DC Microgrids in Buildings and Data Centers

The debate on the use of Direct Current (DC) as a power distribution means has been raging for decades. Recently, one focus of the discussion has been the data center. For various reasons, AC remains the preferred method of power distribution in the data center, despite some disadvantages inherent to AC power. This is particularly interesting when one considers the fact that almost all of the critical payloads in the data center are DC loads. The recent drive toward Smart Grid technology coupled with the potential advantages DC distribution can offer opens the door for serious discussion on the merits of DC microgrids as a viable distribution alternative in the building space and, in particular, the data center. This paper will examine the advantages, issues and challenges of the use of DC for this purpose. Further, the paper will look at the current activity in the standards community, with particular attention given to the current ETSI and EMerge Alliance efforts to formulate a standard that deals with 380V dc power distribution. The paper also will examine the ability of a DC microgrid to facilitate renewable energy use as well as provide high degrees of critical load availability. It will include a discussion of potential system topologies as well as various proof-of-concept sites currently under way. Finally, the current status of safety issues in the use of higher voltage distribution in building spaces will be discussed.