Modern electric trucks now have a range sufficient for domestic routes, and they are also cost-effective. The necessary charging infrastructure remains a source of uncertainty, which is why charging at the depot is an obvious choice for freight carriers: it requires only minimal changes to existing operations and does not rely on a widespread public charging network. The study therefore addressed questions currently on the minds of logistics companies in Germany: Is the required charging capacity feasible with the existing grid connection? How large should the photovoltaic system and battery storage be? How many charging points and what charging capacities are required? How many electric trucks can be charged with the existing energy system, and is an energy management system necessary? For the analysis, the research team examined 140 annual simulations across six scenarios—ranging from an initial deployment of two electric trucks to the electrification of 60 local and 80 long-haul vehicles. The Fraunhofer Institute’s own tools, NRGISE for energy system simulation and OptiCharge for model-predictive charging control, were used, supplemented by a techno-economic assessment. The scenarios take into account various expansion stages, grid connection options, and charging infrastructure concepts. The goal was to develop a cost-optimized expansion plan for the site that would enable the gradual electrification of the truck fleet while staying within the limits of the existing 2 MW grid connection. A key challenge was that charging windows are very limited—and therefore not very flexible—due to the scheduled nature of the system’s operations.

Solar power and battery storage reduce electricity costs by up to 62.5 percent

The study recommends, as a first step, the installation of a stationary battery storage system (1–2 MWh) in combination with a photovoltaic system covering one-quarter of the available roof area (approx. 2,275 kWp). This would allow the building’s energy demand to be met by approximately 60 percent and charging needs by 77 percent from the building’s own PV storage system. This reduces annual electricity costs by up to 62.5 percent compared to uncontrolled operation. As the degree of electrification increases, it is recommended to expand the storage system to 2 MW of power and 4 MWh of capacity, which proves to be economically robust across all scenarios.

A key finding is the high added value of an integrated energy management system (EMS) that coordinates battery storage and charging processes to ensure the grid connection is not exceeded and all vehicles are charged reliably.

For the charging infrastructure, one charging point per vehicle is proposed—with 150 kW for local transport vehicles and 350 kW for long-distance transport vehicles—whereby an AC-coupled low-voltage solution is deemed practical and cost-effective for the initial phase. 

Finally, the study identifies further potential for value creation by opening up the charging infrastructure to external partners, using the storage system for balancing power and balancing group optimization, and through the possibility of energy sharing under Section 42c of the Renewable Energy Act (EEG). The battery storage system can also serve as an emergency reserve: with a capacity of 4 MWh, it can maintain depot operations for at least two hours on more than 50 percent of the days in a year in the event of a grid outage.

“Based on the recommendations from this simulation study, we are now in a position to make informed investment decisions and will move on to concrete implementation in the next step,” explains Gerald Penner, Managing Director of Streck Transportgesellschaft.