DC power grids for buildings

Direct current (DC) power grids are an interesting option for buildings to connect natural DC power sources such as photovoltaic power systems with DC loads like lighting, IT systems as well as speed-controlled electric motors of heating, ventilation and air-conditioning systems. The paper documents learnings, measurements and efficiency differences of a test bed installation with both a 230 V AC and a 380 V DC grid. Both subsystems supply LED luminaires with electricity from utility mains and AC respectively DC grid connected photovoltaic solar power systems. An efficiency advantage of 2 % has been measured with the 2 kW DC grid test bed. 5 % energy savings are described as potential.