Sustainability training

It is perfectly logical to wonder how a data center in a hot desert can be "air-cooled." The confusion usually comes from how we think about cooling and how data centers manage the heat generated by their servers.

Data center servers do not need to be kept at refrigerator temperatures. They can operate with internal air intake temperatures of up to about 85°F (29.4°C) or slightly higher. When the desert air is below 85°F, such as during Arizona winters, spring and autumn, or cooler desert nights, Microsoft can use a method called free-air or adiabatic cooling. Large fans pull outside air into the facility to remove heat from the servers. During these periods, little or no water is required for cooling.

When Arizona's summer temperatures rise above 85°F, traditional data centers have often relied on evaporative cooling towers. These systems move hot air through a continuous stream of water. Some of the water evaporates, carrying heat away from the facility. Although evaporative cooling is highly energy-efficient, it can consume very large amounts of water.

To reduce water consumption, Microsoft can instead use air-cooled chillers. These operate somewhat like the air-conditioning system in a home or vehicle. A sealed refrigeration or water loop circulates continuously through the cooling system. Mechanical compressors remove heat from the internal loop, while fans and heat exchangers transfer that heat into the outside air. Because the cooling fluid remains inside the closed system, there is little or no water loss through evaporation.

Next-generation systems can take this approach further with direct-to-chip closed-loop cooling. A specialized cooling fluid is introduced into the data center's plumbing during construction and then continuously circulated. The fluid passes through cooling components positioned directly over or near the processors, absorbs the heat generated by the chips, travels to external heat exchangers where the heat is released into the surrounding atmosphere, and then returns to the servers to repeat the cycle.

There is a trade-off between water and electricity. Operating air-cooled chillers in 110°F Arizona temperatures requires the compressors and fans to work much harder, increasing electricity consumption. The resulting design can dramatically reduce water consumption while increasing the facility's power requirements. In desert regions such as Arizona, this trade-off can make sense from a resource-management perspective because freshwater is scarce while the electrical infrastructure can support the additional cooling load.

More at https://www.microsoft.com/en-us/microsoft-cloud/blog/2024/12/09/sustainable-by-design-next-generation-datacenters-consume-zero-water-for-cooling/

https://www.youtube.com/watch?v=X_cGjq4z5P4

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hth

Marcin