon footprints. It is also easier to capture heat output from immersion systems for repurposing within district heating, greenhouses, or industrial processes. Immersion cooling also requires little to no water, making it ideal for regions with water scarcity.

Lower Noise Pollution and Better Working Environments

Traditional air-cooled data centres are noisy, with fans and CRAC/CRAH units generating constant high-decibel noise outputs. Immersion cooling eliminates most of this noise because cooling/air distribution fans are removed from servers with cooling is achieved silently through liquid heat transfer. Immersion cooling creates an improved, quieter, and safer operational environment for onsite staff.

Simplified Infrastructure and Reduced Maintenance

Air cooling systems require more extensive supporting infrastructure in terms of raised floors, air handlers, ducting, and aisle containment systems.

In contrast, immersion cooling streamlines data centre design with more compact cooling systems replacing larger HVAC systems. This leads to lower maintenance costs and increases operational reliability. Their compactness can also make it less complex a project when looking to retrofit immersion cooling systems within existing datacentres.

This operational simplicity translates into both lower CapEx (capital expenditure) for new builds and reduced OpEx (operational expenditure) over time.

Future-Ready Datacentres

For datacentres with the higher kW capacity server racks associated with AI, machine learning, blockchain, high-frequency trading, and advanced scientific simulations, liquid cooling makes sense both commercially and operationally. These types of high server load applications require high-density computing and the types of GPUs, TPUs, and other accelerators that generate enormous amounts of heat.

Immersion cooling is more suited than air-cooling for these applications and workloads to prevent the need to throttle back high-power chips, deploy dense server clusters and enable manufacturers to innovate in terms of their hardware design for liquid environments without fan and airflow constraints.
Adoption of immersion cooling is accelerating. Hyperscalers, cloud providers, and colocation operators are piloting or deploying large-scale immersion systems, particularly in regions where sustainability regulations and power constraints are pressing concerns. While upfront costs and retrofitting challenges remain barriers, the long-term benefits, in terms of efficiency, density, and sustainability, make immersion cooling one of the most promising evolutions in data centre design.

Environmental Monitoring Solutions

Whether you operate air or liquid cooling in your datacentre environment, there is still a critical need to install the right environmental monitoring system. These can monitor 24/7 for changes in operating state when it comes to temperature, humidity, air quality and liquid/water leakage and potentially over 20 other environmental factors with automated alerts via email, SMS text and reporting into BMS, DCIM and other onsite monitoring systems. To meet the needs of immersion cooled applications, most of the standard sensors can be used, with the exception of those submerged into the dielectric itself. Traditional sensors can be used as they can be corrosive to the metal sensor containment. If you do want to install environmental monitoring alongside an immersion cooling system, make sure you use suitable sensors. See our case study for environmental monitoring in a liquid-cooled environment.

Conclusion

Traditional air cooling has long been the primary go-to for server rooms and data centres. Whilst manufacturers of such systems continue to innovate in terms of resilience and efficiency, the physics of air movement and handling makes immersion cooling more suited to larger kW capacity server rack environments. The benefits are clear in terms of superior thermal efficiency, dramatic energy savings, higher rack density, longer hardware life, and potentially a stronger alignment with sustainability goals for large-scale users.

For more information on our liquid cooling solutions for server rooms and data centres please contact our Projects Team.