Data centers could be making metro Phoenix even hotter, preliminary research says

Data centers are being built all over the Valley — often to the objections of the people who live near them.

These massive buildings suck up a lot of energy to power AI. But this professor said they could also be making our already hot city even hotter.

David Sailor is the director of Arizona State University’s School of Geographical Sciences and Urban Planning. He and his team conducted new research that shows that data centers are warming surrounding neighborhoods by several degrees — mainly through HVAC systems on the roof to keep all of that computer equipment inside cool.

This is still preliminary research that has yet to be peer reviewed — but it comes as the debate around data centers is intensifying.

The Show spoke with him more about it and he said he’s been interested in what makes a city hot for decades. And there are a few different ways that that happens.

Full conversation

DAVID SAILOR: One of them that has been long known is the effect of anthropogenic waste heat, or simply the heat that's released associated with energy consumption in cities, whether it's from your vehicles or from your buildings.

And so we've been studying this facet of the urban climate for literally for decades. And it was only recently when we were doing a study looking at heat mitigation strategies in Phoenix in particular, where we started to put the two together and ask the question, not just how big of an impact does anthropogenic heat have on the warming of the city, but what does that warming look like when we start to talk about some of the most intense energy consumption in the city, which is in these big energy users like data centers.

LAUREN GILGER: Right, right. There's a stat here that I was reading about how much energy a data center uses. You know, it takes the space of 20 houses maybe, but uses just exponentially more power, right?

SAILOR: Right, right. So it's a great concentrator of energy consumption and as a result, a great concentrator of the waste heat emissions.

GILGER: So let's talk about how you measured this because you basically drove a bunch of cars around data centers, right? Measuring the heat as you went and in various zones around it. Describe this for us.

SAILOR: Right. Well, so we've actually looked at about four or five different data centers in Phoenix. And what we do typically is on any given day, we will instrument typically three or four cars. We'd like to use electric vehicles if at all possible, because then we don't have to worry about any heat emissions from the vehicle itself, or not very much at least.

And what we do is we simply try to drive these cars as close to the data centers we can on regular city streets. And we then move in circular motion sort of into the outer neighborhoods surrounding the data center. So we're trying to make measurements both very close to the data centers, but also maybe half to 1 mile to the north, south, east and west of the data center to see if we can capture a downwind warming effect. And really to identify that downwind effect, we need to make measurements upwind and downwind.

GILGER: So you found some pretty substantial heat impacts, it sounds like, though. Tell us what you found.

SAILOR: Yeah, so it was nothing surprising, really, because, again, we have decades of literature and research on this topic of heat emissions from buildings and cities. And we know that you can elevate the air temperature in the city by several degrees Fahrenheit through the emissions of heat from buildings.

And again, data centers are really such concentrated sources of heat that it was not surprising that we found elevated air temperatures 2 to 4 degrees Fahrenheit higher than upwind of the data center. And those elevated air temperatures were several hundred yards into the neighborhood.

GILGER: So, I mean, like, how close do you have to live to a data center to be impacted by it? Should we be looking around to see if you're a couple of miles from one, when you weren't even aware of it, maybe?

SAILOR: Well, that's exactly what the next step in our research is, is to better understand how that downwind effect spreads and how it varies under different kinds of weather conditions, different kinds of atmospheric stability conditions. And we do expect it to vary quite a bit.

And so we need to get a better handle on it, first of all. I think the short answer is, in a city, most of the microclimate variability associated with any major intervention, whether it's a cooling intervention like a park or a lake, or whether it's a heating and an adverse heating source as associated with, say a data center, we typically find that those downwind effects are typically limited to hundreds of meters, not multiple miles. Let's just put it that way.

GILGER: OK. But more to come there. One of the findings here that it sounds like could be of concern is the nighttime heat impact these data centers could be having.

SAILOR: Yes, absolutely. So what we found in previous research, so this is going back about 20 years now when we were looking at just waste heat emissions in cities, you know, that are typically on the order of maybe 100 watts per square meter of heat emissions for a major U.S. city. And we were finding the largest impacts were both in winter and in summer in the nighttime hours.

We haven't really done that systematic approach where we've looked at multiple hours, day and night. We've just taken a few snapshots during the daytime hours.

But when we do start to look at the effects in the overnight hours, we certainly do expect to see a larger impact at night than during the day. Because for the most part, these data centers are emitting 24-7. So they're emitting the same amount of heat for the most part in the evening hours that they do in the daytime.

GILGER: That's interesting. So are we looking at long term impacts here? Like are you, I know this, is a lot to be still studied, but are you thinking about things like how a proliferation of these data centers across our city, which is already, you know, the hottest big city in the country and getting hotter, we're already breaking records left and right.

Like, are you, are you thinking about how this might add to or make it even harder to live a more difficult urban heat island impact overall, things like that?

SAILOR: Yeah, certainly that'll be part of what we're looking at into the future. Certainly, as you put more and more of these data centers throughout the city, you'll have more of these pockets of elevated air temperature, more urban heat island sort of within the urban heat island, if you will.

And that will, that will result in elevated air temperatures throughout many of our neighborhoods, which comes with elevated energy consumption to deal with that increased heat, elevated water consumption, and of course, elevated risks related to public health.

GILGER: Yeah. So I mean, do you think that cities, local governments, neighborhoods, citizens should be thinking about ways to mitigate that, to balance it even?

SAILOR: Absolutely. That's another aspect of some of the work that we're doing. What can we do in terms of designing data centers to make them have less of an impact downwind in terms of elevating air temperatures in neighborhoods?

And so that can include the data center design itself, some of the HVAC equipment parameters, in terms of how we design HVAC equipment that go on the data centers, but also maybe just simple things like setbacks, you how far a data center has to be from the nearest residential building.

GILGER: And just understanding, it sounds like, what it is that we're, you know, building and what it is that AI costs.