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Hawaii’s biggest solar+battery plant comes online — just in time

Despite supply-chain hurdles and other hiccups, developer Clearway Energy was able to get the solar-and-storage facility running before Oahu’s last coal plant closes.

A large solar plant in Hawaii
The Mililani Solar I project in Oahu (Julian Spector)
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HONOLULU, Hawaii — Supply-chain hangups, tariff scares and limited inventory have hammered solar and storage developers this year. It’s nigh impossible to find a large-scale project hitting its original deadline anywhere in the U.S. But those delays were especially high-stakes in Oahu, Hawaii’s most populous island, which urgently needs new clean energy to replace the power generated by its last coal plant when it shuts down by September 1.

Now, after a year of anxious anticipation, Hawaii has something to celebrate. Facing enormous challenges, developer Clearway Energy delivered Oahu’s largest solar and storage project on time, and it did so months earlier than originally planned. 

Mililani Solar I, located on former sugar-cane fields inland from Pearl Harbor, has been generating 39 megawatts of solar power for the grid since the end of July. But unlike the other solar projects on the island, this one can funnel that production into an onsite battery array that can hold 156 megawatt-hours for use at night. It doesn’t replace the retiring AES coal plant entirely, but, along with other resources, it shores up the grid until a slew of other clean energy projects come to fruition.

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Mililani I enhances grid reliability, and energy from the facility will help ensure a smooth transition as AES retires,” Rebecca Dayhuff Matsushima, vice president of resource procurement at utility Hawaiian Electric, told Canary Media in an email Friday. 

This marks the first of nine clean energy projects expected online in the next couple years as Oahu reorients its power grid around clean energy instead of burning imported oil for electricity. Governor David Ige charted this course when he signed a landmark 100 percent renewable power target into law in 2015

That mission has taken on new economic significance since Russia invaded Ukraine and kicked off a global price spike in oil. Hawaii used to get one-third of its oil from Russia, and now the state pays extra to source it elsewhere. This has hit Hawaii’s drivers and electricity customers hard because most of the state’s electricity comes from oil-burning plants. Hawaiian Electric says clean power like Mililani’s is one-third the cost of oil production these days.

We’re seeing with this project, solar-plus-battery, that we can generate energy at significantly below the cost to produce energy by fossil fuel — as much as two-thirds less,” Ige told Canary Media after an opening ceremony for the plant on Thursday, the island sun beating down on acres of solar panels lining the red dirt behind him. Those states that are seeing the shocks of oil…if they were 100 percent clean, renewable, they wouldn’t have to worry about any of that.”

A group of people at an opening ceremony at a solar-plus-storage facility in Hawaii
Hawaii Governor David Ige (center, in aqua shirt) and others attend an opening ceremony at the Mililani Solar I site. (Julian Spector)

With the U.S. Congress injecting hundreds of billions of dollars into the clean energy industry, Oahu offers a glimpse of what’s to come: challenges in actually building clean energy projects, to be sure, but financial and environmental victories when they’re complete.

Getting solar-storage done in dire circumstances

Early last year, it looked like Oahu might be in trouble. Nine clean energy projects intended to replace the outgoing AES coal plant were hitting all kinds of snags: permitting delays, the unexpected discovery of cultural artifacts in construction zones, essential equipment being jammed up in ports far away. But while other developers slid backward in their timelines, Clearway moved forward.

Early last year, Governor Ige launched the Powering Past Coal Task Force to ensure a smooth grid transition. In response, Clearway reformulated some design and procurement choices to move its start date from November 1 to July 312022

We were very focused on the importance of why this project needed to come online before September 1, when the coal plant was being retired,” said Nicola Park, Clearway’s origination manager running utility-scale development in Hawaii. Everybody had that in mind as a really critical motivating factor behind the mission.”

This required asking regulators to sign off on an amended contract with the new timeline. It also came with a price increase to mobilize all of Clearway’s suppliers and contractors to fast-track their deliveries with overtime work, if necessary. The new contract simultaneously increased the production of the facility, and despite the extra expense, Hawaiian Electric said it still delivers the cheapest kilowatt-hours of all the forthcoming renewables projects. 

Clearway could have given up on its deadlines when its key suppliers couldn’t deliver as scheduled. The bifacial solar panels got held up in Shanghai’s Covid shutdown and then in Long Beach’s port congestion. NEXTracker couldn’t get its usual power-supply equipment for the racking system that follows the sun through its daily arc. 

But the solar panels eventually arrived, and Wärtsilä delivered its cube-like Quantum energy storage units, which can be hoisted off a truck bed and hooked up far more quickly than the bulky containerized systems of earlier grid storage products. NEXTracker re-engineered its trackers around different power equipment to get the job done, Park added. 

A row of large white energy storage batteries at a solar site in Hawaii
Wärtsilä's Quantum energy storage units (Julian Spector)

It’s definitely a testament to our procurement team, and the Clearway team, for the way that we work with our partners and our equipment suppliers across the board,” Park said. 

A turbulent road to success

These were only the latest ups and downs of a project that encapsulates the chaotic early phase of the American renewable energy industry. The parcel, once farmed for sugar cane by legacy Big Five” landowner Castle & Cooke, was acquired for solar development nearly a decade ago by First Wind. Before long, that company got acquired by SunEdison on its march to become the first renewable supermajor.

The drive to accumulate led to SunEdison’s undoing. When the company imploded in 2015 and 2016, independent power producer NRG acquired the rights to develop power at the Mililani site. But the project didn’t sit for long with NRG, whose board had already ousted CEO David Crane for his bets on the clean energy market.

Fund manager Global Infrastructure Partners swooped in to buy up NRG’s renewable development assets in 2018, reconstituting them as Clearway Energy. From there, it took another four years until the site was fully constructed, with the help of engineering and construction firm Moss.

Grid infrastructure takes time. But the pace of development will need to pick up if the U.S. hopes to hit its climate goals by significantly cleaning up the power sector by 2030. Now, at least, the industry is full of well-capitalized companies that can see a project through to completion, and the utility sector en masse has declared its intent to buy a lot more clean energy. New projects need not follow as circuitous a route to completion as Mililani.

Still, the macro factors that have made renewables the top choice for new U.S. power plants aren’t enough. Success requires the kind of tenacious, sweaty work seen at Mililani, to move earth and wrangle parts in spite of whatever obstacles the landscape and global trade might put up.

Julian Spector is senior reporter at Canary Media.