PacifiCorp continues to see dramatic savings from early retirement of some of its coal-fired power plant fleet and switching to renewables and natural gas, in modeling for its 2019 integrated resource plan.
In IRP stakeholder meetings on Sept. 5 and 6, among the five modeling portfolios with the lowest costs—from a total of 30 reviewed—coal unit retirements totaled 667 MW through 2022 and ranged between 2,091 MW and 2,797 MW through the end of 2027.
Scenario P-46 showed a $599 million present value revenue requirement (PVRR)—relative to a base case using current depreciation schedules—by retiring coal units Naughton 1 and 2, and Jim Bridger 3 and 4 in 2025, while keeping Bridger units 1 and 2 operating without pollution control technology until 2028 and 2032, respectively.
In addition, Colstrip units 3 and 4 would retire in 2027, along with all four units at the Johnston plant in Wyoming.
By the end of the modeled period, coal retirements are similar among nearly all cases, with slight variations that depend on the timing of Colstrip units 3 and 4 retirements. In addition, natural gas retirements are the same among all cases.
An earlier IRP study reviewed at a December 2018 stakeholder meeting showed that roughly 60 percent of the company's coal units could be retired in 2022 and replaced with renewables or natural gas-fired generation. At that time, PacifiCorp said it needed to continue to study the reliability impacts of early retirements.
PacifiCorp's current modeling shows new renewable resource acquisitions picking up beyond 2022, and all scenarios include the Gateway South transmission line in 2024, along with 1,920 MW of new wind in eastern Wyoming.
Among the five cases with the lowest PVRR, total new renewables capacity ranges between 3,674 MW and 4,536 MW through 2027, and exceeds 10,000 MW through 2038. Potential new battery capacity ranges between 3,099 MW and 4,558 MW through 2038.
The utility's modeling shows acquisitions of between 521 MW and 589 MW of Class 2 demand side management through 2022, with between 11 MW and 19 MW of Class 1 DSM. Through 2027, Class 2 DSM selections range between 1,237 MW and 1,370 MW; Class 1 DSM ranges between 45 MW and 322 MW.
By 2038, PacifiCorp's modeling indicates between 2,272 MW and 2,471 MW in Class 2 DSM as being cost-effective; Class 1 DSM ranges between 452 MW and 581 MW.
Converting Naughton 3 from coal to natural gas defers acquisition of new natural gas-fired capacity to 2028 or beyond. But by 2038, new peaking capacity ranges from 813 MW to 1,600 MW. One scenario includes adding 1,541 MW of new combined-cycle combustion turbine gas capacity, beginning in 2027 and running through 2038.
The five cases with the lowest PVRR show 185 MW of new peaking gas capacity being added in 2026 and 1,367 MW of new gas capacity on line by 2038.
While most of the modeling scenarios show the company closing all or some of its coal units in Wyoming, most scenarios show PacifiCorp adding solar, gas, wind and battery facilities there. Under scenario P-46, which closes Bridger, Johnston, Colstrip and Naughton early, the utility shows the potential to add 3,966 MW of wind, solar, natural gas and transmission upgrades, also in Wyoming.
In 2023-2027, a period in which there are resource adequacy concerns in the region, PacifiCorp summer average annual market purchases range between 231 MW and 1,053 MW, and reliance on the market grows in cases with more accelerated coal retirements.
Over the long term, the level of summer market purchases is relatively stable among all cases, ranging between 1,241 MW and 1,362 MW.
Winter market purchases are relatively smaller, and more stable among most cases through both the short and middle terms, the IRP material said. Over the long term, winter market purchases are reduced when incremental CCCT capacity is added to the system.
The utility's next IRP meeting will be held Oct. 3 and 4, when PacifiCorp plans to review its preferred portfolio and action plans.
The IRP is expected to be filed with state regulators on Oct. 18.