The United States has vast resources of renewable energy: wind energy on the Great Plains and in the Midwest, solar energy in the Southwest, geothermal energy in the Rocky Mountains and Great Basin, and hydropower in the Northwest and Southeast. Unfortunately, the variability and dispersed nature of renewable energy resources has made it difficult to optimally utilize them, given that the existing electrical grid was not originally set up to transmit electricity over long distances from renewable energy supply centers to major load centers. As a result, renewable energy resources remain significantly underutilized in the U.S., even as the cost of electricity generated from wind and solar sources has declined sharply in recent years. However, recent research indicates that both geographic dispersity and intermittency can become optimized with a comprehensive transmission infrastructure plan that connects the supply of renewable energy to load centers.
The North American Supergrid (NAS or Supergrid) is a proposed 52-node, 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, making clean renewable energy competitive with fossil fuel-generated energy in open markets, creating hundreds of thousands of jobs for several decades, increasing U.S. domestic energy generation, and securing the nation’s electrical transmission infrastructure against modern threats.
The NAS concept is based on research summarized in the MacDonald et al. publication released last year 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 centers with little immediate demand) to large load centers 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 mainly dependent on forecasted technology costs. While the initial study was conducted explicitly for the lower 48 states, we intend to extend our analysis to Canada and Mexico as well.
Carbon dioxide emissions from electricity generation are a major cause of anthropogenic climate change. The deployment of wind and solar power reduces these emissions, but is subject to the variability of the weather. In the present study, we calculate the cost-optimized configuration of variable electrical power generators using weather data with high spatial (13-km) and temporal (60-min) resolution over the contiguous US. Our results show that when using future anticipated costs for wind and solar, carbon dioxide emissions from the US electricity sector can be reduced by up to 80% relative to 1990 levels, without an increase in the levelized cost of electricity. The reductions are possible with current technologies and without electrical storage. Wind and solar power increase their share of electricity production as the system grows to encompass large-scale weather patterns. This reduction in carbon emissions is achieved by moving away from a regionally divided electricity sector to a national system enabled by high-voltage direct-current transmission.
The existing electric power system is comprised of two basic network components – transmission for higher voltage, and distribution for lower-voltage power delivery. The National Electricity with Weather System (NEWS) results indicate that the creation of a third layer HVDC backbone network, or Supergrid, built from low-loss, high-capacity direct current cabling. This Supergrid would effectively create a national market in which all types of generators, from opposite corners of the country, could fairly compete. Thus, increased transmission capacity would turn the enormous size of the country into an advantage by enabling efficient production and delivery of a large amount of electric power across the country rather than relying on the existing patchwork of generating centers with local or regional scale transmission capabilities. The more optimistic cost forecasts for the year 2030 resulted in an optimal system which utilized a large proportion of wind and solar, and decreased U.S. power sector carbon emissions by 80% compared to 1990 levels.
The NAS would also help secure the U.S. electrical grid against both natural and human-caused threats. Modern conveniences and life sustaining infrastructure depend more than ever on the reliability and availability of electricity. If power were to be disrupted for an extended period of time, modern civilization simply could not function. Yet, our electrical transmission infrastructure is troublingly unprepared for modern threats and natural hazards. If a terrorist organization or rogue state, for example, obtained and detonated a nuclear weapon high above the United States, it would send a powerful electromagnetic pulse (EMP) that would overload transmission infrastructure, taking the grid down for years. A similar effect would occur in the event of a solar storm like the famous Carrington event of 1859, a completely unavoidable and unpredictable event. A lone wolf attack or extreme weather event could also carry out structural damages, which can leave municipalities or entire regions without power for days or weeks. The NAS would make significant strides in safeguarding our nation’s transmission system through its configuration and hardware.
The proposed HVDC cables contain a metallic sheath surrounding the conductor (which would be grounded with an Earth-return) and would be placed in an underground configuration whenever possible. Additionally, above ground elements will be encased in shielded structures. These elements will work together to not only prevent against malicious tampering, but also provide a crucial defense against EMP attacks and unpredictable solar storms. The network configuration of the system will provide resilient pathways to maintain the delivery of electricity, even in the case of a line fault. Even if one line were to go down, the Supergrid could reroute power through an alternative pathway and still deliver electricity to where it needs to go.
Even though the costs of building the needed transmission capacity would be roughly $500 billion, analysts have concluded that this proposal can be overwhelmingly privately financed and paid for through consumer bills and that consumer electricity prices would be about the same as the national average. While the costs of electricity infrastructure would increase and be passed to the consumer, the costs of electricity generation would decrease enough to make up for the costs of additional infrastructure.
Over an estimated timeframe of 30 years, roughly 650,000 to 950,000 jobs would be required to build the necessary infrastructure. These jobs would be impossible to outsource to other countries and would likely be located in rural areas since renewable energy capacity is mostly in sparsely populated areas that are typically disadvantaged economically.
Since the MacDonald et al. study, both wind and solar costs have decreased significantly faster than expected and, in high quality, locations are already lower than the other available options including nuclear, coal, or natural gas. This means that the MacDonald et al. study is even more cost advantageous than originally indicated.
Expanding energy transmission infrastructure is the most practical way to improve grid resiliency to modern threats and to reduce power sector greenhouse gas emissions. The need to protect transmission infrastructure against EMP and to reduce greenhouse gas emissions are both key national interests. The NAS would build electricity transmission in a way that addresses both of these issues without overwhelming the national budget. It is a market solution to power sector carbon emissions that enhances national security, provides jobs, and enhances domestic energy use. Initial contacts conducted by our team to various Congressional offices and think tanks suggests that the NAS has high potential for bipartisan backing.
Our studies, as detailed in the upcoming chapters, indicate that the installation and operation of an undergrounded HVDC linked into the existing grid would: (a) 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; (b) improve national security by strengthening cybersecurity, structural integrity, and electromagnetic pulse (EMP) deterrents; 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 document describe the environmental and electrical engineering challenges associated with the implementation of an underground HVDC overlay system and our main conclusions.