Driving down electrical harmonics is key to Google’s CDU cooling initiative for AI data centres

Google has defined a new, more rigorous open-source standard for cooling the next generation of AI data centres. CHRISTIAN LEAL, Global Sales Manager ABB, explains why ultra-low harmonic (ULH) drives are an essential component for any manufacturer with ambitions to pick up Google’s Project Deschutes coolant distribution unit (CDU) baton.

The AI race is heating up. As providers like OpenAI and Anthropic compete to offer ever more sophisticated models and tools, the companies providing the infrastructure – like Google, Microsoft, and Meta – must keep increasing the computing power behind them. That means building more data centres and stacking them with increasingly high-performance processors.

Cooling has always been a priority for data centres. The electronics involved in computing consume a lot of power and therefore give off a lot of heat. Rack a lot of processors together in a server, line up lots of those servers together, and the effect is a bit like lining up rows of ovens and turning them all up to maximum heat at once.

If that heat is allowed to build up inside a data centre, it quickly reaches a point where it can damage the delicate electronics, leading to a shutdown. So data centres need advanced, powerful cooling systems to remove heat as fast as it can build up, allowing the servers to keep working without interruption.

If the servers in a standard data centre are ovens, the ones in a modern AI data centre are rocket engines. The heat buildup on the processors that power AI models is far greater than anything earlier generations of data centres had to cope with. Data centre cooling systems need to take a corresponding leap forward; otherwise, progress will stall, and the forerunners of the AI race could stumble.

Project Deschutes

In 2025, Google announced a leap forward. Codenamed Project Deschutes, it’s a revolutionary solution in several ways. And ABB’s ULH variable speed drives (VSDs) make it possible.

Project Deschutes is a design for a new kind of data centre cooling distribution unit (CDU). It’s revolutionary because it’s open.

Open, in that the CDU itself is open-frame. AI data centres are the Formula One of the data centre world, and Google designed Project Deschutes like a Formula One car: Every component is accessible, making everything quick and easy to inspect, maintain, or replace. No one has to unscrew any panels or squeeze inside cramped server cabinets to hunt down faults, which– at the scale of Google’s data centres and the performance the company aspires to – would be unacceptably inefficient.

And open, too, in that the blueprint for Project Deschutes is public, not proprietary. Google released the specification via the OCP in late 2025, allowing any manufacturer to build and sell Project Deschutes CDUs. This is just as much of an innovation as the technology itself.

Project Deschutes is Google’s fifth-generation liquid-cooled data centre CDU design. The previous four generations were closely guarded secrets. The fifth generation is Google’s gift to the AI industry. A gift, and a challenge to the rest of the industry to catch up to the leader, propelling the whole sector forward.

High performance demands high standard specifications

Google has been using liquid cooling in its data centres since 2018 as utilising water or dielectric fluid to remove heat is up to 3,500 times more effective than air. Microsoft and Meta had both adopted liquid-cooled servers by 2024. Project Deschutes continues the liquid cooling trend.

Like a giant, super-efficient heart, a Deschutes CDU keeps liquid coolant constantly pumping around the server. Each CDU can cool a two-megawatt (MW) AI server. That’s more than powerful enough for any server currently in existence: Less than a year ago, Google, Meta, and Microsoft announced that they were working together to design the first 1MW server.

A few data centre generations ago, 2MW of cooling would have been enough for an entire neighbourhood of servers.

So the specification Google has provided for these CDUs is, unsurprisingly, stringent.

Every component of a Deschutes CDU must be able to operate in constant 50°C heat without power derating, for example. The system must filter any particles bigger than 0.2 microns out of the coolant as it circulates, to protect the delicate chips.

And the requirements for the variable speed drives (VSDs) that control the coolant pumps are just as rigorous. To meet the Deschutes standard, CDUs must incorporate VSDs with advanced telemetry and a total harmonic current distortion (THDi) under 5%.

ABB’s ultra-low harmonic VSDs weren’t developed specifically for Deschutes, or even specifically for data centres, but they were designed to be high-performing. And, so it happens that these drives already perfectly meet Google’s specifications.

The reliable beating heart of the solution

By combining predictive maintenance with high-performance components, Google is aiming for 99.999% data centre uptime.

To support this level of predictive maintenance, the VSD in a Deschutes CDU must report highly detailed data on motor torque, DC power, and insulated gate bipolar transistor (IGBT) temperature to the programmable logic controller.

ABB minimising harmonic distortion

Standard drives draw current in a non-linear manner rather than sinusoidally, resulting in a distorted current waveform known as harmonics. Harmonics are undesirable in all sorts of applications – from ventilation to industrial processes – because they lead equipment such as motors, transformers and cabling to run hotter and less efficiently.

In data centres, it’s even more important to avoid harmonics because they can interrupt the servers’ power supply.

That’s why the acceptable THDi of a drive in a Deschutes CDU is so minimal, which makes ABB’s ULH drives the ideal solution. They are designed to draw current smoothly, generating only a negligible electrical noise.

Boyd, Vertiv, Stulz, major players in the high-performance data centre cooling market, now have the specification they need to start producing CDUs to the standard Google intends the AI industry to embrace. It is crystal clear to me from the specification that the easiest way to guarantee the stability and reliability required of these next-generation CDUs is to integrate into those ABB ULH drives for the pump control.

As the AI race continues to accelerate, Google is undoubtedly already developing the next-generation successor to Project Deschutes. Just as ABB’s drives were ready and waiting to meet the Deschutes specification, ABB will be ready for whatever comes next.

For more information on ABB ULH drives: visit www.abb.com