Towards 100% renewable islands in 2040 via generation expansion planning: The case of São Vicente, Cape Verde

In the energy transition context, islands are identified as particularly challenging regions due to their isolation, and energy dependence; while their excellent renewable resource and rapid growth makes them exceptionally interesting test cases. With the growing number of countries targeting 100% renewable penetration during the next decades, it is important to assess not only how to do so, but also whether we should. This paper focuses on the perspective of a generally overlooked set of regions; island developing nations. Their common challenges and energy policies are exemplified with a comprehensive generation and storage expansion planning (GSEP) for the island of São Vicente, Cape Verde. Formulated as an optimisation problem with hourly resolution, the GSEP minimises investment, maintenance, operation and emissions costs over a 20 year horizon from 2021. The extreme seasonal dependence of wind and solar resources is captured along with the operational dynamics of the generation and storage. Three scenarios are defined, one Business As Usual (BAU) keeping the current operational paradigm, another, Green, aligned with the local government goals, targeting 50 and 100% renewable shares in 2030 and 2040, and, lastly, one finding the Optimal. To reduce uncertainty influence, we consider three load growth levels for each scenario, defined based on expectations from national and international sources, corresponding to 1, 3 and 5%. The robust analysis obtained by combining scenarios and load levels provides a thorough view of Cape Verde's energy system to consider in future energy policy design. Green is the most expensive, BAU represents a 7% cost reduction, while Optimal a 30%, in addition to providing 90% renewable penetration, significant emissions reduction, and enough flexibility to modify the planning course if needed.