Examining Supply-Side Options to Achieve 100% Clean Electricity by 2035 was written by research staff at the National Renewable Energy Laboratory, so its reliance on solar and wind energy to decarbonize the grid by 2035 is not surprising. But that’s a big ask for any variable energy technology, especially if the nation’s largest source of clean power—nuclear energy—is relegated to a supporting role. Massive additions of solar and wind energy on the order of 2 TW would require a supporting infrastructure of new transmission lines, as well as batteries and hydrogen for daily and seasonal energy storage that would drive demand and capacity requirements higher.
In the NREL report, released August 30 by the Department of Energy’s Office of Energy Efficiency & Renewable Energy (DOE-EERE), accelerated demand electrification (ADE) is evaluated in four scenarios: All Options, Infrastructure Renaissance, Constrained, and No Carbon Capture and Storage. In two of those scenarios, no new nuclear power would be added to the grid, but one—the Constrained scenario—acknowledges that “restrictions on renewable energy and transmission deployment make nuclear more cost-competitive.”
Once the model is tweaked to add those constraints, “the model builds about 200 GW of new capacity by 2035, even with modeled restrictions against deployments in 11 states.” Add today’s light water reactors, and the grid could have about 290 GW of nuclear capacity by 2035. Significantly, NREL’s modeling was based on federal and state policies that were current in October 2021, and the Biden administration and Congress have signaled increased support for nuclear energy in the year since.
Winds are shifting in Washington: As DOE-EERE acknowledges, the report was written before the Inflation Reduction Act (IRA) became law, which—together with the Bipartisan Infrastructure Law (BIL)—is expected to reduce greenhouse gas emissions in the United States, partly through support for existing and new nuclear generation. “None of the scenarios presented in the report include the IRA and BIL energy provisions, but their inclusion is not expected to significantly alter the 100 percent systems explored—and the study's insights on the implications of achieving net-zero power sector decarbonization by 2035 are expected to still apply,” said the DOE-EERE in an August 30 press release.
More has changed in the two weeks since the report was released. Diablo Canyon received legislative support in California to run until 2029 and 2030, and both Diablo Canyon and Michigan’s Palisades, which shut down in May, are in the running for civil nuclear credits. The DOE’s Office of Nuclear Energy (NE) on September 13 released a report saying that up to 250 GWe of new nuclear could be deployed on retiring coal power plant sites. Congress is weighing supplemental funding to secure a reliable nuclear fuel supply, while Bloomberg reports that a separate deal could be in the works to speed federal approvals for certain energy projects, including gas pipelines and the transmission infrastructure that would be needed to support a major solar and wind buildout. The time is right to take a closer look at the report.
Ramping up: NREL modeled the “least-cost” generation, energy storage, and transmission investment portfolio under each of four scenarios and concluded that wind and solar energy provide would provide 60–80 percent of electricity generation in 2035, while overall generation capacity would grow to roughly three times the 2020 level by 2035. Meeting that goal would mean increasing the annual deployment of both wind and solar by more than four times current levels.
In all scenarios, significant transmission infrastructure is added around the country, most notably to link the wind-rich regions in the Midwest to areas of high demand in the eastern United States (see graphic). As modeled, new interregional transmission lines totaling from 13,000 miles in the Constrained case to about 91,000 miles in the Infrastructure Renaissance case would increase total transmission capacity from one to almost three times today's capacity by 2035.
“Seasonal mismatch”: The NREL report acknowledges the “last 10 percent challenge”—a steep increase in the cost of modeled systems as they approach 100 percent clean electricity. That increase is driven by what the report delicately terms “the challenge of seasonal mismatch” between variable renewable energy generation and consumption. Anywhere from 120 GW to 350 GW of daily energy storage capacity would be deployed by 2035 across the scenarios, while seasonal storage capacity of 100 GW to 680 GW is represented in the study as clean hydrogen-fueled combustion turbines.
“Achieving seasonal storage of this scale requires substantial development of infrastructure, including fuel storage, transportation and pipeline networks, and additional generation capacity needed to produce clean fuels,” the report states.
Coal-to-nuclear alternative: A separate DOE report, Investigating Benefits and Challenges of Converting Retiring Coal Plants into Nuclear Plants, released just last week by the DOE-NE, outlines a potentially more cost-effective way to add clean energy capacity to the grid. A team of researchers at Argonne, Idaho, and Oak Ridge National Laboratories found that as much as 250 GW of new nuclear capacity could be built at nearly 400 coal power plants that have recently retired or plan to close within the decade.
The DOE-NE report found that nuclear overnight costs of capital could decrease by 15–35 percent, when compared with a greenfield construction project through reuse of existing infrastructure, depending on the reactor type and on how much equipment is repurposed. The analysis considered different scenarios for using the coal plant’s transmission lines, switchyards, cooling ponds or towers, and civil infrastructure, such as roads and office buildings.
Cost, and other factors: NREL’s base model assumes that advanced nuclear deployments would cost $5,600/kW by 2035. Factoring the projected lower costs of nuclear deployments at retired coal sites into that model might change the results. But the potential advantages of a coal-to-nuclear transition cited in the DOE-NE report go beyond cost. Replacing coal power plants with clean baseload energy could provide economic benefits to disadvantaged communities and make good use of existing transmission assets that would otherwise be idled, increasing clean baseload electricity without putting greenfield land to use for electricity generation or transmission.