Liquid vs. Air Cooling: A 5 PFLOPS Berlin Datacenter Reveals the Superior Solution After Five Years of Operations
According to the International Energy Agency, power consumption will double by 2026 compared to 2022, with cooling accounting for around 40% of the energy required[i]. In response, governments are introducing stricter compliance regulations. Liquid cooling is considered as the next generation of cooling technology and is paving the way for energy-efficient and sustainable data centers. However, the question of whether and how to incorporate liquid cooling into data center construction has become a stumbling block for enterprises in forming specific deployment plans.
KAYTUS, a provider of end-to-end AI and liquid cooling solutions, explains in this article when adopting liquid cooling is essential, and introduces the case study of Berlin datacenter, empowering users to make informed decisions about the use of liquid cooling.
Typical liquid cooling applications: AI, HPC and cloud
In fact, the heat dissipation capacity per unit volume of liquid cooling is 3,000 times greater than that of conventional air cooling[ii], making it much more energy efficient. Additionally, the compact design of liquid cooling systems is particularly suitable for high-density deployment, catering to the needs of high-power density cabinets.
KAYTUS believes that liquid cooling is particularly suitable for chips with a power consumption of over 250 W and supports a power density of over 40 kW per cabinet. Common forms of liquid cooling include cold plates and immersion cooling. The cold plate technology is a more mature industry and holds a market share of over 90%. Liquid cooling deployment is well-suited for high-density computing applications such as AI and HPC, with common applications including:
AI and HPC: For typical high-density computing, liquid cooling can be used in large-scale language models (LLMs), autonomous driving, computer vision, engineering/medical simulations, scientific computing and other applications. It helps to meet the demanding requirements for heat dissipation.
Cloud computing: For cloud services supported by hyper-scale data centers, liquid cooling helps to ensure the stable operation of data centers while significantly reducing operational and maintenance costs.
Liquid cooling vs. air cooling - a total cost of ownership (TCO) analysis
Given that liquid cooling is fit for high power density applications such as AI, HPC, and cloud computing, what advantages does it bring compared to air cooling? Let's explore a real-world application of a 5 PFLOPS data center in Berlin, Germany, which utilizes both air and liquid cooling systems. KAYTUS has compiled its five years of deployment and operational data. Although the initial investment for liquid cooling is higher than that of air-cooled data centers, the total cost of ownership (including initial investment and daily operations) for liquid cooling begins to demonstrate advantages after the first year of operation, and this gap continues to widen over time.
According to our actual calculations, a comparison between liquid cooling and air cooling shows the following advantages:
Increased space utilization: Liquid cooling is better suited for high-density deployments. In the data center with 225 servers, liquid cooling reduces the cabinet count from 58 (with air cooling) to just 19—a 67% reduction
Improved energy efficiency: 0.19 lower PUE (Power Usage Effectiveness). It is decreased from 1.34 to 1.15 compared to air cooling. The PUE of liquid cooling is significantly lower and approaches the ideal value of 1.
Green and sustainable: Annual savings of 1.31 million kWh, which equates to a reduction of 35 tons of carbon emissions
[1]: 2U 4-node Ice Lake platform. A single liquid-cooled cabinet can accommodate up to 18 servers, while a single air-cooled cabinet can only accommodate up to 6 servers.
From the case study above, we observe that liquid cooling achieves a PUE closer to 1 than air cooling, meaning that more energy is utilized for computing rather than wasted on cooling and other ancillary tasks
Let's break down the cost savings for users.
Liquid cooling can reduce annual electricity costs by approximately €250,000 while also lowering operational expenses, such as maintenance and space costs, by €130,000. In total, users can expect to save €380,000 per year. And the initial investment difference between liquid cooling and air cooling is €739,000.
Using this amount and the annual savings, €739,000 (LC vs. AC initial investment difference) ÷ €380,000/year (annual savings) ≈ 1.94 years (Payback Period ~2 years). In other words, the additional initial investment in liquid cooling is offset with two years of operation.
From a cost perspective, the initial investment difference between liquid cooling and air cooling is €739,000, while the annual comprehensive savings with liquid cooling amount to approximately €380,000. After three years, the total cost of ownership (TCO) is reduced by around €400,000 (€380,000 × 3 - €739,000), and after five years, the reduction reaches approximately €1.16 million (€380,000 × 5 - €739,000).
By adopting liquid cooling, businesses can directly lower operational costs, with the additional investment compared to air cooling fully amortized in about two years. Over a five-year period, the total cost savings amount to €1.16 million, providing significant financial benefits. At the same time, liquid cooling reduces energy waste, cutting carbon emissions by 35 tons annually, aligning with global sustainability goals. Furthermore, liquid cooling supports higher-density deployments, reducing the number of server cabinets by 67%, which is particularly beneficial for space-constrained data centers.
Based on the operational data, we can draw three key conclusions:
Cost Recovery: The additional investment in liquid cooling compared to air cooling is fully amortized in approximately two years.
Long-Term Savings: After three years, liquid cooling reduces the total cost of ownership by €400,000, and over five years, the savings reach €1.16 million.
Sustainability: Liquid cooling cuts energy consumption by 1.31 million kWh annually, reducing 35 tons of carbon emissions each year.
Advantages of liquid cooling: reliability, high energy efficiency and high density
KAYTUS sees three main advantages of liquid cooling systems:
Better heat dissipation to ensure system stability
Liquid cooling ensures that the operating temperature of the CPU remains between 40°C and 50°C - around 20°C lower than with air cooling. This significantly reduces the risk of failures due to local hotspots and maximizes computing power. In addition, liquid-cooled servers use no or lower-speed fans compared to air-cooled servers, which reduces vibrations and reduces the risk of memory and drive failures.
Improved energy efficiency, declined carbon emissions
The more efficient cooling of IT devices reduces their overall energy consumption. These systems can improve energy efficiency by over 30% compared to conventional air-cooled data centers. This also reduces carbon dioxide emissions, which supports companies' sustainability goals.
Optimizing space utilization with support for high-density computing
Liquid-cooled data centers can accommodate more servers in the same space. Power density per cabinet can be up to 130 kW, enabling higher compute and deployment density and lower total cost of ownership (TCO).
Conclusion
The increasing use of liquid cooling is not only driven by emerging applications such as AI and HPC, but also by the focus on long-term sustainability goals. In this context, the concept of "Green Computing" come up. KAYTUS defines Green Computing as the continuous optimization and improvement of data center IT architecture to enhance energy efficiency across the entire computing lifecycle—from generation and transmission to application. As a key technology, liquid cooling aligns perfectly with this definition. However, when selecting liquid cooling systems, it is important to evaluate the efficiency of the entire computing system - from the components and servers to the upper layer applications. In other words, users should prioritize the liquid cooling solutions that focus on energy efficiency and reliability and are tailored to their specific heat dissipation requirements, data center conditions and cost budgets - from individual nodes and products to the entire system.
Author: Clark Li, Country Manager of KAYTUS for the DACH region
[i] https://www.iea.org/reports/electricity-2024/executive-summary
[ii] At room temperature, the specific heat capacity of water is three times that of air, and its density is 1000 times that of air. The heat dissipation capacity per unit volume= specific heat capacity × density. Consequently, water possesses a heat dissipation capacity that is 3000 times greater than that of air.