If the United States wants to have 100% clean energy by 2035, the nation’s transmission capacity must be able to handle it, and reconductoring existing lines with advanced conductors can be part of the solution.

According to a new report from the Goldman School of Public Policy at the University of California Berkeley and GridLab, “The 2035 4.0 Report,” reconductoring would quadruple capacity within that time compared to the current practice of building new lines, given restrictions on greenfield transmission build-out.

“When advanced conductors are used, reconductoring in existing rights-of-way can substantially increase transmission capacity in the current grid, allowing clean energy to be more fully tapped during the years-longer period it takes to develop the new lines for long-term system needs,” according to the report.

Reconductoring is particularly feasible for the majority of transmission lines in the United States, which are 50 miles or less, according to the report. Advanced conductors, combined with “marginal” substation additions as needed such as reactive power compensation, transformer replacements and relay and breaker upgrades, could up to double the power transfer capacity within an existing right-of-way.

For the 2% of lines that are too long to benefit from reconductoring and compensation, sectionalization¾the addition of new substations with active and reactive power generation sources along the line¾could help improve voltage and angular stability.

Reconductoring could also be done for less than half the price of building new lines, across all voltage levels for similar capacity increases. However, by the mid-2030s, opportunities for reconductoring with present-day advanced conductors are expected to be exhausted, and as such, greenfield transmission development will need to play a larger role in increasing total capacity.

“Given that new transmission lines can often take 10 to 15 years to complete due to hurdles such as permitting and cost allocation, this indicates that the optimal transmission expansion strategy on the path to full grid decarbonization should leverage large-scale reconductoring with advanced conductors in the near-term, while new lines for long-term needs are concurrently planned, permitted and constructed,” the authors wrote.

In a companion report, “Supporting Advanced Conductor Deployment: Barriers and Policy Solutions,” Energy Innovation and GridLab provided recommendations on how policymakers at the federal, state, grid operator and utility levels can address some of the current barriers to reconductoring, including industry unfamiliarity with the technology, lack of comprehensive regional planning and unclear permitting processes.

Policymakers should align utility incentives with the selection of advanced conductors, improve transmission planning, examine efficiency standards for transmission lines, expand federal and state funding support, and develop workforce education and training on advanced conductors.

“By addressing these areas comprehensively, state and federal policymakers can partner with utilities and technology providers to seize the opportunity provided by reconductoring with advanced conductors,” according to the report. “2023 was the hottest year on record, and the U.S. needs solutions to transform to a clean electricity system faster and more affordably. Advanced conductors, alongside other advanced transmission technologies, are a vital and untapped part of that solution.”