When it comes to harnessing the power of the sun, there’s a lot more to it than just throwing down a towel and catching some rays. Ask J.M. Electrical Co. Inc. The Lynnfield, Mass., contractor with 140 electricians just completed an installation that was anything but typical.
In March, J.M. Electrical installed a solar photovoltaic (PV) energy system on the rooftop of a parking structure for Massachusetts General Hospital in Charlestown, Mass. The 476-kilowatt system was designed by solar developer 621 Energy of Concord, Mass. It is expected to generate 568,000 kilowatt-hours in its first year of production, saving the hospital about $95,000 annually.
The system consists of 1,487 solar panels and 17 solar inverters. What was unique about the project was how J.M. Electrical had to work within the peculiar constraints of the location.
The old building has thick walls and floors. In its former life, it was used to store cannonballs, among other things. To avoid increasing the potential for leaks, the client did not want holes drilled in the roof. The client also did not want the panels to be visible from the street. Also, the building is located close to the ocean shore, introducing the possibility of strong winds.
All of this made for a challenging installation. Adam Palmer, J.M. Electrical project manager, said the company hid all the equipment behind roof turrets to eliminate visibility.
“The only way you will see the panels would be if you are on the roof,” he said.
Because of the thick walls, the workers only used rigid conduit. Also, due to possible high winds, the system had to be secured. The client’s aversion to drilling made that task more complicated.
“Everything is held on the roof by ballasts or blocks,” Palmer said. “We only drilled two bolts.”
Because of the wind and the client’s low-visibility demands, the panels had to be positioned at an angle of only 5 degrees. This is a lower angle than usual for the latitude of Massachusetts. Locations farther north of the equator require steeper angles to efficiently catch the sun’s rays.
“[The low angle] could affect the efficiency of the project, but not by that much,” Palmer said.
According to Matthew Guarracino, J.M. Electrical business development manager, 5 degrees is just enough to keep the snow off.
Finally, the unique street location of the project added an additional test. The structure is bordered on all sides by busy thoroughfares that left no room for storage or laydowns. Everything had to be put in place on the roof by crane.
“That required a lot of coordination and safety,” Guarracino said. “We had to move quickly.”