[OptionOfT]

The refrigerant is closed loop, but the condensers are sprayed with water which are much more efficient at removing heat than a fan + air.

I did some research on additional cost of water + increased efficiency of the condenser, but it's not just that. The water needs to be treated, otherwise it leaves way too much sediment.

[matt-p]

AI data centres rarely actually need to resort to using water because they're using DTC and not air cooling, so we're looking at cooling 60 degree Celsius water down to ~40 which you can do compressorless with dry coolers alone. In practice many will use cooling towers instead or aswell but they still don't need to evaporate nearly as much water as a normal low density data centre would per KW.

By the way "spray the condenser" technology is very very rare because it's pretty much worst of both worlds and nowhere near as good or efficient as a cooling tower but much more maintenance than a dry cooler + compressor. Typically for high efficiency modern sites you'd be looking at cooling towers or dry cooler + compressor for water facilities or spray the water directly onto the air (direct or indirect adiabatic) for air based facilities.

To complicate things many (typically city DCs/Colos/ enterprise facilities) are air based facilities that convert to water by using heat exchangers in the datahalls.