A simple AI query uses a bottle of water just to keep the servers cool

Up until a couple years ago, data center cooling was just like cooling your computer. When it gets hot, a fan comes on to blow cool air across the hot chips. In cold places, that might come from outside. In hot places, it might require air conditioning.

But AI is using more and more power, and chips are getting jammed into tighter and tighter spaces, all in the name of harder better faster stronger computations. All of which makes more heat.

“The heat flux is going to be, in the near future, too high for air cooling to always be a satisfactory solution,” said Jonathan Boreyko, a professor of mechanical engineering at Virginia Tech.

That’s where liquid cooling comes in. Instead of fans, some data centers might rely on a pipes, filled with water and ethylene glycol (also known as engine coolant). Those pipes send liquid through the CPUs, which grabs their heat, and shoots it into a cooling tower.

“During that process, some of the water is evaporated, and that's how the heat is actually moved away,” said Eric Masanet, a professor of sustainability in emerging technology at the University of California, Santa Barbara. “It's the same thing that happens when we sweat after a workout. The sweat evaporates, and it takes the heat from our bodies and moves it into the atmosphere.”

Masanet says with air cooling, data centers might have to tack on an extra 30% of their power draw just to keep cool. Switching to liquid drops that cooling tax down to 10%.

That might not sound like much, but new data centers are now ten times the size of the old ones.

“That 10% of power that goes into cooling a gigawatt data center is equivalent to the total power it took to run some of the largest data centers on the planet before AI,” Masanet said.

In addition to the power use, there’s the water use. Researchers at University of California, Riverside, figured out that generating a 100-word email with AI uses about a bottle of fresh water. A hyperscale data center can use up to 5 million gallons of water every day. Which is about the same as a town of 30,000 people.

That water gets used up in two places.

“If you're using a cooling tower, your data center, so that's one place where water could be lost,” said Richard Bonner, chief technology officer at the tech cooling company Accelsius.

The heat in the tower is lost to evaporation. Also, the power plant for the data center likely has its own cooling tower.

“There's more demand for the power, which means there's more demand for the water going to the power plant,” he said.

Just like AI tech, cooling tech is advancing really fast. Masanet said there’s now even a way to eliminate the evaporating cooling tower part altogether.

“Yes, the facilities are getting more efficient, the computing is getting more efficient, but the demand is outstripping those efficiency gains,” he said.