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 gleaned 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. While the initial study was conducted explicitly for the lower 48 states, we intend to extend our analysis to Canada and Mexico as well.
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.
- Approximately two-thirds of the HVDC cable links in the proposed system can feasibly be placed underground along existing rights of way, greatly reducing the time and effort needed to move forward with permitting and construction. Where a link cannot be aligned to be buried and blasting through bedrock is required, construction of traditional aboveground transmission lines may be required. Offshore submarine lines may be utilized to circumvent the usage of this alternative configuration solution if the surrounding environment allows.
- By enabling a diversification of energy sources, the Supergrid will reduce the power sector consumption of water by ~400 billion gallons per year and reduce the power sector withdrawal of water for power generation by ~1.4 trillion gallons per year, resulting in a 65% reduction overall in total fresh-water usage across the power sector.
- The increased use of renewable sources of energy as opposed to traditional fossil fuels would reduce projected 2040 power-sector emissions of SO2 (sulfur dioxide) and particulate matter by a factor of ~7, (measured in weight of metric tons) compared to ‘business as usual’ emissions levels based on current expected 2040 generation contributions to energy production.
- The magnetic fields emitted by properly functioning HVDC cables present a minimal, but not negligible, level of risk to surrounding animal species which utilize the natural magnetic field of the Earth for orientation.
The installation and operation of the Supergrid would result in significant improvements in security and reliability.
- Undergrounding the NAS would greatly reduce the vulnerability of the present grid to physical assaults and intrusions.
- Undergrounding would reduce the vulnerability to naturally occurring GMD and manmade EMP, including particularly to an EMP attack originating from the Democratic People’s Republic of Korea (a threat currently being considered by the U.S. Department of Energy, U.S. Department of Homeland Security, and Congress).
- Undergrounding would reduce vulnerability to natural disasters, including fires, high winds, floods, and other extreme storms.
The installation and operation of the Supergrid appear to be financially viable via funding mechanisms that range from private to public.
- Possible avenues for funding the Supergrid include: private, user-based fees that require no public funding; public-private partnerships (in some states); the Department of Energy Loan Guarantee Program (if certain requirements are met); and U.S. Department of Defense allocation for additional hardening of grid security aspects.
- Direct and indirect estimates of job creation over the 30-year time frame due to construction and operation, including increased employment for generation of energy from renewables, range from ~650,000 to ~950,000 (particularly in construction, operation, and maintenance jobs associated with transmission and equivalent new renewable generation).
- Exclusive of right of way costs and complications, our estimated cost for aboveground installation is ~$580 ($/MW-mile), which is about 20% less than the ~$723 ($/MW-mile) estimated by MacDonald et al. Our estimate is that underground installation costs would be about three times as much, but with lower cost and time for right of way acquisition. Whether above or below ground, we estimate substation costs at ~$250K ($/MW), while MacDonald et al. estimated ~$188K ($/MW). Station costs would remain about the same for aboveground and underground scenarios. The total estimated cost for constructing the proposed NAS is under $500 billion.
- The economic feasibility of the NAS is partially contingent on the future price of natural gas as well as the additional incremental cost of constructing HVDC lines in an underground configuration.
Regulatory reform for the Supergrid can be accomplished by a Regional Transmission Organization (RTO)/Independent System Operator (ISO)-centered framework for effective operation of the Supergrid and measures streamlining the routing and permitting processes.
- A nationally integrated approach that grants siting authority to RTOs and ISOs would be the most preferable regulatory reform for the Supergrid, given the cost and complexity of going through state and local siting authorities.
- Using existing federal and cooperating states’ rights of way for routing cables would greatly expedite build-time, requiring cooperation from key bureaus such as the Bureau of Land Management and the Federal Highway Administration (FHWA). Notably, the FHWA is authorized to grant ROWs for what it considers to be for the public good.
- Streamlining the permitting process involves mitigating barriers to using land for renewable energy transmission. This can be done using three strategies: (1) encouraging states to consider regional and in-state benefits; (2) expanding the legal definition of “public use” to include merchant transmission lines; and (3) incorporating the western and southeastern regions of the country into RTOs or ISOs.
- Routing cables through tribal lands involves further legal complications where the federal government does not have eminent domain authority.