The system that went in is expected to meet about 60 percent of the island’s energy needs – and that will save the taxpayers money. Yes, the project cost $3.6 million, but with diesel Alcatraz was spending about 76 cents for every kilowatt-hour of electricity used. Now, even factoring in the capital costs of the solar power system – buying it and installing it – that figure will drop to 71 cents, NREL said. And, of course, the solar contribution is a whole lot cleaner.

Alcatraz needs power because it draws 1.4 million visitors annually to tour the pen and visit its museum and retail store. The funny thing is, Alcatraz was a prison – with notorious inmates like Al Capone, George “Machine Gun” Kelly and Robert Stroud, the “Birdman of Alcatraz” – for just 30 years, from 1933 to 1963. That means it has now had a longer run as a tourist attraction  than as a prison – this reporter visited Alcatraz on a school field trip in the mid-1970s, not long after Native American protesters ended a long occupation of the island.

image via Byron Stafford/NREL

Asmus reveals in his Alcatraz essay that for a time Alcatraz relied on power from the utility Pacific Gas & Electric, delivered from San Francisco via underwater cable. But when a ship’s anchor accidentally severed the line, Alcatraz turned to diesel generators.

image via Princeton Power Systems/Pike Research

Asmus reports that the generators are still there, providing power when needed as part of a microgrid that operates with gear from Princeton Power Systems. The solar panels – NREL says there are 1,300 of them, adding up to 307-kilowatts; Asmus puts the size of the system at “nearly 1,000” panels and 350-kW – and the backup generators tie into eight Princeton Power Systems inverters, a 1,900-kilowatt-hour bank of lead-acid batteries and a site controller system.

The end result, NREL said, is a system that “produces close to 400,000 kilowatt-hours of electricity a year, reducing carbon dioxide (CO2) emissions by about 337,000 kilograms a year.”

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