By JENNIFER McDERMOTT

CALISTOGA, Calif. (AP) — For residents of this quaint tourist town on the northern edge of Napa Valley, the threat of wildfire is seldom out of mind. The hillside bears burn scars from a 2020 fire that forced all of Calistoga to evacuate, and the 2017 Tubbs fire that killed 22 people in wine country started just a few miles from downtown.

When fire danger required shutting off transmission lines that might spark a blaze, the town relied on a bank of generators in a popular recreation area that belched choking diesel exhaust and rumbled so loudly it drove people away.

But now Calistoga is shifting to a first-of-its-kind system that combines two clean-energy technologies — hydrogen fuel cells and batteries — for enough juice to power the city for about two days. Experts say the technology has potential beyond simply delivering clean backup power in emergencies; they say it’s a steppingstone to supporting the electric grid any day of the year.

As the system was undergoing its final tests in late May in an area that includes a dog park, ball fields, community garden and bike trail, residents said they were grateful to be guaranteed clean energy year-round. Lisa Gift, a resident who also serves on the city council, noted Calistoga is already grappling with climate change that is fueling more intense and frequent wildfires.

“Continuing to depend on fossil fuels was simply not sustainable,” Gift said. “That’s what excited me about this. It’s a clean and reliable energy solution that ensures the safety and resilience of our community.”

Energy Vault, an energy storage company based in California, built the new facility that was to come online in early June. Next year, it could be exporting power to the electric grid whenever needed once its application to fully connect is approved.

The installation sits next to where Pacific Gas & Electric used to set up nine mobile generators every year from late spring through fall. Behind a chain-link fence stand six hydrogen fuel cells standing two stories tall made by Plug Power in New York. Water vapor wafted from one of the fuel cells being tested as The Associated Press got an exclusive tour of the site as it was in final testing.

Shipping containers hold two pairs of Energy Vault’s lithium-ion batteries. Nearby, a cinder block wall surrounds a massive, double-walled steel tank that holds 80,000 gallons (302,833 liters) of extremely cold liquid hydrogen that gets converted to gas to run the fuel cells.

Utility was searching for a cleaner solution

California utilities, especially PG&E, have had to pay large settlements over igniting wildfires. PG&E began cutting power at times to reduce fire risk in 2018, one of California’s deadliest and most destructive wildfire years. It ships diesel generators to about a dozen towns to provide backup power during those periods.

Calistoga, the largest with about 5,000 people, has had its power shut off 10 times. When generators ran, they spewed exhaust with harmful nitrogen oxides, carbon dioxide and soot. PG&E considered replacing Calistoga’s diesel generators with a natural gas version that would pollute less, but opted instead for Energy Vault’s fully clean solution, said Dave Canny, the utility’s vice president for the North Coast Region.

Energy Vault CEO Robert Piconi said other communities, military bases and data centers could all use something similar, but potential customers wanted to see it function first.

“There’s a massive proof point with this project,” he said. “I think it’ll have a lot of implications for how people think about alternative, sustainable solutions.”

The fuel cell maker, Plug Power, is planning for these types of products to be its main business in a decade. Energy Vault said it’s buying clean hydrogen, produced with low or no greenhouse gas emissions, to run the fuel cells in Calistoga.

“This solution is just beautiful,” said Janice Lin, founder and president of the Green Hydrogen Coalition, a nonprofit that advocates for green hydrogen projects to combat climate change. “No noise, no emissions. And it’s renewable. It’s dumping diesel.”

A year-round clean system brings comfort

Calistoga caters to tourists with a main thoroughfare that emphasizes local shops, restaurants, tasting rooms and art galleries over franchise stories. Residents pride themselves on a smalltown vibe, and say Calistoga isn’t posh like much of the rest of Napa Valley.

Some of those residents were concerned at first about the hydrogen, which is flammable and can be explosive. Fire Chief Jed Matcham said the “very, very large tank” got his attention, too.

He collaborated with Energy Vault on emergency planning and training, and said he’s comfortable with the safety measures in place. Energy Vault’s batteries also come with alarms, detectors and piping to extinguish a fire.

The next time PG&E turns off the power to the area to prevent wildfires, it will tell Energy Vault when it’s safe to electrify Calistoga. The batteries will get things back up and running, discharging the energy stored inside them to the local microgrid.

Then the hydrogen fuel cells will take over to generate a steady level of power for a longer period. By working in tandem — the company likened it to the way a hybrid vehicle works — the batteries and fuel cells are expected to keep the lights on for about 48 hours or longer.

Clive Richardson, who owns downtown’s Calistoga Roastery and can typically be found behind the counter, drinking coffee and chatting with customers, said people in Calistoga get on edge when the winds kick up. And he knows what it’s like to have to empty out his store when power goes out — a big hit for a small-business owner.

A year-round clean solution for emergency power gives him a measure of comfort.

“This will give us far more security than we had before,” he said. “It’s fantastic that it’s come. Here we are, little ol’ Calistoga, and we’ve got the first-of-a-kind system that hopefully will be endorsed and go all over the world.”

The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.