Evaluating rooftop PV’s impact on power supply-demand discrepancies in grid decarbonization

To achieve carbon neutrality, the power grid system is shifting toward electricity generation from renewables. In this study, we first develop a transformer-based neural network to analyze high-resolution satellite imagery and estimate the adoption rate of rooftop photovoltaic (PV) systems in Kyushu, the third-largest island in Japan. Furthermore, we examine the projected mismatch between PV generation and demand patterns in Kyushu under different PV penetrations. Finally, we evaluate the potential solutions by different energy storage strategies. Results show that the PVrooftops account for 9.77% of all rooftops, with a total area of 149.62 square kilometers in the Kyushu region. If the adoption rate surpasses 30%, a significant increase in solar curtailment occurs. The effect is more pronounced when the PV adoption rate reaches 50%, with 20.9 TWh of electricity generated by PV panels being curtailed annually, representing 43.4% of the total PV generation. Specifically, the most severe curtailment occurs during transition seasons, with 57.7% and 55.5% of PV generation curtailed in April and May, respectively. To address the surplus PV generation during midday, we calculate an energy storage requirement of 173 GWh, with an associated cost of approximately 39.1 billion USD if battery storage systems were implemented. Nonetheless, a combination of other renewable resources, advancements in cost-effective utility-scale energy storage technologies, and the promotion of grid-interactive flexible electrical loads can help mitigate the extensive investments in energy storage. The findings of this study can help the government and the grid to evaluate and plan for the widespread use of rooftop PV systems.