Right here, right now? The role of spatio-temporal minimum renewable shares for energy system transformation pathways

Energy system optimization models are important tools to provide insights regarding trade-offs and interrelations in cost-efficient transformation pathways towards a climate neutral energy system. Using an optimization model of the European electricity system, we study the influence of either an emission cap or temporally resolved minimum renewable generation shares as means to power system decarbonization. Such minimum shares serve as a stylized representation of novel, more granular procurement or certification schemes for renewable power generation. We observe that decarbonization through minimum shares results in a significant increase in system costs compared to the least cost solution obtained through a direct implementation of the corresponding emission reduction as a cap. Nevertheless, these shares provide direct incentives for expanding renewable generation and storage technologies, thus acting as an additional, potentially more robust decarbonization mechanism.