We had been actively preparing for this moment for a long time. The installation of the 8.58 kW photovoltaic roof array with its 26 modules is a massive step towards our goal of achieving net-zero-energy. So, let’s break down the installation process into digestible pieces.
In preparation for the roof solar array installation, we had to fix various items on and around the roof (see “The roof project” for more information). Elements that were directly related to the solar array were the solar blocking to anchor the array to the roof, and the solar posts installation that will support the array, which we carefully coordinated with Lisa Albrecht from All Bright Solar.
The morning of the installation a crate with our 26 solar modules was dropped off, which were carefully unpacked and hoisted onto the roof. It was not really much of a workout, as the modules themselves were rather light.
Up on the roof, the crew began to mount the railing system to the previously installed solar posts, and laid out the wiring of the array. Next the crew set the modules onto the rails, carefully lined them up and bolted them down. Once they were attached, the crew made the final wiring connections and cut off the rail ends to fit.
Now let’s talk about the hidden elements that went into this installation, such as building code requirements. If you look at the photovoltaic array layout, you may ask why we only had four modules in a row, while there would have been space for six modules.
Chicago building code requires a minimum of 36 inch clearance around the array. My understanding is that this is a fire safety provision, i.e. to make roof access to fire fighters easier.
How about the other direction? Why didn’t we space the rows closer together? Why didn’t we increase the angle of the modules to get a better solar yield?
The answer is: 21. Like December 21st – or the winter solstice. To prevent the modules from casting shadows onto each other, the row spacing and angle of the modules was determined by the sun’s angle at winter solstice.
Are we ready yet to catch some photons? Well, hold your horses! For the photovoltaic array to actually work, we need an inverter, which will be the subject of the next post.
If you find any of the solar terminology confusing, you find answers in the previous blog post “Solar lingo”.