Dominion Energy Inc. submitted a revamped resource plan to South Carolina regulators Feb. 19 that includes a lowest-cost option under which the utility would cease burning coal in the state by 2030 and replace the capacity with natural gas, solar and battery storage.
The Public Service Commission of South Carolina in December 2020 ordered Dominion subsidiary Dominion Energy South Carolina Inc., or DESC, to "modify and refile" its 2020 integrated resource plan, or IRP, (docket 2019-226-E) after finding the company "used several assumptions that require improvement."
"Dominion is required to update its planning assumptions relating to the energy and demand forecast, commodity fuel price inputs, renewable energy forecast, energy efficiency and demand-side management forecasts, and changes to projected retirement dates of existing units in its modified 2020 IRP and in future IRPs," the commission wrote in its directive.
In response, DESC filed its modified plan under which the utility said it analyzed 14 separate generation plans with "Resource Plan 8" receiving the "highest score across the vast majority of the metrics."
Under this plan, Dominion would retire the 684-MW Wateree coal plant, owned by DESC, and the 610-MW Williams coal plant owned by South Carolina Generating Co. Inc. in 2028.
DESC and South Carolina Generating Co. are wholly owned subsidiaries of SCANA Corp., which was acquired by Dominion.
The preferred resource plan also calls for converting the 415-MW dual-fired Cope power plant to run solely on natural gas in 2030.
"The closure of these plants will be a huge health benefit for families and children who have been forced to live, work and play in the shadow of coal-burning plants that pollute their air and the rivers where they boat and fish," Will Harlan, senior representative for the Sierra Club's Beyond Coal campaign in South Carolina, said in a Feb. 23 written statement. "But while we're very glad there's an end in sight for Dominion Energy's coal in South Carolina, adding fracked gas is a [shortsighted] move that means communities in Orangeburg County won't get the safe, clean energy they deserve — and we'll continue to support and work alongside them until they do."
The Wateree and Williams coal capacity would be replaced by a 553-MW combined-cycle gas plant and 523-MW combustion turbine plant in 2028, according to the IRP. The resource plans also calls for the addition of nearly 400 MW of additional natural gas capacity before 2041.
"This replacement generation protects reliability and provides a base of dispatchable generation to support the addition of 1,900 to 2,000 [MW] of solar and 700 to 900 MW of battery storage from 2026 to 2048," DESC wrote. "Reliability would be supported by also adding quick-start aeroderivative [combustion turbines] as needed."
The utility added that its plan "creates a diverse and reliable portfolio of both renewable and dispatchable resources" while allowing for a significant reduction in carbon emissions.
"The modified 2020 [IRP] presents alternative plans that provide customers a path to clean, renewable energy while allowing technologies to mature," DESC spokesperson Rhonda O'Banion said in a Feb. 23 written statement. "This modified 2020 IRP highlights details about how in recent years Dominion Energy South Carolina has reduced our dependence on coal generation, increased our percentage of solar generation, and created a cleaner generation fleet as a result."
The spokesperson called the retirement of the Wateree and Williams coal plants "the most reasonable and prudent path" for the company.
"Specific retirement studies are being prepared that will inform future decision making and will be presented in a future IRP," O'Banion said.
In February 2020, Dominion Energy set a net-zero emissions target for its power generation and natural gas operations and outlined plans to shut down coal plants and ramp up investments in renewables. The company expects enterprise-wide carbon emissions to fall 70% to 80% by 2035 from a 2005 baseline.
"The fact that DESC has modeled the procurement or retirement of any resource in this Modified 2020 IRP does not mean that DESC has made the decision to procure or retire that resource," the utility wrote. "These decisions will be made based on the facts and analysis available at the time they are made."