“Cooling” has become a hot topic within the data center industry, with efficient cooling methods playing an important technical role in sustainability.

When data centers are properly cooled, this drastically extends the lifespan of computing and storage components. The ratings of electrical distribution and wirings include temperature, so when things like busways, busbars, and electrical wires are not cooled and live in higher temperatures, they must be derated. This can mean that larger or additional components are required, and the processes for transporting and installing these additions further add to carbon emissions, which can impact sustainability goals.

Cooling and water consumption

Most data center cooling technologies impact the environment through carbon emissions and water consumption. With widely used traditional methods, it is possible to decrease power usage effectiveness (PUE), and thus the carbon emitted from traditional electricity production by evaporating water for cooling.

Since water is uniquely underpriced for the purposes of cooling, this solution becomes an economical choice for many in the industry. However, evaporative cooling removes millions of gallons of water from the watershed and discharges wastewater with highly concentrated contaminants to the local treatment system.

Excessive water consumption, especially in some drought-stricken regions, may have a more significant environmental impact than carbon emissions, as climate change is decreasing water availability in many places. Scarce water should be conserved for local communities, agriculture, and wildlife that can’t survive without it. With the increasing availability of renewable energy and the use of water-free cooling, it is possible to cool data centers more sustainably and efficiently in a way that does not contribute to climate change or water shortages in the years to come.

Defining efficiency

If you want to know what is the most efficient (and thus, sustainable) cooling technology you must first define the term “efficiency.”

In most cases, the term refers to energy efficiency (via PUE), which in itself is good, but energy efficiency is often achieved through consuming water with additional water treatment and sewer impacts.

Water becomes “invisible” to the energy efficiency calculation, thus making methods like evaporation cooling exceedingly water inefficient, despite being tremendously energy efficient in lowering the PUE. To take a holistic view of sustainability within data center cooling, we have to consider all of the environmental impacts.

In many situations, economizers, also referred to as “free cooling” appear to be an efficient technology, as they take advantage of cool external air to remove heat from data halls, requiring very little energy, and no water consumption. But this method only functions when outside temperatures are cool enough. Consequently, this can’t be the only source of cooling, creating limitations despite its positive sustainability impacts.

Cooling technology: What’s available?

One effective cooling technology is a closed-loop chilled water system that uses energy-efficient chillers. Through extensive modeling, this system provides sufficient cooling with the least electricity use possible and only uses an initial amount of water to prime the system. In the cooler months, all or part of the cooling can be provided without running the refrigerant compressors. When paired with renewable electricity, this system produces negligible carbon emissions with only small amounts coming from occasional backup generator use and refrigerant loss. It consumes no additional water and uses a small amount of electricity. Thus, it is carbon, energy, AND water efficient.

Additionally, there are several cooling methods that can be deployed at the rack level depending on the application.

Immersion cooling, which is often deployed in very high-density footprints is very efficient but tends to come with a big price tag as well as requiring specialized electrical components. Air via a pressurized raised floor is the most flexible method and is able to serve low, medium, and some high-density applications. Flooded room cooling, which is typically deployed in non-raised floor environments, can support a slightly higher density than its pressurized floor counterpart without the concern of floor loading. It does, however, come with layout limitations. Cooling is not a one size fits all mindset, so choosing the correct method can maximize the data center’s efficiency.

On balance, air-cooled chillers in a closed loop provide efficiency and ultimate flexibility without taxing water or sewage, thus creating a more sustainable footprint. This solution remains flexible enough to accommodate the future shift towards immersion cooling or liquid-to-chip cooling.

Right-sizing data center design

In addition to varying cooling methods, data centers can also achieve efficiency and sustainability by right-sizing data center design. Right-sizing coupled with proper cooling distribution leads to the greatest level of efficiency. It is an area where data center operators and building management systems prevent and solve mismatches in supply and return air and water temperatures to normal levels. Operators are constantly monitoring the data center systems, working to provide the most efficient environment without sacrificing reliability. Such is why right-sizing and proper cooling distribution represents another strategy within the drive for efficiency.

Improved resilience and cost savings

Besides overall improvements to sustainability, two other primary benefits for data centers that invest in efficient cooling technology are improved resilience and cost savings. The cost savings benefits are apparent. Electricity is expensive, so the less you use, the more you save. However, it cannot be at the cost of over-utilizing water.

From a risk standpoint, a water shortfall could completely shut down a facility that relies on evaporating water for cooling. Since uptime is crucial to any data center provider, it’s important to prioritize resilience over cost savings. By working to eliminate water-inefficient evaporative cooling in favor of air-cooled chillers, particularly in regions of high-water stress, you can improve resilience to climate change and weather-related disruptions.

As data center developers and operators, we must consider the future when making decisions about the building and cooling of our data centers. Data centers are built to operate for decades, and it is becoming clearer that the environmental, economic, and regulatory conditions that exist today will change.

Water may be inexpensive and plentiful today but doesn’t protect us from shortages a decade from now. Renewable electricity may not be on everyone’s agenda, but a carbon tax would cause electricity prices to rise, and today’s long-term renewable deals could save millions in the future. Our best opportunities lie in analyzing trends and finding ways to prepare for probable outcomes that will improve resilience and future-proof our data centers.

Over time, more data center operators will turn towards efficient cooling technologies which protect their operations from equipment breakdown and also from future climate change threats. We must be planning for the future and continue to implement efficient cooling technologies in the data centers we operate.