Dive Brief:
- Long-duration energy storage could provide significant value to Maine’s grid during multi-day stretches of low wind and solar production, especially during the winter months when heating needs drive up electricity demand, according to a report from the Maine Governor’s Energy Office.
- The report, submitted to state legislators on Feb. 1, also found that in order to incentivize long-duration energy resources on the grid, changes will need to be made to the regional capacity market to ensure the resources are adequately valued and compensated.
- As of January 2023, Maine housed some 63 MW of battery energy storage projects that were either online or planned to come online within the year, as well as some behind-the-meter storage. The state does not have any large hydroelectric pumped storage. However, it is aiming to deploy at least 300 MW of energy storage capacity by the end of 2025, and 400 MW by the end of 2030.
Dive Insight:
Other states around the country are also exploring the potential of long-duration energy storage. A recent report from California regulators, for instance, found that the California Independent System Operator’s footprint could require up to 5 GW of long-duration energy storage, if it retains existing gas resources — and up to 37 GW by 2045, if it is aiming to decarbonize more deeply. And last August, New York Gov. Kathy Hochul, D, doled out nearly $15 million in funding to four long-duration energy storage demonstration projects, including a $12 million award to Form Energy to develop and construct a 10 MW/1,000 MWh iron-air battery project.
Last June, Maine Gov. Janet Mills, D, signed legislation that among other things directed the governor’s office to take a closer look at new and emerging long-duration energy storage technologies that could meet the state’s energy needs.
This resulted in the study submitted to the state legislature’s Joint Standing Committee on Energy, Utilities and Technology earlier this month. The report considered multiple long-duration energy storage technologies, including pumped storage, compressed air, flow batteries and hydrogen-based storage.
The report noted that long-duration storage could play a role in ensuring resource adequacy in the state, especially as the grid in Maine and across New England becomes more renewable. Today, during times when winter electricity demand is high and wind and solar production are low, coal and oil-fired generators kick in to make up the difference. Those two forms of energy comprise around 20% of New England’s electricity generation capacity and are incentivized with capacity payments, according to the report.
However, the ISO New England estimates that as of 2020 more than 7,000 MW of largely coal, oil and nuclear generation had either retired or announced plans to retire. Another 5,000 MW of coal and oil-fired generation are likely to shutter in the coming years as well, according to the grid operator.
“As more end uses like heating and transportation are electrified and electricity generation is decarbonized through high penetrations of renewables and clean resources, longer durations of storage may be able to support and balance the grid during times of high demand and low renewable output through inter-day or multi-day storage,” the report stated.
In addition, long-duration energy storage could also be sited in areas that face congestion, thereby reducing renewable curtailment, according to the report. It could also serve as an alternative to some transmission upgrades, by addressing congestion.
However, the report found that some signals that market rules are evolving to properly compensate long-duration energy storage will be important to shaping this growing industry. Capacity and ancillary markets run by ISO-NE provide capacity credits to storage durations up to four hours, but don’t treat long-duration storage any differently — meaning that today, a 100-hour energy storage system would be treated the same as a four-hour battery, the report noted.
“Evolving capacity accreditation rules in ISO-NE will play a significant role in incentivizing storage of durations greater than four hours,” it said.
