Faced with varying waves of energy storage resources (ESRs), grid operators are taking steps to accommodate the devices that are — for now — mostly sitting in their interconnection queues.

“We can debate the timing and the speed with what change will come, but one thing is for sure, change is coming,” Renuka Chatterjee, MISO’s executive director of system operations, said during the Energy Storage Association’s virtual Policy Forum last week.

Chatterjee said MISO has 9 GW of energy storage, split between stand-alone resources and hybrids, in its queue. CAISO had more than 69 GW of ESR projects in its queue as of last July, topping all other RTOs and ISOs. PJM is second with more than 33 GW of capacity while ERCOT has more than 26 GW of storage resources that have requested at least a screening study. ISO-NE, NYISO and SPP have between 3 GW and 9 GW in their queues.

All of which belies a 2020 study by the Lawrence Berkeley National Laboratory and the Electric Power Research Institute that found RTOs and ISOs had, at the time, 69 GW of storage capacity sitting in their queues.

Nearly 500 MW of new ESR projects were installed during the third quarter of 2020 alone, according to a Wood Mackenzie report. With technology continually improving and prices dropping, the research firm expects 2021 to be another record-breaking year.

“Almost all of the RTOs are going through an energy portfolio change,” Chatterjee said. “If you look at MISO in particular, almost all of our members have some sort of low-carbon goals or commitments they want to achieve. We’re seeing an increasing change in renewables, particularly with wind and solar. … We’re creating options for energy storage to participate as well.”

MISO has already received FERC approval to treat ESRs as transmission assets, but they are limited to transmission-only functions operated by MISO-defined transmission owners and barred from participating in the RTO’s energy markets. (See FERC Greenlights MISO Storage-as-Tx Proposal.)

ERCOT has chosen a different approach after finding itself missing the first waves. Sandip Sharma, the ISO’s director of forward market operations, said the Texas grid operator was stuck at around 80 MW of energy storage for several years before it started seeing interest from the “battery community” and fragmented stakeholder discussions.

The ISO formed a task force to figure out how best to integrate ESRs. In December, ERCOT’s Board of Directors approved the group’s recommendations, which included representing storage devices as a single resource in what is called a “single-model” approach. (See ERCOT Board of Directors Briefs: Dec. 8, 2020.)

“We’re trying to ensure battery operations can have access to the market, as well as maintain their state of charge more flexibly,” Sharma said. “For ESRs to maintain their state of charge, they have to continue to be able to update their energy offers, because the energy offers are constantly changing.”

The new protocol language allows ESRs to decide whether to supply energy at a certain price point or provide ancillary services, Sharma said.

‘The Future That is Coming’

With just one ESR in its 17-state footprint, SPP is playing catch-up as well. The RTO has almost 9 GW of ESRs in its interconnection queue, which is clogged with nearly 78 GW of wind and solar resources under some form of study.

“Our GI queue is backlogged. We’re working to clear that but once we do, we will see a lot of ESRs coming online,” said Bruce Rew, SPP’s senior vice president of operations.

The RTO has tasked an ESR steering committee to coordinate and oversee the various stakeholder groups working on 37 different storage-related initiatives spread over six issue buckets.

“The key thing is we’ve looked at the load-carrying capability of the [ESRs], how we can increase that into our market and use it effectively from a market operations standpoint,” Rew said.

“Getting it right is the key thing for SPP,” Rew said. “ESRs continue to add complexity to our market. Let’s get some experience using ESRs as transmission first, then as an energy resource. We certainly have a lot ahead of us.”

PJM CEO Manu Asthana said PJM is similarly focused on preparing for a future grid where “energy storage is a meaningful part.”

He said the RTO is working with its stakeholders to draft rules that create access to distributed generation, a result of FERC Order 2222, and reform its interconnection queue practices. Both initiatives will enable further integration of ESRs, Asthana said.

“We want durable decisions that are supported by a supermajority of our stakeholders. PJM is committed to creating a level playing field for all resources, including storage,” he said.

CAISO’s storage capacity was approaching 1 GW by the end of 2020, and it has projected 15 GW will eventually be necessary to help reach California’s goal of 100% carbon reduction by 2045. Greg Cook, the ISO’s executive director of market and infrastructure policy, said he expects 3.3 GW, primarily hybrids, to come online in the next couple of years.

“New storage is being added to existing solar sites,” he said.

The ISO is operating under a new resource adequacy provision, Cook said, “as ensuring ESRs are available to be discharged when needed to meet the needs of that next peak load in California can be a challenge.”

“We do plan to have a policy catch-up where we can make multiple uses of those [storage] markets and have triggers for when they’re allowed to be in the market,” he said. “Ultimately, that’s the more efficient way to go.”

NYISO’s Michael DeSocio, director of market design, said his grid operator has embarked on the next phase of accommodating storage — valuing the resources based on their accredited capacity — following FERC’s August acceptance of tariff revisions that subject ESRs to transmission charges. (See NYISO’s 2nd Storage Compliance Almost Hits Mark.)

“There is a huge transition happening,” DeSocio said. “We’re making sure we’re ready for the future that is coming.”