Construction of the nation’s largest transit microgrid is underway in Montgomery County, Md., providing infrastructure to support the Washington, D.C., suburb's ongoing transition to a 100% zero-emission bus transit fleet.

Developed with “energy as a service” provider AlphaStruxure, which will own and operate the microgrid, the project at the county’s existing 475,000-sq-ft equipment maintenance and transit operation center in Rockville will provide 5.65 MW of rooftop and canopy solar direct current generation and 6.88 MWh of battery energy storage. 

Augmenting the microgrid with a 1-MW hydrogen electrolyzer will create the East Coast’s first bus depot to produce green hydrogen on site, allowing the county Dept. of Transportation to add both battery electric and hydrogen fuel cell electric busses to its fleet. Many of these new vehicles will operate on the county’s bus rapid transit networks, which serve a significant number of low-income and minority communities.

Mortenson is the project’s design-build contractor, with WSP USA serving as engineer-of-record. Project cost was not disclosed. Scheduled to operate in 2025, the new microgrid will combine with the county’s two-year-old Brookville Smart Energy Bus Depot, its first fully constructed microgrid powered facility. They will eventually power a total of 335 zero-emissions transit buses, as well as the respective sites’ buildings and facilities.

In addition to the capability of supplying up to 2 MW of renewable energy to the region’s utility grid, the transit center microgrid will be engineered to operate in “island mode” indefinitely, ensuring uninterrupted service during extended grid or power outages and other emergency situations.

The county currently uses more than 3.8 million gallons of fuel per year to operate fossil-fuel-powered buses in metropolitan Washington’s second-largest transit fleet, with some routes up to 300 miles long. It expects the new microgrid will cut emissions by 4,000 metric tons of carbon dioxide annually.

The project received a $1.5-million "Resilient Maryland" grant from the Maryland Energy Administration. The agency expects to receive Infrastructure Investment and Jobs Act funding via the U.S. Energy Dept. for some programs.