The energy transition sometimes encounters challenges on balancing three competing goals, i.e., costs, emissions, and resilience (the so-called Energy Trilemma). Such trade-offs are particularly conspicuous for coastal cities, which usually have more ambitious emission reduction targets and are more likely under threat of extreme weather events, i.e., typhoon. This study develops a bottom-up optimisation framework to assess the sustainable transition of the electricity sector for a typical coastal city of Xiamen, China. The framework optimises the energy portfolio for 20-year-horizon with hourly temporal resolution considering demand-side flexibility of energy storage. By setting multiple optimisation objectives, three representative transition scenarios are evaluated: the least-cost scenario, the least-emissions scenario, and the diversity-optimal scenario. The trade-offs between competing objectives are presented as Pareto frontiers and posterior decision-making methods are further embedded to identify one superior solution and facilitate the policymaking. The optimisation results indicate that with the limited potential of solar and wind and other renewable resources, the electricity transition of Xiamen would rely on the import power to a large extent. An extra 3.9% cost than the least-cost pathway can achieve a pathway with maximum energy diversity to enhance the resilience, whereas 27% more cost than the least-cost pathway is needed to achieve the least-emissions pathway. In addition, the first 10-year modelling results are further verified by comparison with the real-world data to generate valuable insights into sustainable transition pathways of coastal cities.
Keywords energy planning, multi-objective optimisation, Energy Trilemma, energy resilience, energy diversity, coastal cities