How much water will Effingham’s OpenAI data center need? A lot – but not on site.

When Effingham County announced plans for a massive OpenAI data center last month, area residents immediately questioned where it would get its water and how much it would need.

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Data centers have a reputation as water hogs, and the Savannah area has struggled in recent years to meet growing demands for water while protecting its natural water supplies.

The “how much” question was one that even Effingham County seemed unsure of at first. In filing paperwork for a development of regional impact, the county’s senior planner wrote “no clue” in response to the question “Is sufficient water supply capacity available to serve the proposed project?”

About a week later she updated the form to indicate the data center will need 30,000 gallons of water a day. That’s low for an industrial user, about as much as 100 average households use. The authority’s website explains that quantity is for “ordinary workplace uses such as sinks, restrooms, kitchens, cleaning, and sanitation.” It does not include the one-time initial fill of the data center’s closed-loop cooling system. “That initial fill and the project’s final ongoing annual demand are still being determined through final design and water-service planning and will be disclosed when finalized,” the website states.

Complicating the water picture in southern Effingham is the fact that new withdrawals from the Floridan aquifer are off limits in this area, designated a “red zone” to protect this resource from overuse. Any water needed for the data center will have to come from existing supplies, though Effingham is building a multimillion-dollar water treatment center to process large quantities of Savannah River water.

‘Closed loop’ and dry cooling

The closed-loop system OpenAI intends to employ will use dry cooling, OpenAI spokesman Aaron McLear wrote in an email to The Current GA. He explained the system will reject heat to outdoor air using heat exchangers, much like a car radiator. The company does not plan to use evaporative cooling towers, which lose water to the atmosphere.

The closed loop allows the system to be filled once, then “limits ongoing water use to normal makeup and maintenance needs,” he wrote. McLear could not provide a quantity needed to fill or replenish the loop.

“The final equipment configuration is still being designed, so we don’t have more detailed specifications yet,” he wrote.

But Effingham County Manager Tim Callanan did provide an estimate for the initial fill.

“Each building has multiple loops in it, so it’s a million gallons per loop, and so my guess is, it’ll probably be like four buildings, maybe 25 loops, something like that,” Callanan told The Current GA. “So maybe 25 million gallons to fill up everything.”

Akanksha Menon, a Georgia Tech assistant professor and director of the Water-Energy Research Lab, cautioned that even dry cooling can be a thirsty process.

“The regular consumption could be about 100 times less than the water that is needed for cooling, even if we’re talking about using dry coolers for the most part,” she told a crowd of about 70 people at an Aug. 26 data center community information session sponsored by the Effingham County Chamber of Commerce.

‘No free lunch’

While a closed-loop cooling system can dramatically reduce a data center’s water use at the site, it’s not without consequences, said Kelly T. Sanders, Professor and Dr. Teh Fu Yen Early Career Chair at the Sonny Astani Department of Civil and Environmental Engineering at the University of Southern California.

“There’s no free lunch here, and there’s always going to be trade-offs,” she said in an interview with The Current.

“As these data centers go to closed-loop cooling — and it sounds like they’re using a dry cooling system — what that basically means is that they’re using big fans to reject the final amount of heat from the data center facility. And so, what do fans require? They require a lot of electricity,” Sanders said.

Producing electricity requires a lot of water. Much of Georgia’s electricity is generated through a process that uses natural gas, nuclear or coal to boil water into steam to drive a turbine. These heat-driven processes require cooling systems that typically lose water through evaporation. 

“Energy is the number one water user in the state, hands down,” said Tonya Bonitatibus, the Savannah Riverkeeper. “It’s always been that way.”

Much more energy — and water — will be needed to power data centers across the state, she noted.

“Think about it: 14.4 gigawatts right now feeds all of the houses, all of the industries, everybody that is on power right now, and we’re talking about doubling that, like twice over,” Bonitatibus said. “So that is going to put a tremendous strain on water resources.”

Georgia Power and its sister company Southern Nuclear Operating Company, which runs Plant Vogtle, have permits to withdraw more than 1.1 billion gallons of water a day from rivers statewide. About a quarter of that withdrawal, 277 million gallons a day, comes from the Savannah River.

Some of that water is returned to the river, but a huge portion is lost to evaporation, with the average water consumption for power plants in Georgia estimated at 370 gallons/MWh, a research paper Sanders co-authored reported in 2019. A 2020 report prepared for the Georgia Regional Water Planning Councils put the average consumption for combined cycle natural gas power plants at 198 gallons/MWh, though Sanders cautioned the average grid mix is more water intensive than the best natural gas combined cycle plants.

Sanders calculated for The Current the likely water consumption at power plants as a result of supplying electricity to the 3.2 gigawatt data center. It could range from about 4 billion to 8 billion gallons a year, depending on which water consumption data is used. Sanders assumed the data center would be built to capacity and run at that capacity 80% of the time.

That works out to about 11 million to 22 million gallons of water per day of indirect water consumption to run the proposed OpenAI data center in Effingham.

Will it work here?

While a closed-loop cooling system would decrease a data center’s onsite water needs, not everyone is convinced it would work well in Coastal Georgia’s hot, humid climate.

Savannah resident Michelle Addington is a retired architecture professor with research expertise in cooling systems. She taught at Harvard and Yale and was the dean of the School of Architecture at the University of Texas at Austin.

She explained that in dry cooling, the liquid to be cooled is sent to a large outdoor space filled with finned metal plates. As the water slowly moves through, it gives up its heat to the ambient atmosphere. 

“Key driver, the atmosphere must be cooler than the liquid,” she wrote in an email to The Current. That could be a sticking point, especially in sticky weather.

Menon agreed. Her lab has developed cooling system models that analyze water and power consumption for cooling a data center in a given location.

“While we have not run the model for the specific case of Effingham County or Project Camellia, what we have generally found is that closed loop cooling using dry coolers may not be able to dissipate the full heat load when the ambient temperature is high (for example, on a hot summer day),” she wrote in an email to The Current.

“In these cases, it would need to evaporate some water (this is referred to as adiabatic assist where air flows through a wetted media) to provide sufficient cooling. This water consumption is much less than a typical cooling tower, but it is non-zero. Alternately the site can use a chiller with an air-cooled condenser, but this would consume more power than a dry cooler,” she wrote.

Without knowing more about the engineering design of the proposed OpenAI data center, Menon could not estimate how much water would be needed for cooling.

“But I can confirm that (i) average vs. peak consumption will differ based on seasonal variations/climate conditions, and (ii) closed loop does not equate to zero water consumption,” she wrote.

Addington, Sanders and Menon all note a dry cooling system will drives up energy use, resulting in more indirect water consumption.

“If they are really thinking that they can do it with only a closed loop sensible cooling system, then this is the most inefficient means of cooling — thereby more electricity needed pushing up water usage at the power plant,” Addington wrote, using the physics term “sensible,” which refers to a heat transfer that results in the change of a system’s temperature rather than its phase.

McLear, the OpenAI spokesman, said the system will be designed for Southeast Georgia’s summer and extreme-weather conditions but couldn’t provide the name of the firm designing it or any details of how hot is too hot for this system to function.

“The exact maximum outdoor design temperature depends on final equipment selection and system design, so we don’t have a specific temperature at this point,” McLear wrote.