By Michael Brooks

The Federal Energy Regulatory Commission last week rejected a rehearing request on its approval of Commonwealth Edison’s wholesale distribution charge on an energy storage facility (ER15-3).

In its request, the Energy Storage Association contested ComEd’s classification of Energy Vault — a Chicago-based company whose energy storage facility is connected to ComEd’s distribution system and participates in PJM’s ancillary services markets — as a load-serving entity. The association argued that because the commission has previously classified energy storage resources as generators, the charge should not apply, as ComEd has exempted generators from such charges.

“By defining an [energy storage resource] as a market seller it was PJM’s and FERC’s clear intention to ensure battery facilities, such as Energy Vault, would be treated similar to other market sellers, such as generators and pumped storage facilities, rather than as a market buyer or load, which ComEd proposes to do here,” ESA said.

Energy Vault echoed these arguments in its protest to FERC’s November 2014 approval of the charge, which costs the company $3,449 annually.

FERC disagreed, saying that energy storage could be classified as generation, transmission or distribution, depending on the circumstances. In this case, Energy Vault’s battery “spends a substantial share of its operating life being charged by withdrawing energy from the distribution system,” the commission said. “Generation does not.”

“Notwithstanding the label applied to Energy Vault, be it deemed a wholesale customer serving load, generation, market seller or some combination, it is indisputable that Energy Vault seeks to use the ComEd distribution system to both inject into and withdraw power from its batteries,” FERC said. “The Nov. 28, 2014, order was not based on any particular label or classification for Energy Vault, but upon the fact that Energy Vault is using ComEd’s distribution system to withdraw energy for battery charging and therefore should contribute to its costs.”

ComEd exempted generators from wholesale distribution charges in 2009. The company found that reverse flows from renewable generation potentially benefit its system by reducing congestion.

“While a storage device discharging to the distribution system should also provide beneficial counterflow, a storage device differs from generation in that it must spend a substantial amount of time charging,” FERC said. “During charging, it will add to the flow and load on the distribution system just like any other load and, crucially, unlike a generator.”

FERC said that while it does treat energy storage as generation for specific purposes, that does not preclude a transmission owner from recovering the costs of its system through distribution charges.

Energy Vault’s storage facility, E-Vault, is a 100-kW prototype battery system that stores and provides power for the company’s Solar Plugs, solar-powered EV charging stations, including one on Northerly Island in Chicago.