Dive brief:
- Air-cooled condenser rigs in four data centers near Phoenix created thermal plumes that raised temperatures by 1.3 to 4 degrees Fahrenheit in neighborhoods a third of a mile away, Arizona State University researchers found.
- According to the study, the discharge was 14 to 25 degrees F higher than the air immediately around the condenser arrays, Data center waste heat as an emerging urban thermal hazard.
- With the number of data centers in the U.S. expected to double by 2030, those higher temperatures could pose a problem, says lead researcher David Sailor, director of ASU’s School of Geographic Sciences and Urban Planning. “Even if these data centers only contribute to one additional heat island magnitude of one degree or two degrees, which can still have a very significant impact on our lives,” Sailor said in a Tech Xplore report.
Diving knowledge:
By some measures, Phoenix is the the hottest metropolitan area in the USwith the expected temperatures above 100 degrees for much of this summer, according to AccuWeather.
Every one-degree increase in temperature will prompt greater use of air conditioning, which in turn will put more heat into the area, creating “a feedback loop,” the research says. “Data Center Operations [could] increasing the energy burden on surrounding neighborhoods, precisely during the extended summer cooling season,” according to the report.
To measure the impact of data center temperature, the researchers fitted cars with sensors and drove them up and down four data centers to measure the differences. Data centers ranged from 36 megawatts to 169 megawatts. All of them primarily used air-based cooling systems.
“Average air temperatures downwind [were] 0.7-0.9°C warmer than the corresponding upwind areas,” or 1.26 – 1.62 degrees F, the report states. The air temperature downwind warmed by 2.2 degrees Celsius, or about 4 degrees F.
Although there was a measurable increase, the result remains anecdotal, Sailor said in an interview with AI Generation at the end of March, before the study was published. “It really depends on a number of factors,” he said. “The direction of the wind, the speed of the wind, the intensity of the turbulence in the atmosphere itself. Therefore, [it’s] different in the morning and during the night than during the day, when there is much more of what we call mechanical turbulence mixing the heat vertically.”
The impact of heat generated by buildings in general is not that great, Sailor told AI Generation. When the heat from the building is added to the heat generated by cars and industrial processes, there is a measurable impact on area temperatures, but not as much as some people might think, he said. “Typically it’s on the order of 10 to 20 watts per square meter,” he said. Solar radiation during peak summer, on the other hand, is about 1,000 watts per square meter at noon.
But when the measurement moves to energy-intensive buildings, he said, there is a difference of “magnitudes,” about 100 watts per square meter.
The effect becomes even greater when data centers are taken into account, he said. “For a good-sized data center, you can have waste heat emissions on the order of 2,000 to 6,000 watts per square meter,” he said. A 30-megawatt data center “essentially puts as much energy into the environment as 25,000 or 35,000 homes. But it’s in a concentrated area. [of] maybe 20 houses. So imagine that intensity.”
Sailor outlined a handful of steps facilities can take to reduce the impact of the thermal plume.
- Use a more powerful vertical fan to push the hot air higher into the atmosphere so that it is dispersed further before it spreads to nearby neighborhoods. “The vertical speed at which the fans operate will affect how quickly that vertical plume is expelled,” he said, “The plume is mixed at a higher level and dispersed without going directly into neighborhoods.”
- Keep rooftop equipment open instead of surrounding it with parapet walls that are only there for aesthetic purposes. “You can’t see the equipment on the roof,” he said, but “that helps contribute to the possible mixing at the roof level.”
- Use some form of evaporative cooling, which turns the air in air-cooled systems into vapor, releasing less hot air into the atmosphere.
Sailor did not address growth use of liquid cooling systemsthat submerge computer systems in water or in a chemical bath and release less heat.
