Advanced electric storage devices should be treated like limited demand response resources in the capacity market because of their short run times, PJM says.

PJM envisions rating advanced storage devices for six or 10 hours of output, PJM’s Tom Falin said in a presentation Wednesday to a Planning Committee panel developing rules for the technology. That makes them similar to limited DR, which cannot be dispatched for longer than six hours at a time.

As such, the devices may receive lower prices in capacity auctions than less limited products.

Falin said treating storage similar to DR was preferable to another approach PJM considered, a Loss of Load Expectation (LOLE) analysis. Falin cautioned that his comments did not reflect an official PJM position but “some ideas we’ve kicked around.”

PJM members agreed in September to develop rules for allowing storage devices — now generally limited to frequency regulation — to offer into the capacity auctions. (See PJM to Consider Storage as Capacity.)

Under the scenario Falin outlined, storage resources such as batteries or flywheels would be designated as either six- or 10-hour storage devices. For example, a 60 MWh resource could be rated as a 10 MW, 6-hour resource or a 6 MW, 10-hour resource.

Multiple resources of similar design and capacity could be aggregated if they were located on the same bus.

The resource’s unforced capacity (UCAP) value would be determined by the capacity value less an unavailability rate. Resources lacking an operating history would be required to perform a summer and winter capability test.

Also Wednesday, Tom Rutigliano, of Achieving Equilibrium LLC and Janette Dudley of Demansys Energy, briefed the committee on their own proposal for incorporating storage into the Reliability Pricing Model.

They said PJM should use existing rules for generation with as little modification as possible. They would require storage to offer into the day-ahead energy market.

Units that run out of energy would take a forced outage. “Immature units” that have not established forced outage rates, would use average rates for the class of technology involved.

Falin said he will be working with PJM Operations and Markets staff to define dispatch and capacity market rules and energy bidding requirements. The rules will be incorporated in Manual 21: Rules and Procedures for Determination of Generating Capability.