Data Center Liquid Cooling vs Air Cooling – Which is Best?

If you speak with people who work in IT, they may describe the environment in a data center as being uncomfortably cold. This is often true because most data centers run powerful air conditioners to cool down computer hardware, which generates a lot of heat. Without these cooling systems, the data center would be unbearably hot, and in some cases, the hardware could melt, or even catch fire.

As data centers pack more processing capacity into confined spaces, the need for cooling goes up. Air cooling, unfortunately, is not ideal for this challenge. One alternative is to use liquid cooling systems, which are more efficient.

As of today, nearly one-quarter of data centers are using liquid cooling. This article examines the relative merits and challenges of air cooled and liquid cooled data centers. It also compares data center liquid cooling vs air cooling, highlighting where the respective methods are advantageous, and where they are not optimal.

What is Liquid Cooling in Data Centers?

Data center liquid cooling involves the use of fluids to pull heat away from electronic equipment in a data center.

Heat in data center hardware primarily comes from the transistors in integrated circuits. Transistors contain resistors that are similar, in thermal terms, to a toaster’s heating coils. The more cycles they process, the hotter they get. As infrastructure engineers now cram more high-performing circuits into increasingly dense server racks, the need for data center cooling systems goes up. In these compact situations, liquid cooling is better than air.

Liquid cooling data center design can take one of three predominant forms:

• Direct-to-chip—flowing chilled liquids directly onto heat-generating electronic components, such as CPUs and GPUs. The heat exchanger warms up the fluid, which is then pumped back to where it can be re-chilled and circulated again (often referred to as “cold plate cooling”).
• Immersion cooling—this involves placing electronic hardware into a tank containing a non-conducting coolant. The entire server finds itself submerged in this dielectric fluid.
• Coolant circulation system—a system of pumps and pipes that circulates chilled liquids through a data center rack to effect heat exchange (often referred to as “rear door heat exchanger”).

5 Benefits of Data Center Liquid Cooling

Liquid cooling solutions have grown considerably in recent years, and for good reason. The technology involved has kept pace with advancements in data center equipment, ensuring compact hardware can remain cool. IT teams now have a real decision to make when deciding between air-cooled and liquid-cooled​ systems.

Here are some key advantages of liquid cooling in IT infrastructures:

1. Improved Cooling Efficiency – Liquid cooling systems provide enhanced thermal management. This is due to the fact that liquids possess far better thermal conductivity than air and can transfer heat more effectively. This is especially the case when using direct-to-chip systems that target heat-generating sources like CPUs and GPUs directly. This can also lead to improved lifespan of infrastructure hardware and performance over time, which ensures more Uptime!
2. Energy Savings -Liquid-based systems take less energy to power coolant through equipment, which can lead to a lower Power Usage Effectiveness (PUE). PUE is the data center’s measure of energy consumed on computer hardware rather than cooling needs.
3. Space Efficiency – Liquid cooling allows data centers to pack more computing capacity into smaller spaces. High-density server configurations, which can become overheated with air cooling, are also feasible with liquid cooling setups. In addition, reduced use of large air conditioners and fans provides space for more IT equipment in the environment.
4. Lower Operating Costs – In the long term, liquid cooling can be cost-effective in operations. The systems have fewer mechanical components, so there is less wear and tear and consequently lower maintenance expenses.With improved cooling, hardware is less likely to fail due to thermal stress, so there are fewer replacements and service downtime. In some applications, the heat contained by liquid cooling systems can even be reused for other purposes, like heating nearby buildings, saving costs additionally.
5. Greater Environmental Sustainability – Through their minimization of both electricity usage and waste heat, liquid cooling solutions are well-suited to overall sustainability in the data center.

6 Challenges of Liquid Cooling in Data Centers

Choosing between air or liquid cooling should involve a careful look at the challenges inherent in the process. And the analysis is only partly about the technologies themselves. Other factors, like labor and supporting vendors, are also important.

