Managing Higher Densities
As data center operators tackle the challenge of reducing their environmental impact, they are faced with a competing challenge: meeting increased capacity demands and supporting more high-density equipment racks. One of the recommendations in the Gartner report, The Road to a Net Zero Data Center1, is to "use higher efficiency cooling techniques such as … liquid cooling."
Liquid cooling offers the cooling capacity required to protect high-density equipment racks and is typically more efficient than air cooling due to the higher thermal transfer property of fluids compared to air. Organizations considering liquid cooling should work with vendors capable of helping them navigate the introduction of liquid cooling into existing data centers.
This includes identifying the specific liquid cooling technology that is the best fit for the application, the type of fluid that will be used, and the heat load-to-liquid ratio. The variables of heat load, liquid flow rates, and pressure work together to contribute to the overall liquid cooling solution and should be considered early in the process. The type of fluid used will also impact the selection of plumbing materials, as it is essential to ensure wetted material compatibility between the plumbing material and the specific fluid being used.
Commonly used methods of liquid cooling, such as rear-door heat exchangers and direct-to-chip cold plates, work with air cooling systems rather than independently. When planning for liquid cooling, you need to determine how much of the total heat load each system will handle, how much air-cooling capacity the liquid system will displace, and where the liquid cooling system may be introducing new demands on air-cooling systems. Working with vendors with domain knowledge that extends across both liquid and air-cooling technologies can help ensure proper balance between the two systems.
How fluids are distributed within the data center can also impact the success of a liquid cooling deployment. Establishing a secondary cooling loop for the liquid cooling system enables more precise control of the liquid being distributed to the rack. The key component in this loop is the coolant distribution unit (CDU). In most cases, the CDU will use a liquid-to-liquid heat exchanger to capture the heat returned from the racks and reject it through the facility water system.
Finally, risk mitigation must be included in every phase of a liquid cooling project, even when dielectric fluids that don’t pose a risk to IT systems are used. The Open Compute Project has released a paper on leak detection technologies and strategies, Leak Detection and Intervention, which can be helpful in developing risk mitigation strategies.
The challenges associated with taking the next steps on the road to net zero are not insignificant, but as Gartner points out in The Road to a Net Zero Data Center2 “The alternatives are either elderly, less efficient data centers or ones that cannot consume any form of renewable energy, thus becoming a liability for business should emissions taxations be introduced.”
Solutions are available today from data center equipment manufacturers, such as Vertiv, that allow operators to effectively cool high-density racks using liquid cooling..
1,2 Gartner, The Road to a Net Zero Data Center, Tiny Haynes, Philip Dawson, Simon Mingay, 10 June 2021
Real-World Solution 1: Managing Higher Densities
Background:
Silicon Valley-based Colovore delivers a colocation data center environment designed to support next-generation high performance computing (HPC) for applications that include artificial intelligence, virtual reality, and big data. Colovore’s high-density solutions are ideal for these applications because they allow customers to deploy servers in a highly compact footprint that requires much less space and far fewer cabinets than traditional colocation facilities.
Critical Need:
The increase in power usage from HPC coupled with the high operating temperatures of high-density environments required Colovore to implement a robust thermal management solution that would enable compact server footprints that maximize power, cooling, and operating efficiency.
Solution:
Colovore chose the Vertiv™ Liebert® DCD rear-door heat exchangers to deliver efficient and effective high-density cooling. The Liebert DCD liquid cooling modules manage efficient heat removal of up to 35 kW per rack across the entire data center floor. This solution enabled fully packed, top-to-bottom rack deployments with no wasted or unusable rack unit slots and increased operating and capital efficiency due to significant reductions in required cabinets, data center floor space, and energy consumption. The high-density facility also relies on Vertiv UPS systems, power distribution units, and supplemental air- cooling systems.
Real-World Solution 2: Increasing Power System Efficiency
Background:
The University of Southampton, UK, enables its exceptional research and development capabilities and entrepreneurial culture with a forward- thinking IT team and a proactive approach to data center infrastructure. With computing demands continuing to increase, the university identified the need for a new data center that could achieve the dual goals of enabling HPC while ensuring environmental accountability.
Critical Need:
The challenge the university faced during the data center design process was enabling HPC alongside more repetitive processing tasks while optimizing efficiency across the various load profiles.
Solution:
The university chose the modular Vertiv™ Liebert® Trinergy Cube UPS system to meet its current needs for a high-efficiency power system while maintaining the flexibility to adapt to future requirements. The Liebert Trinergy Cube is the first high-power UPS with an adaptive algorithm that continually monitors the power supply and load and automatically selects the most efficient operating mode. With the new facility, the university reduced its data center energy requirements by 300 megawatt-hours per year and annual CO2 production by 160 tons compared to the previous, less efficient facility.
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