Finding ways for long-duration storage to play a greater role in the clean energy transition was a key topic Wednesday at the North America Smart Energy Week summit hosted by the Solar Energy Industries Association and the Smart Electric Power Alliance (SEPA).

“The topic of long-duration storage has been top of mind for many of us in the industry lately, and there does seem to be a growing recognition of the role long-duration energy storage can and should play in the electric grid of the future,” moderator Robert Tucker, SEPA director of industry strategy, said as he introduced the panel.

“Most recently this focus was evidenced by the U.S. Department of Energy’s announced goal to reduce the cost of grid-scale long-duration energy storage by 90% within the decade,” Tucker said. “This goal, which is part of DOE’s Energy Earthshot Initiative, was discussed at its recent Long Duration Storage Shot summit that was held just last week. I attended that summit, which included presentations from members of Congress who all spoke to the importance of energy storage and long-duration energy storage, specifically to achieving our national carbon reduction goals.” (See DOE Targets 90% Cut in Cost of Long-duration Storage.)

Tucker continued the discussion Wednesday with Jaya Bajpai, principal with consultant Gamma Advisory; Erin Childs, senior manager at client advisory firm Strategen; and Frank Jakob, technology manager for energy storage at engineering firm Black & Veatch.

The first question, Tucker said, was how to define long-duration storage. DOE defines it as 10 hours, he said, but should it be defined in longer terms to handle significant power-outages such as Hurricane Ida in New Orleans, last winter’s Texas deep freeze and California’s summer heat storms, all of which typically last days?

Jakob said lithium-ion batteries are limited to four or five hours. Flow batteries are good for intermediate time frames. Pumped hydropower can last 12 hours, but building it is difficult. So newer technologies for long-duration storage will be needed and are starting to be developed, he said.

Bajpai agreed. “What you see now is a tip of the iceberg. There’s a lot more coming,” he said. Utilties understand that two to four hours of battery storage “is just not getting it done.”

Systems with a lot of wind and solar, such as SPP and CAISO, may need storage that can last 10-12 hours; multi-day and multi-week options will come along later this decade or in the early 2030s, he said.

“From a procurement perspective I think you’ll see the hours get longer,” he said.

Incentivizing Storage

Childs said long-duration storage is currently a broad, vague term that covers resources that might last from six hours to 150 hours. Such resources will play very different roles on the grid and need more precise language to describe them, she said. Are they meant to supply power in the evening when the sun goes down in California, or during systemwide crises lasting days or weeks during severe winter or summer weather?

“The overnight versus seasonal is really part of this issue,” she said.

Clockwise from top left: Robert Tucker, SEPA; Erin Childs, Strategen; Jaya Bajpai, Gamma Advisory; Frank Jakob, Black & Veatch | SPI, ESI, and Smart Energy Week

Tucker next asked Childs to give an overview of regulatory and policy issues related to long-duration storage.

Integrated resource planning will be key, she responded. “This is where [public utility] commissions are making decisions about what’s going to be brought onto the grid and the first question is, ‘Is long duration storage even on the list?’”

The California Public Utilities Commission has led the way by ordering investor-owned utilities to procure 1 GW of long-duration storage by 2026, she noted. (See CPUC Orders Additional 11.5 GW but No Gas.)

Bajpai said long-duration storage hasn’t traditionally been part of utilities’ IRP process because it’s expensive and doesn’t necessarily fit conventional supply-and-demand models.

“When you step out of the box of the conventional model, you begin to see that there is actually a much bigger role for flexible, long-duration storage,” he said. “What if I was to give you an 8-, 12- or 16-hour resource that can move power over one, two, three days and that can suddenly flex between applications? That’s something that’s very valuable from a reliability perspective to the utility.”

“I think the biggest issue here is monetizing storage,” Bajpai said. “The reality is that the transition is going to be expensive one way or another … and so I think we need vehicles and instruments that essentially reward long duration storage” as flexible, bidirectional resources, he said.

“The idea that you are compensating folks to be there, to go at a moment’s notice, and to provide a full range of flex options — I think that is powerful, and I think it needs to be compensated,” he said.

‘Time Machines’

Tucker asked the panelists if government policies are more of a roadblock to the adoption of long-duration storage “or is it more about the abilities of the technology that’s available in the marketplace?”

Jakob answered: “The greatest roadblock is the true availability of product in the marketplace that’s been proven [to work].”

Would-be adopters don’t want to be the first to try out an unproven technology, he said.

“I have many clients who want to be first to be third in line to buy new technologies,” Jakob said, prompting smiles from the other panelists.

The largest utilities are likely to be early adopters, he said.

“There are big names in the industry that have been experimenting with all sorts of technologies for decades now, but the run-of-the-mill utilities, those here in the Midwest and in Kansas and Missouri,” aren’t eager to embrace new technologies, he said.

He likened it to the situation 10 years ago when large utilities started to experiment with grid-scale lithium-ion batteries. Now, he said, the bigger utilities will need to experiment with longer-term storage technologies that act as “time machines” for moving energy from when it’s produced to when it’s needed.

Jakob and other panelists cited emerging technologies such using solar mirror arrays to melt aluminum and producing hydrogen from renewable energy. The Los Angeles Department of Water and Power, they noted, is investing in green hydrogen production and storage in the Utah desert. (See NARUC Panel: ‘Green’ Hydrogen Could Lower GHGs.)

“I think we’re going to see a lot more of that because it’s part of the energy storage grand challenge,” Jakob said. “If you want long-duration storage, you need to build a 25 MW or 50 MW 12-hour or 24-hour demonstration unit.”

“There’s going to be major steps with the new driver, that’s now very much in our face, of low-carbon generation,” he said.