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District Energy System Under Downtown Phoenix Cools More Than 40 Buildings

Gary Cheek with NRG Energy Center
Annika Cline/KJZZ
Gary Cheek holds a map of the NRG Energy Center below downtown Phoenix.

The Valley is still going to see highs above 100 during the month of September. For people from cooler places, that can be unfathomable. But it is bearable, thanks to the wonders of air conditioning. There are times where it's a hundred outside but you might need a light jacket in some buildings.

What's more, some of the major buildings that make up the downtown Phoenix skyline are all cooled by the same system. Talking Stick Resort Arena, Comerica Theatre, the Sheraton Hotel and more are all cooled by the biggest version of an air conditioner you've ever heard of, and it's right under the street.

I took a tour of this underground system, with Gary Cheek as my guide. Cheek doesn't actually do a whole lot of tours. He's the Director of Operations and Maintenance at the NRG Energy Center under downtown Phoenix.

"It's pretty much invisible," Cheek said. "People have no idea this plant's underneath the street."

They actually have three main plants around here. We were in the Convention Center Plant, and we took a look at what Cheek calls the ice tanks.

"The water level in here's about 26 feet deep," Cheek explained.

It looks like a really big swimming pool.

"For the most part it's about 32 degrees in here," Cheek said.

It would be a really cold swimming pool. But the temps are perfect for a cooling system that cools more than 40 buildings.

It's incredibly noisy right where the action happens, so Cheek had to shout as he explained that the blue pipes above our heads were bringing back water from customers. Four miles of pipe under the streets deliver the chilled water to keep air conditioners blasting cold air. Then the water comes back to be chilled again.

"Our water just keeps going around in a circle, out to the system, to the customers and back — 24/7, 365," Cheek said.

Where we're standing over the ice tanks is just below the intersection of Washington and 3rd Streets. The people standing above us on the sidewalk can see Symphony Hall, the Phoenix Convention Center and the Bank of America tower. All three are customers of the NRG Energy Center.

"All of CityScape is on here, the retail and the office building, Comerica Theatre, Fourth Avenue Jail," Cheek listed.

And their top customer, at least when the Diamondbacks play a home game, is Chase Field.

"They'll take about 7,000 tons of cooling, and if you think of your house — a house has maybe a couple of three or four ton units on it," he said.

Fans watching the game behind home plate rely on an enormous amount of cooling capacity compared with those watching on the TV at home. What's more, Chase Field does not insulate its field from the heat of the day. They want the sunshine to come in, Cheek said.

"If the ground gets cold, the grass turns yellow. And yellow grass on television doesn't look good for baseball," he said. "So even in the summer when it's 115 or 118 outside, they keep the roof open, get all that sunshine and heat on the grass, and then about 2:30 in the afternoon before a 6:40 game, they start pre-cooling."

And by the first pitch, you have happy grass and happy people — a balance that was trickier when Chase Field wasn't connected to a district system 17 years ago.

The Arizona Diamondbacks website notes that the old air conditioning method didn't cool the ballpark down as quickly. That meant they couldn't keep the roof open for as long as they can now.
It's also more expensive and burdensome for buildings like Chase Field to run their own systems and take care of upkeep and upgrades. Whether it's a ballgame or a conference, the venues around downtown are able to keep visitors cool when they need to but don't have to worry about the system that does all the work.

During our tour we exit the plant through a door, and suddenly we're standing on the carpet in one of the Convention Center halls.

"They're very event-driven," Cheek said of the Phoenix Convention Center. "Right in the middle of the summer, we've had 100,000 people come through here. Doors are open, cold air's flying out, but inside it stays nice and cool."

Other areas in Arizona have taken a liking to district energy in the past couple decades. Tucson now uses a similar system at its convention center. The ASU Tempe and Polytechnic campuses run one, too. And now thanks to a construction boom NRG is scouting locations for a fourth downtown Phoenix plant — one that someday more pedestrians and cars will pass over without knowing what's right below their feet.

Annika Cline was a producer for KJZZ's The Show from 2014 to 2019.