Enhancing Data Center Efficiency with Advanced Cooling Technologies

data center cooling systems

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.

An In-Depth Look at Free, Evaporative, Adiabatic and Mechanical Cooling Systems

  • 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.

External air supplied directly or used to cool return air via heat exchanger.

  • 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).

External or return air cooled by evaporation and directly fed to data center supply.

  • 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.

External air cooled by evaporation and used to cool return air via heat exchanger.

  • 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.

External Air is too hot to achieve 100% cooling with Adiabatic, the DX module is thus integrated to cover the missing capacity.

Crucial Role of Humidity Measurement

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.

  • Condensation Prevention: Data centers are filled with sensitive electronic equipment. Condensation, which can occur if the dew point of the surrounding air exceeds the temperature of any surface in the data center, can lead to short circuits and corrosion. Monitoring and controlling humidity levels prevents such risk.
  • Optimizing Cooling Capacity: The effectiveness of an evaporative cooling system is directly affected by the humidity level in the air; overly humid air will not absorb water efficiently, reducing the system's cooling capacity. Accurate humidity sensors enable real-time adjustments to maintain efficiency. Humidity measurements also constantly assess the effectiveness of evaporation systems, ensuring any loss in performance can be quickly detected.
  • ASHRAE Standards and Reliability: The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) sets guidelines for optimal data center operations, including recommended humidity levels to prevent electrostatic discharge and other humidity-related issues. Compliance with these standards helps ensure the data center operates reliably and avoids downtime.

Technical Insight: Dew Point and Other Psychrometric Values and the Psychrometric Chart

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.

data center cooling systems
Required conditions based on ASHRAE standards source: Research Gate
mechanical cooling chart
Example cooling operation mode based on return/outside air conditions. Source:
https://www.i-acs.co.uk/store/documentation/datasheets/carel/3000054EN.pdf

Advanced Humidity Control Systems: Features and Benefits

For optimal performance of evaporative and free cooling systems, data centers need advanced humidity control systems that offer:

  • Precision and Quick Response: High-accuracy sensors provide real-time humidity readings, allowing for immediate adjustments to the cooling systems, enhancing both energy efficiency and system responsiveness.
  • Integration with DCIM Systems:: High-accuracy sensors provide real-time humidity readings, allowing for immediate adjustments to the cooling systems, enhancing both energy efficiency and system responsiveness.
  • Reliability in Harsh Environments: Given the dynamic environment within data centers, sensors and control systems must be robust and reliable, capable of withstanding high airflow, dust, and varying temperatures.
  • Ease of calibration and preventative maintenance: Downtime is unacceptable in data centers and strict SLAs enforce this. Instruments must therefore be designed with zero downtime maintenance and calibration in mind.

Conclusion

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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External Links

ASHRAE Releases Revised Version of Data Center Standard



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