A low-cost generation mix for Duke Energy’s service territory in North Carolina and South Carolina would add 18 GW of solar by 2030, the Brattle Group found in a modeling study.
That’s more than triple the amount Duke Energy proposed in its “base case with carbon policy” scenario in its 2020 integrated resource plan.
The 18 GW of solar would include 9.5 GW of “economic solar additions” beyond those required under North Carolina’s House Bill 951.
Brattle’s modeling, which did not allow for new gas-fired generators, resulted in a generation mix with costs roughly equal to those of the Duke Energy base case until 2029. After that, annual cost savings rise to $590 million in 2030 and $1.2 billion in 2035.
The cost savings resulted from substituting solar, storage, and wind for Duke Energy’s proposed 3.8 GW of additional gas capacity, and through accelerated retirement of coal plants across Duke Energy Carolinas and Duke Energy Progress.
Solar developer Cypress Creek Renewables funded the Brattle Group study and has an operating solar portfolio of 1.6 GW spanning 14 states.
The Brattle plan would also add 3.6 GW of battery storage, versus 0.6 GW in Duke Energy’s plan, and 3 GW of onshore wind power, versus none in Duke Energy’s plan.
Brattle’s approach would reduce Duke Energy greenhouse gas emissions by 74% relative to 2005, versus a 57% reduction in the Duke Energy base case. The Brattle plan also would yield substantial reductions in emissions of sulfur dioxide, nitrogen oxides, and mercury, which are byproducts of burning coal.
Modeling
Brattle Group analyzed the combined Duke Energy system using the firm’s internal capacity expansion model gridSIM, and ensured that the model run achieved reserve requirements.
Capital costs for generation and storage were based on the National Renewable Energy Laboratory’s 2020 Annual Technology Baseline aggressive case, with regional adjustments from the U.S. Energy Information Administration, and cost data specific to North Carolina where available.
Federal tax credits for renewables and storage were assumed to be extended at full value through Jan. 1, 2027, and then reduced by 20% per year. Standalone storage was assumed to be eligible for the federal investment tax credit. No carbon price was modeled.
Brattle said the analysis did not account for any costs of transmission and distribution system upgrades caused by the shift in resources. Brattle estimated that up to $5.2 billion of additional transmission and distribution investments could be made and still result in cost savings through 2035.
Brattle added that the modeling did not consider “rising costs and declining performance” of solar or wind resources added in less ideal locations.
The Brattle Group’s press release provides a link to a webinar describing the study.
