Urban decarbonization is one of the pillars for strategies to achieve carbon neutrality around the world. However, the current speed of urban decarbonization is insufficient to keep pace with efforts to achieve this goal. Rooftop photovoltaics (PVs) integrated with electric vehicles (EVs) as battery is a promising technology scalable to supply CO₂-free, affordable, and dispatchable electricity in urban environments (“SolarEV City Concept”).

Here, we evaluated Paris, France for the decarbonization potentials of rooftop “PV + EV” in comparison to the surrounding suburban area Ile-de-France and the reference city Kyoto, Japan. We assessed various scenarios by calculating energy sufficiency, self-consumption, self-sufficiency, cost savings, and CO₂ emission reduction of the PV + EV system or PV only system.

We found that above a certain roof coverage 50–60% of the total roof area for Paris or 20–30% for Ile-de-France, PV electricity production regularly exceeds the demand.

Above that roof coverage, feed-in-tariffs (FIT) or storage are needed to further realize the potential of the rooftop PV system. The combination of PVs with EVs is more effective in Ile-de-France than in Paris because large surplus electricity from rooftop PV in suburban area requires large storage. With already low-carbon electricity of France by nuclear power, the maximum potential CO₂ abatement through the implementation of SolarEV City Concept in Paris (0.020 kg_CO2/kWh reduction from 0.063 kg_CO2/kWh) is limited in comparison to that in Kyoto (0.270 kg_CO2/kWh reduction from 0.352 kg_CO2/kWh). However, with declining costs of PVs and EVs in the coming decades, low-cost dispatchable electricity by the PV + EV system throughout Paris and Ile-de-France may facilitate the electrification of CO₂ emitting appliances, potentially allowing rapid CO₂ emission reductions from Paris.

https://www.sciencedirect.com/science/article/abs/pii/S0306261923011261?via%3Dihub