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Former Coal Plant Sites Get Second Life With Energy Storage Systems

Coal plant sites are becoming an increasingly attractive location for utility and energy storage development companies across the U.S. to site new energy storage systems.

Among the advantages of placing energy storage projects at coal plant sites is the ability to reuse existing infrastructure and grid interconnection rights.

Holyoke Gas & Electric Solar Plus Storage Project Built Next to Coal Plant Site

In 2018, ENGIE North America and Massachusetts public power utility Holyoke Gas & Electric unveiled a utility-scale energy storage system at a ceremony at the Mt. Tom Solar Farm in Holyoke, Massachusetts.

Owned and operated by ENGIE North America, the Mt. Tom energy storage system is a 3 MW/6 MWh utility-scale lithium-ion battery and the second such system to be installed in the state, which went commercial in 2018.

The battery draws power directly from the Mt. Tom Solar system, which is the largest community solar project in Massachusetts and is stored for use during peak demand periods.

The system is located adjacent to the former Mt. Tom Coal Plant along the Connecticut River, which ceased operation in 2014.

HG&E currently has a 20-year power purchase agreement with ENGIE.

"Since commercial operation commenced in 2018, the Mt Tom Solar + Battery Storage System continues to stabilize HG&E and ratepayer costs during periods of peak demand and volatile pricing, reduce stress on the local distribution infrastructure, and contribute to the regions low carbon goals,” Kate Sullivan Craven, Director of Marketing & Communications for Holyoke Gas & Electric, told Public Power Current.

“We appreciate ENGIE North America's innovation that transformed the property into a state-of-the-art facility for the benefit of the local community,” she said.

“The people of Holyoke, Massachusetts, and our valued customer, Holyoke Gas & Electric, were on the vanguard in welcoming this pairing of technology into their community as we worked to transform the Mt. Tom site from coal to one producing power from solar + battery storage,” said Julie Vitek, Vice President, Government & Regulatory Affairs at ENGIE.

“The benefits have been real, both environmentally and for grid reliability. With the support of Holyoke’s citizens and HG&E, we were able to breathe new life into this retired coal plant site,” she said.

Study Examined Repurposing of Coal Plant into Energy Storage System

A report funded through a Department of Energy grant examined a scenario that called for repurposing a Duke Energy coal plant into an energy storage system by integrating the retiring asset with a Malta long duration Pumped Heat Energy Storage system (PHES).

“The project validated the technoeconomic benefits of repurposing retiring coal plants into long-duration energy storage using Malta’s PHES,” the report said.

From a technical standpoint, key findings detailed in the report were as follows:

  • Retiring coal plants (and other steam turbine fossil generation) can be repurposed to enable the clean energy transition using Malta’s technology;
  • For older retiring coal plants, repurposing the site and electrical interconnection for a standalone PHES plant is the most economically favorable option;
  • For newer coal plants where there is also a local peaking capacity need, repowering the steam cycle into a hybrid integration with PHES is attractive;
  • A process was developed to assist fossil generation owners in choosing the best path for each plant’s circumstances.

Key findings from an economic standpoint are:

  • Communities facing economic challenges caused by the retirement of fossil generation would benefit from repurposing the plant as long-duration energy storage using Malta’s PHES;
  • On a $/MW basis, repowering retiring coal units into Malta PHES plants can maintain the same number and types of jobs and economic activity;
  • For a 70% carbon reduction scenario, a 10-hour Malta PHES plant is more economic for the asset owner than similar-power 4-hour batteries.

Indiana Project Calls for Battery Storage at Coal Generation Site

In July 2023, AES Indiana filed a petition with Indiana utility regulators for the operation and development of an energy storage project on the existing Petersburg Generating Station property already owned by AES Indiana.

The Pike County Energy Storage project is a standalone project composed of two sets of 100 MW/4-hour (total expected output 800 MWh at 80% of discharge level) that will be connected to two 34.5/345 kV transformers included in a single collector substation.

Batteries will be distributed via independent enclosures that feed separate inverters that interconnect on medium voltage level (34.5 kV).

