Abstract

The internal distribution grid in buildings is, just like the rest om the grid, based onalternating current technology. Though today most of the electricity consumers in a buildinguse direct current in their final stage. Also the use of photovoltaics, battery systems andelectric vehicles are increasing and they also use direct current. Direct current grids inbuildings is an idea to minimize the amount of conversions between AC and DC within thebuilding, instead the idea is to centralize the rectification and thereby lower the conversionlosses.The purpose of this thesis is to investigate the phenomenon DC-grids and the Swedishmarket for it. This is done to find out the feasibility and possibilities of a DC-grid in an officebuilding today. Through a market investigation the solutions and knowledge of this day hasbeen summarized, they are then used to find a recommendation for what parts in an officebuilding that can be supplied with direct current form a DC-grid.According to the investigation there are solutions at the Swedish market for building aninternal DC-grid at 350VDC or +/-380VDC (760VDC) depending on what is the priority in theproject in question. Since not all electricity consumers can use DC a hybrid between AC andDC is most relevant today. Electrical units that can use direct current today are lighting,ventilation, laptops, mobile phones, tablets, servers and smaller office appliances andtelephony. Possibly heat pumps and other pumps might also be able to be supplied by directcurrent. The electrical units that still need to be supplied by AC are the copier rooms, theelevators, the kitchen areas and the garage with the EV chargers.