US Army’s Fort Hunter Liggett Microgrid Answers the Call to Duty During Grid Outage
The new renewable energy microgrid at the Fort Hunter Liggett (FHL) was put to the test in January when a grid malfunction cut off power to the U.S. Army garrison in central California.
The garrison is located at the end of the utility grid in a remote part of the state.
On January 13, malfunctioning regulators shut down Pacific Gas & Electric’s (PG&E) Jolon substation, which feeds the military base. Distribution lines and regulation equipment from nearby King City couldn’t keep pace with the increased load and the Army installation would have been plunged into darkness without its microgrid.
Instead, the microgrid automatically islanded, powering critical facilities, including FHL’s headquarters and daycare facility, with the on-site 3.5-MWh photovoltaic solar system and 2.5-MW/5-MWh battery energy storage resources. Islanding means the microgrid disconnected from the main grid and was able to provide on-site power.
The microgrid operated without issue for seven days straight, according to Amy Phillips, a civilian in the FHL Public Affairs Office.
“The microgrid dynamically powered what was requested by the garrison commander,” Phillips said in an email response to questions from Microgrid Knowledge.
She noted that the microgrid was even able to provide services that it was not designed to do.
“The system is designed to bring and shed loads programmed into it automatically,” she explained. However, “we operated it in a hybrid mode, manually controlling loads to startup and/or shed while keeping parts of its automation online for protection in other areas.”
Microgrid powers critical services
Fort Hunter Liggett celebrated the completion of its $21.8 million microgrid installation in August. It is touted as the Department of Defense’s first-ever microgrid fully powered by renewable energy.
There are no carbon-based energy sources connected to the microgrid.
The outage happened to coincide with a planned microgrid test scheduled for January 20-21. The test included software updates and was designed to assess the microgrid’s functionality.
“This was a great opportunity to test our system endurance during a real-world situation,” said Michelle McLaughlin, the deputy to the Garrison Commander. "The microgrid system did exactly what it is designed to do, powering our critical facilities during power outages to continue our mission."
The microgrid was designed and built by Ameresco, in collaboration with the U.S. Army Corps of Engineers, Lawrence Berkeley National Laboratory and other government and private sector partners. The base is located in Monterey County.
Ameresco has not officially handed the microgrid over to the Army, according to Phillips, however the company has “been very helpful in keeping the installation operational and assisting us in addressing issues as we are nearing the project completion.”
The next step is for the California Energy Commission to commission the microgrid. Commissioning is the process of ensuring the microgrid’s equipment is designed, installed and operating correctly and that the utility has given approval for the system to operate connected with the grid.
Diesel generators also deployed
The garrison’s diesel generators, which are not connected to the microgrid, were also engaged during the outage, supplying power to portions of the base not covered by the microgrid.
The microgrid is capable of operating for up to 14 days on the connected solar and energy storage systems. However, when it became apparent in late January that the PG&E fix would take significant time, and that power could not immediately be restored to the garrison’s housing area, Col. Stephen Trotter, Garrison Commander at Fort Hunter Liggett, authorized PG&E to install two large free-standing generators in the garrison’s cantonment or housing area. The generators were not integrated into the microgrid.
“As the weather was changing and solar windows diminished, there was concern that we could not generate enough power to run selected functions at the base and charge batteries for evening operations,” Phillips said.
The PG&E generators were turned on January 27, taking over for the renewable energy microgrid.
Power issue just resolved
Fort Hunter Liggett is no stranger to grid disruptions. The area is frequently impacted by wildfire-driven power outages.
This, along with the Department of Defense’s goal of supplying 100% of the mission critical load with on-site power by 2030, was a big motivating factor for installing the microgrid.
“If it wasn’t for our microgrid, we’d be in much worse shape,” said Peter Bosmajian, FHL’s director of public works. “It’s been responding well with some tweaks and doing what it’s supposed to do.”
Prior to the January outage, the Army indicated it would add additional battery storage and upgrade some of the older solar panels connected to the FHL microgrid, increasing the garrison’s resilience.
Philips said that PG&E repairs to the Jolon substation are complete and FHL was reconnected to the grid on February 26. The reconnection process required a temporary power disruption and inspection process. PG&E is in the processes of removing the large diesel generators installed to provide temporary power.
“It’s amazing to see the professionalism and teamwork of the garrison staff and tenants,” Col. Stephen Trotter, Garrison Commander at Fort Hunter Liggett, said in a statement. “This incident, without a doubt, proved the resiliency of our community. You know, it truly warms my heart to see our community come together to keep things going.”
