According to a report from Wood Mackenzie, Annapolis, Md., while the shift toward renewable power generation relies on adding transmission capacity, opposition to new lines makes that an uphill battle.

The report noted that the geographical areas of greatest solar and wind resources in the United States and the greatest availability of land are generally in areas that are far from the highest population densities.

“If the U.S. is to even come close to achieving President Joe Biden’s goal of 100% zero-emissions electricity by 2035, new transmission capacity will be essential,” the report stated.

It added that investment in transmission in the United States has risen sharply over the past two decades. However, as more generation comes online in areas with the highest wind and solar resources, evidence of the need for more new transmission capacity has been mounting, too.

“The sum of the real-time shadow prices of transmission (an indicator of the impact of congestion on the grid) has totaled $141 billion so far this year in three major power markets,” according to the report. These three markets are the Electric Reliability Council of Texas, based in Austin; the Midcontinent Independent System Operator, based in Carmel, Ind.; and the Southwest Power Pool, based in Little Rock, Ark. This is almost equal to the $151 billion recorded for the whole of 2016, with almost two-thirds of 2021 yet to come.

One of the roadblocks to building new transmission capacity is difficult in the United States is the nation’s political and legal systems, which give state and local governments, as well as other public entities, the right to delay, or even block, projects.

The report noted that Biden has acknowledged the problem.

“The infrastructure and climate proposals badged as the American Jobs Plan included a new tax credit for grid investment, intended to mobilize ‘tens of billions in private capital off the sidelines—right away,’” according to the report.

Additionally, the administration launched a package including $8.25 billion of loan guarantees and low-cost financing, which is intended to help build high-voltage transmission lines. The U.S. Department of Transportation is also encouraging states to use transportation rights-of-way such as highways to route transmission lines, with the goal of speeding up the permitting process.

The report added that, in addition to building new lines, the United States can make better use of its existing capacity.

Increasingly, they are looking at “dynamic line rating,” which allows capacity to vary according to environmental conditions. For example, a light breeze of just 2 miles per hour blowing across a transmission line can increase its effective available capacity by up to 44%, according to research from the U.S. Department of Energy.

In fact, the report suggested that the case for “dynamic line rating” can be compelling. “We are talking about adding capacity at less than 5% of the cost of new lines,” said Hudson Gilmer, co-founder and CEO of Linevision Inc., a company based in Somerville, Mass., that provides systems for monitoring transmission lines.

However, he added that improvements to the existing grid should be seen as complements to, rather than substitutes for, investment in new lines. “We need both,” he said.