Air Station Miramar: Marine Corps Microgrid Adds New Battery Energy Storage System
After seven years of development, the microgrid at Marine Corps Air Station (MCAS) Miramar near San Diego has achieved yet another milestone with the addition of a 1.5 MW / 3.3 MWh battery energy storage system (BESS).
Designed and installed by Schneider Electric, the BESS increases the microgrid’s energy storage capacity by 1,500kW / 3,300 KWh.
In addition to the BESS, the Miramar microgrid includes a 6.5-MW diesel and natural-gas fired power plant, 2 MW of solar, a 2-MW diesel backup generator and a 3.2-MW renewable landfill gas energy generator. Renewable natural gas (RNG) is generated at the city of San Diego’s landfill and is provided via a power purchase agreement by Opal Fuels, a U.S. producer and distributor of RNG.
The BESS will enable MCAS Miramar to reduce its demand on the local power grid and maximize the use of the renewable landfill gas energy generator when the system is disconnected from the grid in island mode.
BESS improves base resilience and reduces diesel consumption
“Most BESS systems are used as grid forming assets,” Megan Blucher, engineering energy branch manager and interim utility and energy manager at MCAS Miramar, explained in an emailed response to questions from Microgrid Knowledge.
Grid forming assets set the voltage and frequency of the grid, whereas grid following assets adjust to match existing grid conditions.
“Our power plant uses a combination of diesel and natural gas generators as the grid forming assets. The other distributed energy resources that make up our microgrid system, such as the BESS, PV, and other generation sources, are all used in a grid following mode while islanded,” she added.
The BESS, which utilizes lithium-ion nickel manganese cobalt (NMC) batteries, will store energy from the grid when it’s economical to do so without increasing the base’s coincident or non-coincident peak demand charges.
It will also correct the frequency of the overall system when islanded, creating stability by ensuring that block loading of the grid forming assets does not occur. Block loading is the gradual increase of load on a generator until it reaches its full capacity.
In addition to providing more power in islanding situations, the energy stored in the BESS will be the primary energy source used for peak shaving, a job previously handled by the microgrid’s diesel generators.
The diesel generators will still be used for islanding mode, load following and to black start the system, Blucher said, however the BESS will cut the system’s consumption of diesel fuel.
“The diesel generation will now primarily only be used while islanding for stability purposes,” Blucher said.
A good neighbor on hot days
In recent years, the Miramar microgrid has helped California utility San Diego Gas & Electric (SDG&E) avoid several power emergencies. During times of peak demand, the microgrid is disconnected from the local power grid and put in island mode.
This quickly reduces grid load, mitigating the need for rolling blackouts and enabling SDG&E to continue to provide electricity to local homes and businesses during power emergencies or when demand surges.
Even in island mode, base operations continue as normal thanks to the microgrid, which can fully power the 23,000-acre facility for up to 21 days.
“The addition of the BESS will not only increase our generation capacity by 1.5 MW, but also allows us to use the maximum landfill kW output while islanding from the local utility,” Blucher added. This is because the batteries can load follow like diesel generators.
By expanding the base’s power generation capacity, the BESS will further reduce Miramar’s demand on the grid so SDG&E resources can be used to meet the local community’s power needs on the hottest days.
7 years in the making
The addition of the BESS to the MCAS Miramar microgrid has been in the works for seven years, Blucher said.
Some of that time was spent managing the complexities associated with the project’s funding, which came from a California Energy Commission grant through a Cooperative Research and Development Agreement with the University of California, San Diego.
Then there were some technological challenges to be overcome, including manufacturer defects with the initial set of batteries delivered by an early-stage partner not involved in the final project. The team ultimately tapped ELM for the battery system that was used.
Changes were also made to the U.S. military’s United Facilities Criteria (UFC) during the BESS’ design and construction phases. The UFC outlines planning and design requirements, as well as material requirements, for all Department of Defense-led construction projects.
The UFC changes, specifically related to lithium-ion batteries, forced the team to relocate the BESS to a site that would meet the new requirements and could still be connected to the base’s microgrid.
The evolution continues
The U.S. Army, Navy, Air Force and Marine Corps have all made significant investments in microgrid technologies in recent years. The Army plans to build a microgrid at each of its bases worldwide by 2035 and the Navy and Marine Corps have both made similar commitments.
Built by Schneider Electric and Black and Veatch and commissioned in 2021, the microgrid at MCAS Miramar is considered by many to be a model for military installations –– and the microgrid will continue to evolve over time, according to Bulcher, who said the team has proposed projects to expand the system’s battery capacity and solar generation capabilities. They are also looking to improve the microgrid’s communications and control infrastructure.
