Solar-Plus-Storage Project Brings New Energy to California

Clearway Energy’s Daggett Solar + Storage power plant in San Bernardino County is a model for producing renewable energy, and taking advantage of existing infrastructure, at the site of a closed thermal power plant.

The energy transition has many facets. A prominent feature is the repurposing of retired fossil fuel-powered facilities, with those power plants often replaced by renewable energy projects that can take advantage of existing onsite electricity transmission and other infrastructure.

Clearway Energy Group’s Daggett Solar + Storage project, located in Daggett, California, in San Bernardino County east of Los Angeles, is among the largest projects of its type in the U.S. The installation, part of the Daggett Energy Complex, features 482 MW of solar energy generation capacity, along with 280 MW of battery energy storage, which will rise to 394 MW (1.12 GWh) of storage capacity when the final storage phase comes online next year. The facility was built adjacent to the retired Coolwater Generating Station, a 636-MW natural gas-fired power plant that was closed by NRG Energy in January 2015.

Clearway, which began operating as an independent enterprise in summer 2018, was formed when NRG sold its renewable energy platform to Global Infrastructure Partners (Clearway’s co-owner). The Daggett site was quickly identified as one where Clearway could leverage pre-existing infrastructure, and repurpose existing high-voltage substations and transmission lines, to build a renewable energy project.

Clearway’s fleet includes about 9 GW of net owned generating capacity in 26 states. The total includes more than 6.5 GW of solar, wind, and energy storage assets, along with about 2.5 GW of natural gas-fired generation.

The Daggett project is part of climate solutions investor Hannon Armstrong’s 1.6-GW renewable energy investment in Clearway’s portfolio, a deal announced in December 2020. Construction of Daggett began in 2021.

“The Daggett Energy Complex is Clearway’s largest self-developed project to date and was a catalyst in Clearway’s broader energy storage strategy,” said James Kelly, senior director, Project Development, for Clearway Energy Group. “It plays a major role in Clearway’s overall portfolio and in Clearway’s experience as a leading solar and storage developer, owner, and operator.”

Kelly told POWER, “The Coolwater Generating Station, previously owned by Clearway’s predecessor company NRG, is located in one of the sunniest areas of the country and was also the site of one of the first utility-scale solar projects in the U.S. The area’s high-voltage substations and transmission station from the retired gas plant also provided an opportunity to tap into existing energy infrastructure.”

Several groups, including the American Clean Power Association (ACP), have touted Daggett as a model for repurposing a retired thermal power plant site into a renewable energy facility, supporting its selection as a POWER Top Plant award winner for renewable energy.

“This project is clean energy poetry,” said Jason Grumet, ACP’s CEO. “The Daggett facility provides a leading climate solution while bringing jobs and new investments to a local economy that has long relied on traditional energy production. By transitioning a fossil fuel site to provide clean, affordable power, Clearway has demonstrated that all communities can benefit from the clean energy transition.”

Said California Gov. Gavin Newsom: “This is exactly the sort of innovation and big thinking that California needs, repurposing old fossil fuel infrastructure to build one of the biggest solar and battery projects in the country. With projects like this, we’ll achieve a 100% clean electric grid and drastically cut pollution to combat climate change—all while creating good-paying jobs.”

Commercial Operation in October 2023

Daggett Solar + Storage entered commercial operation in October 2023. Along with providing power to thousands of customers across Southern California, officials have estimated the project will offset more than 1 million metric tons of carbon dioxide emissions annually.

The project’s power is contracted with six load-serving entities, including Clean Power Alliance, Constellation, Ava Community Energy (formerly East Bay Community Energy), MCE (a community choice aggregation group), Pacific Gas and Electric (PG&E), and Southern California Public Power Authority (SCPPA). Kelly noted that “San Diego Gas & Electric [SDG&E] is contracted for Daggett’s final 113.5 MW battery storage phase, which is expected to reach commercial operations in 2025.”

The project’s construction created more than 500 local union jobs from the International Brotherhood of Electrical Workers Local 477, and now employs more than a dozen fulltime operations and maintenance positions. Officials said that the project during construction contributed $210 million to the local economy and donated an additional $50,000 to local organizations that serve the community, including schools, fire departments, and community centers. The facility is expected to contribute another $18.5 million in tax revenue over the life of the project.

Kelly said the project “absolutely” could be considered a model for the repurposing of a thermal power plant site to host a renewable energy installation. “The infrastructure that interconnects conventional power plants to the grid doesn’t need to become obsolete when those power plants retire,” said Kelly. “The opportunity is not only about taking advantage of that existing infrastructure; it was also about continuing investments in a community that had long depended on the economic benefits of the former gas plant.”

Overcoming Challenges

Energy projects built in recent years have almost universally had to overcome challenges, particularly when it comes to acquiring needed equipment. Kelly said Daggett was no exception.

“Like many other developers during this period, Daggett was impacted by supply chain delays and shipping issues that caused delays to the construction schedule. We worked closely with our suppliers and off-takers to revise dates and plan accordingly,” said Kelly. The facility uses GridSolv Quantum, Wärtsilä’s fully integrated, modular, and compact energy storage system, and the GEMS Digital Energy Platform, an energy management platform for power system optimization. Wärtsilä also will provide maintenance and performance services for the lifecycle of the energy storage systems.

1. Technicians discuss their work as they stand among the battery energy storage units at the Daggett site. The project’s final phase of energy storage is expected to come online next year. Courtesy: Clearway Energy Group

The first phase of the Daggett project began construction in October 2021, and a second phase of construction started in the second quarter of 2022. As Kelly said earlier, the third phase—an additional 113.5 MW of energy storage (Figure 1)—is underway and will be complete next year.

Ted Bardacke, CEO of the Clean Power Alliance, at the October 2023 ceremony marking the project’s commercial operation, said, “The Daggett facility is a vital asset for the Clean Power Alliance, providing enough energy to power approximately 85,000 homes in Southern California. There were numerous challenges in getting this project across the finish line including the pandemic, supply chain delays, solar panel tariffs, and extraordinary global crises such as the war in Ukraine. I’m glad we were able to work together to bring us to where we are today.”

Kelly said “unknowns” around battery energy storage systems (BESS) also were a major consideration. “When Clearway began developing the Daggett Energy Complex, it was slated to be the largest solar and storage project in the county at the time,” said Kelly. “[BESS] was still a nascent technology with high costs and many unknowns in the early days of Daggett’s development, yet it became clear that the project could reach significant scale as BESS technology matured.”

Kelly continued, “Daggett also came online at a time when California’s grid needed it most. BESS has proven an essential feature of grid reliability in the state, and today the project is among the biggest solar and storage projects in California providing low-cost solar power during peak demand.”

Officials recently said California now has more than 10 GW of battery energy storage online, and announced that on April 16 of this year, batteries contributed more power to the grid than any other technology for a short time during the evening peak of electricity demand.

Community Engagement

Energy project developers often say having the local community involved and engaged during the development period helps smooth the development process. Kelly noted that Clearway embraced that concept from the start with Daggett.

“The team’s focus on early and frequent community engagement proved critical to the project’s success,” said Kelly. “The project development team’s proactive outreach to area residents and institutions, along with engagement in local community events and donations amounting to over $50,000 over the course of development, went above and beyond a typical project’s community engagement strategy.”

Kelly told POWER, “The most important lesson from Daggett and many of Clearway’s other projects is that early and frequent community engagement pays dividends. The development, construction, and now operations teams have all prioritized proactive outreach to area residents and institutions. Those relationships have been critical in building trust and getting ahead of local concerns.”

—Darrell Proctor is senior editor for POWER.