The jaunt Katsanes takes is also a quick reminder of what lures many of the nearly 1.5 million people who annually visit Alcatraz, the centerpiece of the Golden Gate National Recreation Area (GGNRA) and the prison that, from 1934 to 1963, housed hardened criminals such as Al Capone and George “Machine Gun” Kelly.

Atop the blustery roof, one of the most conspicuous features is a red cross that marks the vent hole that inmates Frank Morris and John and Clarence Anglin clambered through in their 1962 escape attempt—an event that was cemented into popular culture by the Clint Eastwood movie "Escape from Alcatraz."

But what prompts Katsanes’ treks to the roof is hardly an impulse for sightseeing or historic reverie. Rather, Katsanes has the Sisyphean job of making sure the 959 solar panels installed here in late 2011 are clear of bird poop—no small feat given that the island is an exceptionally active nesting site for around 40 different species of birds. Unglamorous as it is, it is work that truly matters: The sort of shading caused by the buildup of bird guano on solar panels can drastically reduce the amount of electricity produced.

In some ways, it’s appropriate that the introduction of solar power to one of the most recognized places in the nation involves some ongoing drudgery. “Everything on Alcatraz is a challenge,” says Laura Castellini, the sustainability coordinator for the GGNRA, who had a leading role in planning the project. Indeed, everything involved with building this rooftop solar power plant—be it ferrying materials and workers to and from the island or designing it to meet the nettlesome energy needs on the island—was difficult.

Not surprisingly, one of the biggest challenges was how to incorporate a renewable energy system that could meet the bulk of Alcatraz’s electricity requirements without negatively impacting its historic qualities. “These projects can be a poor marriage between historic preservation and new technologies,” says Paul Scolari, who was a historian at GGNRA when the solar plans were being developed and who worked with the California State Historic Preservation Office to review the proposals. Fortunately, in pulling it off, Alcatraz is showing that it’s a union worth pursuing.

What prompted the greening of Alcatraz involves a nugget of little-known history. In 1969 a ship dragging its anchor in the San Francisco Bay severed the underwater power line connecting Alcatraz to the city. Suddenly cut off from the grid, the prison was forced to keep the lights on by generating electricity from burning coal and fuel oil, and, most recently, using diesel-powered generators.

Compared to the ease of paying a monthly bill to the local utility, the generators were an expensive hassle: Shipping in 60,000 gallons of diesel every year ran up an annual tab of $700,000.

It was also very dirty. In fact, in 2008 the GGNRA unveiled a climate action plan that involved measuring the greenhouse gas emissions from the entire park, which includes Muir Woods National Monument, the Presidio of San Francisco, and many other facilities. “That was eye-opening, because the carbon footprint of energy generation at Alcatraz was almost as high as the rest of the park combined,” says Castellini.

As they puzzled over ways to get cleaner and cheaper energy, there was initially some thought about once again running undersea cables across the nearly 1 ½ miles to San Francisco. But that idea was nixed when the utility said it wanted redundant cables—meaning a main cable and a backup—a requirement that doubled the already high price tag.

“That kind of left solar as the only alternative if we wanted to reduce diesel use,” says Castellini. As luck would have it, while Alcatraz officials were exploring various ways to kick the site’s diesel habit, the American Recovery and Reinvestment Act, better known as the stimulus, was making money available for a wide variety of renewable energy initiatives. Alcatraz was able to put together a proposal quickly enough to garner the $8.7 million required to build a 307-kilowatt photovoltaic (PV) system, along with enough batteries to store energy for use on cloudy days and at night.

Even with financing in place, nothing is easy on Alcatraz. Aside from the technical challenges of designing the solar plant to meet unpredictable surges in energy needs—such as when recently installed elevators start moving—there were significant historic preservation considerations. The plan was to install solar panels on both the roofs of the Main Cellhouse and what’s known as the New Industries Building, the laundry building where Capone once worked a sewing machine.

The Main Cellhouse was never considered problematic, because the building is at the summit of Alcatraz, and the roof has a parapet shielding the panels from view. But putting panels on what was once the laundry building posed a challenge. “The solar panels on the laundry building were going to be visible from places on the island and around the bay,” says Scolari. “Our concern was that they would create a jarring visual element in the historic environment.”

But before the prospect of visible solar panels on the historic building had a chance to derail the project, progress in the solar industry solved the problem. New panels with higher efficiencies—meaning each panel converts a greater proportion of sunlight into usable electricity—meant that the amount of required roof space was slashed to the point that the panels on the Main Cellhouse were sufficient.

While the installation was the biggest hurdle, being sensitive to the historic fabric of Alcatraz still animated all the decisions around the solar design and construction. “One of the main concerns was not to degrade the historic aesthetics,” says Kirby Hays, an operations manager at Hal Hays Construction, the company that built the solar plant. “The last thing you want to do is come in and deliver a great system and take away from that.”

That meant taking obvious steps, like not putting panels over the famous escape hole or doing any damage to the skylights on the roof. More subtly, it altered how the panels were affixed to the roof. “We had to get creative about how we attached the system and still handle the wind load out there,” says Hays. Normally, Hays would have bored holes into the roof, but in this case, the company opted to use a ballasted mounting structure that didn’t require any drilling. “It being historic concrete, we were limited,” he says.

More consequentially, to ensure the panels couldn’t be seen, they had to be placed at an angle that reduced the amount of electricity they would ideally generate. Although compromises were required, Laura Castellini says the solar project is working as hoped. Admittedly, there have been a couple of times when the solar power plant, which first started operating in February 2012, struggled to function properly due to its complex design and the difficult salt-air conditions on the island.

Still, the system is expected to meet more than 100 percent of Alcatraz’s electricity needs during the summer and 40 percent of what’s required in the winter. Although that means that the diesel generators haven’t been completely booted off the island, the estimated 428,000 kilowatt hours of clean energy produced annually should reduce Alcatraz’s carbon emissions by 379 metric tons and, importantly, trim $50,000 from its operating budget.