Energy efficient low-voltage DC-grids for commercial buildings

The European ENIAC R&D project consortium DC Components and Grid (DCC+G) is developing suitable, highly efficient components and sub systems for 380 VDC grid to show the benefits of DC grid concept on test site in an office environment. The newly developed DC grid components and their integration into a generic system are presented in this paper. The targeted overall efficiency saving compared to AC grid is 5% and the energy conversion from PV (photo voltaic) is calculated to be 7% more cost effective compared to traditional PV installations. This paper also shows the realized DC grid prototypesupplying an office building of the Fraunhofer Institute in Erlangen, Germany, and describes general benefits of a DC grid system. The DC grid prototype consists of a DC lighting system, a DC low power supply for IT infrastructure, DC electric vehicle charger, a DC μCHP unit, DC photovoltaic MPPT units, a central rectifier and grid controller unit as well as a mixed AC/DC power monitoring unit. It is shown that less conversion losses and higher distribution efficiency can be achieved with a 380 VDC grid compared to conventional AC grids.