LVDC vs LVAC: A comparison of system losses

Energy transition is at the center of the next decades efforts to maintain global warming below 1.5 °C. Solar energy is considered a key power supply, especially in urban areas where many rooftops are unexploited. Local integration of photovoltaic energy reshapes the electrical energy distribution where consumers become producers. Smart and micro-grids are developed to support local energy communities aiming for self-sufficiency and resilience from global grid. AC (Alternative Current) electricity won during the XIXth century current war opposing to DC (Direct Current) system. New energy assets, like photovoltaic or battery storage systems are DC technologies, requiring a conversion to be connected to AC distribution grid. Each conversion step generates losses decreasing the overall efficiency of renewable energy integration into urban areas. Direct connection of DC equipment through a Low Voltage DC (LVDC) microgrid is considered as one possibility to optimize energy efficiency at district level. The efficiency of an electrical energy distribution LVDC nano-grid implemented at Turku’s Student Village is assessed in this paper. The results are compared with efficiency of the same grid realized in Low Voltage AC (LVAC). The first results show a slight advantage to LVDC distribution. Further improvements could be achieved by including directly connected DC loads and controllable energy generation and optimizing converter ratings.