Why do datacenters continuously use more water instead of recycling the same water in a closed loop system?

Question

Why do datacenters continuously use more water instead of recycling the same water in a closed loop system?

In: 72

Answer 1

DC engineer here.

There are two “basic” DC designs. One that uses little water, and one that continuously consumes water.

Let’s start with the basics. When you remove heat from the air, you tend to strip out humidity. If you’ve ever seen a home furnace with an AC, it has a pipe that typically runs outside or to a drain. This is to catch the condensation due to removing heat.

But why remove humidity? Static electricity. Dryer climates can promote static which is killer for computers.

The little water users typically only consume water to humidity the air for the servers, and also for the people occupying the building. The cooling is typically done by RTUs (roof top units) or CRACs (computer room air chillers). These units in this configuration use DX (direct expansion) to cool. This is the same cooling style as a refrigerator. These take hot air and run it over radiators. The extracted heat is expelled into the atmosphere.

For the continuous users, there are typically two water systems. The first is a closed loop (water or glycol) which feeds CRAHs (computer room air handler). This coolant is chilled by very large water chillers which are also DX. These chillers develop an immense amount of heat which is removed via a second water loop. This loop is “open” which means it touches air.
Household AC units, and RTUs vent the excess heat by using air. Think of the fan on the home units. Water chillers use water to extract the heat. Hot water from the chillers will go to cooling towers. These towers spray water while a large fan pulls air over the water. Doing this makes some of the water evaporate dropping the temperature of the water. Think of this as a giant swamp cooler. The cooler water is then cycled back into the water chillers.
Now because some of the water evaporates, you need to replace it; hence why this style of DC continuously uses water.

I hope that explains it. Feel free to message me if you want to dive deeper!