Why Microsoft is really abandoning evaporative coolers at its Phoenix DCs
Less about love of the planet, more frustrated city officials
Microsoft has agreed not to use evaporative cooling in future datacenters at its PHX 10-11 campus in Goodyear, near Phoenix, Arizona, a move the Windows giant touted as a sustainability improvement because it will reduce water consumption in the drought-prone region.
However, the City of Goodyear's recounting of the events leading up to the decision tells a different story in which Microsoft repeatedly pushed off building necessary treatment, storage, and discharge control systems for the wastewater generated by the existing facilities' evaporative coolers.
This variety of aircon works by passing hot air through what's essentially a large, damp sponge. As water in the sponge evaporates into the atmosphere, it pulls heat out, cooling the air, Dell'Oro Group analyst Lucas Beran explained in an interview with The Register.
These coolers, he adds, are popular among hyperscalers because they only need to run during the hottest months of the year. They are also relatively efficient compared to other cooling technologies.
But while they save electricity they consume plenty of water, and leave plenty of it so contaminated it must be treated at a wastewater plant. That polluted water isn't toxic - it's just so salty it needs to be treated.
It's this issue that the City of Goodyear hopes to have resolved under a new agreement with Microsoft, which requires the cloud provider to discontinue the use of evaporative cooling tech at future datacenter sites. For the IT giant's first three sites, Microsoft is also required to pay $36 million to expand the community's wastewater treatment facility — a little more than a third of the project's projected cost — and complete all previously incomplete site improvements no later than August 2024.
According to Microsoft, the agreement was the result of the corporation's sustainability commitments. "Due to our focus on sustainability and water conservation and our ongoing partnerships with local municipalities, we have made the commitment that future Microsoft datacenters in the greater Phoenix area will use zero water for cooling all year round," a Microsoft spokesperson told The Register.
However, according to the US city's officials, many of these measures wouldn't have been necessary if the biz had kept to its original plan. When Microsoft originally pitched the five-datacenter campus, the company considered water conservation given Phoenix's dry climate and sparse local H2O resources: according to the Salt River Project, the city's water supply is located roughly 150 miles out of town.
Under the original plan, Microsoft would've pretreated its cooling water and industrial discharge onsite and returned roughly five million gallons a day of raw water to Goodyear's surface water treatment plant, where it would be turned into potable fluid.
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"I think at first we were all very optimistic that the cooling water… could become a source of water for drinking, because they were looking to be a little bit more environmentally friendly, a little bit more sustainable," Barbara Chappell, water services director for the City of Goodyear, told The Register.
However, according to the city, Microsoft almost immediately abandoned this plan — apparently due to trouble with the governing regulatory bodies. Microsoft later sought an amendment from the city allowing it to dump its untreated wastewater into the city's sanitary sewer system instead.
The City of Goodyear agreed on condition that Microsoft construct storage improvements and discharge control systems to limit discharges on the existing transmission line to 500,000 gallons per day. Microsoft was also asked to take measures to control contaminants in the water.
According to Chappel, this plan was still sustainable; it just meant Microsoft's wastewater would have to be treated at city facilities, and until a dedicated transmission line was built, volume and concentration of the effluent would need to be controlled.
Yet, with the second datacenter nearing completion, the city says these improvements were never made. What's more, due to the speed at which the city has grown, "there is no additional capacity available to the city's wastewater treatment plant to accept industrial discharges from Microsoft's operations in excess of the 500,000 GPD currently allowed," a city report published earlier this month asserts.
Chappel notes that it's not that the treatment facility has been overwhelmed by Microsoft, so much that the facility in its current state can't meet both the cloud provider's needs and its commitments to the broader community.
Asked whether there was any concern over Microsoft's track record up to this point, Chappel said this was the reason the city sought financial assurances this time around.
Less water, more power
While Microsoft's future datacenters at the site may consume less water, as we've already pointed out, its facilities will likely do so at the expense of greater power consumption.
Refrigerant and chilled water coolers — two alternatives to evaporative cooling — aren't nearly as efficient, Beran explains. And this will likely mean higher greenhouse gas emissions, unless Microsoft can make up for those efficiency losses elsewhere. According to the US Energy Information Administration, 56 percent of Arizona's power comes from the burning of fossil fuels (43 percent natural gas and 13 percent coal).
Higher power consumption could also prove troublesome in a place like Phoenix, where the daytime temperature reaches 100˚F (38˚C) for an average of 145 days of the year and the mercury once reached 122˚F (50˚C). Those temperatures can mean local power utilities run into capacity challenges.
As we've previously reported, this could result in outages in the event of an extreme weather event. "If you need to consume more power to cool your facility because you want to use or need to use less water, it absolutely creates the opportunity for power availability concerns," Beran says.
There are still opportunities for Microsoft to turn the situation around. Microsoft is only now beginning work on its third datacenter on the campus, which, under the agreement with the city, will continue to use evaporative cooling.
This gives Redmond time to evaluate alternative thermal management technologies for the two remaining datacenters. For example, direct liquid cooling or immersion cooling, both of which are significantly more efficient compared to air-cooled systems.
"Microsoft is absolutely a leader in the datacenter industry and helping the datacenter industry achieve sustainable growth. This is a perfect use case example where you could say 'let's use direct liquid cooling or immersion cooling, and we can achieve our goals in this difficult environment'," Beran says.
In his mind, the industry as a whole would benefit heavily from Microsoft stepping up and volunteering to be the guinea pig for the large-scale deployment of these technologies.
However, Beran isn't sure Microsoft is ready to take that risk until liquid and immersion cooling technologies are more mature. ®