Document k9mXZJKbeK4g17rdO8L9M4QLq

PFAS in Two-Phase Immersion Cooling systems for data center cooling 1 Introduction The Wieland Group is one of the world's leading specialists for copper and copper alloys. With headquarter in Germany, the Wieland Group is worldwide active with important production sites in Europe, particularly in Germany, but also in Italy, Austria, Portugal, and the United Kingdom. The Business Unit Thermal Solutions is part of the Wieland Group and offers high-performance products and solutions for refrigeration, air conditioning and heating technology. Since many years the Business Unit is striving for best thermal performance with lowest material and energy input and took over the market leader role for high-performance tubes. Additional products are heat exchangers for refrigeration, air conditioning, heating technology and electronics cooling, for mechanical engineering and for process engineering applications as well as chillers. To develop the most efficient and innovate products, all the challenges, trends, rules, regulations, and innovations are considered to strive for the most sustainable solutions which are also economical, safe and durable. An important product of the Business Unit are two-phase immersion cooling systems for data center cooling. Immersion cooling is only shortly mentioned in the Annex XV Dossier as well as in its Annexes A and E and is discussed from a more general perspective in the chapters for electronics. Although not explicitly mentioned, it is clear from the text, that these passages refer to wellestablished single-phase immersion cooling systems. A substantial further development of singlephase immersion cooling is two-phase immersion cooling (2-PIC) which has significant technical advantages over single-phase immersion cooling systems, but also has different requirements on cooling fluids. 2-PIC is operated with cooling fluids, which fall under the scope of the proposed PFAS restriction, but is not evaluated in the Annex XV Dossier and its Annexes. The Thermal Solutions Business Unit therefore welcomes the opportunity to comment on this new technology. We will describe how 2-PIC works, discuss why the technical alternatives to PFAS identified in Annex E of the Annex XV dossier for single-phase immersion cooling are not applicable to 2-PIC, and justify why a derogation is needed for this application. 2 Two-Phase Immersion Cooling General Introduction Two-phase immersion cooling (2-PIC) is the most energy-efficient solution for data center cooling that has gained significant attention in recent years. In this method, servers and electronic components are fully submerged in a dielectric liquid coolant that boils on contact with hot components, absorbing and efficiently dissipating heat. This approach offers numerous advantages over traditional air-cooling methods, making it an attractive option for data centers seeking improved energy efficiency, reduced water consumption, and increased computing performance. Immersion cooling fluids must be non-flammable, non-combustible, without flash point, dielectric, and the boiling points must be between 45 to75 C. The fluids used so far are all falling in the current PFAS restriction proposal and would prevent future innovative cooling of data centers, edge-boxes, power-electronics which would lead to a significant increase of energy consumption and of CO2 emissions. Page 1/8 Two-Phase Immersion Cooling (2-PIC) vs. Single-Phase Immersion Cooling (1-PIC) There are two types of immersion cooling systems: single-phase (1-PIC) and two-phase (2-PIC) as simplified described below1. Single-phase immersion cooling and two-phase immersion cooling are both innovative techniques for cooling electronic components, such as computer servers, by immersing them in a dielectric liquid. Some technical descriptions as well as the pros and cons: In single-phase immersion cooling, the electronic components are submerged in a dielectric fluid that remains in a liquid state throughout the cooling process. The heat generated by the components is transferred to the liquid, which then carries the heat away from the components. In two-phase immersion cooling, the dielectric fluid undergoes a phase change from liquid to vapor as it absorbs heat from the electronic components. This vapor then rises to a condenser where it releases heat and condenses back into liquid, which is then recirculated to the components whereby the two-phase cooling can handle higher heat fluxes and offers superior cooling performance, making it suitable for high-performance computing applications. Also, the phase change process provides