They use adiabatic gas coolers on their refrigeration systems. Basically there is a perpetually wet piece of media that air runs through before it gets to the refrigeration coils. By running through that wet media you precool the air basically down to the current dewpoint by evaporating water and therefore you’re cooling the refrigeration coils with colder air which leads to more efficient opperation and reduces the size of the gas coolers required. From what I’ve seen a lot of these datacenters are also switching to CO2 based refirgeration systems which are generally better except the low critical temp of CO2 mean that their efficiency starts to drop quickly once the ambient temp gets much above 80F. Using adiabatic coolers mostly removes that shortfall.