As AI accelerates demand for high-performance computing, the data center industry faces a defining challenge: how to provide significantly higher power densities without compromising sustainability or operational efficiency.

For European data center operator Data4, the answer lies in rethinking cooling architecture from the ground up. The company’s latest initiative – its first deployment of direct liquid cooling (DLC) at industrial scale in a colocation environment – signals a bold step toward that future.

Responding to a new era of customer demands

By the end of 2023, demand from Data4’s most advanced customers had reached a critical threshold. The need to accommodate workloads powered by energy-intensive GPUs was clear, and traditional air-cooling systems were no longer sufficient.

In response, Data4 fast-tracked the launch of a new DLC infrastructure on its Marcoussis campus, retrofitting an existing data center, DC01, as a testing ground for what it calls 'DLC by Design.'

The goal was ambitious: deliver a solution capable of supporting up to 130 kilowatts per rack, all while ensuring operational reliability, maintainability, and measurable sustainability gains.

To achieve this, Data4 assembled a dedicated team of experts, not just in IT and infrastructure but also in fluid dynamics – skills more commonly associated with aerospace engineering than data center design.

Engineering a new cooling paradigm

One of the core technical challenges was the development of a new generation of cooling distribution units (CDUs). In close collaboration with key partners such as Schneider Electric and Danfoss, Data4 optimized the CDU design to minimize thermal pinch and reduce dependency on the primary cooling loop.

Special attention was given to filtration and redundancy, essential components for ensuring continuous performance in a high-density, high-stakes environment.

The cooling loop itself was reengineered using prefabricated stainless-steel piping made from 50 percent recycled material. This choice not only reduced the carbon footprint of in-room distribution by 70 percent compared to traditional black steel, but also improved modularity and installation speed.

Compared to traditional black steel, the piping system – developed in collaboration with Victaulic – allowed for faster installation with minimal disruption to the existing infrastructure.

Redefining operational boundaries in colocation

In a colocation context, DLC introduces a fundamental shift in the interface between the data center operator and its clients. Unlike air cooling, where the infrastructure boundary is typically at the rack level, DLC requires a direct hydraulic connection between the rack and the facility’s chilled water system.

This means that any issue – such as a leak or incorrect manipulation by a client – can propagate across the entire cooling loop, potentially affecting multiple tenants.

This shift necessitates new protocols for risk management, operational responsibility, and client onboarding. Data4 has implemented enhanced monitoring and containment strategies to mitigate these risks, while also preparing protocols for sharing responsibilities and ensuring safe operation.

Proving the environmental value of DLC

Beyond engineering feats, the project serves as a proof of concept for a more sustainable model of retrofitting. According to a life-cycle analysis conducted by APL, the new DLC system reduces the overall environmental impact by 40 percent compared to conventional air-only cooling. This includes gains from materials optimization, equipment rationalization, and energy savings during operation.

To validate its approach, Data4 developed a rigorous commissioning protocol in partnership with the Uptime Institute. Every phase of deployment, from testing to performance validation, was reviewed by third-party experts to ensure alignment with industry best practices. The result is not only a high-performance cooling solution, but also a replicable model that builds trust with clients and partners alike.

Accelerating commissioning with hybrid load banks

Commissioning is a critical phase in the RFS (ready for service) timeline of any data center project. It is often time-consuming, especially when validating complex cooling systems. To streamline this process, Data4 developed hybrid load banks in collaboration with Rentaload, capable of testing up to 140kW in liquid cooling and an additional 60kW in air.

These load banks simulate real-world workloads and allow for simultaneous validation of both heat dissipation paths – air and liquid – accelerating commissioning and improving confidence in system performance before client deployment.

Innovation through collaboration

The DLC solution was co-developed with an ecosystem of strategic partners including Schneider Electric, Danfoss, Victaulic, Belimo, Rentaload, APL, and Ceme – the latter responsible for coordinating on-the-ground deployment. 

This multi-stakeholder approach enabled Data4 to move quickly: the solution was developed in just six months and implemented in three, demonstrating the agility of the team and the maturity of the ecosystem.

Scaling for the future of AI workloads

What makes this project a turning point is not just the technology itself, but the scale at which Data4 is now prepared to roll it out. With over 250 megawatts of capacity under design across its European sites, the company is laying the foundation for widescale adoption. It sees DLC not just as a technological upgrade, but as a strategic enabler for resilient, high-performance infrastructure.

In an industry where sustainability and performance are often framed as trade-offs, Data4 is making the case that they can – and must – go hand in hand. By reengineering its data center ecosystem around liquid cooling, the company is not only addressing the demands of AI workloads but also advancing its commitment to reduce the carbon footprint of every new megawatt built by 38 percent by 2030.

A blueprint for the next generation of data centers

DLC by Design is more than an engineering milestone. It is a statement of intent from Data4: to lead the transformation toward a digital infrastructure that is efficient, scalable, and ready for the next era of computing.