*4.4. Impact of Weather on Energy Transition Plans*

The stochastic nature of demand and renewable energy sources was the primary motivation for developing the weather-driven approach since energy transition recommendations should consider scenarios that will test the limits of the planned energy mix. The variations are significant at 400 MW to 600 MW coal capacity, as seen from the results. In Japan's case, this translates to 1–3 coal power plants, but for smaller nations with smaller plants, this could be composed of more than five plants that should be on standby in the event of an extreme weather condition. Coordinating smaller plants will require more dialogue and agreements between the government and plant operators. Consequently, the

government could also run standby plants to ensure the reliability of the system. It has also been shown that weather influences the potential for CO2 reduction and the system's overall annual generation cost. Beyond coal decommissioning, weather will remain a necessary variable in energy planning since it influences the demand, which is the primary source of stochasticity in the analysis. As more VREs are added to the green energy transition, weather becomes a crucial variable for both wind and solar. Rainfall data could also influence hydropower generation, which was not explored in this study. It could also influence the viability of PHES since this requires sufficient water reservoirs affected by rain and water evaporation. Little is known about wave energy's potential, but the weather will also influence it since it depends on nature.
