Are Data Center Cooling Trends Reversing?

The global hyperscale data center market continues to grow. By 2027, reports expect 38 million square feet of hyperscale data center space will be on the market. According to recent market research, North America contributed 40% of the hyperscale market investment, leading the global growth.  


The power density per rack (kilowatts [kW] per cabinet) is also growing per the Uptime Institute, which is critical in data center design, capacity planning, and cooling and power provisioning. Though most rack densities fall below 20kW, the industry sees a drastic rise in density requirements due to compute-intensive workloads driven by Artificial Intelligence (AI), virtual reality, and more. When densities rise above 20kW per rack, the economics of using water as opposed to air to cool data centers is more efficient. 


Hyperscale providers like Microsoft, Google, Facebook, and Amazon deserve credit for pushing innovation and energy efficiency in the industry. However, while the industry champions energy-efficient design ideas, the impact on water usage for large data centers has been minimized. Hyperscale data centers use billions of water per day, even in areas deprived of water, and local municipalities are asking residents to conserve their water usage. For example, in recent news, Microsoft announced they were switching to air-cooled solutions from water cooling in their Phoenix data center because the utility cannot provide enough water to meet the data center's demands.


Sites like Microsoft and others from Google, Facebook, and Amazon favor direct evaporative cooling. Various strategies fall under the 'direct evaporative cooling' category, but the basic premise is taking air directly from outside and adding water to the air stream. By 'evaporating' the water, you are cooling down the air that moves into the data center. 


For example, Amazon has discussed their preference for evaporative cooling by using water-soaked 'cooling pads.' Evaporative cooling can reduce energy consumption, which is a positive benefit. However, it does require the use of potable water. As a reminder, potable water, also known as drinking water, comes from surface water and groundwater sources and is treated to levels that meet state and federal standards for consumption. 


Google has requested a million gallons per day of water (or more) for their data centers. That is one million gallons per day for a single data center. In most cases, hyperscalers are building 'campuses' with multiple data centers on a single site. To understand the impact, if a data center campus uses 3-5 million gallons of water daily, that's the same amount needed for a city of 30,000-50,000 people. 


Pressure has increased on hyperscalers to reduce water usage. Some, like Microsoft and Amazon, have pledged to be "water neutral" or "water positive" by 2030. The more significant change to watch in the hyperscale market will be the switch from water-based to air-based cooling strategies or the utilization of "closed-loop" chiller technologies that do not require potable water. 


There is a delicate balance to consider as the hyperscale industry shifts cooling solutions. As densities rise, the industry needs a power-efficient way to cool these systems, and air has traditionally been less energy efficient than water for high densities. However, as water scarcity issues become increasingly evident, the industry must reimagine how air-cooled technologies can effectively maintain cooling setpoints and meet and exceed energy efficiency goals and requirements.