An integrated framework for systematically identifying optimal high-voltage transmission routes in renewable energy systems

Global commitments to net-zero emissions, and increasing electricity demand, require an unprecedented scale of new transmission infrastructure. Yet, most existing planning approaches rely on simplified models or incremental upgrades, overlooking the complex interplay of renewable resource availability, grid balancing needs, and the challenges of routing lines across vast terrains. In this paper, we introduce an integrated transmission expansion planning method that seamlessly unifies strategic system-wide balancing with high-resolution Geographic Information System routing analysis. Using the Australian electricity system as a case study, we find that new high-voltage alternating-current lines can unlock large amounts of geographically optimal solar and wind resources while enhancing reliability, and that targeted high-voltage direct-current lines reduce system costs by up to 18% by bridging distant resource–demand mismatches during winter lulls. This comprehensive framework identifies major new corridors critical for rapid decarbonization and can be readily adapted to other regions facing similar challenges.