Synergies of electrical and sectoral integration: Analysing geographical multi-node scenarios with sector coupling variations for a transition towards a fully renewables-based energy system

The cost-optimal pathway for moving from the current fossil-fuel based energy system to 100% renewables is still an open question. This work presents the first study that analyses the transition towards a 100% renewable energy system under different spatial resolutions (1-node, 6-nodes electrically isolated and interconnected) and various coupling configurations for the power, heat, transport and desalination sectors. With the LUT Energy System Transition Model for the case of Chile, 12 scenarios were investigated in an hourly resolution and considering more than one hundred energy-related technologies. The results show that: (1) 1-node systems deliver too simplistic results for key metrics; (2) power sector simulations can lead to a strongly distorted resources allocation compared to scenarios that include other sectors; (3) a multi-node model better reflects transmission bottlenecks and local resources, and; (4) the lowest-cost solution is reached when power transmission lines are considered. Thus, it is concluded that a cost-optimal, balanced, and realistic solution to reach a fully defossilised energy system is transitioning towards a multi-node, interconnected, and fully sector-coupled energy system. This can be called, in short, the 'Power-to-X economy', which in the case of Chile would more accurately be a 'Solar-to-X economy', given the high solar share found in the simulations.