Key challenges with liquid cooling to consider include:

1. Potentially higher upfront costs—While liquid cooling can deliver cost savings in terms of energy consumption, liquid cooling systems tend to be more expensive to implement. For instance, each rack may require special equipment. They typically have a higher capital expense (CapEx) than air cooling solutions.
2. Skill deficits— Liquid cooling solutions are relatively new, and not all data center technicians will be familiar with them. They may need to learn new skills.
3. Potential reliance on specialized vendors—It may be necessary to use a liquid cooling support vendor instead of training in-house personnel. This can be expensive and may lead to vendor lock-in for a cooling solution.
4. Slowing down of data center operations—Liquid cooling, especially immersion solutions, may make it difficult to deploy or “swap out” hardware quickly and easily. Immersion cooling tanks are complex pieces of equipment to construct and disassemble.
5. Loss of flexibility in data center hardware choices—Not all hardware will be compatible with liquid cooling, so adoption of liquid cooling may reduce hardware choices for data center operators and their clients. This, in turn, may limit the data center’s agility to handle diverse workloads.
6. Risks of leaks—Although this fear may be overblown, the potential for liquids to leak and damage hardware can be an issue. Liquid cooling equipment must be set up and installed by a reputable supplier.

What is Air Cooling in Data Centers?

Air cooling in data centers is an approach to cooling down heat-generating electronic equipment by pumping chilled air over hardware components.

There are a variety of methods to implement air cooling, but the most common involves a data center operating a large, centralized air conditioning system that generates cold air, for example, a chilled water plant.

The resulting cold air is pumped, via ducts, through “cold aisles.” After being heated up by the electronics, the air is ducted out through a “hot aisle” back to the air conditioning center for re-cooling and recirculation.

4 Benefits of Data Center Air Cooling

Air cooling solutions have been around for a long time, especially when compared to liquid-cooled methods. Here are some key advantages of the traditional air cooling approach.

1. A familiar, proven technology—Air conditioning has been around for over a century, so IT engineers are comfortable using it.
2. Broad and diverse supplier base—Data center operators have their pick of manufacturers and support vendors for air conditioning systems. Additionally, quick repairs are more common.
3. Little risk of damage to electronics—Air does not generally harm electronics.
4. Allows for agility—Data center staff can modify air cooling hardware quickly. This allows for greater flexibility in adjusting to different hardware conditions or reacting to changing data center environment (such as an increased volume of devices).

4 Challenges of Air Cooling in Data Centers

Air cooling in data centers is not without its disadvantages. Though these technologies have been around for a longer time, this may also be a detriment, as they may fail to cater to technical advancements in the data center.

Here are some of the more common disadvantages of an air cooling option:

1. Inefficiency—Cooling efficiency is an issue for air cooling when assessing liquid vs air cooling. Liquids are far more efficient at thermal exchange. Water, for example, is a heat conductor that’s far more efficient than air (via Thermtest). As a result, it takes less energy to chill liquids that have drawn heat away from hot hardware than it does to cool down warm air.
2. High operating costs—The lower efficiency of air cooling leads to higher energy costs for the equivalent level of cooling.
3. Lack of sustainability—The need for large amounts of electricity almost always translates into greater carbon emissions. The exceptions are cases where a data center can use renewable energy resources like wind or solar power. These cases are relatively rare, however.The high carbon footprint goes against sustainability strategies and impedes compliance with regulations mandating reductions in carbon pollution.
4. Limits to effectiveness—As computer hardware becomes higher performing, and data center racks become denser, air cooling reaches the limit of its effectiveness. At some point, the air conditioning cannot keep up with the hardware.

An option is to add even more air conditioning capacity, which is costly and may, in fact, be impossible due to the limits of the power grid. Or, alternatively, other cooling solutions can be explored.

7 Factors to Consider for Air Cooling vs Liquid Cooling in the Data Center​

Simply put, the difference between liquid cooling and air cooling is the ability of liquids to cool down hot data center hardware, rather than relying on cool air (in air cooling solutions).

There is no one-size-fits-all approach when it comes to analyzing liquid and air cooling technologies. A lot will be dependent on the specific data center infrastructure in place and the demands of the IT team. Though personal circumstances must be considered, here are seven additional factors to analyze when choosing between liquid cooling or air cooling.