The project will be located on a 26-acre footprint and is expected to be eligible for 40% Investment Tax Credit because it is located in an “energy community” as defined in the Inflation Reduction Act.

The commercial operation date is expected by December 1, 2024.

Form Energy Partners with Xcel Energy on Energy Storage Projects

Form Energy, Inc. in January 2023 announced that it had entered into definitive agreements with Xcel Energy to deploy its iron-air battery systems at two of Xcel Energy's retiring coal plant sites.

“The storage technology will allow Xcel Energy to integrate more low-cost, renewable energy into its system and maintain reliability as it retires the coal plants in the coming years and transitions to a highly renewable future,” a news release said.

Xcel Energy–Minnesota will deploy a 10 MW/1,000 MWh multi-day storage system at the Sherburne County Generating Station in Becker, Minnesota. On July 6, the Minnesota Public Utilities Commission approved the energy storage pilot at Xcel Energy’s site in Becker, Minn.

Xcel Energy–Colorado will deploy a 10 MW /1,000 MWh multi-day storage system at the Comanche Generating Station in Pueblo, Colorado.

Both projects are expected to come online as early as 2025 and are subject to regulatory approvals in their respective states.

More recently, Xcel Energy in July 2023 issued a request for proposals for clean energy projects located in Wisconsin with commercial operation dates from 2027 to 2029. The projects will help to replace the capacity of the Allen S. King plant, a coal-fired plant in Oak Park Heights, Minnesota that is scheduled to retire in 2028.

Xcel Energy plans to reuse existing grid connections at the King plant site.

“We’ve proposed to retire all coal operations company-wide by the end of 2030,” Theo Keith, a spokesperson for Xcel Energy, told Public Power Current.

“Investing in solar and storage projects at retiring coal plant sites has multiple advantages. First, reusing existing infrastructure and grid interconnection rights allows us to provide power to customers in the most efficient and cost-effective way. Second, these projects allow us to bring new investments to communities where we’ve lived and worked for decades,” he said.

Company Proposes Energy Storage at Former Coal Plant Site in New York

Meanwhile, at a Town Board Meeting in Lansing, N.Y., in July, Ben Broder, Director of Development and Policy Strategy at Colorado-based Bear Peak Power, made a presentation about a proposal that would place a battery energy storage system at the site of the Cayuga Power Plant, a shuttered coal-fired plant.

“This particular project is very exciting because we’re able to put to use an existing interconnection and substation that was used formerly by the Cayuga coal plant,” he said at the meeting.

Broder said that the project would be a 200-megawatt, four-hour duration battery energy storage system. “The footprint of the entire project is only 5.7 acres,” he said.  Bear Peak Power has entered into a lease option with the Cayuga Operating Company for the purpose of developing and building the storage system.

In terms of the project’s timeline, Broder said it is expected to be completed in the second quarter of 2026.

Coal Plant Site in New Jersey to Host Energy Storage System

In neighboring New Jersey, the Logan Generating Plant, one of New Jersey’s last coal plants to retire, was demolished in late 2022.

At the demolition, Starwood Energy, owner of the plant, announced plans to build grid-scale battery storage on the site and use existing interconnection rights from the old coal plant to connect new offshore wind transmission lines.

Storage Project Would Located at Former Coal Plant Site in Nevada

In late June, the Town Advisory Board for Moapa, Nev., approved a plan presented by investor-owned NV Energy that calls for the installation of a battery storage system at the site of the Reid Gardner Power Station, a now-shuttered coal-fired power plant near Moapa.

In a presentation at the June 27 Moapa Town Advisory Board meeting, Mark Sullivan, a Senior Land Use Consultant with NV Energy, said that the 220-MW lithium-ion project is designed for peak time hours.

In May of this year, the Nevada Public Utilities Commission issued an order related to NV Energy’s integrated resource plan in which it said it was unable to approve the utility’s proposal for a 200-MW grid tied battery energy storage system to be located at the Valmy coal-fired power plant site in Nevada.

Specifically, the PUC said that it was “premature and unreasonable” to approve the $466 million battery energy storage system investment at Valmy as a cost-effective replacement for the coal plant “without all the necessary facts.”

