Sustainable Data Centers

The Path to a Net Water-Positive Data Center

A few years ago, we had an opportunity to conduct a case study about the embodied water of electricity and the tradeoffs with onsite water consumption for cooling.

In 2019, our largest data center in Carrollton, Texas (DFW1) consumed 13.3 million gallons of water onsite through its hybrid air- and water-cooled system. In 2020, informed by the results of our Water Risk Assessment, which indicated that Central Texas is a high water-stress region, we upgraded the facility to a water-free cooling design. This had the impact of slightly raising the average Power Usage Effectiveness (PUE) from 1.37 to 1.39 while reducing the onsite water use by 65%. The remaining 4.6 million gallons of water were used for landscape irrigation, fire system maintenance, and domestic water for DFW1’s 60,000 ft2 of office space. Only a portion of these 4.6 million gallons is actually consumed (the irrigation), and the rest is discharged to the water treatment works, but for our case study we counted it all as water consumption to be conservative.

This 65% decrease looks great in theory, but we wondered if the supply chain water for the extra electricity would mean that the total water consumed by the facility stayed the same or even increased due to the upgrade. Using the World Resource Institute’s emissions factors for water consumption in the local electrical grid, we estimated the total water consumed (onsite and for electricity generation) by DFW1 in 2019 and 2020. While we discovered that supply chain water greatly outstripped the water used onsite, DFW1’s overall water use still decreased by more than 5 million gallons between 2019 and 2020 due to its switch to a water-free cooling design. This result challenges the conventional wisdom that consuming water for cooling saves total water, at least in today’s supply chain.

Moreover, beginning in 2021 a portion of DFW1’s electricity is supplied by a new solar electricity contract. Based on the WRI’s tool, solar electricity has a water consumption factor of zero, thus reducing our energy supply chain water consumption accordingly. As you can see in the adjacent table, the total water consumed at DFW1 in 2021 was more than 40 million gallons lower than the consumption in 2019.

Also beginning in 2020, we purchased Water Restoration Credits to offset our onsite water use at DFW1, restoring 20% more water than we consumed in order to achieve our net positive water designation. As we increase the percentage of DFW1’s electricity that comes from renewable sources, in pursuit of our net zero by 2030 goal, it’s easy to imagine a future when the facility uses 100% renewable electricity for the full promise of a net zero carbon and net positive water data center.

DFW1 Onsite and Supply Chain Water Consumption

Water Consumption (gal)	2019	2020	2021
Cooling Technology	Hybrid	Water-free	Water-free
Onsite Water	13,261,000	4,611,000	3,230,000
Energy Supply Chain Water	84,015,000	87,806,000	52,670,000
Total Water	97,276,000	92,417,000	55,900,000
Water Restored	0	5,533,000	3,700,000
Regional Water Impact	97,276,000	86,884,000	52,200,000

Water emission factors from WRI’s Guidance for Calculating Water Use Embedded in Purchased Electricity