Rewiring the power grid

Posted: February 21, 2025

Expanding renewables and electrifying industries at the scale required by the energy transition means huge investment in the power grid.

By 2030, countries around the world may need to spend more than $3 trillion on grid infrastructure to build new lines and replace old ones. In total, that would add an additional 18 million kilometers of transmission and distribution lines.^[1]

But even now, many countries’ grid expansions are already bogged down in a morass of restrictive regulation, lengthy permit procedures and public opposition to power lines. That’s why some utilities are now taking a harder look at getting more out of their existing assets.

Power grids: a critical bottleneck in the energy transition

One surprisingly simple fix to this conundrum is to install new and better wires on the high-voltage lines that already criss-cross countries.

Reconductoring specifically involves replacing traditional transmission lines with advanced conductors capable of carrying more power. Most of the grid uses a technology that’s been around since the early 1900s: wires with a steel core surrounded by strands of aluminum. The problem is those lines start to sag when they heat up from heavy use, meaning grid operators have to be careful not to overload them—or risk outages or fires.

But wires made of carbon fiber wrapped in trapezoidal pieces of aluminum, a more recent design, don’t have that issue. As a result, they can carry roughly twice as much power at a given diameter.

Some utilities have already been deploying these advanced conductors for years. Belgian utility Elia, for instance, has been replacing hundreds of miles of wires on one of its key transmission corridors since 2021. The company says the upgrade promises to raise load transfer capacity by up to 40%.

Jean-Francois Goffinet, a senior expert at Elia’s engineering arm, makes a simple case for the upgrade: “Improvement in the transmission system infrastructure is the most important requirement for enabling the energy transition.” 

On top of the capacity bump, Goffinet says the wires’ custom monitoring solution allows Elia to carry out inspections within minutes by simply attaching a transmitter and receiver to either end of the conductor. Afterwards, the company can access all the collected data from a cloud-based project database.

The advanced wires used by the utility consist of a composite carbon and glass fiber core; its manufacturer says it has already been used across more than 1,250 projects in over 60 countries.

Reconductoring the U.S. transmission grid

In fact, more than 90,000 miles of advanced conductors have been installed worldwide as of 2023. That includes several successful projects in the U.S.

In 2005, Minnesota utility Xcel Energy turned to reconductoring when facing a typical problem: it needed to expand capacity on a critical line in the Twin Cities that crossed an interstate and two major highways, residential and industrial zones, as well as several protected nature areas.  

Building new transmission towers would have meant large-scale construction and getting permits from multiple agencies—in other words, a lengthy and costly process with considerable risk. Instead, the company decided to restring the lines, which took eight weeks of light construction and only a 30-day notification to a single regulator.

On a larger scale, AEP replaced 240 miles of wires on an existing line with advanced conductors in Texas’ Lower Rio Grande Valley in 2012. It took less than three years and increased the lines’ carrying capacity by 40%.^[2] By contrast, it can take well over a decade to build new transmission infrastructure; because of the complexities involved, the rate of new installations of high-voltage lines in the U.S. has been dropping for years.

Nevertheless, many U.S. utilities have been slow to embrace reconductoring, partly because they’re relatively unfamiliar with the technology. But regulatory and bureaucratic hurdles are also to blame, according to a report released last year by consultancy GridLab and Energy Innovation, a policy thinktank.^[3]

They found that the fragmented U.S. power system—involving three separate grids, thousands of utilities and a patchwork of planners and regulators—tends to hold back innovation. On top of that, the structure of utility compensation rewards companies for building new lines over upgrading existing infrastructure.

Wider adoption of advanced conductors could be a huge boon to the U.S. green energy transition. The so-called interconnection queue—projects waiting for approval to hook up to the grid—has ballooned in recent years, reaching more than 1,570 gigawatts of generation and 1,030 gigawatts of storage in 2023 (most of it zero-carbon).^[4]

In many cases, it offers a much better option than building more lines. A companion study by GridLab and researchers from the University of California, Berkeley, found that upgrading existing lines could nearly double capacity at less than half the cost of building new ones in most places. By 2035, it could provide more than 80% of the new transmission needed across the country to achieve 90% clean electricity.^[5]

“You’re not acquiring a new right of way; you’re not building new towers,” said Amol Phadke, a scientist at the University of California at Berkeley and one of the authors of the study. “So it can be done much faster.” 

Smart sensors for grid optimization

To be sure, there are other ways to better utilize existing lines.

Another technology widely adopted in Europe and starting to find use in the U.S. are spherical sensors that attach to existing power lines to measure their temperature in real time. As with advanced conductors, this allows utilities to safely send more power through the line.

Made by Heimdall Power, a Norwegian hardware and software company, these “magic balls” can be installed by a drone and draw power directly from the wire they wrap around. Four of the sensors can raise capacity on a single line by up to 42.8%, according to a pilot study carried out by Minnesota-based Great River Energy.

“Think about the temperature on the line as being the speed limit,” Jørgen Festervoll, Heimdall’s CEO, told Fast Company last year. “Without the software and sensor, like the ones Heimdall Power provides, you’re driving without a speedometer.” 

Some utilities have similarly used temporary sensors to gain a better understanding of how much they can raise capacity. Energinet installed dynamic line rating sensors on some of its transmission lines in Denmark in recent years, measuring conductor temperature, sag, wind measurements and real-time ampacity to adjust its capacity models. Once the readings are taken, the sensors can be re-installed on the next line.

Another grid-enhancing technology is topology optimization, which works like a navigation app, assessing power flows on each section of the grid and suggesting better configurations to reroute around bottlenecks.

Although analysts agree that new transmission lines will ultimately be needed, it seems clear utilities can still go a long way by simply using what they have.

^{[1] https://www.rystadenergy.com/news/power-grids-investments-energy-transition-permitting-policies
[2] https://www.quantaenergized.com/wp-content/uploads/2015/05/EEI-Energy-Biz_pages.pdf
[3] https://www.2035report.com/wp-content/uploads/2024/05/5.3-Reconductoring-policy-report.pdf
[4] https://emp.lbl.gov/publications/queued-2024-edition-characteristics
[5] https://www.2035report.com/wp-content/uploads/2024/04/GridLab_2035-Reconductoring-Technical-Report.pdf}