Comment by cm2187
1 month ago
Stupid question: datacenters need water for cooling right? But they don't boil that water, ie it comes out of the datacenter just a little warmer? If that is the case does it matter to the city? The warmer water can still be used for agriculture or any other common usage.
There are multiple ways. Closed loops, well not big deal you fill up and there is slight evaporation losses, but you could ship that in in tanker truck maybe once every few years.
Next is open loop cooling using secondary loop. Take a river, lake or sea. Pump some water from it, pass through heat exchanger and pump back out. Manageable for most of the year. Worse version is pump ground water and return it to these. Depletes the ground water...
And finally evaporative cooling. Which is boiling, but not at boiling point. Water goes to sky. No immediate return to local ground water or downstream the river... In this case you actually do in sense use up the water. Kinda like burning fossil fuels returns co2 to atmosphere. It will later turn to biomass, but that is a separate cycle.
The CO2 cycle is problematic because of timelines. We are releasing millions of years of CO2 accumulation.
Rain is more of a location problem. The evaporated water returns as rain quickly, but maybe somewhere else, such as over ocean. And the aquifer compresses and loses water retention ability.
It's not a stupid question but: technically, after passing through Google's facility that is now gray water, and you can't use that for agriculture or any other 'common usage' without a whole raft of work and you can't just dump it into the aquifer either.
But if it just went through some heat exchangers, it's not like if it was dirty? As far as I know, nuclear power plants return the water they consume to the rivers they extracted it from.
Heat exchangers could easily contaminate the water. If they're not kept hot enough they could be breeding ground for Legionella and a whole raft of other bacteria. Clean water is science, not just a matter of bulk pumping stuff from one place to another (though that's definitely a part of it). Water treatment plants are complex and have a ton of QA on their product. You can't just run it into a factory and pretend it is the same stuff going in modulo some increase in temperature.
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Don't they reuse the water by cooling it outside the data center? Most power plants do that.
Yes, but that does not mean it is now clean water. Anything could happen between the moment Google ingests it and spits it back out, the assumption that it is 'just' a little warmer is nice but it misses the option of for instance contamination from a secondary circuit or various substances leaching into the water used as a coolant.
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If they can return it to the river how can't it flow to agriculture?
It’s gray water, and just as how I can’t dump gray water from my RV camper into the river, neither can a data center. After running through a heat exchanger there can be all kinds of crap in that water.
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> it comes out of the datacenter just a little warmer
Exact values matter. Some power plants had been found dumping +10 C water into lakes/rivers, while they had permit only for +5, and it totally destroyed local ecosystem. And most efficient (in terms of money) is evaporation cooling, where at least part of water is "lost".
A lot of it gets converted to water vapor in the evaporative coolers, so it doesn't flow out -- it becomes humidity or clouds. The coolers do also produce waste water, but with all the minerals left behind after evaporation it's not suitable for drinking.