[Beowulf] Google greywater cooling

Prentice Bisbal prentice at ias.edu
Fri Mar 23 06:47:18 PDT 2012

On 03/21/2012 08:45 PM, Ellis H. Wilson III wrote:
> On 03/21/2012 10:11 AM, Hearns, John wrote:
>> Flagging up yet another Register article I’m afraid, but it is interesting
>> http://www.theregister.co.uk/2012/03/20/google_greywater_data_center_cooling/
> Certainly interesting.  I missed this one in my El Reg RSS.  Does anyone 
> have references on a (modern) picture of what their servers look like? 
> In other words, they are particularly vague in the article and the 
> associated video on how they actually use this water to do the cooling. 
>   I assume it is not "real" water cooling, but utilizing that water in 
> their air conditioning units somehow.  I cannot imagine they use the 
> water to re-humidify their server rooms, since rooms smelling of piss 
> and chlorine probably isn't appreciated by any but the most green of 
> environmentalists.

That water is first sent through a Google-built sidestream treatment
plant, which sterilizes, filters, and clorinates it, cleaning it just
enough for it to be used in the data center's evaporative cooling towers.

The water that doesn't evaporate away during that process is then
further purified in Google's on-premises Effluent Treatment Plant.
"There, we treat the water once again to disinfect it," Brown writes,
"remove mineral solids and send it back out to the Chattahoochee –
clean, clear and safe."

Based on the above description, this is the most likely scenario:

The greywater flows down the outside of heat exchangers in the cooling
tower. As it evaporates, the change of state removes a lot of the heat
from the liquid inside the heat exchanger (probably also water, but
clean, treated water). The chilled water inside the heat exchanger then
flows into heat exchangers inside the data center CRACs where it absorbs
heat from the warm data center air., cooling the air.

Any time you use water in a closed-loop system (chilled water cooling or
steam heating, for example). It needs to be very clean, and have
additional chemicals added to it prevent corrosion or mineral buildup
inside the pipes, so greywater would probably never be used inside one
of these systems.

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