re: How real is a water scarcity threat, re: Building Data Centers?

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referencing closed loop systems. That’s not all that meaningful as it pertains to water consumption.

Are they rejecting heat to air, using fans? I’d heard that was less popular due to noise.

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Yes, works just like a car engine. Circulate the fluid through a closed system and cool the fluid with fans blowing over fin and tube coolers.

Its less popular than evaporative because closed loop is more expensive to build and operate than evaporative. Evaporative cooling towers have gigantic fans and pumps as well. Evaporative towers are usually noisier due to the waterfall noise. Closed loop systems are fan and pumps only. There is no silent system, but open loop raw water cooling is quietest.

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I genuinely want to learn more. The only “no big deal” comments I’ve seen are referencing closed loop systems. That’s not all that meaningful as it pertains to water consumption.

Are they rejecting heat to air, using fans? I’d heard that was less popular due to noise.

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We have some actual numbers for the Meta data center in Louisiana, as a few others in the thread have mentioned.

The data center is permitted for 8.4 billion gallons per year. Meta says they expect their actual usage to average 500-600 million gallons per year. It appears that all of this water will come from the Mississippi River Alluvial Aquifer via wells drilled by Meta.

To put that into perspective, ExxonMobil Baton Rouge Refinery/Chemical withdrew 7.3 billion gallons from the Southern Hills Aquifer in 2020 (it was the easiest recent datapoint to find) and I think most people agree that their well water usage is problematic. So at best Meta’s data center groundwater usage will be 5-10% of Exxon BR’s groundwater usage, while at worst it will be 115% of Exxon BR’s.

It’s also worth noting that the projected Meta water usage is only for the data center itself. It does not include the water usage for the 5.2 GW of power the data center will consume, which is a staggering number (CCGT generators consume an average of 2.8 gallons per kWh according to EIA) but I have to assume most/all of that will be clarified river water.

When you put it all together I think the impact on cost of electricity is a bigger concern as many have stated. If these data centers were clarifying river water, it would be a complete non-issue. However, I think the fact that so many are drilling their own wells is still at least grounds for concern, especially when nobody really knows how far the boom will go. We should be doing more across the board to ensure sustainability of our aquifers, IMHO.

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Yes, works just like a car engine. Circulate the fluid through a closed system and cool the fluid with fans blowing over fin and tube coolers.

It’s less popular than evaporative because closed loop is more expensive to build and operate than evaporative. Evaporative cooling towers have gigantic fans and pumps as well. Evaporative towers are usually noisier due to the waterfall noise. Closed loop systems are fan and pumps only. There is no silent system, but open loop raw water cooling is quietest.

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A couple of things here:

1. Cooling towers are not noisier than air-cooled exchangers once you account for the amount of heat rejection you get from each. An individual cooling tower might be noisier than the same footprint of air-cooled exchangers. But it’s not noisier than a group of air-cooled exchangers with the same overall duty.

2. A “closed loop” system does not necessarily mean a system without any evaporative cooling. The description is certainly being used to imply that all of the water is recycled, but that’s not what it actually means. It means that the cooling medium itself - the liquid that is being used to cool the GPU’s and/or air inside the data center - exists in a closed loop.

But there are multiple ways the heat can get rejected from that closed loop. It can happen via air-cooled exchangers, as you suggested. It can happen via chillers (vapor compression refrigeration). And it can happen via evaporative cooling on a second loop.

“Closed loop cooling towers” are absolutely a thing - they are basically a hybrid between an air-cooled exchanger (“fin fan”) and a cooling tower. The cooling medium circulates through coils, while a fan draws air across those coils. Meanwhile there are also nozzles that spray water across the outside of those coils. Some of that water evaporates, providing additional cooling. These systems use less water than “open” cooling towers but at the cost of lower energy efficiency.

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Meta says they expect their actual usage to average 500-600 million gallons per year. It appears that all of this water will come from the Mississippi River Alluvial Aquifer via wells drilled by Meta.

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Which is less than the water that was previously used for irrigation on the same farm land.

I'm still concerned about power and natural gas costs ballooning out of control. But the water issues for the META data center are not going to slow the project down at all.

Not sure about the other data centers going up in other parts of the state. Not much is known about Amazon at this time. I've seen one report that they're going to pull water from Caddo Lake, and others that say that they're going to use municipal water (also possible that they're building out multiple facilities and both are true.)