What transmission is required to achieve net-zero emissions in the Northwest by 2050?
Electricity transmission is the backbone of a net-zero emissions energy system, delivering clean renewable energy to a largely electrified society. While transmission expansion faces significant challenges that include cost uncertainties as well as potential siting and permitting difficulties, the NZNW Energy Pathways analysis shows that expanding transmission lowers overall decarbonization costs for the Northwest. More importantly, expanding transmission maximizes the chances of meeting net-zero emission targets.
The NZNW Energy Pathways study modeled a Core Case that assumes the four Northwest states will achieve net-zero emissions by 2050 with relatively unconstrained technology availability, as well as aggressive electrification and efficiency. In addition to the Core Case, we modeled several scenarios to understand the impacts of constrained transmission expansion and changes in transmission cost. The key takeaways from the scenarios are:
Expanding transmission across the Northwest lowers total decarbonization costs and increases options for meeting future net-zero goals.
While expanding transmission across Western states will be difficult, without it, permitting challenges shift to local areas, which will also pose issues.
Lowering Northwest electric loads shifts the region’s energy production elsewhere, and the Northwest imports energy in the form of fuels via pipeline.
Transmission planning must start now to overcome the challenges of building interstate transmission.
Intertie Expansions That Will Lower Decarbonization Costs and Expand Resources
The Core Case assumes relatively unconstrained transmission expansion aligned with available potential identified in The Nature Conservancy Power of Place-West study (TNC PoP), a study designed to guide energy planners in executing net-zero strategies that will maximize benefits for climate, nature, and people.
The additional transmission scenarios explore the impacts of constrained transmission expansion, limited renewable energy development, reconductoring options, and changes in transmission cost.
The analysis does not represent the nodal transmission system in the region but uses a zonal transmission model. Therefore, the results focus on state-to-state transmission interties, rather than specific transmission lines. Cost estimates for interconnecting new plants, expansion of in-state transmission, and expansion of distribution based on peak load requirements are represented in the model, but their specific topology is not.
The following intertie expansions are key to lowering the costs of decarbonization and expanding the resource options available to reach net-zero throughout the Western grid:
Montana-Washington: This intertie is extremely valuable and would build out to 11.2 gigawatts (GW) capacity by 2050 to enable exports of low-cost, high-capacity wind from Montana to Washington, Oregon, and Northern California load centers.
Montana-Wyoming: This intertie connects two renewable production centers to each other, rather than renewable production centers to load centers, and creates more supply diversity for the coastal markets (Oregon, Washington, and California) that get power from Montana and Wyoming wind.
Electricity is exported in both directions in increasing amounts as this intertie expands.
On net, more electricity is exported from Wyoming to Montana, contributing to electricity exports to coastal Northwest states, as well as new electrolysis and direct air capture loads in Montana in the 2040s.
Wyoming-Colorado and Wyoming-California South: Exports south drive expansion of Wyoming wind and expand markets for Northwest electricity exports.
During some hours of the year, renewables are imported from Wyoming to Montana, and in other hours they are exported. The expansion of transmission to Colorado and California allows greater exports from the Northwest during those hours because it provides access to markets that need them.
By the 2040s, transmission is important to reach net-zero emissions economically. Most new capacity is added to connect renewables, largely wind, in Montana and Wyoming to the coastal loads in Washington, Oregon, and California. Build-out happens gradually from 2030 to 2050 in the model, but transmission is more likely to be built sporadically over the 20 years, and costs will be a key determinant. The lower the cost of intertie expansion, the earlier and greater the expansion would be.
More Extensive Transmission Lowers Total Decarbonization Costs
The visualization below shows the cost impacts of the sensitivity scenarios. Costs are presented as total present value costs and shown for the entire U.S. due to the interconnected nature of the transmission system. For the total present value costs, the cost difference in each year is discounted back to 2021 dollars using a 3% annual discount rate.
Overall, it is cheaper to have a more interconnected network, even with the higher TNC PoP transmission costs used in this study. When transmission expansion is unconstrained, new transmission is built in large part to access low-cost and high-capacity factor resources that are far away and are complementary in production shape to other resources. For example, wind in Montana is a valuable output shape for the Southwest, where a significant amount of clean solar energy is produced in the middle of the day.
High-quality wind is generally not available in large quantities close to the largest load centers in the West. If transmission is constrained, access to those wind resources is limited and leads to increased reliance on local resources throughout the West, particularly solar in California and Arizona.
More extensive transmission lowers total decarbonization costs and increases options for meeting future net-zero goals. In addition to cost uncertainties, multiple factors impact the feasibility of transmission expansion, including:
Physical factors, such as line length, terrain, land use, and fire risk.
Whether the line is contained in a single planning area and/or state, or whether it crosses multiple jurisdictions.
Whether markets exist to make development of the line profitable.
Whether market structures or policies mitigate risks to transmission developers.
Transmission expansion allows access to imports from other states, and exports from renewable-rich regions allow renewables to be located where they are most feasible. Limiting transmission, on the other hand, puts greater stress on siting and permitting local resources, a major challenge to achieving net-zero emission targets by 2050.