Sunlight and power (No. 223 on the list of the best solar contractors of 2021) has installed solar power on many different roof types in the San Francisco Bay Area. Tiled roofs, shingle roofs, flat roofs, metal roofs – the Berkeley installer has seen them all in the past 45 years. But none were as cramped as the company’s 2020 installation at the University of California San Francisco Medical Center in Mission Bay.
The plan was to install a 244-kW solar panel using a specially designed steel structure as the base of the system that would span over a raised roof section of the UCSF Medical Center. Everything was laid out in the design documents, but what SLP installers immediately discovered was that they had only 1/4 inch of wiggle room with the attachments.
“There’s a lot of slack with rail, and then with L feet, there’s a lot of vertical adjustment,” said Scott Hosterman, senior project engineer at SLP. “I mean, we rarely get into this tight situation because we’re working with trusses or concrete and we’ve got plus-or-minus 5 inches. When something comes up, we can slide things, we can push the cantilever and give ourselves more room. ”
At first touch they were off by a sixteenth of an inch. That measurement spread across 30 module rows meant the system would run out of place and not fit. SLP worked with general contractors TCB Builders to drill precise attachment points into the steel foundation.
The steel beams were placed about 20 ft from the roof, so to get installers to that height, SLP placed plywood on top of wooden planks stacked in the slots of the I-beams to create a surface for contractors to walk along and install modules.
SLP installers worked end-to-end this way, installing 678 SunPower modules. Given the limited working area of the building and the desire to maximize power, modules were placed in an east-west orientation.
“East-west lends itself to zero loss of space,” Hosterman said. “You can stack east-west, creating an almost continuous envelope of solar energy.”
The SLP crew worked through the early months of the Mission Bay pandemic when shutdowns due to COVID-19 restrictions were common. The hospital had set time windows for when the solar contractors could work. Everyone had to carry an ID and were temperature checked every time they entered the building. As electricity ran into the building, contractors worked in an “airtight cart” as a precaution.
In addition, the air quality in California was poor and the installers and steel workers worked in relentless heat atop a six-story building. And the project was finished in July, just before wildfire ash started falling on San Francisco.
“Even nearly a year later, we haven’t worked on another project like this,” said Xavier Garcia, project manager at SLP. “We have challenging clients, challenging locations, challenging weather, challenging installation, challenging AHJs, but not the project itself.”
He added that with the many parties involved in building this array and the conditions under which it was built, SLP walked away with some lessons learned from this project.
“One is that we know we can make it happen, because in the worst case scenario we’ve already done it once – and we did it well,” said Garcia.
This story was featured exclusively in our Top Solar Contractors 2021 issue. Check out the issue and full list of the best solar installers in the US here.