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To say Humboldt County is beautiful is an understatement.
It is situated along the northern California coast hard against the Pacific Ocean, with old growth redwoods rising thick out of the mountainous landscape. Mild summers are the norm. Deep sea currents beat ceaselessly against ancient rock.
And Humboldt County is a dangerous place, isolated and vulnerable due to many natural factors. The danger comes from the high possibility of forest fires, floods, earthquakes, tsunamis, and landslides. The relative isolation stems from having only three highways, each of them also at risk to closures due to the aforementioned weather events.
All of this together makes Humboldt County ideal for a zero-carbon microgrid to boost energy resiliency and sustainability at its key transportation points along the Redwood Coast. If all else should fail, the Redwood Coast Airport and U.S. Coast Guard Sector Humboldt Bay Air Station—which oversees hundreds of miles of coast from Sonoma County to Oregon—need to operate at full capacity. No other option is acceptable.
“We are prone to natural disasters; it’s not a question of if, it’s a question of when,” said Peter Lehman, founding director of the Schatz Energy Research Center at California State Polytechnic University, Humboldt (Cal Poly Humboldt). If any of those things happen, from tsunamis to devastating wildfires, he added, “The only artery is the airport. If there’s no power, the airport and the Coast Guard can’t operate.”
Construction on the Redwood Coast Airport Microgrid—delayed a year by COVID-19 workforce and supply chain concerns—began more than a year ago and was completed in late 2021.
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The Redwood Coast Energy Authority, one of California’s state-approved Community Choice Aggregators, stepped up as the generation system owner/operator for the airport microgrid and leases the land where the microgrid is located from Humboldt County government. Payments on the lease are made by supplying zero-carbon electricity to the county, Lehman noted.
The RCEA worked with Schatz Center researchers and the local utility to come up with the microgrid plan. It took these relationships interconnecting and about four years of work to put all the pieces together.
“To say it’s complicated is an understatement,” Lehman added. “This is the first front-of-the-meter, multi-customer microgrid in the PG&E (Pacific Gas & Electric) service territory.”
Well, not all of the microgrid is front of the meter. The 2.5-MW solar photovoltaic array is allocated two ways—2.2 MW is front-of-the-meter and generates power directly plugged into a 2.3-MW/8.8-MWh energy storage system consisting of three Tesla Megapack batteries, which is selling into the California Independent System Operator (CAISO) market.
The remaining 300 kW solar is behind-the-meter, and it directly supplies the airport facility with electricity as the lease payment. The microgrid controller communicates directly with PG&E’s distribution control center and CAISO, and the microgrid site includes electric vehicle charging stations capable of demand response services.
All of that solar and battery almost always will be enough to sustain the facilities during extended grid outages while lowering the carbon emission profile.
“The airport has a diesel generator backup, the Coast Guard Air Station has a diesel generator, but they depend on diesel fuel getting in,” which is no certainty given the sometimes harsh conditions, Lehman pointed out. “What is true now is that the diesel generators almost never need to come on. They will serve as very deep backup.”
The Schatz Energy Research Center and Redwood Coast Energy Authority have spent decades working on ideas to “green” the energy supply in response to the climate impacts in the region.
The first microgrid installed in Humboldt County involved a collaboration between the Schatz Center and the Blue Lake Rancheria. This microgrid provides power resiliency to the tribal campus in response to the same weather and geological dangers there.
The nearby Blue Lake Rancheria project has been in operation for about five years. It includes a 420-kW solar PV array, 1-MW, 2-MWh battery storage system and legacy 1-MW diesel generator.
“The Rancheria serves as a Red Cross disaster shelter for Humboldt County,” Lehman said. “They have food service and, in the event of an emergency, people go there. It has served that purpose several times and proved to be a life saver.”
One could hardly ask more of a microgrid. The whole purpose of such a system is to provide energy resiliency for mission critical services in the face of disaster. Given California’s vulnerability to drought, wildfire, and seismic activity, this is happening more and more. “Welcome to the future,” Lehman observed.
The future also is about learning from the past, and it must be noted that the Redwood Coast Airport Microgrid is a research and demonstration project. The Redwood Coast Energy Authority and Schatz Center researchers are working with PG&E, CAISO, and others to test how a fully automated, unmanned, and purely renewable microgrid system can function as the primary energy supply and also deliver services to the grid without endangering it.
“This is the first time that PG&E is allowing a third-party to form an islanded section on its distribution network,” Lehman said. “As you can imagine they are nervous about that. To their credit, they saw that this was important development, and they worked with us.”
In this direct current-coupled system, the solar PV power generated goes directly to the battery at the airport. Downstream of the battery is an inverter bank to flip the power to alternating current for distribution on the grid.
Every day since operations began has offered new lessons and successes to instill confidence in the project going forward.
“We’ve learned how to do it,” Lehman said. With inverter-based generation, fault protection is more difficult. “With an inverter, we don’t have infinite fault current. That was an issue we had to solve.” Schweitzer Engineering Laboratories and Tesla also worked with Schatz, RCEA, and PG&E on the solar-storage-controls microgrid project.
Lehman is proud of the team effort and the crucial learnings it’s producing. “We have plowed a heckuva lot new ground to do this,” he said.
Read the rest of our EnergyTech Mission Critical Microgrids Series.
The Pittsburgh International Airport Microgrid
Microgrids for War Zones and Emergency Rooms
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(Rod Walton, senior editor for EnergyTech, is a 14-year veteran of covering the energy industry both as a newspaper and trade journalist. He can be reached at [email protected]).
