An exhaustively researched report examining the use of the U.S. interstate highway system as a ready-made corridor for expansion of the nation’s high-voltage transmission system, as well as a broadband internet access, concludes it can be done relatively quickly and at a lower cost than siting new transmission corridors.

Prepared for the Minnesota Department of Transportation by Seattle-based NGI Consulting and The Ray, an Atlanta nonprofit, the 81-page analysis offers national conclusions. It argues that “NextGen Highways” ought to include buried HVDC transmission lines co-located with fiber-optic cables.

The recommendation to open interstate rights of way (ROWs) is in line with policy changes issued in 2021 by the U.S. Department of Transportation giving state DOTs the option to allow utilities to site energy infrastructure, including pipelines and even renewable energy projects, within interstate ROWs.

The release of the massive study also comes a year after the Biden administration announced the availability of $5 billion in loan guarantees to encourage the expansion of the grid, noting that decarbonizing transportation will require the grid to double or even triple in size.

The transportation sector accounted for 29% of carbon emission in 2019, more than power generation did, according to EPA, making transportation decarbonization a priority issue.

The report argues that state departments of transportation should:

• • • “site and build fiber in a way that allows for buried HVDC transmission to be co-located at a later date;
    • “develop and invest in their relationship with utilities, public utilities commissions and other state agencies with transmission siting jurisdiction; [and]
    • “determine the amount of operational funding required to support the co-location of electric and communications infrastructure in their ROW.”

The report’s recommendation of underground HVDC power lines is no accident. HVDC power lines can move power long distances without line losses and without inducing currents in nearby conducting materials. And unlike AC lines, HVDC lines can connect systems operating at different AC frequencies. Yet few HVDC lines have been built in the U.S., according to the report.

“Unlike the U.S. Interstate Highway System, the U.S. power grid is composed of many discrete regions. Modeling study after modeling study has shown that connecting these regions is critical to cost-effective grid decarbonization,” the report states. “It is also critical for grid reliability and resiliency.

“Despite the importance of connecting the electric grid regions using interregional transmission lines, project after project has failed in the U.S. Since 2014, the U.S. has not built a single gigawatt of interregional transmission capacity. Meanwhile, China, Europe, South America and India have collectively built nearly 350 GW of interregional transmission capacity.

“Most recently, the construction of the New England Clean Energy Connect transmission line was stopped indefinitely by a public referendum in November 2021. This was an incredible result given that the New England Clean Energy Connect had already received the required regulatory approvals and was in the process of being built.”

One of the most important conclusions of the study is that decarbonizing the grid itself — moving clean power to where it is needed, particularly for charging electric vehicles — will be less costly using HVDC transmission lines.

“As seen in Europe and now in New York state, buried HVDC transmission is being used to build the interregional transmission required to cost-effectively and reliably decarbonize the electric grid,” the report said.

And in one of the dozens of supplemental documents attached to the report, the analysts explain in more detail that “many of the richest wind and solar resources are located far from the urban load centers where most of the country’s energy is consumed. The nation’s transmission infrastructure must at least double to accommodate the exponential growth of wind and solar that will accompany decarbonization.

“Without the addition of significant multiregional transmission, system planners will need to overbuild local renewable resources in order to manage weather patterns and meet demand, resulting in extreme curtailment of local wind and solar resources, even if high levels of storage capacity are available, dramatically increasing costs.”

Additionally, the expected development of solid-state converters to replace conventional transformers will allow for the development of medium- and high-voltage charging stations, the report postulates, further arguing that the buildout of HVDC converter stations will create “economic development zones … logical locations to site fleet and over-the-road EV charging infrastructure and data centers.”

While the study makes national recommendations, its analysis initially focuses on state DOTs because they control highway corridors and ROWs.

Most states, including Minnesota, have not permitted overhead transmission lines to run along highways because of the possibility of vehicular accidents. Many states limit transmission line intrusions to crossing over highways, the report found.

Wisconsin is one of the few states that does allow transmission lines to parallel highways inside the ROW and, according to the report, has permitted the construction of an overhead line to run inside an ROW after state lawmakers approved the practice in 2003.

That legislation requires utilities and grid companies building new transmission to first consider existing utility corridors and then highway and railroad corridors and even recreational trails before seeking to establish new utility corridors. The Wisconsin Department of Transportation (WisDOT) then amended its policies to reflect the new law, as did the state Public Service Commission (PSCW).

“In 2009, as a result of Act 89, WisDOT’s updated utility accommodation policy, and the development of new transmission infrastructure, WisDOT and PSCW entered into a cooperative agreement ‘to ensure that whenever practical, WisDOT and PSCW shall utilize existing transportation or transmission corridors instead of creating new corridors for electric transmission facilities.’ …

“The legislation, policy and agreements described [here] have fostered a collaborative and trusting relationship between Wisconsin utilities and WisDOT and have resulted in the efficient, cost-effective and successful siting of over 800 miles of transmission infrastructure in and along interstate and highway ROW in Wisconsin,” the report notes, adding that “Wisconsin has the playbook for siting transmission in DOT ROW.”

The Great Plains Institute, based in Minneapolis; Satterfield Consulting in Madison, Wis.; 5 Lakes Energy of Lansing, Mich.; and consultant Tracy Warren in D.C. assisted with the research and release of the report.

In a statement, Morgan Putnam, founder of NGI Consulting, announced the release of the report and what the team expects to do next.

“Given the positive findings from this study, we will be launching a NextGen Highways Coalition later this year. The coalition will facilitate conversations between state DOTs, transmission developers and governors to support the co-location of buried fiber and transmission in highway and interstate ROW.”