By Amanda Durish Cook

CARMEL, Ind. — After criticizing Ameren Illinois for miscalculating its summer peak load forecast, Dynegy last week called on MISO to develop a new process for verifying load forecasts produced by load-serving entities.

Dynegy’s Mark Volpe said that while Zone 4 in Southern Illinois represents just 8% of total MISO capacity, it showed the largest under-procurement in the RTO’s Planning Resource Auction, when reserves came up 467.8 MW short of requirements when the summer peak occurred July 20.

The reason, according to Dynegy: Ameren’s portion of the Zone 4 load forecast for the July 2017 peak dropped 484 MW, or 6.4%, from the previous year to 7,069 MW. That led to an overall zone peak forecast of 8,925 MW, down 481 MW, compared with last year’s actual peak of 9,500 MW.

Dynegy said that none of the other zones in MISO showed a similar drop in load forecast.

“This raised our eyebrows at Dynegy,” Volpe said during an Oct. 11 Resource Adequacy Subcommittee meeting.

“We questioned MISO repeatedly on the reasonableness of the forecast, and MISO continually defended the Ameren Illinois load forecast as plausible and reasonable, given gains related to investment in energy efficiency programs, a decrease in commercial and industrial load, and an overall downturn in the economy,” Volpe said.

As required by its Tariff, MISO asks resources to provide forecasts of annual coincident, monthly non-coincident and local resource zone peak demand for use in producing annual load forecasts.

“MISO should have worked closer with Ameren to resolve what we see as an understatement of load forecast in Zone 4. Given the benefit of hindsight of the July 20 peak load … it seems to us that our concerns were pretty valid,” Volpe said.

Consumers Energy’s Jeff Beattie pointed out the Zone 4 planning reserve sharing group easily compensated for the 468-MW shortage.

“To me, that’s one of the benefits of being in an RTO,” Beattie said.

“You’re right — from a macro perspective, things are fine,” Volpe said, adding that he was more interested in the year-over-year changes to load forecasts.

Volpe said MISO does not currently have provisions to perform an after-the-fact examination of forecasts provided by LSEs. He suggested that an independent third party could provide a “look back” of the load forecasts to check for accuracy.

“None of us like penalties, of course, but I think we need to put on our thinking caps and find a way to review whether a load-serving entity came close to its planning reserve margin,” Volpe said. “We’re concerned with overall system reliability, and we have to realize that this impacts all connected to the transmission system.”

Minnesota Public Utilities Commission staff member Hwikwon Ham asked Volpe who would pay for the third-party review. Volpe said costs would have to be worked out if MISO pursues the proposal.

MISO Executive Director of Strategy Shawn McFarlane said the RTO will address the presentation at the November meeting. Kevin Sherd, MISO director of forward operations planning, said the RTO continues to support its existing load forecasting process.

“Quite frankly, we think the forecasts are good on a reasonable, one-year-out basis,” Sherd said.

Improving the Independent Load Forecast?

Volpe suggested that Purdue University — the same third party that produces independent load forecasts used to evaluate the MISO’s own predictions — could verify LSE load forecasts.

But MISO said last month that after three years of using forecasts prepared by Purdue, the process could use improvement, although it did not propose possible changes.

The university’s State Utility Forecasting Group generates forecasts for all 15 MISO states using public data from the Energy Information Administration. The forecast includes summer and winter values for annual energy use in MISO’s 10 local resource zones and aggregate, coincident and non-coincident peak demand predictions for each zone. MISO is nearing the end of a three-year contract with Purdue to provide the forecasts.

MISO said that after three iterations of the third-party forecasts, it has refined its methodology based on stakeholder wishes, leading to use of Applied Energy Group and electric generation expansion analysis system data to create predictions of generation and renewable growth, instead of simply relying state mandates and goals.

“We’ve used the forecast to date for comparison,” MISO Director of Planning Jeff Webb explained earlier this month, noting that the RTO first consults resource adequacy requirements under Module E of its Tariff, then compares the independent forecast against aggregated forecasts submitted by LSEs and transmission owners to determine reserve requirements.