Researchers develop alternatives to Arizona’s water-hungry industrial cooling systems

In Phoenix and other hot and arid areas, industrial manufacturing facilities face a growing dilemma: how to keep their operations cool while using less water. Evaporative cooling, the dominant method used in desert large-scale industrial systems, consumes large amounts of water to keep buildings and equipment safe. For example, a single semiconductor fabrication plant can evaporate up to five million gallons of water per day. 

But what if there were a way to cool these systems without losing water to the atmosphere?

Nariman Mahabadi is researching the answer to that question. An assistant professor in the School of Sustainable Engineering and the Built Environment at ASU, Mahabadi is leading a project focused on mitigating the evaporative water loss in large scale industrial manufacturing. The project is supported by the Global Center of Water Technology, led by professor Paul Westerhoff, through the Arizona Water Innovation Initiative.

Mahabadi’s journey to this work is rooted in his early exposure to large-scale engineering projects when he spent summers visiting job sites with his civil engineer father, and his fascination with the complexity of soil and subsurface systems. After earning his doctorate at ASU in 2016, he held research and faculty positions at Stanford and the University of Akron, before returning to ASU as faculty in 2023, drawn by a desire to work on real-world problems facing Arizona residents.

Using the subsurface to cool instead of water

Mahabadi and his team, which includes Regents’ Professor Edward Kavazanjian, doctoral student Mani Kumar Rambothu and undergraduates Kevin Slaney and Angelica Gigli, are investigating the potential of ground coupled heat pump systems to reduce water loss by shifting from air-based evaporative cooling to a closed-loop system that leverages the earth’s consistent underground temperature. 

Unlike traditional cooling towers that evaporate water into the air, the heat pumps circulate a fluid through underground pipes where heat is absorbed or released, depending on the season. 

“You’re still collecting heat from the building,” Mahabadi says, “but instead of releasing it into the air or using evaporation, we’re sending it underground, where the temperature is stable and naturally cooler in summer time.”

The systems can be shallow – on the order of 10-15 feet below the surface in a “slinky” arrangement – or deep, utilizing a “U” shaped pipe that may be hundreds of feet down. Either way, the process uses far less water and can maintain stable cooling performance year-round, even during Phoenix’s sweltering summers.

This is not new technology, but there are some challenges, Mahabadi notes. Arizona’s unique challenge is that while ground coupled heat pumps are well-established in wetter climates like the northeast or Florida, where moist soil makes for ideal heat exchange, the dry desert soils of Arizona present a major obstacle. That’s where Mahabadi’s team is innovating.

“The entire idea is if it is really feasible to use these ground coupled heat pump systems in Arizona,” Mahabadi explains. “We know they work in other parts of the country, but Phoenix has very unique soil and climate conditions. We need to understand if this technology can be adapted here—and how.”

After completing a promising computational simulation taking into account things like soil composition and underground temperature gradients as the first phase of the project, Mahabadi and his team have determined that if they are able to feasibly improve the thermal properties of soil, ground coupled heat pump systems can work well in Arizona, especially for large buildings.

“Our simulations show that in some cases, the energy performance can even be better than conventional systems,” he says. “But the real benefit is the water savings. That’s the game-changer in Arizona.” 

The second phase of the project, now underway, involves small-scale lab experiments exploring a few promising approaches to improve the thermal performance of dry soils. One is the use of recycled materials, such as scrap aluminum, which have high thermal conductivity. 

Another is biological, inspired by nature. Mahabadi and his team are collaborating with ASU’s Center for Bio-mediated and Bio-inspired Geotechnics to inject reactive solutions that stimulate existing soil microbes to precipitate calcium carbonate, effectively enhancing the soil’s thermal performance without excavation or water use. 

“We’re trying to improve the thermal properties of soil without adding water,” Mahabadi says. “That’s the core challenge. Our larger goal is to see if these systems can actually work in this climate, in this soil and at the scale that industry needs. And not just technically, but economically and practically, too.”

The final phase of the project will take the research into the field, using a modular building at ASU’s Polytechnic Campus to test the system under real environmental conditions.

Looking ahead

With Phoenix’s rapid industrial growth and limited water supplies, Mahabadi’s work is both timely and potentially transformative. This work has already attracted the interest of industry partners. 

“This isn’t just a lab experiment,” Mahabadi emphasizes. “We’re designing solutions with real-world application in mind. We’re already talking to manufacturers like Intel who are interested in reducing their water use. They’re ready for options.”

The potential impact is enormous. Facilities like hospitals, universities, data centers and even Department of Defense sites, which reportedly operate thousands of evaporative cooling towers, could benefit from this technology. And while the focus is on large-scale applications, Mahabadi notes there may eventually be opportunities to adapt the systems for residential use as well.

Ultimately, this project marks a shift in Mahabadi’s career from theoretical research to tackling a tangible problem with wide-reaching consequences. 

“I’m really grateful for the opportunity to work on something that could make a difference in my community,” he says. “This wasn’t in my research portfolio before, but now it’s central to what we’re doing.”

If successful, Mahabadi’s team could help manufacturers dramatically cut their water use while maintaining—or even improving—their energy efficiency. It also supports Arizona’s broader push toward water sustainability by targeting a sector that has traditionally been overlooked in water conservation discussions.

“Evaporative water cooling is the most common and low-cost method for commercial, industrial and institutional buildings to operate HVAC and associated indoor air conditioning. Unfortunately it is a major consumer of tap water, evaporating it to the air,” says Westerhoff. “This project is providing groundbreaking and practical strategies to reducing reliance on water-intensive evaporative cooling, potentially conserving hundreds to thousands of acre-feet of water per year.”

By demonstrating the feasibility of ground coupled heat pumps for cooling large-scale operations, the project offers a replicable water conservation model for other desert cities and regions.