Previous works in the literature have proven that, at best, bout 40% of the energy generated by a solar PV system is used by the traction grid it is connected to. This is because of the severe generation and load mismatch caused by the transport timetables which mean that there is no load for the PV system for the long periods of time between vehicles arriving to a stop. This means that there is no continuous “base load” for the PV generation. Consequently, the effective energy cost of a solar system installed at a traction grid is more than 2.5 times higher than that of the installed capacity since only 40% of its energy is used, and the rest is curtailed. Another possibility not to lose this energy is to use energy storage systems, yet those are expensive, lossy, and require large installation spaces.

On the other hand, residential households face the opposite problem. Solar PV systems connected to households have a base load, but lack the peaks of energy demand that can consume the peak solar generation at noon and around it.

A study by Diab et.al looks at two case studies of trolleybus traction substations  in the city of Arnhem, The Netherlands: a high-traffic substation and a low-traffic substation.

The paper looks at a multi-stakeholder PV system shared between traction substations and nearby residential dwellings connected as shown in the figure above, by using the AC distribution grid to which both systems are connected. In the shared system, the residential demand provides a base load to the PV system, while the traction demand provides peak demand periods. Together, this would offer a considerably better matching of generation and load, and thus make the whole system more techno-economically feasible by reducing the need for storage, AC grid exchange, and curtailment. Moreover, rooftop PV systems would offer the traction substations the otherwise-scarce urban space to install the PV panels.

The innovative multi-stakeholder PV system has proved to deliver more energy directly to its loads when compared to either single-stakeholder system. What is worth emphasizing is that this was observed for any combination of traffic intensity and any number of households. This innovative solution is therefore definitely worth implementing on the wide scale and becoming a standardized system.