Solving Tomorrow’s Cooling Challenges with Liquid Cooling

AI has been around for years, but the explosion of interest is due to recent advances in generative AI (GenAI). The move to GenAI is ramping up. According to a recent Cisco study of more than 8,000 companies, 97% of global organizations reported that the urgency to deploy AI-powered technologies has increased in their company in the past six months.² 

Forrester adds, “Between July and September 2023, the number of enterprises that are in the experimentation and expansion stages of implementing GenAI jumped from 62% to 71%, representing one of the fastest mass adoption rates of a new technology in the enterprise.”³

GenAI is truly a game changer, and the world is already experiencing the first wave of an AI deluge that will impact data center cooling needs in two ways. First, the increasing thermal design power (TDP) of chips designed for AI and other high-density technologies directly leads to more heat in the data center. IDTechEx's report on thermal management for data centers points out, “With the increasing demand for high-performance computing in sectors like AI, cloud computing, and crypto mining, the TDP of chips increased 4X from 2006 to 2022.”⁴

While an average server in a data center generates about 1.5kW of heat, the latest AI server using Nvidia's new GPUs can generate five or six times as much heat.⁵

Second, power density – the amount of power used by a fully populated server rack, measured in kilowatts (kW) per rack – is also rising, and higher power density generates more heat. Average server rack density has doubled in the past six years, from 5 kW to 8-10 kW, and experts say this number could double again by 2025.⁷ 

Types of Liquid Cooling

All this means that data center operators have to find innovative ways to cool servers, and liquid cooling is positioned as a very attractive solution.

Data centers have three basic liquid cooling options: 

• Rear-door heat exchangers – A liquid heat exchanger replaces the back door of the rack. Fans blow hot air from servers through the exchanger, which circulates coolant to dissipate heat. Although this option uses a liquid cooling technique, it is actually a hybrid solution because it also incorporates air cooling by employing fans.
• Direct-to-chip liquid cooling – Cool liquid is circulated via tubes to cold plates directly adjacent to the hardware components. When the liquid absorbs the heat from the equipment, it is transferred to a heat exchanger or cooling device, and then sent back to the cold plates. Direct-to-chip liquid cooling is available as single-phase cold plates or a two-phase system utilizing evaporation units. 
• Immersion cooling – Server components are submerged in a container of dielectric liquid, and the heat is transferred to the coolant. In single-phase immersion cooling, coolant is continuously circulated to a heat exchanger. In two-phase immersion cooling, the liquid is brought to a boil and turned to gas to expel the heat. According to ResearchAndMarkets.com, “Immersion cooling bridges the gap between traditional and future data centers. It not only improves the data infrastructure system efficiency but also cuts by a huge margin the amount of energy consumed. This leads to reduced energy bills and carbon footprint.”⁸
  
  

The Many Benefits of Liquid Cooling

The entire data center industry is talking about liquid cooling because it offers several compelling advantages including:

• Support for new technologies: For the reasons outlined above, liquid cooling enables the expansion of high-compute, high-density applications such as GenAI, big data analytics, the Internet of Things (IoT), blockchain and cryptocurrency. 

• Efficient heat conductivity: Consultant Jeff Schuster from Enabled Energy says liquid cooling can increase heat rejection by 23 times because of the thermal conductivity of water versus air.⁹

• Reduced energy usage: “The largest energy consumers in the traditional cooling loop are the fans blowing air into data center floors and the chiller that provides those fans with chilled water. With liquid cooling, these big energy users are being eliminated … Based on the direct comparison of liquid cooling to air cooling, liquid cooling uses just 20% of the energy of air-cooled data centers,” explains Schuster.⁹

• Reduced water usage: Although it seems counter-intuitive, liquid cooling actually uses less water than conventional air cooling. Wendy Torell, Senior Research Analyst at the Data Center Science Center, calculates that a 20 MW data center consumes the equivalent water of 2,500 people, which increases operational expenses and strains water resources. On the other hand, “Liquid cooling reduces, and often eliminates, water usage from the cooling system,” Torell adds.¹⁰

• Extended device life: Cooling vendor JetCool explains, “Liquid cooling also extends the lifetime of devices. The semiconductors in servers are highly sensitive to temperature, whose operating lifetime is often limited by the maximum chip temperature while running. Just a 10°C decrease in average operating temperature can more than double the lifetime of the semiconductor.”¹¹

• Noise reduction: Liquid cooling is quieter than other forms of cooling; fans and chillers are eliminated.

• Space conservation: Liquid cooling equipment takes up significantly less space than cooling alternatives, largely due to the removal of fans. Torell from the Data Center Science Center elaborates, “As densities rise, rack count may go down, but the ratio of physical space dedicated to air cooling equipment increases, diminishing the gains of the higher density racks. With liquid cooling, you have an opportunity to reduce the overall data center footprint for a given IT load through significant compaction.”¹⁰
  
  

Is Liquid Cooling the Future of the Data Center?

With these many advantages in mind, the market forecast for the data center liquid cooling market predicts high growth, from almost $5 billion in 2024 to almost $15 billion in the next 5 years.¹²

The capability to keep servers cool is fundamental to data center operation, but in the face of a paradigm shift in computing performance cooling presents a new challenge. Liquid cooling potentially is a solution for increasing compute power demands and ensuring data center performance as well as sustainability. 

Ready to dig deeper into how CoreSite can integrate liquid cooling into your colocation deployment? Get in touch with us here – and don’t forget to check out our entire data center optimization series on CoreSite’s YouTube channel.