efficient heat removal, reducing the risk of hotspots and due to the phase change, less fluid is required for cooling, which can lead to cost savings. Two-phase immersion cooling systems are more complex to design and control due to the need for vapor handling and condensation process, since managing boiling and condensation can be challenging and requires precise control to maintain system stability. In summary, single-phase immersion cooling is simpler and more suited for applications with moderate cooling requirements, while two-phase immersion cooling offers higher cooling efficiency but comes with increased complexity and challenges. The choice between the two techniques depends on the specific cooling needs where single-phase immersion cooling will be on the limit for the newest high-power chips and coming more and more on its limitations, also to see in the graph below2 1 https://liquidstack.com/white-papers/fluorinated-cooling-fluids-101 2 https://www.datacenterfrontier.com/data-center-cooling/whitepaper/21437208/tmgcore-approaching-the-heat-limit-with-liquidimmersion-technology Page 2/8 Introduction Two-Phase Immersion Cooling In traditional cooled data centers, a substantial portion of the energy consumption is dedicated to cooling IT equipment, as modern servers generate significant amounts of heat during operation. Conventional cooling methods rely on raised floor designs, computer room air conditioning (CRAC) units, and complex airflow management systems. However, these approaches are often inefficient, requiring high energy input and occupying valuable floor space. Two-phase immersion cooling offers an alternative approach that addresses these challenges by submerging IT equipment directly in a non-conductive coolant. Operating Principle of Two-Phase Immersion Cooling The two-phase immersion cooling process involves two stages: boiling and condensation. The coolant, which is in liquid form at room temperature, comes into direct contact with the hot components of the servers. As the heat is absorbed, the coolant undergoes a phase change and turns into vapor (boiling). The vapor then rises to the top of the immersion tank, where it comes into contact with cooler surfaces (typically high-performance condenser tubes) and condenses back into liquid form. This condensed liquid flows back to the bottom of the tank, completing the cycle. This efficient heat transfer mechanism eliminates the need for complex pumps and is a very efficient energy-saving cooling process. Page 3/8 Enhanced Heat Dissipation Two-phase immersion cooling provides a more effective method of heat dissipation compared to current solutions. The boiling process allows the coolant to directly reach and cover all heatgenerating components uniformly, ensuring efficient thermal contact. As a result, 2-PIC can remove heat more rapidly and evenly, preventing hotspots and potential overheating of critical IT components. Energy Efficiency One of the most significant advantages of two-phase immersion cooling is its high energy efficiency. The direct contact of the coolant with the servers maximizes heat transfer efficiency, enabling more effective cooling with significantly lower energy consumption. As a result, data centers using 2-PIC can achieve substantial reductions in power usage, leading to reduced operational costs and improved overall energy efficiency. Future and innovate data center cooling needs to be at zero emission as close as possible. The necessity therefore is to cool with water and to reuse the heat as much as possible. This can be done in two ways, reuse the heat for heating buildings and support hot water supply as well as to cool buildings using absorption heat pumps etc. In addition, no additional chillers would be required since the water inlet temperature could go up to 60 C (depending on the boiling point of the refrigerant). In 2018, the energy consumption of data centers in the EU was 76.8 TWh. This is expected to rise to 98.5 TWh by 2030, a 28 % increase. This increase in absolute terms can as well be seen in relative terms: within the EU, data centers accounted for 2.7 % of electricity demand in 2018 and will reach 3.21 % by 2030, if development continues the current trajectory3. Increase in energy efficiency will be vital to help mitigate the rise in energy consumption by data centers and it cannot be achieved by air-cooling. Power usage effectiveness (PUE)4, the common standard for measuring the energy efficiency of a data centers, has recently reached a plateau due to the limitation of the efficiency of air-cooling technologies, which is the predominant in most data centers. The