Data center capacity is growing rapidly, but for every MB of data transmitted, or floating point operation (FLOP) performed by AI, more energy is used. In data centers, only 60-80% of total energy is used to run the server hardware and IT equipment; 20-40% of energy is instead being used to cool the critical server hardware. The very latest data centers, using highly efficient cooling, now consume just 10% of the total energy for cooling. This is largely achieved through highly advanced and efficient free or evaporative cooling technologies.
Free Cooling (FC): Known as "economiser mode", this method uses external air to assist in cooling the data center, circumventing the need for energy-intensive mechanical cooling systems or evaporative systems. This mode is particularly effective during the colder months or at night.
Direct Evaporative Cooling (DEC): This method leverages the natural process of water evaporation to remove heat. Specialized systems spray or disperse water onto a specialist heat exchanger material, the water efficiently evaporates, absorbing heat during this process and thus cooling the air; however, this significantly affects the humidity of the air passing into the data center. The effectiveness of this method hinges on the ambient air's ability to absorb moisture (which is directly related to its humidity and temperature).
Indirect Evaporative (Adiabatic) Cooling (IEC): Adiabatic cooling systems increase the effectiveness of free cooling and avoid the limitations of evaporative cooling. Like evaporative cooling, water evaporation is used to cool the external air. This cooled air is then used via a heat exchanger to cool the supply air. In this way, the humidity levels can be carefully controlled.
DX/CW (Mechanical) Cooling: Finally, there are conditions that require additional cooling. Direct Expansion (DX) and chilled water (CW) coils can provide additional cooling. Typically, these systems are sized to provide partial back-up for the overall cooling load.
Accurate humidity measurements are vital for both cooling technologies to function optimally. The right balance of humidity ensures system efficiency, prevents hardware damage due to condensation, and maintains operational reliability.
Dew Point: This is the temperature at which air is saturated with moisture and dew forms. Understanding dew point is crucial for data center managers because it helps predict when condensation is likely to occur, which is critical for preventing moisture-related damages in sensitive environments.
Other Psychrometric Values: These include relative humidity, wet bulb temperature, and specific humidity, all of which play a role in determining the air properties in a data center environment. Understanding these values helps in designing and operating HVAC systems efficiently, ensuring they respond accurately to changes in both internal heat loads and external weather conditions.
Psychrometric Chart: The ASHRAE chart below shows the desired conditions for data center IT hardware. The role of the data center is to manage the cooling air to be within this critical window. Deep understanding of humidity, dew point and temperature ensures the most efficient systems can be used to condition the air; this will vary constantly based on data center load, outside air conditions and energy tariffs.
For optimal performance of evaporative and free cooling systems, data centers need advanced humidity control systems that offer:
As data centers continue to evolve towards more energy-efficient and environmentally friendly operations, the integration of technologies like evaporative cooling and free cooling, combined with precise environmental monitoring, continue to form the cornerstone of a modern data center infrastructure strategy. Accurate measurement and control of temperature, humidity and other psychrometric values not only ensure compliance with standards like those set by ASHRAE but also enhance overall operational efficiency, sustainability, and reliability. By prioritizing advanced environmental management systems, data centers can achieve significant improvements in both performance and cost-effectiveness, aligning operational objectives with broader environmental goals.
At PST, we are proud to provide instrumentation and consultancy to many of the most efficient data center manufacturers and end users. Our unique portfolio covers not only efficient control but also safety, calibration and servicing. Contact us for more information about our humidity, temperature, differential pressure, oxygen and liquid level instruments.
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