Energy Storage

ISO New England Files Proposal to Use Storage as Transmission Resource

ISO New England in late December filed with the Federal Energy Regulatory Commission for approval to treat energy storage as a transmission asset.

The proposed change would create a new, separate class of storage resources that would not participate in the ISO’s wholesale electric power markets and would be purpose-built as transmission equipment and known as storage as a transmission-only asset (SATOA).

In the filing, made in conjunction with New England Participating Transmission Owners and the New England Power Pool, ISO New England said SATOA resources would have “minimal effect on wholesale electricity prices” because they would not be participating in those markets.

Under the proposal, SATOA resources would be owned and maintained by transmission companies, but ISO New England system operators would control their use. The resources would be used under rare system conditions to prevent localized overloading after at least two unplanned equipment outages on the transmission system, ISO New England said.

Construction of SATOA resources by transmission companies would depend on selection in the open regional system planning process administered by ISO New England, similar to the way the ISO now handles reliability-based system upgrades.

Energy storage resources, such as batteries and pumped hydroelectric facilities, already participate in ISO New England’s wholesale electricity markets by buying and selling capacity, energy, or ancillary services. In ISO New England’s most recent forward capacity auction, held in February 2022, more than 700 MW of battery storage secured capacity supply obligations.

To illustrate how SATOA resources could be used, ISO New England offered an example of a town served by three transmission lines. The town uses 100 megawatts of electricity and each transmission line is designed to supply 75 MW. If one transmission line were to be knocked out by a storm, the other two lines would continue to supply all the electricity the town needs with no problem. If the storm took down two lines, the remaining third line would be overloaded and a power outage would be imminent. But if there were a SATOA in the area, ISO system operators could activate it to provide power and relieve the strain on the transmission line.

Energy storage is growing rapidly in New England. Battery storage projects made up about 20 percent of the proposed generating capacity in the ISO’s generator interconnection queue as of May 2022, compared with 10 percent in July 2020 and less than 1 percent in May 2017.

The ISO has asked FERC to approve its rule change request by March 29 to allow implementation by a target date of July 1, 2024.