Adding transmission capacity between the Eastern and Western interconnections would reduce costs by allowing wind, solar and natural gas-fired generation to flow more freely across broad regions, according to a recently published study by the National Renewable Energy Laboratory (NREL).
Increasing transfer capacity between the two grids could produce $2.50 in benefits for every dollar spent on the new transmission facilities, NREL said Monday.
"The ability to transfer [wind and solar] across regions could be incredibly valuable — whether that's in periods of power system stress, like extreme weather, or during a typical day when we want to take advantage of the best available resources," Josh Novacheck, NREL senior research engineer and technical lead for the study, said.
Seven high-voltage links allow only 1,320 MW to move between the Eastern and Western interconnections, according to a pre-print version of the study published late last month in the journal IEEE Transactions on Power Systems.
The interconnection facilities are aging rapidly, so replacing and upgrading them presents an opportunity for modernizing the U.S. electric grid, according to Greg Brinkman, NREL senior research engineer and co-author of the study.
The study, first released a year ago, comes as the Biden administration, Congress and the Federal Energy Regulatory Commission are considering ways to increase transmission development, which could help renewable energy facilities in remote areas reach major population centers.
Divided by a seam that runs from Montana to New Mexico, the Eastern Interconnection hosts 700,000 MW of generating capacity and the Western Interconnection has about 250,000 MW, according to the report.
In a multi-year research effort, NREL and its partners explored four options for bolstering the links between the U.S.'s two major interconnections, which largely operate independently of each other.
The study found that increasing transmission capacity made the power system more flexible, allowing electric supply and demand to be balanced with less overall installed capacity.
The researchers didn't include increased grid resilience as a benefit of adding transmission capacity so the gains from building more links between the interconnections could be higher, according to Brinkman.
The study can help decision-makers evaluate ways to strengthen the grid, according to NREL.
The study was finished in 2019, but the Department of Energy in October that year decided not to release it, according to a lawsuit filed by the Center for Biological Diversity in the U.S. District Court for the District of Columbia.
DOE political appointees feared the report could hurt the prospects for coal-fired generation, which the Trump administration supported, according to the environmental group.