lower the PUE, the higher the energy efficiency. For a decade, data centers made great progress reducing PUE levels. From 2007 to 2017, the average PUE in data centers fell from 2.5 to 1.58. Unfortunately, data center PUE has flatlined since. According to the Uptime Institute's Global Data Center Survey 2021, the average data 3 European Union. (n.d.). Lex - 32012L0027 - en - EUR-lex. EUR-Lex. https://eurlex.europa.eu/eli/dir/2012/27/oj 4 https://www.idtechex.com/en/research-article/webinar-navigating-the-liquid-cooling-dominance-in-data-centers/29616 Page 4/8 center PUE globally is now 1.57. This means facility functions add nearly 60% to the energy use of IT.5 To make matters worse, servers and chips are becoming more and more powerful, emitting more heat: Even with optimized energy efficiency, the amount of power required to cool data centers with air-cooling is still increasing.6 2-PIC has the best-in-class power usage effectiveness (PUE) compared to alternative technologies for data center cooling, as the table below outlines in detail.7 An average PUE of 1.7 achieved by air-cooling with chillers - see table below8 - means that for every 100 W of heat dissipated by a chip, an additional 70 W of power consumption is necessary for cooling. Other air-cooling technologies, such as water-side and direct evaporative cooling, decrease PUE (increase energy efficiency) but may increase water consumption. For cold plate technology, the cooling power consumption is 8 % (8 W per 100 W of server heat) for an average PUE of 1.08. For 1-PIC (single-phase immersion cooling), the cooling power is reduced to 5 % (5 W per 100 W of server heat), but still more than double of what 2-PIC can achieve, at only 2% (2 W per 100 W of server heat) of cooling power or a PUE of 1.02. Table 1 also shows that the maximum server cooling capacity - or the most heat that can be removed by the cooling technology - is greater than 4 kW for 2-PIC. In case of 1-PIC, it is limited to 2 kW, which means a data center cooled with 1-PIC would need at least twice as many immersion tanks than one designed for 2-PIC. The adoption of 2-PIC will play a critical role in dramatically increasing data centers' energy efficiency (decrease PUE) and reducing the size of data center buildings. Based on the expected numbers of 98.5 TWh by 2030 the higher efficiency of 2-PIC compared to 1PIC has a dramatical impact on the energy consumption and means approximately additional 2,96 TWh additionally reduced energy consumption, for the Peak Loads up to 3,94 TWh combined with an about 50 % reduced data center footprint using 2-PIC systems. Cooling Technology Chillers (air-cooled) Water-Side (air-cooled) Direct Evaporative (air-cooled) CPU Cold Plates 1-PIC 2-PIC Average PUE 1.70 1.19 1.12 1.08 1.05 1.02 Peak PUE 2.00 1.25 1.20 1.13 1.07 1.03 Server Fan Overhead 5% 6% 6% 3% 0% 0% Max Server Cooling 700 W 700 W 700 W 2 kW 2 kW >4 kW 5 Yavor.trampov. (2022a, March 8). Data Center Energy Efficiency via 2-phase immersion cooling: LiquidStack blog. (https://liquidstack.com/blog/why-data-center-efficiency-gains-have-stalled-since-2018%20) 6 LiquidStack. (2022). Why Data Center Efficiency Gains Have Stalled Since 2018. LiquidStack blog. https://liquidstack.com/blog/why-datacenter-efficiency-gains-have-stalled-since-2018). 7 (Hitchens, K. (2022). Liquid Immersion Cooling Pushes the Heat Limit. Data Center Frontier. https://www.datacenterfrontier.com/whitepapers/article/11427611/liquid-immersion-cooling-pushes-the-heat-limit. 8 Comparison of the Main Data Center Cooling Technologies' PUE. Misra, P. A., Manousakis, I., Choukse, E. et al. (2022). Overclocking in immersion-cooled datacenters. IEEE Micro, 42(4), 10-17. https://doi.org/10.1109/mm.2022.3163107 Page 5/8 Higher energy efficiency (lower PUE) means lower cooling energy consumption which translates into lower indirect CO2 emissions due to cooling. When combined with low-GWP fluids such as HFOs, users can drastically reduce CO2 emissions to the lowest value among other cooling technologies. As demonstrated above, 2-PIC is best in class energy efficiency and will play a key role in helping the EU and the globe mitigate the unavoidable increase of energy use (and indirect CO2 emissions) from data centers while also supporting the EU reach its energy efficiency and net zero goals. Applications for 2-PIC are growing and data center infrastructure continues to become more critical in AI, telecommunications, military, and traditional data storage end use applications. Improved Server Performance Data centers implementing two-phase immersion cooling can benefit from enhanced server performance. Lower