Since many alternative energy sources as well as electronics and controls technologies are based on DC current, DC grids have been investigated more intensely in the last decade. DC grids with a centralized AC/DC conversion have proven to be advantageous in server farms.
While LED lighting is also a DC current related technology, an obvious choice would be to use DC grids for them. Prof. Eberhard Waffenschmidt from the Cologne University of Applied Science in conjunction with Philips Research presents the results of an office building DC lamp system installation with photovoltaic (PV) support.
In a system that is optimized for self-consumption of photovoltaic (PV) energy, the PV energy harvested during the day is stored in battery storage and used in the evening. If all components are connected to the AC grid, losses in the AC to DC (and vice versa) converters end up to be 10% to 13% of the output power (Figure 6a).  In a DC system, these losses can be completely avoided (Figure 7b). Reference [5] shows a similar result for such a system, where operation including PV and battery is considered.
Voltage Selection: The supply voltage of the DC grid also has an influence on the losses. Low voltages like 24V or 48V have the advantage of being safe to touch and commercially available devices exist.