The Path to a Net Water Positive Data Center

Highlight Story: The Path to a Net Water-Positive Data Center

Over the last three years, we’ve had an opportunity to conduct a case study about our sustainable-focused approach to achieve a net water positive data center, grappling with the embodied water of electricity and the tradeoffs with onsite water consumption for cooling.

Woman riding a bike with trees in the city.

Sustainable Data Centers: The Path to Net Water Positive

In 2019, our largest data center in Carrollton, Texas 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 100% 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% to 4.6 million gallons used for landscape irrigation, fire system maintenance, and domestic water for Carrollton’s 60,000 ft2 of office space. Only a portion of this 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 Carrollton in 2019 and 2020. While we discovered that supply chain water greatly outstripped the water used onsite, Carrollton’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, a new renewable electricity source that we invested in during 2020 will cover an estimated 70% of Carrollton’s power needs with renewable solar electricity beginning in 2021. Based on the WRI’s tool, solar electricity has a water consumption factor of zero, thus reducing our energy supply chain water consumption by 70%. As you can see in the adjacent table, the total water consumed at Carrollton in 2021 will be less than a third of the consumption in 2019, demonstrating the promise of our onsite water-free cooling enabling a truly water-free cooling future for this facility.

Also in 2020, we purchased Water Restoration Credits to offset our onsite water use at Carrollton, restoring 20% more water than we consumed in order to achieve our net positive water designation. From here, it’s easy to imagine a future when the facility uses 100% renewable electricity for the full promise of net zero carbon with net positive water data centers.

Photo of water dropping into a puddle.

Carrollton 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 4,500,000
Energy Supply Chain Water  84,015,000 87,806,000 26,520,000
Total Water  97,276,000 92,417,000 31,020,000
Water Restored  0 5,533,000 5,400,000
Regional Water Impact  97,276,000 86,884,000 25,620,000
 

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