Dive Brief:

• During a public webinar on Tuesday, Tennessee Valley Authority staff qualified that no new solar resources would be added until 2023 in the various capacity scenarios modeled in the draft of its latest 20-year integrated resource plan (IRP).
• While "solar backed up by gas and/or storage is the more optimal choice" for new generation added by 2038, according to TVA, the draft IRP does not include near term additions due to a lack of immediate need for resources.
• The draft IRP and its associated environmental impact statement were released for public comment on Feb. 15, the day after the TVA board of directors voted for the early retirement of its Bull Run coal plant and Unit 3 of the Paradise coal plant. The draft IRP portfolios will be revised to reflect the plant retirements in the base case scenario, Jane Elliott, part of TVA's enterprise planning group, said during the webinar.

Dive Insight:

Without accounting for the new plant retirements in its base case scenarios, TVA's draft IRP included the build out of 4 to 9 GW of solar by 2038 in several of the 30 separate scenarios modeled.

However, solar resources wouldn't be added until 2023 as the capacity is not needed immediately, Elliott said. "Second, it really does depend on the trajectory of solar pricing and our models tell us that as we approach the mid-2020s, that it's the most economic time to add solar."

"TVA is continuing to increase its investment in solar through programs that make sense by not putting an undue cost burden on all consumers of TVA power," Scott Brooks, TVA spokesperson, told Utility Dive via email.

After initial praise for the TVA decision on the Paradise and Bull Run plants, environmental advocates saw a missed opportunity in leading a transition from coal generation to renewable resources.

Coal capacity remains in every 2038 scenario, "even in a scenario where we've tried to envision a regulatory driver on carbon," Hunter Hydas, TVA's IRP project manager, said during the webinar.

​As adding renewables can replace the operating costs of existing coal resources, starting a gradual shift to solar "will save customers in the long run and it will smooth transition and create a reliable market for solar developers to enter into," Joe Daniel, senior energy analyst at the Union of Concerned Scientists, told Utility Dive.

The generation scenarios assessed in the draft IRP did not add wind, hydro or baseload resources, with the exception of one case where small modular reactors were modeled to promote resiliency in the system.

"There's a lot of opportunities for TVA to go out and procure even more solar and not limit themselves to a single resource," Daniel said. "There's wind that can be transmitted over transmission lines to TVA territory and there's energy efficiency."

TVA will be conducting break-even analyses ahead of the release of the final IRP for the resources that were not selected, Elliott said in the webinar. The analysis will calculate how much lower costs would need to be for a resource to be economic in TVA's portfolio.

Prices for solar have come down "appreciably more" than wind prices have, Elliott said. In addition, solar resources are a better matchup for the system's summer needs than wind.

In the final IRP expected this summer, TVA won't pick just one of the 30 resource portfolios, but will approach a strategy or a combination of portfolios, Hydas said.

"We will look at what is a strategy that TVA will want to employ and how flexible is it to meet the needs of whatever scenario may play out," Hydas said.

TVA staff identified gas, energy storage and demand response additions as different ways to increase reliability and flexibility.

"There was a strategy in the draft IRP to promote efficient load shape and it emphasized energy efficiency, demand response, electrification and storage," Elliott said.

Other ways to manage load shape were evaluated, such as applying a "time-of-use structure to charging of electric vehicles and distributed storage batteries that would shift that load as well," she said.

"Energy efficiency levels are relatively similar across the portfolios," according to the webinar presentation. It's less energy efficiency than past portfolios have had, according to TVA's Hydas.

"Energy efficiency is a great tool to help [low income customers] reduce their energy burdens," UCS' Daniel said. "What we would like to see is TVA aggressively pursue all of the energy efficiency that they can."

"We have reduced emphasis on energy efficiency programs because there's less need for programmatic energy efficiency," Hydas said. "The codes and standards promulgated by DOE, the Department of Energy, they're driving efficiencies at the C&I and the residential scale independent of the electric utility."