Universität Stuttgart
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Item Open Access Findings from measurements of the electric power demand of air compressors(2021) Hummel, Ulf; Radgen, Peter; Ülker, Sercan; Schelle, RalphThe compressed air electric ratio (CAER) describes the ratio of the real electric power demand to the nominal mechanical power of an air compressor. The CAER is an important indicator as the electric power demand of air compressors varies throughout its operation dependent on compressor technology, pressure ratio, and free air delivery. The nameplate power of the compressor drive motor is not sufficient for evaluating the electric power demand; therefore, the CAER plays an important role in assessing the electric operating power demand. In this paper, results from measurements of fixed speed and variable speed (VFD) compressors are presented with the analysis of key influencing factors of the CAER. The data show that the pressure ratio of operating pressure to the maximum design outlet pressure has the largest impact on the CAER. For VFD compressors, the CAER is represented as a linear function dependent on the respective load. Fixed and variable speed compressors’ CAERs are always dependent on the load condition. In idle condition, the CAER was measured to be 0.2. In full load condition with a pressure ratio of 0.6, the CAER averages at a value of 0.87, meaning a 90 kW compressor at 0.6 pressure ratio draws 78.3 kW electric power.Item Open Access Optimized data center site selection : mesoclimatic effects on data center energy consumption and costs(2021) Turek, Dirk; Radgen, PeterThe effect of the location on the energy consumption of data centers has already been studied in detail on the macro-climatic level. To take advantage of these effects, however, it is usually necessary for the location of data centers to cross international borders. The influence of site changes within national borders and in a small radius of < 100 km has not yet been quantified. To investigate this, a dynamic mathematical model of the temperature-dependent components of a reference data center was created and the influence on the energy consumption in an area of 240 × 215 km in Germany was investigated. It could be shown that even small changes of the location within a 10 km radius of a location lead to annual energy savings in the recirculating chiller of 9.12% on average (maximum 56.58%). With a freedom of location of 100 km within national borders, savings of 37.35% on average (maximum 76.11%) are even possible. Location-dependent optimizations are therefore also relevant at local and national level with regard to their influence on energy consumption, and the consideration of mesoclimatic aspects should be an elementary part of the site selection process for data centers in the future.