The Commission said that the retirement of the Valmy plant by the previously approved date of 2025 is a significant priority for the PUC.

It directed the utility to provide additional details about the retirement of the plant including “a complete solution” for the plant’s retirement.

In July 2023, the utility outlined a plan to convert the existing coal-fueled plant at the North Valmy Generating Station – the lone coal plant in NV Energy’s portfolio – to a natural gas-fueled plant.

The North Valmy Generating Station – located in northern Nevada near Battle Mountain – “is a critical generating plant that is necessary to provide reliable power for northern Nevada customers. Refueling the North Valmy Generating Station with natural gas allows NV Energy to reduce carbon emissions by almost 50% through the elimination of coal while ensuring the company has a facility in that part of the state that can operate around the clock to meet the energy needs of our customers,” NV Energy said.

Program Offers Incentives to Install Storage Facilities at Former Coal Plant Sites

In June 2022, Illinois Gov. JB Pritzker and the Illinois Department of Commerce and Economic Opportunity announced the participants of the Coal-to-Solar Energy Storage Grant Program.

As part of the program, five coal plant sites -- which are already closed or in the process of closing -- were selected to participate. The program provides incentives for companies to install energy storage facilities at the sites of former coal plants.

Guided by criteria outlined in CEJA legislation, the five coal plant sites will receive a total of $280.5 million over a ten-year period (capped at $28.05 million per year), with the first payments issued in 2025 when the facilities are expected to be commercially operational. The amount of funding received by each project corresponds to the megawatts of stored energy capacity at the facilities.

The plants were selected through a competitive review process which permitted up to five plant sites to be selected.

In order to qualify, the plants must have burned coal, have a generating capacity of at least 150 MW of electricity, and make a commitment to hiring a diverse workforce and apprentices.

The program provides $110,000 per megawatt of stored solar energy (with a yearly cap of $28.05 million for all recipients) and each project must have a storage capacity of a minimum of 37 MW.

In 2021, the Illinois General Assembly passed SB 2408, the Energy Transition Act, an omnibus energy package that cleared a path for Vistra Corp. to build and operate up to 300 MW of utility-scale solar and 150 MW of battery energy storage facilities at nine retired or to-be-retired coal plant sites across central and southern Illinois.

Hawaii 185-MW Storage Project Would be Located at Former Coal Plant Site

In Hawaii, an energy storage project being developed by Plus Power will be located on roughly eight acres of land in Kapolei on the island of Oahu, where it will interconnect at a Hawaiian Electric substation.

The 185-MW/ 565 MWh battery storage project will provide load shifting and fast-frequency response services to Hawaiian Electric, enhancing grid reliability and accelerating the integration of readily available renewable energy.

The project received approval from the Hawaii Public Utilities Commission in May 2021.

The project will help replace an AES coal-fired plant that closed on September 1, 2022, supporting the state’s goal of shifting from fossil fuels to 100 percent renewable energy generation, Plus Power said.

Trend is Also Seen in Other Countries

The trend of siting energy storage facilities at coal plant sites is not limited to the U.S., with several other countries seeing the emergence of similar plans.

In August 2023, SSE Renewables started construction on a 150MW/300MWh battery energy storage system at Ferrybridge, West Yorkshire, U.K., with a groundbreaking ceremony. A coal-fired plant was located at the site until its decommissioning by SSE in 2016.

In Australia, ENGIE and its partners Eku Energy and Fluence in June of this year announced the commissioning of the Hazelwood Battery Energy Storage System, a utility-scale battery of 150 MW/150 MWh, located on the site of the former Hazelwood coal-fired power plant.

Meanwhile, ESS Tech Inc., a manufacturer of long-duration energy storage systems, and LEAG, a major German energy provider, in June 2023 signed an initial agreement to deploy renewable generation and long-duration energy storage using ESS iron flow battery technology.  

LEAG and ESS plan to build a 50 MW/500 MWh iron flow battery system at the Boxberg coal-fired power plant site in Germany, to be commissioned in 2027.

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