Immersion Cooling for Data Center Cooling -Innovation Speaks it All!

With the rapid rise in the digital economy, the highly integrated world is literary pushing all the technologies to operate at an ever-increasing pace. It is fundamentally changing the way we live and communicate in almost every aspect of our daily lives. Data is the new “Oil, which would create an effective and integrated digital network that will be the backbone for robust digital economy. Currently, India being the second largest online market in the world after China with almost 600 Mn active internet users. As the penetration is queued towards urban centers making a huge opportunity for internet driven business and to top that India’s growing data center industry offers a four-billion-dollar potential for Indian industries. The Indian government’s move to bring a data center parks policy is also significant as it comes at a time when India is perusing global tech giants to store personal user data locally. It would need to have the capacity to create and consume this infrastructure as well as drive investments into data centers to create a powerful digital ecosystem.

The COVID-19 pandemic showed a paradigm shift in the way world functions. Starting from work-from -home culture, boost in e-commerce business, various digital platforms in-home data consumption has surged like early March 2020 saw an 18% increase in data usage compared to the same period in 2019, with data usage of smartphones rising by 34%. However, these centers come at a tremendous cost in energy consumption, water use, footprint and more. It’s clear — we need faster, smarter, more energy-efficient and more sustainable data centers.
 

Figure 1:A typical datacent (Image source: 3M)
 

Energy efficient cooling is critical to building more sustainable data center operations. Cooling applications are experiencing a rapid transformation, with sustainability drivers creating all new challenges. On average, as much as 40% of a data center’s power consumption goes toward cooling the servers. Fortunately, the technology to make these cooling systems more energy efficient and reliable already exists.

What are the different Cooling technologies used for data center?
There are several ways to cool the data centers based on the size of the facility, cooling power require to suffice the computing capacity as well as the cost components.

Traditionally, datacenters have been majorly employing air cooling technology due to its simple working principle and efficacy in maintaining safer operating temperature range. Basically, the cold air is allowed to be circulated through the heat dissipating source (servers). It takes up the heat via heat exchange principle. It could further be classified as room based, row-based or rack based depending on the system design and efficiency requirements.

But there are always some limitations attached to the air-cooling design. With the rise of power-hungry serves, air cooling technology find it is hard to keep up with increasing power densities and high process loads. But it is just not inadequacies with heat removal, there are pretty much sensitive servers are out there which are quite prone to particulate and gaseous contamination.

To bring more efficacy into the datacenters, there is always a quest to find new types of datacenter system management as well as the innovative cooling concepts. In the current article, we have discussed about the next-generation liquid cooling, specifically immersion cooling systems.

What is liquid cooling?
With the increase in computing density, liquids would be more efficient at in thermal dissipation compared to that of air. Alongside, it can also address the issues like faster functionality, space reductions, noise reductions and most importantly avoiding the contaminants.

The liquid cooling technology has been majorly classified as following categories.

1. Direct-to-chip Cooling
Direct-to-chip cooling dissipates heat by pumping fluid through cold plates attached to heat sources, the electronic components. The fluid circulates externally around the electronics without any direct contacts with the components. Major fluid medium includes non-dielectric fluids (e.g., water glycol) but in next-gen cooling system can also integrates dielectric fluids in these current applications. Direct-to-chip cooling can be implemented using single-phase and twophase technologies.

Figure 2 : Direct-to-chip cooling (Image Source : 3M)
 

2. Immersion Cooling
Immersion cooling has been proven as one of the cutting-edge solutions for data center cooling Data center immersion cooling. Here the electronics components /IT servers are immersed directly in a non- conductive fluid helps improve thermal design by directly immersing IT hardware in a non-conductive liquid. Heat generated by the electronic components is effectively dissipated through the fluid. As the fluid acts as an active pathway for heat dissipation, it reduces the use of extra active cooling components, such as thermal interface materials, heat sinks and fans. These improvements increase energy efficiency and enable higher packaging densities.

a) Single-phase Immersion Cooling
In single-phase immersion cooling, fluid remains retains its liquid phase. Electronic components are directly immersed in dielectric liquid in a sealed enclosure where heat from electronic components is transferred to the fluid. Pumps are often used to flow the heated fluid to a heat exchanger, where it is cooled and cycled back into the enclosure. This continual cycle helps to keep the whole enclosure at a constant low temperature.
 

