Is 2023 the year for liquid cooling?

Is 2023 the year for liquid cooling? Looking from outside the industry, you’d think that’s unlikely.

After all, air-cooled data centers are almost universal. Data centers, large and small, mostly use various kinds of air cooling. Whether they’re using refrigerant-based chillers, evaporative cooling, or free air, almost every data center blast cool air through IT equipment in racks and collects the hot air in order to keep servers and storage up and running at peak efficiency.

But everyone in the industry knows that air-cooled data centers aren’t particularly efficient: PUE is stubbornly stuck at 1.55. With the rising costs of power and power distribution and the recognition that “between 30% to 55% of a data center’s energy consumption goes into powering its cooling and ventilation systems,” most leading data centers want cooling that utilizes less power.

That’s where liquid cooling comes in.

There’s ample evidence for interest in liquid cooling as a tool for greater efficiency. The Uptime Institute, in their 2022 Global Data Center Survey, reported that “Performance requirements and expectations around efficiency will likely push a growing number of operators (and their IT tenants) toward direct liquid cooling (DLC). Greater adoption of DLC could contribute to greater efficiency gains through the 2020s and beyond, both in new builds and retrofits. Commercial DLC offerings are likely to mature and standardize, especially as more large operators deploy at scale — as expected.”

This interest in liquid cooling shouldn’t be a surprise. It could be said that the rise of air cooled data centers is an aberration in the history of IT, and it probably shouldn’t have ever happened in the first place.

Early computers were liquid cooled. Ever since the IBM System 360, liquid cooling has been associated with complex, expensive, heavy-duty “Big Iron” infrastructure that cost millions of dollars, required a team of specialists to install it, and generated so much heat (one model required 79 kW/hour of liquid cooling capacity) you could warm an office building with it.

But since the late 1990s, with the advent of x86 based servers, air cooling has been the predominant way to deal with computing heat production. Beginning with commercial or residential air conditioning for server closets and server rooms, air cooling has evolved to the point that we now see tens of thousands of CRACs, widely deployed in data centers of all sizes. Anyone who has stepped into a data center knows that’s it’s filled with loud blasts of chilled air in order to cope with the heat production of servers and other IT equipment. Data center cooling is almost synonymous with chilled air.

Almost.

It’s possible that the end is in sight for refrigerant based air chillers in the data center. 

Why?

1. Data centers are becoming too hot. Today’s servers, with the hottest processors and GPUs in history, are producing more than 1kW of heat per rack unit — or more than 40kW per rack. Many data centers simply cannot produce enough chilled air to keep those servers from overheating.
2. Climates are unpredictable. Climate change is making data center cooling a more unpredictable activity. Old assumptions about sizing data center cooling capacity are being thrown out the window, and in the past few years, large data centers have done down during the summer due to cooling failures.
3. Providers need sustainable efficiency. Also, data center providers, whether hyperscale, colocation, or enterprise, are looking for more economical and sustainable ways to cool data centers.

And that expectation was well-founded. Already, the largest companies have trialed or adopted liquid cooling.

1. Microsoft rolled out immersion cooling for production workloads back in 2021.
2. Google has used liquid cooling for some AI workloads since 2018.
3. Meta recently announced, at the Open Compute Summit, that they have a roadmap for direct-to-chip liquid cooling for AI infrastructure, and they announced a pause on data center construction as they’re working on new designs to accommodate this new AI infrastructure.

Where hyperscalers lead, the rest of the industry will ultimately follow. And they are following.

1. The market for data center liquid cooling is predicted to grow at a 15% CAGR,
2. Investors are doubling down on data center cooling.
3. Established data center infrastructure companies are investing in liquid cooling or launching their own products.
4. Innovations like the Nautilus approach are being developed and deployed throughout the world.

However, widespread adoption faces some hurdles.

1. Retrofitting existing air cooled data centers will be complicated, disruptive, and expensive. Smaller data centers will be easier to convert, so we can expect to see more liquid cooling utilization in sub-25,000 square foot data centers.
2. Supply chain issues still afflict the data center industry. Some vendors are reporting seventy week lead times for chillers.
3. Server manufacturers are adopting an incremental approach to supporting liquid cooling. Vendors like Dell, Inspur, and Supermicro have some models that are intended for liquid cooling, but many of their models are still intended for conventional air cooled data centers. Other specialist vendors like Hypertec 
4. Standards for liquid cooling haven’t been fully defined, leading some data center providers toward a wait-and-see approach.

Whether or not 2023 is going to be THE year for liquid cooling, I think we can all agree that it will be an interesting year for liquid cooling. Expect more innovation, more deployment, and ultimately, more advantages for early adopters willing to take a risk on leading-edge cooling for their data centers.