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Data centers generate an immense amount of heat. Cooling this conglomerate of delicate electrical machinery has been an ongoing challenge.
Engineers are constantly looking for an improved cooling system for data centers that is efficient, cheap, and sustainable. Recent trends have been geared toward implementing water cooling as the solution for data centers.
How does water cooling work? What are the various water cooling options? Is it worth the investment? And is it really better than air cooling?
This article will answer those questions and much more.
Contents:
1. The History of Liquid Cooling
4. Pros and Cons of Water Cooling
Although it is often mistaken for new technology, liquid cooling has been used since the 1940s to cool transformers, and IBM used it for its System 360 in the 60s. Cars use liquid cooling, and desktop PCs can have it, too.
However, water cooling as a cooling solution for data centers has become more prevalent in recent years.
In the water cooling process, a liquid — usually water — is pumped through the IT equipment and absorbs the heat. It travels through the system and dissipates the heat it absorbs.
There are several methods of water cooling, which we will explain in detail in the coming sections.
There are several different methods of liquid cooling. Each has its own benefits and risks.
Immersive liquid cooling completely or partially submerges the electric components in a dielectric fluid.
This is one of the quietest of all liquid cooling technologies, since there is no need for fans of any kind.
Within immersion cooling systems, there are three different types:
One type uses a sealed IT Chassis, which holds the server immersed in a dielectric liquid. This liquid is cooled passively or pumped through a CDU, heat exchanger, or fluid cooler.
This heat exchanger can be inside the chassis, or the liquid can be transferred to an exterior cooler through a closed circuit.
The open tub liquid immersion cooling option can be either a one-phase or two-phase approach. The single-phase open tub stacks multiple servers on a vertical plane in one big tub of dielectric fluid.
Like the IT chassis method, the liquid can be cooled by a system inside the tub, or connected to a heat exchanger outside the tub through a water circuit.
The two-phase open tub method is set up like the single-phase, with vertically stacked servers. However, two-phase immersion cooling differs in the fluid changes from a liquid to a gas during the cooling process.
Single-phase direct-to-chip liquid cooling uses a cold plate placed directly on the components that generate the most heat. The liquid is circulated through the cold plate. With this method, you will still need a fan to produce airflow to cool the rest of the components.
Two-phase direct-to-chip liquid cooling uses the same idea. However, the liquid will change states into a vapor and then is cooled in a condenser outside the server. It then returns to a liquid form and is routed back to the cold plate as coolant.
Another liquid cooling option is rear door heat exchangers (RDHx). This system uses fans to draw hot air away from the servers and into the radiator coils filled with refrigerant.
The coils absorb the heat. The heated coolant then travels through a cooling distribution unit into an evaporative cooling tower or dry cooler. It is then rerouted back to the coils to absorb more heat and repeat the cycle.
Choosing which liquid cooling system to install in your data center can be a difficult decision to make. Factors that should be considered are the cost, efficiency, energy usage, and specific cooling requirements.
Many times, the best option involves a combination of more than one system for various types of equipment.
Make sure you have all the facts before designing your data center. Read The Processes of Building a Datacenter.
Is the investment in a new liquid cooling system worth it? And what are the potential drawbacks?
Read on to weigh the pros and cons of water cooling for your data center.
Below are the many reasons big corporations like Meta are switching to liquid cooling solutions.
Cooling is the highest draw of non-IT power in a data center. Switching to liquid cooling reduces your cooling energy consumption by 80%.
Water cooling can improve your PUE by up to .5 on the measurement scale. Although this may seem like a slight improvement, it significantly reduces overall energy consumption.
Aside from the initial installation cost, water cooling offers many ways to save costs. Since it drastically reduces the energy needed for cooling your IT equipment, you save a lot of energy.
Although liquid cooling often uses water, it is recycled, reducing the cost of consumption. Liquid cooling is even more cost-efficient as power density increases.
Liquid cooling eliminates the need for many of the space-consuming cooling equipment. CRACs, compressors, and chillers can all be removed. This allows for either more room for servers, or the ability to settle on a smaller data center, which is also cost-effective.
Water cooling is adaptable to high-power-density equipment. Higher-capacity CPUs and GPUs are becoming more common. New technology can create much more heat from the intensive workloads they produce.
Technology like generative AI, machine learning, blockchain computing, and supercomputing can produce up to 40-120kW of heat per rack. Water cooling is the only system on the market that can handle these temperatures.
Since liquid cooling is dedicated to one server or rack, you can tune each system to the proper degree. New technologies can have big swings in power consumption, creating the need for more intense cooling. This would be isolated to certain servers or racks.
You can increase the cooling capacity for one server while maintaining lower temperatures where there isn’t a need.
Liquid cooling is much quieter than noisy fans. While some liquid cooling options still require fans, such as RDHx, the noise is less intense.
Liquid immersion is nearly silent.
Since some urban areas have regulations on noise, finding a quieter cooling system may be necessary for your data center, not just more pleasant.
Water cooling uses less water and energy to run, minimizing your carbon footprint.
Many governments are cracking down on data centers to be more sustainable. This push is one of the main reasons to develop a more energy-efficient cooling option — like liquid cooling.
It can make it easier for you to provide the community with heat reuse. This is when the heat produced by a data center is used as a heat source for homes in nearby cities.
Also, future retrofitting needs in the next decade are slim.
Even though water has been proven to cool significantly better than air conditioning, some people are still hesitant to use water cooling systems, and here’s why:
As with any system that has liquid, leaking is always a risk. But you can prepare a contingency plan, like installing a leak detection system.
In addition, a negative-pressure liquid cooling system uses a vacuum to pull liquid away from IT equipment.
You can also consider dialectic liquids, such as deionized water, which can have a less detrimental effect on your electrical components.
Liquid cooling systems are dedicated to individual components. If the system fails, that part will be down until the system is fixed. Downtime is often not an option for data centers.
Subpar water can have debris and cause buildup in the system. This blockage could be catastrophic. Only the purest water will do for liquid cooling.
Liquid cooling is better than air cooling for a straightforward reason: water has 23.5 times more thermal conductivity than air. This makes it a much more efficient method, without a doubt.
Additionally, instead of trying to blow the heat away from a distance, water cooling systems can remove it from closer to the heat source.
Air cooling systems can be configured with room air conditioning units, units for each row, or a unit for each rack. However, the more complex these systems become, the more energy they require.
Although some data centers are lucky enough to be located in a region where they can take advantage of free air cooling from the cold weather outside by opening their windows, this isn’t the case for everyone.
One liquid cooling method, immersion cooling, removes the heat immediately. Water cooling absorbs the heat and draws it away from the equipment instead of simply blowing it in one direction.
The cost to use both liquid and air cooling systems is about equal until power density increases. At a certain point, air cooling will not only need to be increased, but it can simply be insufficient.
When cooling needs increase, air cooling systems become much more complicated.
Today’s high-density racks use more kW than the older generations, which rarely exceed 20 kW. Some racks nowadays require 30kW or more, some up to 50 kW. Even the most complicated air cooling system can’t handle that heat.
Water cooling is much better for the environment. We’ve already established that it uses significantly less energy and water than traditional air cooling. But it can also provide cooling for a greater workload.
Liquid-cooled data centers are gaining popularity due to their many benefits. With the evolution of these needs, air cooling options may no longer be viable for data center operators.
And with the increase of artificial intelligence and its need for high-performance computing, traditional air systems simply fall short of the ability to cool such hyperscale edge applications.
Are you looking to build a data center but need clarification on the metrics to ensure your systems have the cooling capacity they need? Contact FMP Construction to discuss your data center project and its cooling requirements.
