In June 2022, local and state leaders, organizations, partners, and the public commemorated the successful commercial operation of a collaborative and innovative project in Humboldt County – California’s first 100% renewable energy, front-of-the-meter, multi-customer microgrid. The Redwood Coast Airport Microgrid (RCAM) was designed to provide energy resilience for the regional airport and U.S. Coast Guard Air Station during power outages, and electricity to the Redwood Coast Energy Authority’s (RCEA’s) customers while the electric grid is operating normally.

No one could have expected such rigorous real-world testing of the system so soon, but on December 20, a 6.4 magnitude earthquake knocked out power to more than 70,000 electric customers in Humboldt County and the microgrid automatically and seamlessly disconnected or “islanded” from the electric grid as planned.

“The Redwood Coast Airport Microgrid performed flawlessly during and after Humboldt County’s strong 6.4 temblor last December,” said Peter Lehman, Founding Director of the Schatz Energy Research Center. “Operating through a worst case of difficult conditions—the winter solstice, rainy weather, a partially discharged battery—the microgrid seamlessly provided power to the airport and the Coast Guard Air Station, keeping one of the County’s lifelines up and running for nearly 15 hours during a widespread grid outage.”

The microgrid was called into service multiple times after the earthquake due to winter storm outages, ranging from 30 minutes to 8 or more hours each time. The seamless operation allows county staff to focus on critical tasks and spend less time managing backup generators at the site.

The lessons learned from this innovative project is the need to fine-tune when and how much energy will be discharged from the batteries into the grid. The microgrid includes two main components: a smaller net-metered (NEM) solar array, and a larger solar+storage system. On a typical day, the energy generated from the NEM array feeds directly to the airport and other electric meters to offset their electricity usage. The larger solar array generates energy to store in the batteries and delivers power to California’s wholesale energy market when demand and electricity prices are high. The energy provided to the wholesale market serves either RCEA customer load or provides critical ancillary services to the California Independent System Operator (CAISO), but in all cases the timing is when the grid needs it most. By storing power in the batteries, the microgrid is able to provide clean energy when demand is highest after the sun has set.

The one-two punch delivered by the earthquake and subsequent winter storms prompted RCEA to adjust its operating protocols to hold battery capacity at a 60% minimum reserve when conditions forecast the potential for an outage, rather than letting it go down to around 25% during energy market participation. Although earthquakes remain unpredictable, this “storm watch” approach can improve performance with forecasted weather conditions.

The RCAM project was developed and is managed through a first-of-its-kind partnership between the County of Humboldt, the Redwood Coast Energy Authority (RCEA), the Schatz Energy Research Center at Cal Poly Humboldt PG&E, Schweitzer Engineering Labs, Tesla, Inc., The Energy Authority and TRC.

RCEA and its partners will continue efforts to prepare the region for future challenges and help essential services stay online when they are most needed.