Executive Summary

The North American Supergrid (NAS or Supergrid) would make electricity infrastructure more resilient and greatly reduce power sector carbon emissions.

The North American Supergrid is a proposed nodal high voltage direct current (HVDC), largely underground transmission network that would extend across the lower 48 states, thus creating a national electricity market. The Supergrid would create a resilient backbone to the existing system and make clean renewable energy competitive with fossil fuel-generated energy in open markets. Adding the Supergrid atop the existing regional alternating current distribution system would provide the flexibility and reliability that would enable expanded use of electricity across the economy, without altering how electricity is currently used in homes or businesses. This would also afford electromagnetic pulse (EMP) and geomagnetic disturbance (GMD) protection not garnered from the current system, as well as much-needed fortification against increasingly common natural disasters.

The NAS concept is based on research summarized in the MacDonald et al. publication released in 2016 in Nature Climate Change. Through extensive temporal and spatial modelling of the variable weather patterns present in the continental United States, the MacDonald et al. publication surmised that solar and wind power penetration into the electric grid could be achieved through the construction of an integrated national electricity market, without raising electricity costs or sacrificing the reliability of power delivery to consumers. MacDonald et al. idealized that a single national market (built from low-loss, high-capacity direct current cabling) would allow the instantaneous transmission of excess power (often generated in areas with little immediate demand) to large load areas where it can be utilized, better integrating both large scale utilities as well as distributed systems in a non-preferential market based solely on cost. The optimization technique is unbiased towards any one energy source and is mainly dependent on forecasted technology costs. The authors estimated that the evolution in the electricity market that such a grid would prompt could result in nearly an 80% reduction in power-sector carbon emissions, as low-cost wind and solar generated power would displace more expensive fossil fuel based electricity generation in a competitive market.

Preliminary analyses by the Climate Institute confirm both feasibility and cost-effectiveness.

While MacDonald et al.’s article explored the potential benefits and implications of a North American Supergrid, quite a number of other practical aspects were left for additional investigation. The Climate Institute, a Washington-based non-governmental organization that has a three-decade record of bringing innovative approaches to wider attention, has conducted a number of feasibility analyses to assess the practical challenges associated with the creation of a mostly underground HVDC transmission overlay system, considering practical aspects such as how best to meet the need for rights of way, compatibility of soils and HVDC cabling, natural-disaster and national-security co-benefits from undergrounding, and the projected costs for a few representative network lines. As explained briefly below and more fully in the associated chapters, our studies indicate that the NAS would: (a) improve national security by strengthening cybersecurity, structural integrity, and EMP deterrents; (b) be feasible at modest cost and would contribute to mitigation of climate change by allowing a much higher penetration by renewables than is projected to be possible with the present grid system; and (c) be a cost-effective addition to the electric grid, even in the absence of a price placed on carbon and assuming there is not a sustained drop in average natural gas prices persisting over the next three decades. The technical sections of this policy brief document the environmental and electrical engineering challenges associated with the implementation of an underground HVDC overlay system and our main conclusions, as summarized in the following paragraphs The installation of the North American Supergrid comes with inherent feasibility challenges, and its operation might result in environmental consequences that range from minimally adverse to highly beneficial.

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