Liquid cooling for data centers: the options

As needs and requirements for data center technologies expand, so does the obligation of finding reliable cooling systems that guarantee energy and cost efficiency. In this context, liquid cooling for data centers has become a key promising alternative to data center water cooling and air-based solutions.

Today, the present and future of data center technologies generates both opportunities and challenges to be addressed. Among the later, state-of-the-art advancements are finding key opportunities in optimizing data center cooling. 

Briefly put, data center cooling refers to the structures in charge of ensuring adequate temperature values for data centers. Far from being an inconsequential choice, these play a key role in how these complexes operate. In such a context, performance, energy consumption or cooling fluid flow must be considered with two goals: protecting electronic components and ensuring cost-efficiency.

While big technological companies have been able to install their data centers in cold regions such as the Arctic, a majority of smaller players in the field are currently on the search of reliable and cost-effective methods for data center cooling. In fact, the case of ARANER’s work at the Al Ashghal Data Center is a particularly strong example that involves achieving groundbreaking cooling efficiencies in a location where warm temperatures are the norm.

Through the expertise of industrial cooling engineers, operators are finding new ways of achieving these in state-of-the-art data center cooling solutions. This is where liquid cooling for data centers comes in. Let’s take a look at what they are and the most efficient shape a liquid cooled server can take today.

What is liquid cooling for data centers

Liquid cooling for data centers describes a series of practices and processes in which liquids (in various configurations) are used to maintain adequate temperature levels in data centers. 

In a way, liquid cooling for data centers can also be defined as opposed to traditional models, which relied on air-cooled systems. These function on the premise of hot air leaving the data center premises via a Computer Room Air Conditioning (CRAC) system monitoring temperature and humidity levels and rejecting heat through convection after air is supplied.

On the contrary, liquid-cooled systems use liquids to provide cooling, although other dedicated equipment is also employed, such as a Computer Room Air Handler (CRAH). These build on a general rule which prescribes that liquids are more efficient conductors for heat than air.

As we’ve mentioned, this includes a variety of configurations. Some conventional liquid cooling efforts involve the use of pumps and external radiators, and water as a liquid. These are known as data center water cooling. Other models, such as liquid immersion models, mean heat exchanges take place by means of a heat exchanger (such as a radiator). Current cutting-edge efforts are focused on liquid immersion cooling. 

This technique, which builds up from other liquid cooling techniques, involves submerging informatic equipment in a dielectric, thermally-conductive liquid that effectively reduces temperatures. Among the advantages of liquid immersion cooling are this model’s versatility:  it can be applied to different systems, from computer components (hardware) to full servers, as part of more sophisticated operations.

Liquid immersion cooling and water cooling: two options for liquid cooling for data centers

There are a number of differences between these two types of liquid cooling options for data centers. 

On the one hand, immersion cooling uses a working fluid able to transfer heat away from the electronics. There are different options for this liquid, including transformer oils or electrical cooling oils, among other options

On the other hand, because water is potentially harmful to electronics, it’s flown through a watertight loop and thus isolated from the source. Heat removal must necessarily take place in an indirect manner

Efficiency and liquid cooling for data centers

Data centers are currently facing a variety of challenges, from increasing rack densities (and the ensuing extension of energy demands) all in the face of increasing energy prices at a global scale.

Tackling cooling for data centers thus becomes a key strategic decision that allows operators to act on a process that is directly depending on the choices at their hands. In other words, finding energy-efficient alternatives for data center cooling can make a difference between a data center that runs efficiently and one where resource depletion is the norm.

However, the choice of liquid cooling for data centers must be guided by professional cooling engineers, able to consider all factors that can play a part in optimal performance. From the center’s location and environmental conditions, to usage models and rack and room level airflow protocols, several things must be considered in order to find the right system to push efficiency to the maximum. 

This is particularly important in the case of especially powerful servers:  as equipment presents higher power needs, it generates added heat, a case in which it may be beneficial to consider liquid immersion cooling. As a general rule, it can be established that power densities above 15 kW per rack can typically benefit from liquid immersion cooling and its energy efficiency.

Design considerations for liquid cooling for data centers

We’ve mentioned above that cooling engineers must consider how each data center presents unique requirements for cooling. However, there are also several standards providing guidelines for effective and efficient data cooling optimization.

This is the case of ASHRAE (American Society of Heating and Air-Conditioning Engineers) and the thermal guidelines for data centers, which incorporate several specifications aimed at providing help for designing data center cooling models. These include very specific prescriptions about recommended temperatures. 

ASHRAE guidelines advise temperature values to be kept between 18°C and 27°C. These may vary depending on redundancy levels, IT equipment and its design criteria and the specific purpose of the data center that is being considered. The guidelines also specify absolute upper and lower temperatures and three levels of equipment conditions or situations (reliability temperatures, functional temperatures and damage temperatures.

Additionally, other guidelines to be considered when designing data centers include  particulate air contamination standards (such as ISO 14644-11 Class 8 and ANSI/ASHRAE Standard 127-2007); and recommendations by the 2008 ASHRAE book for inlet facility air and the ANSI / ISA-71,04-2013 severity level G1 for gaseous contamination.

The advantages of liquid cooling for data centers

• Efficiency. Liquid immersion cooling has been said to provide up to 1000 times more efficient cooling than air-cooling techniques (traditional cooling methods that are based on chillers, heat pumps or HVAC solutions), thanks to the fact that liquids remain more efficient conductors for heat than air.
• Lower operational costs: certain liquid cooling models are responsible for decreasing the cost of cooling data centers. In fact, liquid immersion cooling has been involved in generating up to 99% electricity savings in terms of operational costs.
  
• Reliability: optimized cooling in data centers ensures equipment can run reliably even in contexts where High-Performance Computing (HPC) is involved, where power demand can add up ten times.
• Control: as opposed to air-cooling techniques, liquid immersion cooling techniques means cooling operations can be directed to specific equipment or areas.
• Easy application: liquid cooling options don’t involve rearranging plumbing systems.
• Versatile: a wide range of options can be considered when it comes to liquid cooling, including data center water cooling system and liquid immersion cooling with  non-conductive fluids, hot water cooling or chilled rear dolls. Hybrid models are also available. 
• Easier, less risky maintenance. When it comes to liquid immersion cooling, it’s important to mention that this method offers certain advantages over other liquid cooling options for data centers. As such, regarding potential disaster recovery planning, it’s not necessary to consider issues such as rust or leakages, which are in fact typical of other systems combining electrical components and water.

How to choose the right liquid cooling for data centers technologies 

Not all liquid cooling for data center solutions are the same. The choice of the best data cooling technology must be guided by criteria around cost efficiencies, types of technologies present in the data center and other considerations regarding each project’s installation, maintenance and management requirements. 

Cooling engineers must thus adopt a holistic approach to design the right liquid cooling for data center model, which takes into account the specific needs of each project and its potential for full optimization. 

At Araner, we commit to designing data center cooling technologies that match each project’s needs and achieve the maximum sustainability and efficiency. We thus design and implement liquid cooling options for data centers, helping companies generate optimized data center environments with a flexible, plug-and-play approach that is also able to comply with the industry’s highest standards. 

Learn more about cutting-edge data cooling and liquid cooling options and how we work to develop the project each operator needs. Download our free Data Center Reference Ebook or read more about our work in the Al-Ashghal Case Study, a data center cooling solution based on a naturally-stratified water storage tank and a state-of-the-art Thermal Energy Storage (TES) system. You can also get in touch with us to speak directly to our team and discover how we can push data center cooling efficiencies to the maximum.