Spatial scaling in renewable energy networks

Defossiliation of the energy system is crucial in the face of the impending risks of climate change. Electricity generation by burning fossil fuels is being displaced by renewable energy sources like hydro, wind and solar, driven by support schemes and falling costs from technological advances as well as manufacturing scale effects. The unavoidable shift from flexibly dispatchable generation to weather-dependent spatio-temporally varying generators transforms the generation and distribution of electricity into highly interdependent complex systems in multiple dimensions and disciplines: In time, different scales, stretching from intra-day, diurnal, synoptic to seasonal oscillations of the weather interact with years and decades of planning and construction of capacity. In space, long-range correlations and local variations of weather systems as well as local bottlenecks in transmission networks affect solutions. The investment decisions about technological mix and spatial distribution of capacity follow economic principles, within restrictions which adapt in social feedback loops to public opinion and lobbyist influences. In this work, a family of self-consistent models is developed which map physical steady-state operation, capacity investments and exogeneous restrictions of a European electricity system, in higher simultaneous spatial and temporal detail as well as scope than has previously been computationally tractable. Increasing the spatial detail of the renewable resources and co-optimizing the expansion of only a few transmission lines, reveals solutions to serve the European electricity demand at about today’s electricity cost with only 5% of its carbon-dioxide emissions; and importantly their electricity mix differs from the findings at low spatial resolution. As important intermediate steps, • new algorithms for the convex optimization of electricity system infrastructure are derived from graph-theoretic decompositions of network flows. Only these enable the investigation of model detail beyond previous computational limitations. • a comprehensive European electricity network model down to individual substations at the transmission voltage levels is built by combining and completing data from freely available sources. • a network reduction technique is developed to approximate the detailed model at a sequence of spatial resolutions to investigate the role of spatial scale, and identify a level of spatial resolution which captures all relevant detail, but is still computationally tractable. • a method to trace the flow of power through the network, which is related to a vector diffusion process on a directed flow graph embedded in a network, is used to analyse the resulting technology mix and its interactions with the power network The open-source nature of the model and restriction to freely available data encourages an accessible and transparent discussion about the future European electricity system, primarily based on renewable wind and solar resources