operating temperatures due to efficient cooling result in reduced thermal throttling, allowing servers to operate closer to their peak performance levels. This can lead to improved computational performance and better overall system reliability. Compact Design and High Density The compact nature of two-phase immersion cooling systems allows for increased IT equipment density within the same physical footprint. With traditional air-cooling methods, significant space is dedicated to airflow management and cooling infrastructure. In contrast, 2-PIC eliminates the need for raised floors and large cooling systems, enabling data center operators to optimize space utilization and to accommodate more servers in the same facility and therewith also reduce the impact on the environment due to reduced earth sealing. This is particularly important for future high power density servers and computer which are necessary e.g., for autonomous driving, virtual reality, AI. Reduced Environmental Impact & Sustainability Benefits As the world becomes increasingly conscious of environmental issues, data centers are under pressure to adopt more sustainable practices. Two-phase immersion cooling aligns with these sustainability goals by offering an eco-friendlier cooling solution. The dielectric liquids used in 2-PIC like Novec 649 (CAS-Nr. 756-13-8) are non-hazardous and have low global warming potential (GWP) and ozone depletion potential (ODP). Furthermore, 2-PIC systems' energy efficiency reduces the data center's overall carbon footprint. A recent case study demonstrates that a two-phase immersion cooled data center can provide 100% water reduction, 40% mechanical power reduction (versus air-cooling with chillers) and requires 60% less floor space than air cooled data centers based on9 10. Along the same lines, 2-PIC's highest in class energy efficiency combined with the use of a very low GWP fluid yields the lowest CO2 equivalent emissions of all data center cooling technologies. 11 However, operation of 2-PIC is only possible with cooling fluids that fall under the proposed PFAS restriction. The fluids are used in a closed system to avoid emissions during the operation cycle. To reduce any fluid loss even further, it is also possible to use the system within a sealed and filtered container. 9 Major J., Padilla F. & Slyziuk E. et al. (2022). Two-phase liquid immersion cooling 2022 case study. LiquidStack. https://liquidstack.com/case-studies/two-phase-liquid-immersion-cooling-2022-case-study 10 LiquidStack & Chemours. (2022). Two-Phase vs Single-Phase Immersion Cooling Fluids: Deconstructing Myths with Science. LiquidStack / Chemours. https://liquidstack.com/white-papers/fluorinated-cooling-fluids-101 11 Misra, P. A., Manousakis, I., Choukse, E. et al. (2022). Overclocking in immersion-cooled datacenters. IEEE Micro, 42(4), 10-17. https://doi.org/10.1109/mm.2022.3163107 Page 6/8 Low Water Consumption Traditional cooling methods, such as water-based cooling towers, consume significant amounts of water for heat dissipation. Two-phase immersion cooling eliminates the need for water cooling, further reducing the data center's water consumption and associated environmental impacts. Noise Reduction Air-cooled data centers generate considerable noise from cooling fans and air handling units. Twophase immersion cooling, which operates without the need for fans, significantly reduces noise levels within the data center environment, leading to a quieter and more comfortable working environment for personnel. Scalability and Modularity Two-phase immersion cooling systems are highly scalable and modular, making them suitable for various data center sizes and configurations. Data center operators can easily expand their cooling infrastructure by adding more immersion tanks and servers as needed. Additionally, 2-PIC systems can be prefabricated and delivered as modular units, simplifying installation, and reducing downtime during upgrades or expansions. Enhanced Reliability The absence of moving parts, such as cooling fans, in two-phase immersion cooling systems contributes to their enhanced reliability. Fewer mechanical components mean reduced points of failure and decreased maintenance requirements, resulting in improved overall system reliability and uptime. Near zero emissions and no risk The dielectric liquids used in 2-PIC are non-hazardous and have low global warming potential (GWP) and ozone depletion potential (ODP). In addition, 2-PIC devices are operated as closed systems. Through proper tank design and materials, vapor management as well as proper described procedures for operation, maintenance