DC Distribution System for Data Center

This dissertation, "DC Distribution System for Data Center" by Marjan, Javanshir, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled "DC Distribution System for Data Center" submitted by Marjan Javanshir for the degree of Master of Philosophy at the University of Hong Kong Several converging factors have spurred the recent interest in DC power delivery. One of the most important is that an increasing number of microprocessor-based electronic devices use DC power internally, converted inside the device from standard AC supply [1]. As a result, DC power delivery in data centers has exceptionally promising potential applications because of its densely packed racks of servers that all rely on DC power. The power losses due to the use of power conversion devices from both outside and within equipment result in a large loss of electrical power. To avoid multiple power conversions, all data processing equipment could be directly supplied by a dedicated DC distribution system. Such a system is the topic of this study. In this thesis, an alternative approach for delivering power to the computational equipment in data centers using DC power is introduced, and its efficiency compared to the traditional approach using AC power. Initially, general investigations of different AC and DC distribution systems are performed by evaluating current and power loss ratios. Moreover, if the voltage level is not predetermined by the AC system, one of the major issues is the proper choice of the DC voltage level. Thus, the optimal voltage level is determined. To facilitate practical application, it is important that the shift from AC to DC distribution can be done with minimal changes. Therefore, a retrofit DC distribution system for data centers is presented in a case study assessing its overall energy consumption improvement over a traditional AC distribution system. Results indicate clearly that the total system losses decrease using DC, leading to energy saving. Lastly, the economics of replacing conventional power back-up systems in data center by DC equipment are analyzed. DC system flywheel energy storage can be used as a substitute for batteries to provide back-up power to the UPS, which in turn could be directly connected to the DC distribution system. Life-cycle cost analysis illustrates the cost-effectiveness of flywheel systems over batteries. Similarly, microturbines with DC generation can replace conventional fuel-fired AC standby generator back-up. Although the economics suggest that microturbines are not attractive for data center standby power generation when compared with traditional standby generation, microturbines could be an excellent alternative, if reducing emissions is a concern. (373) DOI: 10.5353/th_b3934495 Subjects: Electric currents, DirectElectric power systemsElectronic data processing departments - Power supply