"So what does Google do? They evaporate the water! What a waste."
Quite literally a drop in the bucket. The back of my envelope has too much written on it at the moment, but if you look at the total water flow in that watershed and multiply it by the heat of vapoization of water you get a staggeringly large energy flow. There's no way; absolutely no way at all a few megawatts of server heating would be measurable at all. None.
Google's total worldwide power usage is about 220 megawatts, calculate the amount of water starting at about 20 deg. C average needed to evaporate to carry away all that energy and that works out to about 700 million gallons of water needed per year. Which is about one or two days of water usage for Atlanta. Keep in mind that this is for all of google's data centers worldwide. For only the servers that are actually in Georgia the amount of water carried away is incredibly small compared to total usage.
Also I didn't account for radiative cooling which is probably fairly significant but likely not more than, say, 50% of the necessary cooling load.
1 megawatt * 1 hour = 3,600,000,000 joules
Water takes 2,257,000 joules / kg to evaporate
Which works out to ~1,600 kg or 422 gallons of water per hour per MW.
However, I don't think they actually want to evaporate all that much water which leaves a lot of residue issues and instead focus on heating a much larger volume of water.
PS: The article is also wrong in that they don't directly cool hot air from their servers with this water. They are cooling air heated by there cooling system and depending on how hot the air from there servers are they may simply vent that if it's warmer than the outside air.
> Basically a 100' square catch basin on the roof of the building would provide all the water they need. Noise.
Which raises the question: Why don't they just do that? I'd imagine it would be less effort to process, and even though you do need to have a buffer against low rainfall periods, water is one of the easiest things to store.
O, I agree it's Noise. However, the reason they don't use a catch basin / just pay for it is Atlanta's high average humidity. There are going to be days where little water is going to evaporate in those cooling towers and most of their energy is going to simply raise the temperature of a large volume of water. So, having access to say 100 times the flow they need is vary helpful.
Quite literally a drop in the bucket. The back of my envelope has too much written on it at the moment, but if you look at the total water flow in that watershed and multiply it by the heat of vapoization of water you get a staggeringly large energy flow. There's no way; absolutely no way at all a few megawatts of server heating would be measurable at all. None.