and service, the loss of the cooling fluid is reduced to a minimum. This is one of the key factors during production and product qualification. Due to the current business in heat exchanger design and quality control there are very strict leakage rates defined which are controlled via a Helium leakage test of each tank. Further technologies like room ventilation and filtration will further reduce the emission of the cooling fluid to the environment close to zero. End of life / Recycling The immersion cooling container as well as the fluid will be recycled at the end of the life cycle. A professional recycling strategy will avoid any fluid loss and enables a closed product cycle. Non-PFAS alternatives in 2-PIC The Annex XV-Dossier states that there is "Sufficiently strong evidence that technically feasible alternatives exist for heat transfer fluids for immersion cooling" (Table 8.RO1, page 104) and "Given the evidence pointing to the existence of technically and economically feasible alternatives at EiF for heat transfer fluid for immersion cooling and liquid crystal displays, in combination with the inconclusive evidence pointing to the non-existence of technically and economically feasible alternatives at EiF in all other uses, no derogation is proposed" (Table 9.RO2, page 134). Annex E of the Annex XV-Dossier than identifies "Mineral oils, synthetic oils, natural oils, Hydrocarbon fluids as alternatives in heat transfer fluids for immersion cooling (no current but possible future use)" as potential non-PFAS alternatives (Annex E, Table E.128, page 396). Page 7/8 wieland These statements regarding non-PFAS alternatives are based on the evaluation of single-phase immersion cooling systems. They are not applicable to two-phase immersion cooling systems. For 2PIC, non-PFAS alternatives are not yet available. The non-PFAS alternatives identified for singlephase immersion cooling are not suitable for two-phase immersion cooling since most of them are flammable which means a higher risk during operation. In addition, the evaporation temperature of the oil-based fluids is much too high to achieve evaporation on the hot surface and enable an efficient two-phase heat transfer to remove the heat. Manufacturer of cooling fluids are currently working towards cooling fluids that can be used in 2-PIC and that are not very persistent and bio-accumulative, e.g., degradable fluorinated substances (e.g., cooling fluid Opteon 2P50 by Chemours). The work on degradable fluorinated cooling fluids is already at an advanced stage, but it will still take some time before the products will be available on the market. 3 Conclusion Two-phase immersion cooling is a highly energy-efficient solution for data center cooling that offers numerous benefits over traditional methods and single-phase immersion cooling. Its efficient heat dissipation, improved server performance, compact design, near zero emission in the environment, and scalability make it an attractive choice for data center operators looking to enhance energy efficiency, reduce operating costs, and embrace sustainable cooling practices. With ongoing advancements and growing interest from industry leaders, two-phase immersion cooling is expected to play a significant role in shaping the future of data center cooling. PFAS used in 2-PIC are safe and operated in close systems posing no risk to workers, the environment or society. Manufacturers of cooling fluids used in 2-PIC are working on the development of non-persistent and non-bio-accumulative cooling fluids. Wieland is therefore asking ECHA to consider a derogation from the proposed PFAS restriction for two-phase immersion cooling for 12 years in order to allow the manufacturers sufficient time to develop non-PFAS alternatives. The current restriction proposal would ban a pioneering and innovative electronics cooling technology. To follow the fast-growing data center market and to be able to provide the most energy-efficient cooling solution it is necessary to be able to use the current PFAS fluids until new fluids are commercially available. The potential reduction of PFAS emissions to the environment due to the banning of two-phase immersion cooling systems for data center cooling is disproportionate to its negative impact regarding increasing energy consumption and CO2 emission as less efficient options remain in the market and the increase data demand will need to be provided to lower performing solutions. For further questions please contact: Dr. Achim Gotterbarm Vice President Global R&D and Business Development BU Thermal Solution Wieland-Werke AG E-Mail: @wieland.com Page 8/8