RE/SOURCED pilot: Practical implementation of a DC microgrid

The RE/SOURCED project, an Urban Innovative Actions initiative in Zwevegem, Belgium, seeks to develop a circular, medium-sized, and self-sufficient energy system within the redevelopment of the Transfo site, a former coal-fired power station. Covering 10 hectares and integrating offices, residential housing, and social amenities, the site offers a diverse energy consumption profile, making it an ideal environment for uniting residents and consumers in an energy community living lab. Central to this project is the design and implementation of a low-voltage direct current (LVDC) microgrid, which optimizes energy generation, storage, and consumption. The project embraces circular economy principles by focusing on material repurposing, refurbishment, and energy efficiency.

Building on the implementation of the LVDC microgrid, the RE/SOURCED project features a radial DC backbone connected to the public AC grid through a bidirectional AC/DC inverter. To the authors' knowledge, this DC project is the first of its kind to be operated by the Distribution System Operator (DSO). The choice to use DC for interconnecting distributed renewable energy sources and storage systems offers significant advantages in energy efficiency by reducing conversion losses and minimizing material use. Energy is generated primarily from multiple photovoltaic (PV) installations and a combined heat and power (CHP) plant, while storage is facilitated by a stationary battery. The direct DC consumption is utilized by electric vehicle (EV) charging stations, and the remaining energy is either consumed on-site or injected into the public AC grid.  A comprehensive energy management system (EMS) monitors and optimizes all energy flows within the microgrid by utilizing historical and real-time data, as well as weather forecasts.

This paper addresses the practical challenges encountered in designing and implementing a DC microgrid, particularly focusing on the technical and operational hurdles. One major challenge involves the fundamental differences between AC and DC protection and switching equipment. Unlike AC systems, DC lacks a natural zero-crossing  , requiring more complex protection devices. These DC protection solutions are still underdeveloped and not widely available on the market.  Another challenge is the absence of standardized technical guidelines for DC networks, including the lack of a standard voltage level [5]. Grounding and network operations also require careful consideration due to the potential for corrosive DC leakage currents and the capacitive behavior of DC-grids. Additionally, the limited availability of DC components and the general lack of expertise among installers further complicate the deployment of such systems.

The outcome of the RE/SOURCED project  is a unipolar DC backbone operating at a nominal voltage of 700 V, supported by a 500 kVA central inverter. The system integrates four PV installations with a total capacity of 400 kWp, a 306 kWh second life battery, a CHP unit generating 40 kWe, and an EV charging park with a capacity of 236 kW. This configuration provides a practical demonstration  of the potential for DC microgrids in mixed-use developments, offering valuable insights into the transition toward more efficient and sustainable urban energy systems.