Figure 3: Two-phase immersion cooling (Image Source: 3M)


Figure 4 : Single-phase immersion cooling (Image Source: 3M)
 

b) Two-phase immersion cooling
In two-phase immersion cooling, electronic components are directly immersed in dielectric liquid in a sealed enclosure where heat from electronic components causes the fluid to boil, generating vapor. Now the vapor condenses on a heat exchanger within the tank, transferring heat to facility water that flows outside of the data center.

Advantages of Immersion cooling
Immersion cooling offers many benefits compared to traditional air cooling, including increased thermal efficiency (i.e., lower PUE), performance and reliability of data centers.

Immersion cooling also eliminates the need for complex airflow management. Optimized immersion-cooled data centers can lead to reductions in capital and operating expenses, as well as a reduction in construction time and complexity. The increased compute density from immersion cooling allows for more flexible data center layouts and removes barriers to data center location choices such as areas with high real estate costs or space limitations.

Finally, immersion cooling appropriate fluids can help to eliminate the tradeoff between water usage, energy efficiency and cost control by eliminating the need for chillers and complex controls used in air cooling. This helps reduced power usage for water needed to cool the data center, instead, utilizing natural water temperatures in many climates to allow for full capacity cooling without evaporation infrastructure.
 

Figure 5:Source : Alibaba comparison of various cooling technologies at the Open Compute Summit 2018
 

Immersion Cooling -A winning streak?
Looking at one of the comparison studies done by Alibaba, immersion cooling emerges as a clear winner in terms of overall efficiency. (Fig.6)
 

Figure 6 :Source “Engineering Workshop: Advanced Cooling” (Tuma, Gross, Lau, Benge) presentation at the Open Compute Summit 2018 (Air Cooled system vs 3MTM Novec immersion cooled System).
 

Not only the efficiency, but there are also several studies has been done to have a more realistic view about the overall cost efficiency of immersion cooling with respect to air cooling technology.

The case study is based on building a 30MW data center in Iowa, US. The result shows that in terms of the Capex, immersion cooling required simpler design with fewer components which reduce the capex compared with air cooling to $6.5M/MW. Also, there is marginal reduction in electricity costs saving on immersion cooling as the PUE improved and cooling electricity reduced.

Over the past few years, immersion cooling technology has been running forefront in server cooling in a series of technology demonstrations, which have been recognized by the industry for best-in-class energy efficiency. This new cooling technology is proving to significantly increase power density, reduce energy consumption and deployment time.

There are several examples like Alibaba, who creatively brought the immersion cooling technology in by using single phase immersion cooling in hyperscale system ¹ . Hyper-scale cloud computing operations find value with cost savings and flexible hardware configurations. Also there has been successful deployment of two-phase immersion cooling in Bitfury, where Bitcoin miners drive down costs to maximize their return on investment²

Are we evolving?
Let’s have the reality check if we are really evolving with the technology advancement. A next-generation data center is right around the corner. Say it Hyperscale, Supercomputing, HPCs, edge computing or cryptocurrency. Immersion cooling has proven to be geographically and environmentally agnostic. Along with great cooling performance, it also helps with increased hardware reliability, power and water usage effectiveness and extend life of assets. In a nutshell, immersion cooling is definitely going to pave a better roadmap to future of power density needs with reduced capital and operational expenses.

- Dr. Pranati Sahoo, Senior Technical Engineer, Transport & Energy Business Group-3M India