LVDC for buildings in the Netherlands

Abstract

Current energy concerns like growing energy demand, the desire for a clean environment and energy conservation started thrusting the society towards distributed renewable electricity generation (DG) technologies. These technologies such as PV solar, Fuel Cells (FC) and urban wind produce Direct Current (DC). The electronic equipment such as laptops, PCs, communication systems, LED lighting, batteries, Electric Vehicles (EV) and Fuel Cell Electric Vehicles (FCEV) also operate in DC. But the present-day electricity distribution system is based on Alternating Current (AC). From this conventional system, the conversion losses can be substantial when DC generation and DC loads are operated. For which, several (DC/AC – AC/DC) conversion steps are required. These conversion losses can be mitigated by removing the intermediate conversion steps and distributing DC power to the DC loads directly. For which, the main aim of the thesis focuses on the technical and commercial potential of Low Voltage DC (LVDC) grids for buildings in the Netherlands. DC office is a small office building at The Green Village (TGV) in TU Delft where a 350 Vdc LVDC system is installed for experimental purposes. The experiments are carried out using both LVDC and LVAC grids in DC Office project. The obtained experimental data are randomized using Matlab to create a year-long load profile. The results are used for discussing the LVDC technical potential in terms of overall efficiency and energy savings. From these results cost-savings are calculated. Along with this, usage of copper and aluminum as electrical conductor in buildings and its investment cost-savings are discussed. For the commercial potential of LVDC grids for buildings in the Netherlands, the Function of Innovation Systems (FIS) approach is used to identify the corresponding LVDC stakeholders, research, pilot projects, rules and regulations and policies for development. For the technical potential, there are three different cases formulated for analysis. They are ACTube case, DCLED case and ACLED case. In the experiments, tubelights are used in the ACTube case and LEDs are used in the DCLED case, in-order to neglect the energy savings obtained from LED technology, ACLED case is assumed. The overall efficiency of the LVDC grid (DCLED case) is 94.82% and the LVAC grid (ACTube case) is 88.16% and the LVAC grid (ACLED case) is 88.67%. From all these cases, the LVDC grid is around 6.5% more efficient than LVAC grid in small buildings similar to the DC Office. The energy savings obtained by LVDC grid replacing LVAC grid (ACTube) is 2013 kWh/year, and if tubelights in AC are replaced with LEDs in AC, then 1854 kWh/year is estimated to be saved. The cost-savings are calculated from the energy savings obtained by replacing LVAC grid (ACTube case) with LVDC grid (DCLED case). Considering the total lifetime of the LVDC system as 12 years, the cost savings obtained are € 221.43/year achieving payback in 6 years. For the commercial potential, using seven functions of FIS it is identified that there are several stakeholders interested in LVDC projects and are responsible for pilot projects. The government also is implementing the new NPR 9090 as the rules and guidelines for LVDC grid installations in buildings. It is also identified that people have positive acceptance of the LVDC grid in their houses. But the knowledge sharing about LVDC among the society is currently lacking. Moreover, the AC electricity distributors are interested in shifting towards the DC micro grid distribution.