1. Sustainability Impact

Setting aside the economic and technical aspects of the choice, it’s important to consider how air or liquid cooling will affect your data center’s environmental sustainability. The two cooling methods have different carbon footprints, with air cooling usually creating more carbon emissions.

Water use is also an issue. Air cooling systems often use a great deal of water, usually for cooling through evaporation. This is not suitable for locations with limited water resources. Liquid cooling helps avoid this problem.

2. Costs

Liquid cooling vs air cooling data center costs are factors that cannot be ignored. In general, liquid cooling solutions are costlier to implement but less expensive to operate than air cooling. For instance, air cooling requires large fans, chillers, and HVAC systems that draw significant power.

It’s useful to get the full cost picture. For instance, if you have to contract with specialized vendors for liquid cooling support, that might negate its cost advantages.

3. Ease of implementation

There is a lot of effort, time, and expense that go into implementing air cooled vs water cooled systems. And though liquid cooling is generally harder to implement, it may be more scalable, so adding capacity or increasing rack density will likely be easier with liquid cooling.

4. Location

Location matters when analyzing air cooled vs liquid cooled systems. Certain warmer places, like Las Vegas, are sub-optimal for air cooling. Conversely, locations with existing cold air, like Alaska, may not be desirable for situating a data center; however, the air is naturally fitting for air cooling approaches.

5. Future-Proofing and Scalability

When assessing air vs liquid cooling for data centers, future-proofing and scalability are important considerations. Air cooling can be hard to scale if additional electrical power is not available in an area. What’s more, too much stress on the electrical circuit could lead to a power outage.

As technology develops and hardware units become denser with more processing power, air cooling is a sub-optimal approach.

6. Performance

Deploying servers with fast chips can improve application performance, but the increase in heat can be problematic if an air-based system is already maxed out.

It could be argued that if infrastructure performance is vital and hardware must run vigorously, within a confined space, then liquid cooling may be the more suitable option.

7. Ongoing Maintenance

What will it cost to maintain each type of cooling solution? Or, on a related note, what kind of skills will you need to have in-house or hire out? Liquid cooling systems may be more challenging and costly to maintain than ones based on air cooling.

Liquid cooling vs Air – Table Summary

This table compares some of the key features between liquid cooling vs air cooling in the data center mentioned above. It should be noted that these are generalizations and comparisons may change from vendor to vendor.

What is the Advantage of Liquid Cooling over Air Cooling in the Data Center?

Generally, here is why liquid cooling is considered a better option than air cooling in the data center:

• Lower operating costs
• Better energy efficiency
• Stronger support for high density racks
• Lower noise levels

However, is air cooled or liquid cooled better? As established, the decision will depend on the current circumstances of the data center environment. No data center is the same, and liquid cooling may not always be the better option.

For example, a data center that expects to host varying workloads that change regularly is probably not a good candidate for liquid cooling. This is because altering or upgrading hardware is more challenging with liquid cooling. In such cases, air cooling —despite being more expensive and less sustainable —may be the better business decision. Alternatively, if you have a long-term plan for a specific workload, such as video processing, then deploying a dedicated liquid cooling system makes sense.

Liquid Cooling Solutions from Park Place Technologies

Air cooling technology in IT environments has been around for a long time and has certainly been effective. However, there’s a reason why liquid cooling technology has comparatively grown at an astronomical rate in recent years.

The rise of higher-powered computing, driven by AI and advanced workloads, has created a need for more scalable and efficient cooling solutions. As the number and capacity of data centers grows year over year, cooling solutions must keep pace with higher-density server configurations.

At Park Place Technologies, we understand that for our customers’ hardware to perform to its best, especially in today’s demanding IT landscape, liquid cooling solutions are often the answer.

We offer two advanced cooling solutions: direct-to-chip cooling and immersion cooling. We can serve as your trusted partner in determining which solution best fits your environment—or whether a hybrid approach using both technologies is the right move.

Contact us today to learn more about how these innovative cooling solutions can support your data center’s performance and growth.