Solar installations at interstate exits have the potential to generate some 36 terawatts of energy per year — which equals about 1 percent of U.S. electricity consumption — according to a report by the Webber Energy Group at the University of Texas in Austin. The mapping tool was developed in partnership with The Ray, a section of Interstate 85 in Georgia that is often a site for testing innovations in highway technology. About 127,500 acres of rights of way — about 200 miles of interstate frontage — are suitable for these types of solar installations.
Several installations in states like Georgia, Oregon, Maryland and Massachusetts are already producing power.
The Oregon Department of Transportation (ODOT) partnered with Portland General Electric (PGE) to produce two solar sites. The first one, a pilot in 2008 on Interstate 5, installed about 600 panels to produce about 104 kilowatts. A second project in 2012 installed 7,000 solar panels to produce 1.75 megawatts, say ODOT officials.
“At both sites ODOT provides the land, however, the agency doesn’t not own, operate or maintain the solar arrays,” explained Geoff Crook, climate office policy lead for the Oregon Department of Transportation.
A 2018 project on The Ray installed a 1-megawatt solar installation — about 2,600 solar panels — in partnership with Georgia Power in an exit right-of-way area. The utility owns the energy and the installation, and assumes maintenance for the area, said Allie Kelly, a spokesperson for The Ray. The site also serves as a pilot site to explore the planting of native wildflowers to encourage pollinators.
The UT report, which functions largely as a planning tool for policymakers wanting to explore transitioning right-of-way areas into solar farms, outlines various approaches to structuring arrangements with utilities, such as cost-shares, lease agreements, power purchase agreements, net metering and more. The planning tool also outlines areas which may not be good locations for a solar installation, such as sites with underground oil or gas lines running through them, since these often require routine maintenance.
"This report sought to provide policymakers and perspective companies with data that showed the potential in their locations as well as how they might start to engage with those that currently manage the roads and electricity grids,” said Joshua D. Rhodes, one of the authors of the UT report.
The answer to locating a good site for solar installation, said Crook, should be based on a thorough site feasibility study to determine the optimum size, configuration and performance.
“Detailed qualities that make for a good site include solar access, or the amount of sunlight and shading received by the site, the site's proximity and access to existing electric grid infrastructure, maintenance access, and the site's physical properties,” said Crook.
Researchers at UT Austin also concede the data used to determine the right-of-way acreage along interstates across all states in the Lower 48 is spotty since most state departments of transportation do not maintain easily accessible GIS data related to highway ROWs. The report highlighted the Iowa Department of Transportation for the state’s detailed accessible GIS data showing the ROW boundaries along its interstates.
“One of the main findings of the report was that, with better data, we could provide better estimates,” said Rhodes, referring to the acreage estimates available for solar installations. “Better data would also likely result in higher estimates.”
In Oregon, the state decided to move forward with the projects because they satisfied state policy objectives related to increasing renewable energy generation and reducing greenhouse gases, said Crook.
“It also supports local jobs and adds value to the existing public right-of-way asset,” he added.
However, for now, Oregon is not expected to expand on the program of locating solar panels along its interstates, “due to changes in leadership, resources and priorities,” said Crook.
Solar projects on highway rights of way have the potential to do so much more than simply idle mowing equipment, said Rhodes.
“I think these lands can play an important part of the energy transition,” he remarked, calling attention to these sorts of projects which can satisfy clean energy goals. “But regulations and uncertainty on how to proceed can be large obstacles, this report hoped to bridge that gap, show the potential, and get the conversations started about how to make it work.”
