By Amanda Durish Cook

CARMEL, Ind. — A recent MISO study slightly overestimated actual capacity offers in the 2018/19 Planning Resource Auction, stakeholders learned this week.

The RTO’s loss-of-load expectation (LOLE) study predicted about 143.3 GW of capacity in the Planning Resource Auction, while the auction itself attracted about 141.8 GW in offers, MISO Resource Adequacy Senior Engineer William Buchanan reported during a May 9 Resource Adequacy Subcommittee meeting.

MISO said three factors played into the difference between the study results and auction outcome:

• PJM completed its third Incremental Auction in early March after the LOLE analysis was complete, which increased exports.
• The LOLE used forecasts submitted in November 2016, while the PRA relied on forecasts with reduced load growth submitted in November 2017.
• The LOLE study was completed before the latest round of Attachment Y retirement notice submittals, which were not included in modeling.

Buchanan also said a year-over-year decrease in transmission losses shaved peak load by about 426 MW.

MISO cleared 135 GW of capacity during the 2018/19 PRA last month, with nine of its 10 local resource zones clearing at $10/MW-day. The lone outlier was Zone 1 — covering parts of Wisconsin, Minnesota and the Dakotas — which cleared at $1/MW-day. (See MISO Clears at $10/MW-day in 2018/19 Capacity Auction.)

In more detailed results released this week, MISO cleared slightly less than 49 GW of coal capacity, down 3.3 GW from last year’s cleared volumes, while natural gas capacity was up about 2 GW at 51 GW. Cleared wind capacity remained relatively static at 2.2 GW, while solar capacity more than doubled from 180 MW to 461 MW. Nuclear capacity remained steady at 12.5 GW.

Capacity Import Limit Change

Some MISO stakeholders said they were caught off guard by an unexpected drop in capacity import limits used in the auction compared with preliminary auction data.

Consumers Energy’s Jeff Beattie asked why the auction’s actual CILs changed from the first published limits by “hundreds of megawatts.” He said the changes were a departure from previous years, when draft preliminary and final preliminary CILs remained relatively static.

“Zone 5 changed by more than 500 MW in the capacity import limit,” Beattie said.

Harmon said the RTO simply updated the limits for known exports out of the system to non-MISO load as it became aware of the changes. He said MISO may investigate requiring stakeholders to provide more information earlier.

From February to mid-March, when limits were finalized, MISO’s preliminary CILs fluctuated anywhere from 752 MW in Missouri’s Zone 5 to no change in Michigan’s Zone 7.

Vistra Energy’s Mark Volpe said MISO could do more to telegraph the limit changes to its stakeholders ahead of the auction.

“We did not hear a discussion as to why they changed. MISO needs to be more transparent,” Beattie said.

Laura Rauch, MISO manager of resource adequacy coordination, said the RTO would try to improve transparency in next year’s auction.

Exelon’s David Bloom said he was “begging” MISO to make preliminary PRA data easier to locate on its website.

MISO will meanwhile continue to make predictions for out-year capacity import and export limits, but it will use a new process of analyzing only those zones expected to bind on their import or export limits — or fall short of procuring local clearing requirements. MISO’s Matt Sutton said the RTO will now review those zones with its Loss of Load Expectation Working Group (LOLEWG) and then perform analyses on selected zones. Results will first be shared with the LOLEWG.

Sutton said the technical design of the new process will also be taken up at the LOLEWG.

MISO last month said it would revise its practice of forecasting long-term capacity import and export limits after proposing in early spring to discontinue them. (See “Reprieve for Out-year Import and Export Limit Estimates,” MISO Resource Adequacy Subcommittee Briefs: April 11, 2018.)