A reliable energy system for Japan with merit order dispatch, high variable renewable share and no nuclear power

In the context of Japanese energy targets for 2030 and the long-term strategy towards zero carbon emissions by 2050, this study estimates the impact of several measures for increasing the renewable generation share while maintaining a reliable energy system. To do so, the authors attempted to reproduce the expected 2030 energy mix according to the 5th Strategic Energy Plan, and then formulated two different alternative scenarios: a European-style merit order dispatch in Scenario 1, and the replacement of nuclear generation with renewables in Scenario 2. The simulations were carried out using the Energy System simulation model (EnSym), which was newly developed by the authors. EnSym simulates the hourly generation of all major resources, including variable renewables, using meteorological data. Spatially, EnSym also simulates the electricity transmission grid of Japan, allowing to understand how changes in grid capacity, dispatch framework and energy policy can impact the overall system. The results show that merely switching to a merit order dispatch could increase the use of renewable generation by 1.5% (to 22.6%). Further, replacing nuclear power resulted in a renewable share of 58.2%, which would include 300 GW of solar PV, 45 GW wind, 36 GW biomass and 23 GW geothermal capacity (while leaving all other generating capacity constant at 2021 levels). Based on these results, the authors also provide recommendations for changes to the next, 6th, Strategic Energy Plan.