By Amanda Durish Cook

INDIANAPOLIS — FERC last week accepted a generation interconnection agreement between MISO and the first utility-scale battery storage project in the footprint.

The commission approved a GIA for Indianapolis Power & Light’s Harding Street Station Battery Energy Storage System, which is planned to go online this month, in spite of IPL’s protests that the project was being mischaracterized. IPL had urged the commission to view the storage facility as a transmission asset.

The agreement isn’t a straightforward storage-to-grid situation. The contract includes Harding Street’s two existing gas turbine generators — designated as black start resources — alongside the newly constructed 20-MW storage facility. The batteries — eight 2.5-MW blocks — will use the existing interconnection facilities of the two existing gas turbine generator units, which connect to the Harding Street South substation. The commission accepted the GIA “in the interest of expeditiously connecting the battery facility to MISO’s transmission grid” but said that it will not create a precedent for future storage facilities (ER16-1211-001).

“The Harding Street GIA is narrowly focused on the terms necessary to interconnect Indianapolis Power’s battery facility and two existing combustion-turbine generators; the commission’s action in this proceeding, therefore, does not prejudge potential improvements to the procedures or agreements that govern the interconnection of electric storage resources in the future,” FERC explained.

Comprehensive Market Rules Needed

The commission also said that more comprehensive market rules for storage are needed.

“Although we accept the Harding Street GIA … we appreciate that MISO’s pro forma GIA was not originally intended to govern the interconnection of electric storage resources to MISO’s transmission grid,” the commission said.

MISO and IPL disagreed over whether the pro forma agreement was an appropriate vehicle for the project. The RTO contended interconnecting under the GIA was correct, while the utility insisted that the storage facility should not be subjected to GIA provisions or referred to as a “generating facility.”

FERC said a “generating facility” designation was appropriate because the pro forma definition includes “device(s) for the production and/or storage for later injection of electricity identified in the interconnection request.” The commission also pointed out IPL’s battery storage was bundled with two other generating units. However, the commission ordered MISO to add one instance of “energy storage resource” to the agreement.

MISO regarded the battery facility as an upgrade because it shares the same interconnection facilities as the existing generation. IPL had objected to this treatment, maintaining that the non-generating battery facility is a transmission asset that provides ancillary services.

IPL had also argued that the GIA’s appendix does not apply to storage, but FERC decided it was unnecessary to “delete non-applicable provisions of a pro forma GIA.”

The agreement was approved as MISO is considering expanding its definition of demand response resources to include medium-term energy storage. In April, stakeholders urged MISO to develop a cost of new entry for storage technology. MISO said a final proposal to change Tariff or Business Practices Manual revisions to accommodate near-term storage would be presented late summer or early fall. (See MISO Stakeholders Provide Ideas on Incorporating Storage.)