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DEGREE is investigating a method for increasing energy efficiency in data centers by dynamically controlling cooling circuit temperatures, and is developing guidelines for implementing the resulting concepts.

The operation of cooling systems is a major consumer of electrical energy in data centers, second only to that necessary to power the servers. At present, it is often responsible for up to one third of the total energy demand. The most energy-efficient type of cooling is "free cooling." Here, waste heat is released directly into the environment via wet or dry cooling towers. This avoids the need for energy-intensive active cooling, such as compression or adsorption chillers. Free cooling only works, however, if the temperature of the heat to be discharged is greater than the outside temperature. One current trend in server design is towards higher operating temperatures to enable more efficient cooling. At the same time, however, increasing the cooling temperature can also have negative effects. Higher operating temperatures lead to higher power consumption for numerous components, especially for semiconductor chips. In addition, computing performance and the service life of IT components decrease.

The research project DEGREE is addressing this problem of optimizing the trade-off between the lowest possible operating temperatures and a maximum of free cooling by implementing dynamic cooling circuit flow temperatures. Here, the flow temperatures are raised just enough to ensure that free cooling is always possible, while at the same time avoiding unnecessarily high flow temperatures.

Due to the different temperature dependencies of the various components, the entire system of cooling and IT components must be considered. As a proof of concept, this methodology is being implemented and tested at the High-Performance Computing Center Stuttgart (HLRS). For this purpose, a thermal simulation model of the HLRS will be created and validated using real operating data. The model will be constructed in such a way that it can be transferred to other data centers in ways that can accommodate their specific characteristics.

The transfer of knowledge between research and practice will be ensured by the participation of the industrial partners ICT Facilities GmbH and T.P.I. Trippe und Partner Ingenieurgesellschaft mbH. The results of the project will be presented and published in a guide for other data centres. In this way, DEGREE will contribute to limiting energy demand in the operation of data centers and help to minimize their impact on climate.


15. June 2021 -
14. June 2023




Deutsche Bundesstiftung Umwelt

Project partners

  • University of Stuttgart Institute for Building Energetics, Thermotechnology and Energy Storage (IGTE)
  • High-Performance Computing Center Stuttgart (HLRS)
  • ICT Facilities GmbH
  • T.P.I. Trippe und Partner Ingenieurgesellschaft mbH