Healdsburg debuts biggest floating solar farm in nation

Over the last four months, two ponds at Healdsburg’s wastewater treatment plant were transformed by workers assembling rows of solar panels and pushing them out one by one to float gently on the water’s surface.

The project covered roughly half the combined 15 acres of ponds with 11,600 panels. It is likely the largest floating solar farm in the United States, the builders said, and will provide 8% of the city’s annual electrical needs.

The farm puts Healdsburg’s municipal power utility, itself a unique electricity model in the county, at the cutting edge of solar energy development. Floating solar farms are quickly gaining popularity in the U.S., backers say, particularly in places like Sonoma County where the price of land is dear.

“You couldn’t go out and buy a bunch of vineyard land for a solar project and make it economical,” Healdsburg utilities director Terry Crowley said. Floating solar farms are cost effective as the price of solar panels continues to drop, and are easy to build, Crowley said. Workers began assembling this one in mid-October and mostly finished by mid-January.

“It’s just new to California,” he said.

Windsor two years ago deployed a smaller floating solar installation to power its wastewater treatment plant. The new Healdsburg project is set to provide enough power to cover the annual supply of roughly 1,120 households.

The two-sided panels capture the sun’s energy as it strikes them from above, and also from below when sunlight reflects off the water. Metal cables anchor the floating farm to the ponds’ banks, while floating walkways give technicians and wastewater treatment plant workers the ability to check the panels.

On Thursday, tracks from what looked to be a raccoon’s dust-covered paws arced across one panel. Ducks sat on the farm’s last row of panels before open water.

Cleaning bird droppings will be part of the panel upkeep, Healdsburg wastewater treatment manager Rob Scates said. But that work will be left for White Pine Renewables, the company that owns and operates the project. The nearly 4.8 megawatt solar installation — the first local solar project for Healdsburg — will provide electricity to the city under a 25-year contract.

Crowley said the project is set to have no net increase on customer rates, which are set by the City Council and are up to 40% or 50% below PG&E’s. The city’s electrical utility serves a total of 5,739 metered customers, according to its website.

It was a desire to shade the recycled wastewater, not capture the sun’s energy, that first led city officials down the road to the solar installation, Crowley said. The city hoped to prevent algae from blooming in the two ponds — which hold treated water from the city’s municipal sewer system.

Healdsburg gives the treated water away to vineyards — that’s the only permitted reuse for now, Crowley said. Preventing algae growth could allow Healdsburg to sell the recycled water to new agricultural users like fruit orchards or cattle pastures, monetizing the recycled wastewater to generate more savings for the city.

The city looked at purchasing larger numbers of floating black plastic tiles to create shade — which still bob in the uncovered parts of the ponds. But the solar farm was a way to shade the pond, prevent evaporation and at the same time, help power Healdsburg, Crowley said.

The city’s 25-year power purchasing agreement is with White Pine, which along with co-developer Noria Energy paid to build the project. City officials don’t know what the project cost the developers, Crowley said, though their estimates run anywhere from $9 million to $12 million.

The project brings Healdsburg a significant step closer to reaching its goal of securing 60% of its energy supply from renewable sources by 2025 — a more aggressive benchmark than the state’s equivalent 2030 mandate. With the floating solar farm, 48% of Healdsburg’s electricity comes from renewable sources, Crowley said.

The largest share of that renewable supply — 40% of the total load — has come for decades from The Geysers geothermal fields in the Mayacama Mountains, visible from the treatment plant.

Through a regional power wholesaler, the city also has a deal for electricity from a new solar plant in Southern California that is set to come online next year, Crowley said. With that, he projects Healdsburg will hit 56% renewable energy by the end of 2022.

Healdsburg operates the lone municipal utility in Sonoma County, meaning the city is responsible for the power supply as well as grid equipment and maintenance within city limits. Outside the city, PG&E is the dominant utility in the region, though Sonoma Clean Power, the public agency, now purchases electricity for 87% of the eligible customers in Sonoma and Mendocino counties.

Like other California municipalities, including Sonoma County, Healdsburg is interested in developing microgrids — renewable energy-based electrical systems that can operate independently of the state’s utility giants.

During the 2019 Kincade fire, Healdsburg lost electricity for four days, Crowley said. One day soon, the solar panels at the wastewater treatment plant could become part of a microgrid that could power the city’s emergency services building, and perhaps even a gas station and grocery store, Crowley said. Such capabilities could stave off disaster in the next extended blackout.

A microgrid needs battery technology to store the solar energy. While panel costs have plummeted, battery technology remains expensive. The city has no concrete plans for installation yet but would like to find a company to contract with within the next two years, Crowley said.

Local governments statewide are weighing steep battery costs against the value of electrical independence, said Andrew Campbell, director of the UC Berkeley’s Energy Institute at Haas Business School. Climate change-fueled natural disasters make a strong case for energy independence for critical facilities, he said, even while the public pushes utilities like PG&E to disaster-proof the wider electrical grid.

“The case for keeping those (essential buildings) online is so high it’s worth paying a higher price” for a microgrid, Campbell said.

In the meantime, the field for floating solar farms like Healdsburg’s is growing.

“The projects are getting more frequent and also larger,” Jon Wank, Noria Energy’s CEO, said. Along with land costs, it is often cheaper to float panels than build ground installations, he said.

“When we started these two years ago 500 kilowatts would’ve been large,” he said. Windsor once had the state’s largest plant, a producer of 1.8 megawatts built in 2019. Healdsburg’s new plant produces nearly 4.8 megawatts, edging out a New Jersey project that produced 4.4 megawatts for the title of nation’s largest.

Wank does not think Healdsburg will get to wear the belt long. “The over/under bet is a year,” he said.

You can reach Staff Writer Andrew Graham at 707-526-8667 or andrew.graham@pressdemocrat.com. On Twitter @AndrewGraham88

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