From 1934 to 1963, the Alcatraz Federal Penitentiary was the preeminent prison of the United States. Indeed, it was declared inescapable. Surrounded by the cold, rapid waters of the San Francisco Bay, a mile from the coast and outfitted with advanced security systems, officials believed that inmates would never escape its concrete walls — at least not alive.
Five inmates, however, did escape. Their whereabouts remain unknown, and officially they are presumed drowned. But a tourist, as he crosses the bay on a ferry from Fisherman’s Wharf, might consider an alternate ending. He looks up at the prison and down at the bay. He considers the water temperature and the distance to the coast. He thinks he could make it.
What’s important to the National Park Service is that, in this moment of wonder, he does not think about solar power. But as he and a million other tourists step foot onto Alcatraz Island this year, they are visiting a 100-year-old structure that is powered in part by a solar array. Only a lighthouse offers a view of the 959 SunPower panels on the cell-house roof, and officials say that’s the way it should be.
“Because Alcatraz is a historic landmark, we couldn’t alter that by putting on this massive installation of solar panels that were visible, even from the city,” says Alexandra Picavet, a spokesperson for the park service’s Golden Gate National Recreation Area. “All of the solar panels are below the parapet wall.”
That may sound simple enough. Just put the panels below the parapet wall. But when it came to the racking, engineering challenges came from two directions: environmental conditions — primarily the wind, which also contained corrosive salt — and the historical integrity of the building.
SunLink, a Bay Area balance-of-system components provider that prides itself on its ability to solve difficult engineering problems, was brought in to design the racking. The company had worked on other high-profile landmarks — Google headquarters, the San Francisco International Airport and the Atlantic City Convention Center — but nothing quite as well known as Alcatraz.
The prison sits high in the middle of a bay. The wind sweeps in from the Pacific Ocean, funnels through the steel beams of the Golden Gate Bridge and shoots directly at “The Rock.” “In engineering wind parlance, it’s in what’s called an ‘Exposure D,’” says SunLink CEO Chris Tilley. Wind exposure category D is a designation for areas that face the highest wind loads.
The prison roof reaches heights of 40 feet and experiences a wind load similar to a coastal lighthouse. Leaning on extensive research and development, SunLink went to work developing the best system for the former prison.
This wasn’t the first time the park service had tried to install solar on Alcatraz, according to the National Renewable Energy Laboratory, which collaborated on the solar projects then and now. In the 1990s, contractors had installed some mounting before a group protested the array, which would have been on the industries building, a place where Al Capone ran a sewing machine and Machine Gun Kelly did the laundry. The protesters said the installation would be visible.
When funds became available through the American Recovery and Reinvestment Act, the $3.6 million project got a second chance. The park service and NREL sought to put a 307-KW photovoltaic installation on the roof of the cell house. The electricity would run into 2,000-amp-hour battery strings (storing power for cloudy days) and supplanting energy created on the island by a pollution-spewing diesel generator. The island is not connected to the mainland for power, which a misplaced anchor took care of decades ago.
But in addition to challenges with wind and visibility, the cell house itself has quirks. It’s an ancient concrete structure that wasn’t built with the same building codes used today.
“When you put a solar system on a building like that, you need to make sure you’re not damaging it in any way,” Tilley says. “Understanding what the materials are and how to attach from an engineering point of view — all of those things can be calculated based on tests or other things to make sure there won’t be a problem with the building.”
The company used its SunLink RMS mounting system as a base product, one which Tilley says has been extensively tested in wind tunnels and is made from aluminum and stainless steel. It also mounts panels at 5, 10, 15 and 20 degrees. At the time of the installation, RMS was SunLink’s primary product. The company now distributes Core RMS for tilts less than 10 degrees and in extreme conditions, and Precision RMS, with feet that adjust on-site to accommodate rooftop anomalies, enhancing the company’s ability to install at irregular sites.
Tilley says that each SunLink installation is specific to the project, though, because of the interchangeable components in each system. “You may have a strong link in one place because you really need it for this project, but the basic geometry of the system is the same,” he explains.
But the solution for Alcatraz also required custom components, which differentiates it from nearly all of SunLink’s previous installations. One such custom piece was the lateral link, which connects subsegments of an array. Because the park service wanted a certain size system on the roof, nearly all the available roof space had to be used to place solar panels. This custom lateral link allowed SunLink to maintain the structural integrity of the system and make it stronger, while installing over deep drainage crickets that installers would normally avoid.
“One of the key aspects of SunLink’s approach to designing mounting systems is trying to keep everything strongly interconnected,” Tilley says. “The more interconnected a system can be — and by that I mean structural components going north, south, east and west — the better you can deal with loads.” The design is rated for high wind speeds that will both push and pull on the system.
The system also used customized short connector posts to keep a low profile and resolve waterproofing issues specific to the site. Special flashing and waterproof foot boxes were also used on the rooftop. Finally, the company chose a combination of 5- and 15-degree tilt angles to ensure the system was out of sight while maximizing efficiency in relation to roof slope.
After the mechanical matters were sorted out and the design was approved, it was simply a matter of planning — but it was not simple. Bryan Bucci, who was a project manager and now works in marketing for SunLink, was charged with coordinating all logistical components associated with the project.
“This was a huge project,” he says. “When it was handed to me, I had to take a breath and be like, ‘All right’ — sort of get fired up for it.”
Bucci broke the project down to a daily plan. He set goals and kept priorities. He documented every e-mail and phone call. He organized weekly conference calls with a dozen of the system’s stakeholders. He says these things were essentially his role with any installation as a project manager, but Alcatraz required more.
With installation beginning in September 2011 and ending in June, a barge — not the normal ferry — was required to transport the materials to the island. All the skids, pallets, boxes of metal and aluminum, combiner boxes and inverters then had to be craned to the roof, where the installation was staged.
The installers, who were not affiliated with SunLink, often arrived in the early morning, sometimes before sunlight and as fog obscured the bay. The wind was fierce, and workers sometimes had to tape their helmets to their heads. Their fingers were nearly frozen from the morning chill. But they got the work done and were often leaving the island just as the first visitors arrived.
A sign that said solar was being installed greeted visitors as they arrived. No one could see the project, though. And today, the solar system is collecting energy and cutting down on the costly diesel generator’s use by 60%.
“This is fantastic for us because we’re a Bay Area company,” says Tilley. “It’s great for our employees to go across the Golden Gate Bridge and look down over there and know that’s one of our projects.” SPW
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