Holistic design & optimization of renewable energy systems - an african-european case study

The global energy transition requires a large-scale shift to renewable energy carriers worldwide. Since renewable resources are distributed unevenly across the world, future renewable energy systems will inevitably rely on energy trade between regions with abundant renewable potential and those with limited resources but high demand. A prominent example frequently discussed in the literature is the African–European energy systems, where Africa’s vast solar and wind resources could both help bridge domestic energy gaps and support Europe’s decarbonization and diversification goals, thereby contributing to the global energy transition. While the global energy transition offers significant opportunities for both energy suppliers and importers, it also introduces new challenges for the design of future energy systems. Addressing these challenges requires a holistic framework to ensure that the energy transition is not only economically affordable but also equitable, sustainable, and secure. These objectives form the four pillars of the energy transition: affordability, equity, environmental sustainability, and security. Although existing frameworks in the literature emphasize the importance of balancing different pillars of the energy transition conceptually, most quantitative energy system optimization studies—particularly in the African-European context—continue to focus primarily on affordability for the design of future renewable energy systems. Yet identifying pathways for a successful energy transition requires integrated modeling approaches that explicitly analyze the trade-offs across multiple pillars. Against this background, this dissertation develops and applies a framework for the holistic design and optimization of renewable energy systems that balances affordability with the broader pillars of the energy transition. Focusing on the case study of African-European renewable energy systems, a core optimization model is developed that represents energy production in Africa, including diverse renewable resources, production and transportation pathways, as well as the export of renewable energy carriers to Europe. The framework of this dissertation comprises three research papers. While affordability is consistently modeled through an economic objective function minimizing total system costs, each paper extends the core model to incorporate additional pillars of the energy transition. The first paper addresses equity by integrating Gini-based formulations of economic value-added distribution across Africa. This paper examines the trade-offs between affordability and equity, demonstrating that more equitable energy systems can be achieved at modest additional costs. The second paper evaluates environmental sustainability by introducing distinct life cycle assessment (LCA)-based objective functions that represent different impact categories. The results show how the strategic selection of production and transportation technologies, as well as energy suppliers, can help manage the trade-offs between costs, equity, and environmental burdens. Finally, the third paper focuses on energy security by introducing a composite risk measure that combines country-specific and network-specific risks of supply disruption in African-European energy systems. The results demonstrate that cost-minimal systems often concentrate energy production in North Africa, in line with current energy planning approaches. In contrast, more diversified energy system configurations mitigate disruption risk at a higher cost. Finally, the findings of all research papers illustrate that no single solution can simultaneously optimize multiple pillars of the energy transition. However, balanced improvements across pillars can be achieved through the identification of compromise solutions. Taken together, the papers in this dissertation underscore the need to adopt a multi-pillar perspective in the design of African–European renewable energy systems. This dissertation offers several key contributions. Methodologically, it contributes by extending energy system models to integrate multiple pillars of the energy transition beyond affordability. It introduces novel formulations of Gini-based distributional equity, LCA-based environmental objectives, and a composite risk measure within multi-objective optimization models, thereby providing the foundation for holistic renewable system design. Practically, the dissertation provides strategic insights for both African and European decision makers, highlighting the need to move beyond current export-oriented system designs centered solely on affordability and to incorporate broader pillars of the transition into planning. It further emphasizes the role of Africa’s renewable potential in supporting domestic energy access and regional development, while also contributing to Europe’s renewable energy transition. The dissertation also acknowledges several limitations, such as the exclusion of uncertainties, temporal variability, and intra-country heterogeneity. Future research should address these aspects by incorporating uncertainty in energy supply and demand, integrating temporal dynamics, enhancing the spatial resolution of the analysis, and extending the geographical scope to include additional energy suppliers beyond Africa. Overall, this dissertation links optimization-based system design with holistic energy assessment to demonstrate how future African–European renewable energy systems can be designed to be affordable, equitable, environmentally sustainable, and secure against risks. By applying methodological contributions in a real-world context, this dissertation positions the African-European energy partnership as both feasible and policy-relevant, offering guidance for decision makers seeking to advance sustainable intercontinental energy cooperation.