Direct Liquid Cooling in Data Centres

Cooling is important in data centres since without proper heat removal, components can hit dangerously high temperatures — with all sorts of reliability and safety consequences.

The importance increases as nowadays data centre infrastructure produces substantial heat supporting the world of AI. In an effort to serve the growing needs of AI and high-performance computing workloads, power-hungry processors use an increasing amount of energy and produce more heat.

Some data centre cooling methods, such as traditional air-cooling systems, have managed to carry away heat from working servers, using airflow, heat sinks, and chillers, but they have limited capability and efficiency, and therefore might struggle to handle the growing amount of heat from high performance workloads. Data centres must adopt more sustainable cooling methods to remain efficient, competitive, and environmentally friendly.

Direct liquid cooling, or known as DLC, may provide the answer. It’s more efficient than traditional methods — according to some estimates, between 30 and 90 per cent more efficient than air cooling¹. This brings crucial sustainability and performance benefits to high-performance computing environments.

With such an upside, these advanced cooling methods will support the increasing heat management needs of both modern and future data centres and meet the demands of AI workloads. Let’s see how.

Why liquid cooling?

Before diving into direct liquid cooling, let’s understand more about liquid cooling and how it plays a pivotal role in Artificial Intelligence (AI) and High Performance Computing (HPC) needs.

What is liquid cooling?

Liquid cooling is a heat management technique for removing excess heat from computing components. It works by sending liquid coolants to heat-generating components. The cold liquid comes into contact with the components directly, removing heat in the process. The fluid is then circulated to be cooled again.

Liquid cooling solutions take an efficient and targeted approach. They directly cool the most critical components, creating a more efficient, sustainable, and scalable solution, perfect for AI and HPC workloads.

The main types of liquid cooling solutions

There are two primary types of liquid cooling:

Direct liquid cooling: Sometimes known as direct to chip, this technique uses cool liquid to target the equipment consuming the most power and generating the most heat, such as CPUs and GPUs.
Immersion cooling: This takes a more general approach by submerging hardware into a non-conductive dielectric fluid which absorbs heat very efficiently. While immersion cooling is less common, it is also essential to the future of data centre cooling strategies.

Liquid cooling is gaining popularity in data centres due to its superior cooling capabilities. Deployments are using more power than ever, with high-performance workloads like AI models creating enormous amounts of heat. Both direct liquid cooling and immersion cooling methods provide efficient solutions to mitigate this challenge.

How does direct liquid cooling work?

The direct liquid cooling process typically works in the following order:

Cold plates mounted on processors and other power-hungry equipment absorb excess heat, preventing them from overheating.
The liquid transfers through the coolant distribution unit (CDU) into a heat exchanger.
The heat exchanger cools the liquid through air exposure or other methods, allowing it to be used again. At this point, heat is expelled from the circuit.
The liquid is sent through the cooling loop again, ready to remove heat from other components.

Benefits of direct liquid cooling

There are several important advantages of direct liquid cooling:

Energy efficiency: Direct liquid cooling can help reduce power usage effectiveness (PUE) in data centres. It keeps components at lower temperatures more efficiently than air cooling, allowing them to operate faster without hitting dangerous temperature thresholds.
Sustainability: Using direct liquid cooling can help create green data centres. For example, it requires fewer noise-producing elements, such as fans, compared to air cooling systems. This helps drastically reduce noise levels. Meanwhile, liquid cooling uses less water than air cooling — saving up to half of a centre’s water consumption— helping reduce the overall carbon footprint.²
Flexibility: Liquid cooling can often easily integrate with existing data centre designs and rack densities with only minor retrofitting needed.
Better capacity: Liquid cooling removes heat more efficiently than air cooling. This allows for denser equipment, optimised space usage and improved operations across the facility.

Overall, direct liquid cooling offers substantial energy efficiency, flexibility, and capacity benefits. These lead to cost savings, improved performance, and a reduced environmental impact, making it a valuable technology for data centres.

Challenges in direct liquid cooling

While implementing direct liquid cooling brings many benefits, there are also some considerations:

Any leakage of fluid can lead to overheating and potential damage. It’s also essential to comply with regulatory and environmental standards for liquid use in data centres.
Setting up liquid cooling requires an upfront investment. It can sometimes be tricky to install and requires specialist maintenance.
Improper disposal of cooling fluids can have environmental consequences.

While these challenges exist, modern liquid cooling systems and responsible data centre operators, such as Digital Realty, incorporate robust safety measures to reduce their likelihood. Redundancy, monitoring, and ongoing innovations can also make the technology safer and more environmentally friendly.

Enhancing data centre efficiency with direct liquid cooling

Modern data centres must provide high-performance computing resources while simultaneously improving power consumption efficiency and hitting environmental targets. Direct liquid cooling is vital to meeting this challenge.

Digital Realty is committed to improving efficiency. We offer high-performing computing solutions at our Cloud House data centre, our greenest data centre in the London region, which uses a pioneering dock water cooling system that is up to 20 times more energy-efficient than traditional cooling systems. Contact us to learn more.

Frequently asked questions (FAQs)

What is liquid cooling in data centres?

Liquid cooling technology uses fluids, like water, to remove heat from computing components. Liquid cooling can be targeted at only the most crucial equipment in data centre suites, providing many important energy consumption and sustainability benefits.

How do data centres use water to cool?

Some data centres use water circulation to remove heat from equipment. These liquid-cooled servers expel heat into water systems, which are then carried to heat exchangers for cooling. This can improve efficiency compared to traditional air-cooled systems.

What is direct contact liquid cooling?

Direct contact liquid cooling infrastructure removes heat from computer components by transferring it into a liquid circulation system. By creating direct contact between high-density components and heat-absorbing liquid, IT equipment can be kept within safe working temperatures.

Is immersion cooling better than direct liquid cooling?

Both immersion and direct liquid cooling (DLC) improve efficiency compared to traditional cooling methods. While immersion cooling can sometimes slightly outperform DLC, it can be more costly and challenging to implement.

External links

¹Liquid cooling efficiency boost: https://techhq.com/2023/10/could-liquid-cooling-for-data-centers-help-save-the-planet/

²Liquid cooling efficiency study: https://datacenters.lbl.gov/liquid-cooling