Abstract
The fragmented nature of the contiguous United States’ electric grid, with limited inter-regional transmission capacity between the Eastern, Western and Texas interconnections, presents a significant challenge to integrating large-scale renewable energy and achieving decarbonization goals. This dissertation proposes and evaluates a national High Voltage Direct Current (HVDC) Macrogrid, an ultra high-capacity transmission overlay, to address this challenge. The research presented utilizes a Co-optimized Expansion Planning (CEP) model to assess the technical and economic feasibility of various Macrogrid topologies. These topologies connect major load centers with high-quality renewable resource zones, with particular emphasis on integrating up to 200 GW of Atlantic coast offshore wind (OSW). Results demonstrate that the Macrogrid facilitates over 90% carbon-free energy penetration by 2050 without explicit carbon constraints, driven by the economic dispatch of diverse renewable resources and increased interregional transmission capacity. The Macrogrid significantly reduces the need for additional expensive onshore AC transmission upgrades in the Eastern Interconnection with increasing levels of OSW. The study also explores the policy, regulatory and practical implementation challenges associated with building such a large-scale infrastructure project, including funding, permitting, right-of-way acquisition and stakeholder engagement. The Macrogrid’s inherent benefits – enhanced deliverability, reliability and resilience, reduced congestion, access to lower-cost generation and enhanced national energy security – provide a compelling economic and operational justification, even in the absence of strong renewable energy mandates.