Liquid cooling: the necessary breakthrough to counter data center overheating
For decades, the hum of fans and the blast of air conditioning defined the standard soundscape of our server rooms. That era is over, giving way to a new physical reality. With the rise of Generative Artificial Intelligence (AI), Machine Learning (ML), and High-Performance Computing (HPC), thermal density in server racks has reached levels that air cooling can no longer handle effectively.
At Voltekko, we witness this paradigm shift every day. It’s no longer a question of “if”, but “when”. Liquid cooling in data centers is no longer a niche technology reserved for supercomputers—it’s a core building block for any modern data center aiming to balance performance, density, and environmental responsibility.
Analysis of an inevitable transition.
The thermodynamic dead end of all-air systems
To grasp the urgency, we need to face the numbers.
Just five years ago, a density of 5 to 8 kW per rack was standard. Today, with the widespread integration of next-gen GPUs (like NVIDIA’s H100 or Blackwell series), we’re seeing standard requests ranging from 30 kW to 50 kW per rack, with peaks reaching up to 100 kW.
Air, as a heat transfer fluid, becomes inefficient at these levels. Trying to cool a 50 kW rack with air is like trying to put out a fire with a squirt gun:
- Noise becomes unbearable, exceeding safety thresholds for technicians.
- Space is wasted on ever-larger cooling systems (CRAH/CRAC).
- Energy is wasted just to move air around, drastically harming your PUE (Power Usage Effectiveness).
This is where the physics of liquid cooling comes into play. Water conducts heat roughly 3000 times better than air. Switching to liquid means accepting a new heat transfer vector to keep pace with Moore’s Law.
Direct-to-chip vs immersion: a technology showdown
While the need is undisputed, the method still sparks debate. Two main approaches dominate today’s liquid cooling market.
Direct-to-chip (DTC) cooling
This is the most “reassuring” option for operators used to traditional infrastructure. A liquid circuit (glycol water or dielectric fluid) circulates through cold plates placed directly on the hottest components (CPU, GPU, RAM).
- Advantage: It retains the standard “rack” format. Existing racks can often be retrofitted with manifolds and a CDU (Coolant Distribution Unit).
- Limitation: It captures only 70 to 80% of the heat. The remainder still needs to be dissipated via ambient air, requiring a hybrid cooling system.
Immersion cooling
This is the disruptive option. Servers are fully submerged in tanks filled with non-conductive dielectric fluid.
- Advantage: Near-total heat capture (close to 100%). No fans run inside the server, reducing IT power consumption by 10 to 15% instantly.
- Limitation: Maintenance. Replacing a RAM stick means removing the server from the fluid, requiring specific tools and procedures (lift carts, drip-dry zones).
The real-world challenges of integration
Let’s be realistic: introducing liquid into IT rooms still scares many CIOs. The fear of water leakage on critical equipment is a strong psychological barrier. Yet today’s technologies have reached industrial-grade maturity.
At Voltekko, we recommend monitoring three critical points during implementation:
Weight management
Liquid is heavy. A Direct-to-Chip rack or immersion tank weighs significantly more than a standard air-cooled rack. Floor load capacity (concrete slab or raised floor) must be reassessed. Structural reinforcement is often required for high-density deployments.
CDU (Coolant Distribution Unit) complexity
The CDU is the heart of the system. It connects the building’s water loop (FWS) to the technological circuit (TCS). Proper sizing is critical: it must manage flow rate, pressure, and filtration with full redundancy. If the CDU fails, the entire row of servers enters thermal protection mode within seconds.
Maintenance and skills
Your ops teams know how to change an air filter. But can they purge a hydraulic circuit or handle quick disconnects? Switching to liquid requires your facility management teams to level up their technical expertise.
A game-changing lever for green IT
Beyond raw performance, liquid cooling is your strongest ally for ESG goals. By eliminating server fans and drastically reducing the need for energy-hungry chillers, it’s possible to reach PUE levels below 1.1, or even 1.05 with immersion.
Even better, liquid cooling produces high-temperature output water (often between 40°C and 60°C). Unlike hot air, which is hard to capture, this hot water is easy to transport and can be repurposed for district heating or nearby industrial processes. This is how the data center—historically a resource-hungry structure—can transform into an energy provider.