A behemoth 132-foot-long, 80,000-gallon liquid hydrogen tank that will be used to power a first-of-its-kind renewable energy microgrid caused quite the scene – and some traffic – this week as it reached its final destination in Calistoga following a monthslong journey from Minnesota, where the chamber was built.
The tank’s arrival signals the last stages of a yearslong effort to provide a permanent solution for power outages that have heavily impacted Calistogans since 2018 when Pacific Gas and Electric Co. began implementing Public Safety Power Shutoffs in high fire threat areas. The hydrogen tank will replace the mobile diesel generators that emit pollutants and can be both unreliable and loud.
Called the Calistoga Resiliency Center, the hybrid system will rely on hydrogen fuel cells and lithium-ion batteries and will be able to independently power more than 2,000 PG&E customers on the city’s main electrical grid in the event of a PSPS.
The new microgrid project is being overseen by Energy Vault, a Switzerland-based global energy storage company PG&E hired to manufacture, install and manage the renewable-energy system. It is being built on an acre of city property on lower Washington Street next to the city’s dog park, near the Little League field.
“This is a part of our robust microgrid solution offerings,” said PG&E spokesperson Paul Doherty. “Microgrids are playing an increasingly important role in enhancing resilience for not only critical facilities, but for communities.”
Working with companies like Energy Vault to integrate new technologies as they are doing to power Calistoga, he said, will allow the utility “to pave the way for more microgrids to be deployed” throughout the PG&E service area of Northern and Central California.
After the Tubbs fire in 2017, PG&E began conducting PSPSs when weather forecasts called for low humidity coupled with high winds. Calistoga, along with nearby areas including Angwin, Placerville and Colfax, had been especially vulnerable to the fire-related outages. In these heavily affected cities, PG&E has worked to create eco-friendly “resiliency zones.”
Following the frequent blackouts that affected the city, in 2020, PG&E constructed the temporary microgrid (now being replaced) that used mobile diesel generators to provide emergency backup power to downtown Calistoga and its surrounding neighborhoods. Calistoga customers living on the west side of the Napa River weren’t among those that the microgrid could power and, according to Doherty, neither would they receive power from the new microgrid, which will energize the same footprint.
In early 2022, PG&E began soliciting proposals for the hydrogen-powered microgrid. The utility company has been authorized by the California Public Utility commission to spend up to $46.3 million on the project over a span of 10.5 years.
According to a statement from Energy Vault, the microgrid will be able to provide power using cleaner energy continuously for up to 48 hours and is expected to be completed and fully operational before the end of this year.
“This breakthrough collaboration between PG&E and Energy Vault provides sort of a template for renewable community-scale microgrids as we continue to build that portfolio of non-diesel, not fossil-based, temporary generation solutions,” said Doherty.
Upon its completion, the system, according to an Energy Vault statement, will be the largest utility-scale green hydrogen energy storage project in the U.S.
The microgrid, in addition to being less polluting than the diesel generators, will also be permanent – the generators were hauled in and out – and will be quieter as well. It will be powered by renewable hydrogen that is produced through the electrolysis of water.
“This process is powered by entirely by renewable energy, so it generates no polluting emissions into the atmosphere and is the cleanest and most sustainable hydrogen,” the Energy Vault statement said of the system that was designed by the company specifically to meet the needs of the city of Calistoga and of PG&E.
Craig Horne, a senior vice president at Energy Vault, addressed some safety concerns that have circulated on NextDoor.com about the safety of the hydrogen tank, saying numerous industry studies have shown the system is safe, and strict hydrogen-handling protocols were implemented in the Calistoga liquid tank design.
“When you look at the potential consequences from different things that could happen with the tank in regard to safety, it's similar in nature to the corner gas stations there in Calistoga if you look at the probability of an event and the extent of the impact,” Horne said. “There’s no difference.”
He added that the hydrogen, which has not yet been loaded into the tank, will always be handled by trained professionals in a facility engineered for safety and that the liquid hydrogen is in an insulation space, inside an outer tank which provides a “thermal shield.”
