Liquid cooling technology - a new way to save energy and reduce consumption for data centers
In the era of digital economy and the Internet of Things, the calculation and processing of massive data require the continuous expansion of the infrastructure scale of data centers, which also brings about the problem of a sharp increase in energy consumption. According to the "Research Report on the Development of China's" New Infrastructure ", by 2025, global data centers will account for the largest share of global energy consumption, up to 33%. In China, the power consumption of national data centers has been increasing at a rate of over 12% for eight consecutive years, and the proportion of electricity consumption in society will continue to increase in the future.
The energy consumption of data centers mainly comes from two aspects: the power consumption of the servers themselves, and the cooling power required for server cooling. With the improvement of computing power in data centers, the biggest investment for newly built data centers is not the building itself, but the equipment cost to ensure power supply and the cost of cooling the data center. According to statistics, the refrigeration system in data centers accounts for about 40% of the energy consumption of the entire data center.
Liquid cooling technology refers to the use of liquid as a heat transfer medium to exchange heat for heating components and take away heat, rather than indirectly cooling through air like air cooling. Liquid has a better thermal conductivity effect, 25 times that of air, and a faster and better temperature transfer effect. Meanwhile, due to the large specific heat capacity of liquids, their temperature does not change significantly after absorbing a large amount of heat, thus stabilizing the CPU temperature. Liquid cooling technology can be divided into three types: spray type, immersion type, and cold plate type.
Spray type liquid cooling :
Store liquid and open holes on the top of the chassis, allowing the coolant to spray on the heating element according to its position and heat generation size, achieving the purpose of equipment cooling. The sprayed liquid comes into direct contact with the cooled device, resulting in high cooling efficiency; However, during the spraying process, the liquid will experience drifting and evaporation when encountering high-temperature objects. Mist droplets and gases will be emitted along the gaps in the chassis holes to the outside of the chassis, causing a decrease in the cleanliness of the computer room environment or affecting other equipment.
Immersion type liquid cooling:
Electronic components are directly immersed in a dielectric liquid, which is placed in a sealed but easily accessible container, and heat is transferred from the electronic components to the liquid. Usually, a circulating pump is used to flow the heated electronic fluoride solution to a heat exchanger, where it cools and circulates back into the container. Immersion type can be divided into two types: single-phase and two-phase. In single-phase immersion liquid cooling, the electronic fluorine liquid remains in a liquid state; In two-phase immersion liquid cooling, the boiling and condensation process of electronic fluorination liquid exponentially improves the heat transfer efficiency of the liquid.
Cold plate liquid cooling:
Directly cooling the chip by circulating liquid medium through a pump through a cold plate assembled into electronic components for heat dissipation. Liquids do not come into direct contact with electronic devices. Although non dielectric liquids (such as water/ethylene glycol) are commonly used for direct chip cooling, dielectric electronic fluorinating liquids can also be used for direct chip applications, reducing leakage related risks and improving hardware/IT equipment reliability. Single phase and two-phase technologies can be used to achieve direct chip cooling.
At present, liquid cooling technology has been applied and validated in some domestic and foreign data centers. For example:
Alibaba Cloud: In 2018, Alibaba Cloud launched the world's first supercomputing cluster based on immersive liquid cooling technology - X-Dragon Super Computing Cluster. This cluster adopts a two-phase immersion liquid cooling solution, completely immersing servers in fluoride solution and achieving efficient heat dissipation through boiling and condensation of fluoride solution. According to Alibaba Cloud, this cluster can reduce server power consumption by 50%, improve cooling efficiency by 80%, and save data center space and maintenance costs.
Tencent Cloud built the world's first data center based on spray liquid cooling technology, Guiyang T3 Data Center, in Guizhou in 2019. The data center adopts a spray liquid cooling scheme, which sprays fluoride solution in an atomized form above the server and achieves heat dissipation through heat exchange between the fluoride solution and air. According to Tencent Cloud, the data center can reduce PUE to below 1.2, save 30% of computer room space, and improve server performance and reliability.
Microsoft sank Project Natick, a data center based on submerged liquid cooling technology, under the sea in Scotland in 2020. The data center adopts a single-phase immersion liquid cooling scheme, completely immersing the server in a nitrogen filled pressure vessel and using seawater for heat dissipation. According to Microsoft, the data center is capable of achieving self-sufficient energy supply and has higher reliability and security.
With the continuous expansion of data center scale, increasing computing density, increasing energy costs, and increasing environmental requirements, traditional air cooling technology is no longer able to meet the development needs of data centers. Liquid cooling technology, on the other hand, has obvious advantages such as energy conservation and consumption reduction, environmental adaptability, flexible design, waste heat utilization, and environmental friendliness, making it the future development direction of data center cooling technology.
