Welcome to Alcatraz: One of the largest microgrids in the United States

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Microgrids are small-scale electricity grids that can power everything from university campuses in urban settings to buildings in hard-to-reach neighborhoods — like Alcatraz Island, in the San Francisco Bay.

Alcatraz is famous for its high-security penitentiary. In its day, during the 30 years it was open in the mid-20th century, Alcatraz housed some of America’s most dangerous criminals. The prisoners are long gone, but today Alcatraz Island is a popular California tourist destination. And it has gained new fame for having one of the largest microgrids in the United States.

Solar panels on top of Alcatraz prison (National Park Service/Al Greening)
This 305-kilowatt solar array on top of the main prison building helps power Alcatraz Island. (NPS/Al Greening)

The Alcatraz microgrid is a hybrid system that utilizes both solar and diesel power. Solar panels generate electricity that is fed to storage batteries and power inverters. When the batteries run down, diesel generators kick in, recharging them until the sun comes out and the solar panels can take over.

Since its 2012 installation, the microgrid has reduced fuel consumption by 45 percent, big savings for the National Park Service, which manages the island. It also greatly reduced carbon emissions in the bay.

That’s a good thing for the wildlife on the island. Alcatraz was named by Spanish explorers after a type of seabird that once nested there.