Data centers produce enormous amounts of heat, and the way they remove it is changing fast. Let's take a look at the cooling systems being used today and the ideas that may shape the future of data center cooling.
Every data center has the same basic problem: computers create heat. The more computing power packed into a building, the more heat has to be removed.
For years, many large data centers relied heavily on traditional cooling systems that used significant amounts of water. As AI and high-performance computing have increased the amount of heat generated inside server racks, operators have started exploring newer ways to cool equipment with less water and greater efficiency.
Some of those technologies are already becoming common. Others are still emerging. A few, like putting data centers in space, are still more concept than mainstream reality.
Here is a simple look at how some of the major cooling approaches work.
Traditional Evaporative Cooling
This is the method you know. All of the memes about data centers using so much water? This is why.
Traditional cooling towers have been widely used because they are effective and relatively simple. The basic idea is similar to how sweating cools your body: warm water from the data center is sent to a cooling tower, where some of it evaporates into the air. That evaporation carries heat away, and the remaining cooler water is circulated back through the system.
The downside is that the water that evaporates is gone and has to be replaced. Cooling towers also concentrate minerals and other dissolved material in the water that remains. To keep those concentrations from becoming too high, some of the water has to be removed as blowdown and replaced with fresh water.
That combination of evaporation and blowdown is why traditional evaporative cooling can use so much water. For large data centers operating around the clock, especially in hot climates, the total can be substantial.
Closed-Loop Cooling
This is the industry's current standard rebuttal to your water memes.
Closed-loop systems are often discussed as a major way to reduce data center water use because, instead of constantly evaporating water into the atmosphere, they circulate the same coolant through a sealed loop. The coolant absorbs heat from the equipment, carries that heat somewhere else, cools back down, and then returns to repeat the process.
Because the fluid stays inside the loop rather than being continuously lost through evaporation, closed-loop systems can use dramatically less make-up water during normal operation.
That does not necessarily mean they use zero water. Some closed-loop systems still transfer heat to equipment elsewhere in the facility that may use water. The systems also need to be filled initially, flushed during construction, and occasionally drained or serviced.
Compared with systems that continuously evaporate water, however, the reduction can be significant.
Direct-to-Chip Liquid Cooling
As computer chips become more powerful, one increasingly common approach is to bring the coolant much closer to the heat.
With direct-to-chip cooling, a small metal plate called a cold plate sits directly on top of high-heat components such as CPUs and GPUs. Liquid flows through the plate, absorbs heat from the chip, and carries that heat away.
It is a little like placing a cold pack directly on something hot instead of trying to cool the entire space around it. Because liquid can carry away heat much more efficiently than air, direct-to-chip cooling is gaining traction for AI and other high-density computing.
Many of these systems also operate in closed loops, helping reduce ongoing water demand while handling much more heat in a smaller area.
Immersion Cooling
Immersion cooling sounds unusual because it is exactly what the name suggests: the servers are placed directly into liquid.
The liquid is not water. It is a specially designed dielectric fluid that does not conduct electricity, allowing it to surround electronic components without shorting them out. Instead of moving cooled air around the equipment, the fluid absorbs heat directly from the servers.
There are two primary versions. In single-phase immersion cooling, the fluid remains liquid as it heats up and circulates through a cooling system. In two-phase immersion cooling, the fluid actually boils around the hot electronics. The vapor rises, cools, condenses back into liquid, and returns to the system.
Immersion cooling can handle extremely high heat loads and reduce the need for fans and large air-handling systems. It is already used in some specialized applications, although it is not yet as common as direct-to-chip cooling.
Free Cooling
Another approach sounds almost too simple: use the conditions outside when the weather allows it.
In cooler climates, data centers can sometimes take advantage of naturally low outdoor temperatures or cool water sources to remove heat without relying as heavily on mechanical cooling equipment. This is often called free cooling or economization.
It does not mean the cooling is literally free, but it can significantly reduce the energy needed to keep equipment at the right temperature. How useful it is depends heavily on climate, humidity, facility design, and the amount of heat the data center is producing.
