Thrive in sunshine, brace for thunder: Least-cost robust power system investments under political shocks

Energy system planning literature often focuses on either normal operating conditions or on shock scenarios. Systems designed only for normal years struggle during crises like fuel shortages or trade restrictions, leading to lost load or excessively high prices, while systems optimized entirely for shocks can result in overinvestment in generation technologies with high capital costs. In this paper, we address this limitation by incorporating both normal years and shocks in one single optimization model, using a partial equilibrium electricity market model. Using Switzerland as a case study, we demonstrate how varying the severity and frequency of shocks affects the optimal technology mix. In the case of Switzerland, robust planning of the generation mix becomes crucial only at trade capacity reductions of more than 70%. When gas import is unavailable during the shock period, liquid fuel becomes optimal in severe trade capacity reduction scenarios happening between once in 100 years to once in 10 years. As the frequency of these shocks increases, higher CAPEX technologies, such as renewables, become more favourable, with nuclear emerging as a viable option only if severe trade shocks happen every other year. Our findings underscore the importance of balancing cost-efficiency with system resilience to ensure robust energy system planning. • Introduces a robust energy system planning model considering operation in both normal and shock years. • Highlights the importance of shock severity and occurrence frequency on system planning. • Demonstrates optimal technology mix changes based on shock severity and frequency. • Highlights the role of gas and liquid fuel power plants in managing severe trade capacity reductions.