As the amount of data we create grows, largely driven by technologies such as the Internet of Things (IoT), data centers are facing increasing demand, rising power densities and higher wattages at the node and rack levels. This situation, of course, results in more heat that data centers must remove to protect their equipment. The typical cooling solution data centers have employed is air cooling, but the rising demand on their services is causing them to explore alternative solutions, according to research published by BSRIA. They’re looking for more flexible, powerful and cost-effective layouts and technologies.
Liquid cooling is one of these technologies and has recently been the subject of much interest among data center operators. Today, only about 14 percent of data operators use liquid cooling, but experts predict that increasing power densities and other factors will force many to switch from air to liquid in the coming years. According to Stratistics Market Research Consulting (MRC), the global market for liquid cooling for data centers was $0.82 billion in 2016. The firm forecasted that the market would grow to $4.55 billion by 2023 at a compound annual growth rate (CAGR) of 27.7 percent for the forecast period.
Liquid cooling offers numerous benefits that air cooling and other systems can’t. Despite these advantages, the technology has yet to become widespread owing to several challenges. Overcoming these difficulties, however, could lead to more-efficient, more-powerful data centers.
What Is Liquid Cooling?
Liquid cooling differs from other cooling solutions in various ways. One type of liquid-based system pumps liquid through pipes around the equipment that needs to be cooled. This liquid absorbs the heat produced by the electronics and moves it away.
A standard pumped liquid-cooling loop system includes a pump, fluid lines, a cold plate and a heat exchanger or sink. Valves and reservoirs may also control the volume and flow of the liquid. The pump moves the fluid throughout the loop, causing it to pass by or come in contact with cold plates, which are positioned by the equipment that needs to be cooled. These cold plates may contain numerous small channels or porous media that help move the liquid and heat around. As the liquid passes over the cold plate, it picks up heat. It then uses the heat exchanger to dissipate that heat to another fluid that removes it from the electronic equipment.
A variation on these pumped liquid systems is oscillating liquid cooling, which uses a mechanical actuator to create an oscillating movement of the liquid as well as disrupted liquid-wall boundary layers. The oscillation of the fluid moves the heat from the input to the dissipation area. Controlling the performance involves changing the amplitude and frequency of the actuator. This approach can increase heat-absorption efficiency.
Another developing liquid-cooling technology is jet impingement, which directs a jet of liquid toward the equipment to be cooled. This method is best suited to applications with high-heat flux capabilities and unconventional form factors.
How Can Liquid Cooling Benefit Data Centers?
Liquid cooling has numerous benefits that make it a potentially powerful solution for data centers. Perhaps its biggest draw is the agility and flexibility it affords. Liquid cooling allows data center operators to increase cooling in specific places without having to change the entire system. This capability enables them to adjust their cooling setup on the basis of changing business needs and provides more-precise cooling.
Companies can use liquid cooling for individual racks that have high densities. Since power density is a growing problem, this approach could be an ideal solution. Using liquids to cool equipment is also typically more efficient. Water has a higher thermal conductivity than air, meaning it can transfer heat more quickly. It also has a greater specific heat capacity, which means it can absorb more heat for a given temperature increase.
Switching to liquid can decrease a facility’s overall power consumption and improve its power usage effectiveness (PUE), a measure of data center energy efficiency. Reduced power usage, of course, leads to lower energy costs. This reduced power consumption also comes with environmental benefits, as it cuts emissions associated with power generation. Some advanced liquid-cooling technologies can also readily recycle the hot water to power water turbines, provide central heating or perform other services, rather than treating it as waste.
Another benefit of liquid cooling is that it’s much quieter than air cooling, giving data centers more flexibility in where they can locate.
What Are the Challenges to Adoption?
Although liquid cooling is a potential solution to the problems facing many data centers, a number of concerns have hindered its widespread adoption.
- Lack of standards: One challenge is a lack of standards for liquid-cooling systems. It’s partly because the technology remains rare in data centers. The lack of standardization makes the installation of liquid-cooling equipment more complicated. Data center operators can’t simply connect it and get started. It takes a bit more work than standard air cooling systems to install. As the technology becomes more prominent, standardization is likely to increase.
- Potential leaks: Although every technology can malfunction, the possibility of leaking liquid has led some companies to avoid liquid cooling. Depending on the type of liquid, these leaks could damage expensive equipment and cause safety hazards. Corrosion is a major risk factor for leaks, and it’s one that cooling-technology companies are working to fix. They’re also working on solutions that enable pipes to seal if a leak occurs automatically. Companies can address the problem by containerizing racks so that if a leak occurs, the damage is contained to that rack.
- Safety risks: Leaks could present safety hazards that have caused some companies to hesitate to adopt liquid cooling. If a system that uses water has a leak, it creates the danger of electrocution. Pooling water could also be a slip hazard. Systems that use a dielectric liquid, on the other hand, present no electrocution risk, since these liquids don’t conduct electricity.
- Operational complexity: Another barrier to the adoption of liquid-cooling technologies is the potential increase in operational complexity. Data center operators may be hesitant to introduce new technology, especially if they plan to use some of their existing air-cooling equipment alongside it. They may want to avoid multiple systems with various components, as it means more points of failure. There’s also the additional responsibility of managing numerous system types.
- Capital costs: Installing new liquid-cooling technologies can involve high capital costs, especially compared with continuing to operate existing equipment. The increased efficiency that liquid cooling offers can reduce operational costs over the lifetime of the equipment, but getting started still requires a substantial investment. Because of these challenges, liquid-cooling adoption may be limited, at least for now, to data centers with substantial funding. Some companies may start to see benefits from increased efficiency right away, but many are still below the power densities that necessitate liquid cooling.
And some facilities may not experience such demand for a long time. If an operator isn’t planning to handle data from advanced technologies such as artificial intelligence or the IoT, they may not need the increased cooling capacity. As these technologies become more prevalent, such data centers will become rarer. The type of cooling solution that works best, though, still comes down to the needs and resources of each individual facility.
The Future of Data Center Cooling
Data centers are changing to keep up with the rapid increase in the number of Internet-connected devices. They’re handling more data and working with higher power densities. They’re also increasing in size and having to be more agile in their operations.
To implement these changes, many data centers may need to adopt new technologies, such as liquid cooling. These systems are well suited to meeting the challenges data centers face today, but a number of hurdles stand in the way of widespread adoption. As technologies improve and liquid cooling becomes more commonplace, many of these obstacles will dissipate. Data centers and cooling-technology firms that start looking into these solutions now, though, will be making a smart investment in their futures and putting themselves ahead of the competition, as liquid cooling may play an integral role in the data center of the future.
About the Author
Kayla Matthews is a technology writer and reporter, contributing to websites like VentureBeat, Vice, MakeUseOf and TechnoBuffalo. Visit ProductivityBytes.com to read more recent posts by Kayla.