Waterless and Low-Water Liquid Cooling
Some newer systems are taking the closed-loop idea further by trying to combine the efficiency of liquid cooling with little or no ongoing water use.
These systems may use specialized coolants instead of water and circulate them in sealed loops directly to high-heat components. The goal is to capture heat efficiently without creating the same dependence on evaporative cooling towers and continuous supplies of make-up water.
These approaches are still developing, but they become especially attractive in places where access to water is becoming a major constraint on data center growth.
What About Putting Data Centers in Space?
This is where the conversation gets much more futuristic.
Several companies are exploring the idea of putting computing infrastructure in orbit, where solar power is abundant and data centers would not compete with communities for land or water.
At first glance, space sounds like the ultimate cooling solution. After all, space is extremely cold. The problem is that cooling something in space is actually much more difficult than that makes it sound.
On Earth, heat can be transferred into air or water and carried away. In space, there is no surrounding air, so heat has to be released primarily through thermal radiation. That requires radiator panels that release heat away from the spacecraft.
In other words, putting a data center in space could eliminate the need for a traditional cooling tower, but it creates an entirely different thermal engineering challenge. Launch costs, radiation exposure, maintenance, communications, and getting rid of heat all remain significant hurdles.
Orbital data centers may eventually make sense for certain applications, but they are still a long way from replacing the facilities being built on Earth today.
Why Cooling Technology Matters So Much
Cooling is no longer just an engineering decision. It can affect how much electricity a data center uses, how much water it needs, where the facility can realistically be built, and how easily a project gains support from the surrounding community.
Traditional evaporative cooling works well, but it can place significant demand on local water supplies. Closed-loop and direct-to-chip systems can reduce that demand considerably, while immersion and other developing technologies offer ways to handle increasingly dense computing without simply scaling up traditional cooling towers.
There is no single best cooling system for every data center. Climate, computing density, available water, facility design, cost, maintenance needs, and the type of equipment being operated all influence the decision.
Less Water Does Not Mean No Wastewater
Even the newest cooling systems still have a wastewater story.
Closed-loop systems need to be filled and flushed, and the fluid moving through those loops may contain glycol, corrosion inhibitors, suspended solids, or dissolved metals. Maintenance can also require systems to be drained, cleaned, and refilled.
Traditional cooling towers generate blowdown, while direct-to-chip and immersion systems can create different maintenance fluids and residuals that eventually need to be managed. As cooling systems use less water overall, understanding the chemistry of the smaller waste streams they do generate can become even more important.
For data center developers and operators, the question is therefore not only how much water a cooling system uses. It is also what happens to that water or cooling fluid when the system is commissioned, serviced, changed, or eventually replaced.
Cooling Is Getting More Targeted
The biggest trend across these technologies is that data centers are becoming more precise about where and how they remove heat.
Traditional evaporative systems have supported data centers for decades, but increasingly powerful AI hardware is pushing cooling closer to the equipment generating the heat. Direct-to-chip systems bring liquid directly to processors, while immersion cooling surrounds the hardware itself.
At the same time, closed-loop systems are reducing the need to continually replace water lost through evaporation, and emerging technologies are looking for ways to reduce water demand even further.
As AI pushes more computing power into smaller spaces, that combination of more targeted cooling and lower water use is likely to become increasingly important.
At Valicor, we work with data center contractors and operators managing wastewater generated during construction, commissioning, system flushing, cooling-loop maintenance, and ongoing operations. As cooling technologies change, the volume and makeup of those wastewater streams will change with them, making early planning increasingly important.
References
- DOE overview of data center cooling and direct liquid systems: Cooling Water Efficiency Opportunities for Federal Data Centers
- Google’s 2026 closed-loop rack cooling system for retrofitting air-cooled data centers: Google Brazos Liquid Cooling System
- Microsoft’s plain-language illustration of direct-to-chip cooling: Microsoft Liquid Cooling Overview
- A useful explainer on the technical challenges of orbital data centers, especially heat rejection: How hard is it to build orbital data centers, actually?