By Amanda Durish Cook

CARMEL, Ind. — MISO will ask for at least another year to comply with FERC Order 841, saying the intricacy and expense of incorporating storage into its markets is greater than it originally anticipated.

MISO leaders say the original Dec. 3 go-live date to comply with the order is no longer feasible given FERC’s recent deficiency letter in response to the RTO’s proposed storage participation model. MISO was counting on the commission accepting its filing this month to maintain a strict timeline for adapting its market to storage participation.

FERC earlier this month issued separate deficiency letters to all six jurisdictional RTOs and ISOs regarding their plans for energy storage participation. (See FERC Asks RTOs for more Details on Storage Rules.) The commission specifically asked MISO for several more details and explanations related to its phased participation approach, proposed commitment statuses, complexities for distribution system storage resources, conflicting offers and bids, and make-whole payments. The RTO has until early May to respond.

MISO Director of Market Design Kevin Vannoy said the combination of a later-than-anticipated FERC order, remaining uncertainty about what the commission will decide after the RTO’s response and holding work on software changes because of that uncertainty led to the request.

“In our response to this request, we are going to ask for a deferral,” Vannoy told the Energy Storage Task Force on Thursday.

Vannoy said the deferral would be “no earlier than a number of months after a clean order.” When pressed, he said the RTO could request for 12 to 18 months from when FERC fully accepts its filing.

The “cost and complexity” of implementing new bid parameters for storage was greater than MISO predicted in 2018, Vannoy said. Work also remains on how energy storage operators will communicate data to the RTO, he added.

MISO is in the process of answering FERC’s multiple questions in the 10-page deficiency letter, he said.

“We didn’t see anything in there one way or the other that they were leaning towards rejecting or accepting the filing. We think they simply need more explanation,” Vannoy said of the commission’s tone in the letter.

FERC also asked MISO to explain a provision that prohibits distribution-level storage resources from pseudo-tying into a different balancing authority. Vannoy said RTO leadership feels that pseudo-tying storage is beyond the scope of the final rule.

MISO had warned stakeholders in mid-April that it was anticipating a “significant delay” in developing a functioning model for storage participation.

During an April 11 Market Subcommittee meeting, Vannoy said MISO staff have been discussing the deficiency letters with other RTOs. He said MISO is limited by what its legacy market platform can handle as it’s gradually swapped out for a new cloud-based market platform. MISO Senior IT Director Curtis Reister said the RTO is targeting a complete replacement of the platform by 2024, and rolling out a new market user interface — the site market participants use to submit bids and offers — in mid-2021. (See MISO Seeking Multiple Vendors for Market Platform Redesign.)

The Energy Storage Task Force meanwhile is set to sunset in June. Task force Chair John Fernandes said that through next month, the group will create a spreadsheet of storage issues that other stakeholder groups can concentrate on, focusing heavily on how the RTO will integrate hybrid resources that contain storage assets.